KR100962512B1 - Amethod for preparing kenaf and polypropylene biocomposites - Google Patents

Abstract

The present invention relates to a method for producing a natural fiber / polypropylene biocomposite, and more particularly, to a method for producing a biocomposite composed of an electron beam-treated natural fiber and polypropylene.

The natural fiber / polypropylene biocomposite prepared by the present invention showed an improvement in mechanical properties and dynamic mechanical thermal properties compared to polypropylene, and in particular, it is possible to increase flexural strength, flexural modulus, tensile strength and tensile modulus.

Natural fiber, polypropylene, biocomposite material, electron beam treatment

Description

Method for preparing natural fiber and polypropylene biocomposites {Amethod for preparing kenaf and polypropylene biocomposites}

The present invention relates to a method for producing a natural fiber / polypropylene biocomposite, and more particularly, to a method for producing a biocomposite composed of an electron beam treated natural fiber and polypropylene.

The advantages of biocomposites that mix between biodegradable natural fibers and biodegradable or non-biodegradable polymer matrices include environmentally friendly, lightweight, CO ₂ reduction, and ease of processing. Water absorption, limited thermal stability, irregular fiber shapes, and the like.

Kenaf fiber, which is a kind of natural fiber, is composed of 45-57% cellulose, 21-23% hemicellulose, 8-13% lignin, and others (peptin, wax), which is not only low cost but also low density (1.42 g / cm ³⁾ ) And has been used in the manufacture of ropes, twine, clothing and paper.

Such kenaf fibers have acceptable mechanical properties, easy assembly, good dimensional stability, tubular / cellular structure, as described above.

Prior arts related to such biocomposites made of natural fibers and polymers can be found in Korean Patent Application No. 10-2000-7004507. The patent application relates to a composite material of a resin and cellulose or lignocellulosic fibers, which discloses a composite material consisting of kenaf (claim 5) and polypropylene (claim 10) as a thermoplastic resin.

In addition, Korean Patent Application No. 10-2002-7014189 may be cited as a prior art related to moldable pellets based on a composition of natural fibers and thermoplastic polymers. The patent application relates to a moldable material comprising a natural fiber strand comprising a majority of wrapped fibers, and a sheath of a thermoplastic material, wherein the natural fiber is kenaf (claim 2) and a thermoplastic material is polypropylene (claim). It provides a moldable material consisting of 4). However, in these techniques, there is no disclosure about a special technique for improving the mechanical properties and the like as in the present invention.

Thus, the present inventors came to complete the present invention while studying a method that can effectively improve mechanical properties and the like while providing such a biocomposite, and also provide ease of processing.

That is, an object of the present invention is to provide a method that is easy to process as well as improve the mechanical properties, etc. in producing a biocomposite material based on natural fibers / polypropylene.

In order to achieve this object, the present invention

In preparing natural fiber / polypropylene biocomposites,

The natural fiber may be Kenaf, Jute, Coir, rice straw, Sisal, Flax, Hemp or Banana, but using electron beam Modify,

The surface modified natural fiber and polypropylene composite material are mixed using a twin screw extruder,

The mixed composite material provides a method for producing a natural fiber / polypropylene biocomposite, which is molded as a biocomposite by compression molding or injection molding.

In addition, the present invention provides a compression molded natural fiber / PP biocomposite material having a flexural strength up to about 100 MPa, flexural modulus up to about 5 GPa, tensile strength up to about 60 MPa, modulus up to about 5 GPa. .

Furthermore, the present invention provides a biocomposite material of injection-molded natural fiber / polypropylene obtained by the above method, the flexural strength of up to about 100 MPa, the flexural modulus of up to about 5 GPa, the tensile strength of up to about 60 MPa, the elastic modulus of up to about 5 GPa. To provide.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In the present invention, in manufacturing a natural fiber / polypropylene biocomposite, the natural fiber is Kenaf, Jute, Coir, rice straw, Sisal, Flax, hemp ( Hemp) or Banana (Banana) is used to modify the surface by using an electron beam.

In this case, the electron beam condition is sufficient in the range of 1-100 kGy, and is most preferable in view of enhanced physical properties in the range of 20 kGy or less, particularly in the range of 5-20 kGy.

The surface modified natural fibers and polypropylene composites are mixed using a twin screw extruder. The internal temperature profile of the extruder is 130, 150, 160, 180 ℃, the rotation speed is 20-250rpm, feed rate is 0.5-10kg / hr, side feed rate of natural fiber is 3-100kg / hr and natural fiber The content was 10-60 wt%, and accordingly the polypropylene content is characterized by 40-90 wt%.

At this time, the feed rate in the extruder is 2kg / hr, the side feed rate of the natural fiber is 23kg / hr and the natural fiber content is 30 wt% dispersion of natural island oil dispersed in polypropylene resin, uniformity of the extrudate, and obtained When comprehensively considering the effect of improving the properties of the biocomposite material, it is preferable to other content ratios.

The mixed composite material is molded as a biocomposite material by compression molding or injection molding.

Specific compression molding conditions are sufficient to be performed for 10-60 minutes at 150-