CN102156147A - Method for detecting film forming stability of polypropylene in bidirectional stretching by using thermal analysis method - Google Patents

Abstract

The invention discloses a method for detecting film forming stability of polypropylene in bidirectional stretching by using a thermal analysis method. The method is characterized by comprising the following steps of: preparing polypropylene resin into a thermal analysis test standard sample; performing heating and cooling scanning on the polypropylene by using a differential scanning calorimeter (DSC), and detecting crystallization and melting behavior parameters of the polypropylene material; then designing a thermal treatment program of the polypropylene material according to the crystallization and melting behavior parameters of the material; and performing multi-step thermal treatment on the material, and analyzing the film forming stability when the polypropylene resin is processed by analyzing the results obtained by thermal grading treatment and using calculation of thickness and molecular structure parameters of a polypropylene wafer. The method timely provides film forming stability information of the polypropylene for production and application, and is simple, convenient, quick, efficient and strong in accuracy.

Description

Detection of film-forming stability of polypropylene in biaxial stretching by thermal analysis

technical field

The present invention relates to the detection of film-forming stability of polypropylene in biaxial stretching by means of thermal analysis, specifically using a differential calorimetry scanner (DSC) to detect biaxially stretched polypropylene resin through step-by-step heat treatment. The invention relates to a method for film-forming stability in a production process, belonging to the field of characterization of polymer materials.

Background technique

In recent years, the application of biaxially oriented polypropylene film in the field of packaging has grown rapidly. With the development of production technology, the stretching rate of film is required to be faster and faster in the production process, which requires the film-forming stability of polypropylene resin to be better and better. If the quality of the polypropylene material does not meet the specified requirements, problems such as film rupture and uneven surface will occur during production, which will affect economic benefits.

Currently, the methods for characterizing the film-forming stability of polypropylene resins in the production of biaxially oriented films are limited and have many disadvantages. The method generally adopted is only the test of xylene room temperature soluble matter, but this method is relatively rough and can only be used as a simple criterion and is not accurate; another method is to carry out trial production of polypropylene resin on a large production device, However, this method is extremely expensive and requires a large amount of resin, and it is difficult to provide information for quickly characterizing the film formation of the resin for practical applications and industrial production. Therefore, there is an urgent need for a relatively simple and efficient test method for predicting the film-forming stability of polypropylene resin in practical applications.

Contents of the invention

The purpose of the present invention is to provide to detect the film-forming stability of polypropylene in biaxial stretching with thermal analysis method for the deficiencies in the prior art, and it is characterized in that this method is easy to use, detects polypropylene resin rapidly, accurately and efficiently. The film-forming stability in the production process of the biaxially stretched film can obtain the structural information of the polypropylene resin, so as to predict the film-forming stability of polypropylene.

The purpose of the present invention is achieved by the following technical measures

Testing the film-forming stability of polypropylene in biaxial stretching by thermal analysis involves the following steps:

(1) Polypropylene resin is made into a thermal analysis test standard sample with uniform thickness;

(2) Carry out thermal analysis and heating and scanning processing on polypropylene resin to obtain the crystallization and melting behavior parameters of the material:

The sample stays at a temperature of 180-210°C for 2-7 minutes to eliminate any residual thermal history, then lowers the temperature to 25-50°C at a cooling rate of 7-12°C/min, stays for 1-5 minutes, and then cools down to 7-12 ℃/min heating rate to 180 ~ 210 ℃, record the cooling crystallization curve and heating melting curve;

The crystallization temperature T _c , crystallization start temperature T _conset and crystallization end temperature T _cendset of the material are obtained from the cooling crystallization curve, and the melting point T _m , melting start temperature T _monset , melting end temperature T _mendset and melting point of the material are obtained from the heating melting curve Relative crystallinity X _c ;

(3) Heat treatment procedure for thermal classification:

Keep the above sample at a temperature of 180-210°C for 2-7 minutes to eliminate any residual thermal history, then lower the temperature to 25-50°C at a cooling rate of 5-20°C/min, stay for 1-5 minutes, Heating at a heating rate of 20°C/min to the first self-nucleation-annealing temperature T _s1 = 164-170°C, staying at t _s =5-40min, cooling to 25-50°C at a rate of 5-20°C/min, Stay for 1-5min; continue heating to the second self-nucleation-annealing temperature T _s2 = 160-163°C, stay for _ts = 5-40min, cool down to 25-50°C at a rate of 5-20°C/min, and stay 1～5min; heat up to the third self-nucleation-annealing temperature T _s3 = 155～159℃ at a heating rate of 5～20℃/min, and stay at _ts =5～40min. In this way, through continuous heating and cooling treatment, The sample is heat-treated at successively lower self-nucleation-annealing temperatures, each self-nucleation-annealing temperature is lower than the previous self-nucleation temperature by △T=2～7°C, when the sample is After staying at temperature T _sn =135-142°C for t _s =5-40min, cool down to 25-50°C, stay for 1-5min, raise the temperature to 180-210°C at a heating rate of 5-20°C/min, and record the final melting curve;

(4) Carry out mathematical fitting and theoretical calculation on the thermal classification test results of the material, and analyze the stability of the polypropylene material when it is stretched into a film:

a. Calculation of the relative content of each melting peak

Use professional peak fitting processing software to perform peak fitting processing on the final melting curve, separate the curve into independent melting peaks, and calculate the melting point and relative content of each peak;

b. Calculation of wafer thickness distribution curve

Calculate the wafer thickness corresponding to each melting peak of the thermal classification curve, and then calculate the wafer thickness distribution of polypropylene resin, use the Thomson-Gibbs equation (1) to calculate the wafer thickness L corresponding to each melting peak of the thermal classification curve, and then calculate the polypropylene resin Resin wafer thickness distribution:

${\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

where _Tm is the melting temperature of polypropylene, _Tm0 is the equilibrium melting point of polypropylene, _ΔH0 is ^the melting enthalpy of polypropylene, and σ is the surface free energy of polypropylene;

c. Calculation of wafer thickness distribution parameters

Use formula (2) and formula (3) to calculate the number average wafer thickness L _n and weight average wafer thickness L _w of the material respectively, use formula (4) to calculate the wafer thickness distribution coefficient I of the material:

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L\; j\; no"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span><figure-callout\; id="1"\; label="L\; j\; no"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{{}_{}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="j\; L\; j"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">j</figure-callout></span><figure-callout\; id="2"\; label="j\; L\; j"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">\; </figure-callout>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{}}^{}{{\mathrm{<span\; class="notranslate">\; j</span>}}_{}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Wherein, L ₁ , L ₂ ... L _j is the wafer thickness of the melting peak, n ₁ , n ₂ ... n _j is the relative percentage of the melting peak area;

In addition, the thermal classification melting curve is directly processed by formula (1) to obtain the distribution curve of the wafer thickness of each sample that can be quantitatively compared, so as to reflect the inhomogeneity of the molecular structure regularity, and then analyze the aggregation according to the results. The film-forming stability of acrylic resin is good or bad.

Performance Testing

Thermal analysis technology was used to detect the film-forming stability of polypropylene in biaxial stretching. The test results are shown in Figure 1-3 and Tables 1-6. The results show that: from PP-1 to PP-5, in the thermal classification curve , the relative content of the high-temperature melting peak gradually decreases, the relative content of the middle-low temperature melting peak gradually increases, and the average wafer thickness of the resin gradually decreases, indicating that from PP-1 to PP-5, the relative content of high-isotactic components of the resin gradually increases. The relative content of lower isotactic components gradually increased. Due to the content change of high and low isotactic components, the thickness of the resin wafer decreases, the stability of film formation gradually increases, and the rate of film rupture gradually decreases. The results of this thermal analysis detection method are consistent with the detection results of large-scale film drawing equipment.

Description of drawings

Figure 1.a is the DSC cooling crystallization curves of five isotactic polypropylene samples under the thermal fractionation procedure of Example 1.

Fig. 1.b is the DSC temperature rising melting curve of 5 kinds of isotactic polypropylene samples under the thermal classification program of Example 1.

Fig. 2 is the thermal classification melting curve of 5 kinds of isotactic polypropylene samples under the thermal classification procedure of Example 1.

Fig. 3 is the wafer thickness distribution curve of 5 kinds of isotactic polypropylene samples under the thermal classification procedure of Example 1.

Detailed ways

The present invention is specifically described below through the examples. It is necessary to point out that the present examples are only used to further illustrate the present invention, and should not be construed as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the contents of the present invention described above.

Example 1

Testing the film-forming stability of polypropylene in biaxial stretching by thermal analysis involves the following steps:

①Experimental samples: five isotactic polypropylenes with different molecular structures and film-forming stability, numbered PP-1, PP-2, PP-3, PP-4, PP-5. Five polypropylene resins were tested on a large-scale film-drawing machine. The results showed that from PP-1 to PP-5, the film rupture rate of the resins gradually decreased, and the film-forming stability became better and better.

②Use a compression molding machine to press the sample into a thin plate with uniform thickness to prepare a special test sample for thermal analysis.

③Stay the sample at 180°C for 2 minutes, then lower the temperature to 25°C at a cooling rate of 7°C/min, stay for 1 minute, heat the sample to 180°C at a heating rate of 7°C/min, record the cooling crystallization curve and temperature rise Melting curve, the results are shown in Figure 1.a and Figure 1.b;

The crystallization temperature T _c , crystallization start temperature T _conset and crystallization end temperature T _cendset of the material are obtained from Figure 1.a, and the melting point T _m , melting start temperature T _monset , and melting end temperature of the material are obtained from Figure 1.b T _mendset and relative crystallinity X _c ;

④Stay the above sample at a temperature of 180°C for 2min, then lower the temperature to 25°C at a cooling rate of 5°C/min, stay for 1min, and heat to the first self-nucleation-annealing temperature T at a heating rate of 5°C/min _s1 = 163°C, stay for t _s = 5min, cool down to 25°C at a cooling rate of 5°C/min, stay for 1min; continue heating to the second self-nucleation-annealing temperature T _s2 = 160°C, stay for t _s = 5min , cool the sample to 25°C and stay for 1min; raise the temperature to the third self-nucleation-annealing temperature T _s3 = 157°C at a heating rate of 5°C/min, and stay for _ts = 5min, thus, through continuous heating and cooling , the sample is heat-treated at successively lower self-nucleation-annealing temperatures, each self-nucleation-annealing temperature is lower than the previous self-nucleation temperature by △T=3°C, when the sample is at the last self-nucleation-annealing temperature After staying at T _sn =136°C for t _s =5min, cool down to 25°C, stay for 1min, raise the temperature to 180°C at a heating rate of 5°C/min, and record the final melting curve. The experimental results are shown in Figure 2;

⑤ Carry out mathematical fitting and theoretical calculation on the thermal classification test results of the material, and analyze the stability of the polypropylene material when it is stretched into a film:

a. Calculation of the relative content of each melting peak

Use professional peak fitting processing software to perform peak split fitting processing on the final melting curve, separate the curve into independent melting peaks, and calculate the melting point and relative content of each peak. The peak split results are listed in Table 1;

b. Calculation of wafer thickness distribution curve

Calculate the wafer thickness corresponding to each melting peak of the thermal classification curve, and then calculate the wafer thickness distribution of polypropylene resin, use the Thomson-Gibbs equation (1) to calculate the wafer thickness L corresponding to each melting peak of the thermal classification curve, and then calculate the polypropylene resin Resin wafer thickness distribution:

${\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, T _m is the melting temperature of polypropylene, the equilibrium melting point of polypropylene T _m ⁰ =460K, the melting enthalpy of polypropylene △H ₀ =184×10 ⁶ J/m ³ , the surface free energy of polypropylene σ=0.0496 J/ ^m2 ;

c. Calculation of wafer thickness distribution parameters

The number average wafer thickness L _n and the weight average wafer thickness L _w of the material were calculated using formula (2) and formula (3), and the wafer thickness distribution coefficient I of the material was calculated using formula (4). The experimental results are listed in Table 2:

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="j\; L\; j"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">j</figure-callout></span><figure-callout\; id="2"\; label="j\; L\; j"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">\; </figure-callout>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{}}^{}{{\mathrm{<span\; class="notranslate">\; j</span>}}_{}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Wherein, L ₁ , L ₂ ... L _j is the wafer thickness of the melting peak, n ₁ , n ₂ ... n _j is the relative percentage of the melting peak area;

In addition, the thermal classification melting curve is directly processed by formula (1) to obtain the distribution curve of the wafer thickness of each sample that can be quantitatively compared, so as to reflect the inhomogeneity of the molecular structure regularity, and then analyze the aggregation according to the results. The film-forming stability of acrylic resin is good or bad. The results are shown in Figure 3.

From the results in Table 1 and Figure 2, it can be seen that from PP-1 to PP-5, on the thermal classification curve of the samples, the relative content of the high-temperature melting peak gradually decreases, and the content of the secondary high-temperature melting peak gradually increases. It can be seen from Table 2 and Figure 3 that from PP-1 to PP-5, the content of thicker wafers gradually decreases, the content of thinner wafers gradually increases, the average wafer thickness decreases, and the wafer thickness distribution index increases. The above results show that from PP-1 to PP-5, the content of high isotactic components decreases, and the thickness of the resin wafer decreases. It can be seen that in the process of processing, from PP-1 to PP-5, the content of polypropylene resin decreases. The stability of film formation gradually increased, while the rate of film rupture gradually decreased. This result is consistent with the test results of a large film stretching machine.

Example 2

Testing the film-forming stability of polypropylene in biaxial stretching by thermal analysis involves the following steps:

①Experimental samples: five isotactic polypropylenes with different molecular structures and film-forming stability, numbered PP-1, PP-2, PP-3, PP-4, PP-5. Five polypropylene resins were tested on a large-scale film-drawing machine. The results showed that from PP-1 to PP-5, the film rupture rate of the resins gradually decreased, and the film-forming stability became better and better.

②Use a compression molding machine to press the sample into a thin plate with uniform thickness to prepare a special test sample for thermal analysis.

③Stay the sample at 210°C for 7 minutes, then lower the temperature to 50°C at a cooling rate of 12°C/min, stay for 5 minutes, heat the sample to 210°C at a heating rate of 12°C/min, record the cooling crystallization curve and temperature rise melting curve;

The crystallization temperature T _c , crystallization start temperature T _conset and crystallization end temperature T _cendset of the material are obtained from the crystallization curve, and the melting point T _m , melting start temperature T _monset , melting end temperature T _mendset and relative Crystallinity X _c ;

④Stay the above sample at 210°C for 7min, then lower the temperature to 50°C at a cooling rate of 20°C/min, stay for 5min, and heat to the first self-nucleation-annealing temperature T at a heating rate of 20°C/min _s1 =170°C, stay at t _s =40min, cool down to 50°C at a rate of 20°C/min, and stay for 5min; continue heating to the second self-nucleation-annealing temperature T _s2 =163°C, stay at t _s =40min, Cool down to 50°C at a rate of 20°C/min, and stay for 5 minutes; raise the temperature to the third self-nucleation-annealing temperature T _s3 = 157°C at a rate of 20°C/min, and stay at t _s =40min. In this way, through continuous The temperature rise and fall treatment, the sample is heat-treated at successively lower self-nucleation-annealing temperatures, and each self-nucleation-annealing temperature is lower than the previous self-nucleation temperature by △T=7°C. Nucleation-annealing temperature T _sn =136°C, stay at t _s =40min, then cool down to 50°C, stay for 5min, raise the temperature to 210°C at a heating rate of 20°C/min, and record the final melting curve;

⑤ Carry out mathematical fitting and theoretical calculation on the thermal classification test results of the material, and analyze the stability of the polypropylene material when it is stretched into a film:

a. Calculation of the relative content of each melting peak

Use professional peak fitting processing software to perform peak split fitting processing on the final melting curve, separate the curve into independent melting peaks, and calculate the melting point and relative content of each peak. The peak split results are listed in Table 3;

b. Calculation of wafer thickness distribution curve

Calculate the wafer thickness corresponding to each melting peak of the thermal classification curve, and then calculate the wafer thickness distribution of polypropylene resin, use the Thomson-Gibbs equation (1) to calculate the wafer thickness L corresponding to each melting peak of the thermal classification curve, and then calculate the polypropylene resin Resin wafer thickness distribution:

${\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, T _m is the melting temperature of polypropylene, the equilibrium melting point of polypropylene T _m ⁰ =460K, the melting enthalpy of polypropylene △H ₀ =184×10 ⁶ J/m ³ , the surface free energy of polypropylene σ=0.0496 J/ ^m2 ;

c. Calculation of wafer thickness distribution parameters

Use formula (2) and formula (3) to calculate the number average wafer thickness _Ln and weight average wafer thickness _Lw of material respectively, use formula (4) to calculate the wafer thickness distribution coefficient I of material, the experimental results are listed in Table 4:

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="j\; L\; j"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">j</figure-callout></span><figure-callout\; id="2"\; label="j\; L\; j"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">\; </figure-callout>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{}}^{}{{\mathrm{<span\; class="notranslate">\; j</span>}}_{}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Wherein, L ₁ , L ₂ ... L _j is the wafer thickness of the melting peak, n ₁ , n ₂ ... n _j is the relative percentage of the melting peak area;

In addition, the thermal classification melting curve is directly processed by formula (1) to obtain the distribution curve of the wafer thickness of each sample that can be quantitatively compared, so as to reflect the inhomogeneity of the molecular structure regularity, and then analyze the aggregation according to the results. The film-forming stability of acrylic resin is good or bad.

From the results in Table 3 and Table 4, it can be seen that from PP-1 to PP-5, on the thermal classification curve of the samples, the relative content of the high-temperature melting peak gradually decreases, and the content of the secondary high-temperature melting peak gradually increases. The average wafer thickness that can be formed becomes smaller, and the wafer thickness distribution index becomes larger; the content of high isotactic components gradually decreases, while the content of medium and low isotactic components gradually increases. The above results show that from PP-1 to PP-5, due to the decrease in the content of high isotactic components, the thickness of the resin wafer decreases, and the resin is more likely to be stretched into a film during processing, and the stability of the film is gradually increased. film rate gradually decreased. This result is consistent with the test results of a large film stretching machine.

Example 3

Testing the film-forming stability of polypropylene in biaxial stretching by thermal analysis involves the following steps:

①Experimental samples: five isotactic polypropylenes with different molecular structures and film-forming stability, numbered PP-1, PP-2, PP-3, PP-4, PP-5. Five polypropylene resins were tested on a large-scale film-drawing machine. The results showed that from PP-1 to PP-5, the film rupture rate of the resins gradually decreased, and the film-forming stability became better and better.

②Use a compression molding machine to press the sample into a thin plate with uniform thickness to prepare a special test sample for thermal analysis.

③Stay the sample at 210°C for 5 minutes, then lower the temperature to 40°C at a cooling rate of 9°C/min, stay for 3 minutes, heat the sample to 200°C at a heating rate of 9°C/min, record the cooling crystallization curve and temperature rise melting curve;

The crystallization temperature T _c , crystallization start temperature T _conset and crystallization end temperature T _cendset of the material are obtained from the crystallization curve, and the melting point T _m , melting start temperature T _monset , melting end temperature T _mendset and relative Crystallinity X _c ;

④Stay the above sample at 200°C for 5min, then lower the temperature to 40°C at a cooling rate of 15°C/min, stay for 3min, and heat to the first self-nucleation-annealing temperature T at a heating rate of 15°C/min _s1 = 167°C, stay for t _s = 20min, drop to 40°C at a cooling rate of 15°C/min, stay for 3min; continue heating to the second self-nucleation-annealing temperature T _s2 = 162°C, stay for t _s = 20min , lower the temperature to 40°C at a cooling rate of 15°C/min, and stay for 3 minutes; raise the temperature to the third self-nucleation-annealing temperature T _s3 =157°C at a heating rate of 15°C/min, and stay at t _s =20min, so, Through continuous temperature rise and fall treatment, the sample is heat-treated at successively lower self-nucleation-annealing temperatures, each self-nucleation-annealing temperature is lower than the previous self-nucleation temperature After the self-nucleation-annealing temperature T _sn =137°C, stay at t _s =20min, cool down to 40°C, stay for 3min, raise the temperature to 200°C at a heating rate of 15°C/min, and record the final melting curve;

⑤ Carry out mathematical fitting and theoretical calculation on the thermal classification test results of the material, and analyze the stability of the polypropylene material when it is stretched into a film:

a. Calculation of the relative content of each melting peak

Use professional peak fitting processing software to perform peak fitting processing on the final melting curve, separate the curve into independent melting peaks, and calculate the melting point and relative content of each peak. The peak split results are listed in Table 5;

b. Calculation of wafer thickness distribution curve

Calculate the wafer thickness corresponding to each melting peak of the thermal classification curve, and then calculate the wafer thickness distribution of polypropylene resin, use the Thomson-Gibbs equation (1) to calculate the wafer thickness L corresponding to each melting peak of the thermal classification curve, and then calculate the polypropylene resin Resin wafer thickness distribution:

${\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, T _m is the melting temperature of polypropylene, the equilibrium melting point of polypropylene T _m ⁰ =460K, the melting enthalpy of polypropylene △H ₀ =184×10 ⁶ J/m ³ , the surface free energy of polypropylene σ=0.0496 J/ ^m2 ;

c. Calculation of wafer thickness distribution parameters

Use formula (2) and formula (3) to calculate number average wafer thickness _Ln and weight average wafer thickness _Lw of material respectively, use formula (4) to calculate the wafer thickness distribution coefficient I of material, experimental result is listed in Table 6:

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="j\; L\; j"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">j</figure-callout></span><figure-callout\; id="2"\; label="j\; L\; j"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">\; </figure-callout>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{}}^{}{{\mathrm{<span\; class="notranslate">\; j</span>}}_{}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="L"\; filenames="HDA0000049116180000011.png,HDA0000049116180000012.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Wherein, L ₁ , L ₂ ... L _j is the wafer thickness of the melting peak, n ₁ , n ₂ ... n _j is the relative percentage of the melting peak area;

In addition, the thermal classification melting curve is directly processed by formula (1) to obtain the distribution curve of the wafer thickness of each sample that can be quantitatively compared, so as to reflect the inhomogeneity of the molecular structure regularity, and then analyze the aggregation according to the results. The film stability of acrylic resin is good or bad.

From the results in Table 5 and Table 6, it can be seen that from PP-1 to PP-5, on the thermal classification curve of the samples, the relative content of the high-temperature melting peak gradually decreases, and the content of the secondary high-temperature melting peak gradually increases. The average wafer thickness that can be formed becomes smaller, and the wafer thickness distribution index becomes larger; the content of high isotactic components gradually decreases, while the content of medium and low isotactic components gradually increases. The above results show that from PP-1 to PP-5, due to the decrease in the content of high isotactic components, the thickness of the resin wafer decreases, and the resin is more likely to be stretched into a film during processing, and the stability of the film is gradually increased. film rate gradually decreased. This result is consistent with the test results of a large film stretching machine.

Table 1 The melting curve peak splitting results of 5 isotactic polypropylene samples under the thermal classification procedure of Example 1

Table 2 The wafer thickness distribution parameters of 5 isotactic polypropylene samples under the thermal classification procedure of Example 1

Table 3 The melting curve peak splitting results of 5 isotactic polypropylene samples under the thermal classification procedure of Example 2

Table 4 The wafer thickness distribution parameters of 5 isotactic polypropylene samples under the thermal classification procedure of Example 2

Table 5 5 isotactic polypropylene samples under the thermal classification procedure of embodiment 3 The results of the melting curve peak division

Table 6 The wafer thickness distribution parameters of 5 isotactic polypropylene samples under the thermal classification procedure of Example 3

Claims (1)

1. detect the one-tenth membrane stability of polypropylene in two-way stretch with heat analysis method, it is characterized in that this method may further comprise the steps:

(1) acrylic resin is made the hot analytical test standard model of thickness homogeneous;

(2) acrylic resin is carried out heat and analyzes the heating and cooling scan process, obtain the crystallization and the melting behavior parameter of material:

Sample is stopped 2～7min down for 180～210 ℃ in temperature, to eliminate any residual thermal history, then, sample is reduced to 25～50 ℃ with the rate of temperature fall of 7～12 ℃/min, stop 1～5min, heating rate with 7～12 ℃/min is heated to 180～210 ℃ with sample, record decrease temperature crystalline curve and intensification melting curve subsequently;

Obtain the Tc T of material from the decrease temperature crystalline curve _c, crystallization onset temperature T _ConsetWith crystallization final temperature T _Cendset, obtain the fusing point T of material from the intensification melting curve _m, melt initiation temperature degree T _Monset, fusion final temperature T _MendsetWith relative crystallinity X _c

(3) heat treatment process of hot classification:

Above-mentioned sample is stopped 2～7min down for 180～210 ℃ in temperature, to eliminate any residual thermal history, then, reduce to 25～50 ℃ with the rate of temperature fall of 5～20 ℃/min, stop 1～5min, be heated to first spontaneous nucleation-annealing temperature T with the heating rate of 5～20 ℃/min _S1=164～170 ℃, stop t _s=5～40min is cooled to 25～50 ℃ with the speed of 5～20 ℃/min, stops 1～5min; Continue to be heated to second spontaneous nucleation-annealing temperature T _S2=160～163 ℃, stop t _s=5～40min is cooled to 25～50 ℃ with the speed of 5～20 ℃/min, stops 1～5min; Heating rate with 5～20 ℃/min is warming up to the 3rd spontaneous nucleation-annealing temperature T _S3=155～159 ℃, stop t _s=5～40min, so, handle, sample is heat-treated under the spontaneous nucleation-annealing temperature that reduces successively by continuous heating and cooling, each spontaneous nucleation-annealing temperature is than the low △ T=2 of a last spontaneous nucleation temperature～7 ℃, as sample spontaneous nucleation-annealing temperature T in the end _Sn=135～142 ℃ stop t down _sBehind=5～40min, be cooled to 25～50 ℃, stop 1～5min, be warming up to 180～210 ℃, write down final melting curve with the heating rate of 5～20 ℃/min;

(4) polyacrylic hot hierarchical test result is carried out mathematics match and Theoretical Calculation, analyzes the stability of polypropylene material when the stretching film forming:

A. the calculating of each melting peak relative content

Use professional swarming process of fitting treatment software that final melting curve is carried out the swarming process of fitting treatment, curve is separated into melting peak independent of each other, and calculate the fusing point and the relative content at each peak;

B. the calculating of wafer thickness distribution curve

Calculate the pairing wafer thickness of each melting peak of hot grading curve, and then the wafer thickness distribution situation of calculating acrylic resin, utilize Thomson-Gibbs equation (1) to calculate the pairing wafer thickness L of each melting peak of hot grading curve, and then calculate the wafer thickness distribution situation of acrylic resin:

$T_m={T_m}^0(1-\frac{2\mathrm{\&sigma;}}{\mathrm{\&Delta;}{H}_{0}L})---\left(1\right)$

In the formula, T _mBe polyacrylic melt temperature, T _m ⁰Be polyacrylic equilibrium melting point, △ H ₀Be polyacrylic melting enthalpy, σ is polyacrylic surface free energy;

C. the calculating of wafer thickness distribution parameter

(2) formula of use and (3) formula are calculated polyacrylic number average wafer thickness L respectively _nWith weight average wafer thickness L _w, use (4) formula to calculate the wafer thickness distribution coefficient I of material:

$L_n=\frac{n_1{L}_1+n_2{L}_2+n_3{L}_3+n_4{L}_4+,K,+n_j{L}_j}{n_1+n_2+n_3+n_4+,...,+n_j}=\mathrm{\&Sigma;}{f}_i{L}_i---\left(2\right)$

$L_w=\frac{n_1{L_1}^2+n_2{L_2}^2+n_3{L_3}^2+n_4{L_4}^2+,K,+n_j{L_j}^2}{n_1{L}_1+n_2{L}_2+n_3{L}_3+n_4{L}_4+,...,+n_j{L}_j}=\frac{\mathrm{\&Sigma;}{f}_i{L_i}^2}{\mathrm{\&Sigma;}{f}_i{L}_i}---\left(3\right)$

$I=\frac{L_w}{L_n}---\left(4\right)$

Wherein, L ₁, L ₂... L _jBe the wafer thickness of melting peak, n ₁, n ₂... n _jIt is the relative percentage composition of melting peak area;

In addition, directly using (1) formula to carry out homogenization to hot classification melting curve handles, obtain the distribution curve of the wafer thickness of each sample that can quantitative comparison, thereby the unevenness of molecular structure regularity is reflected, and then according to the one-tenth membrane stability quality of interpretation of result acrylic resin.

Images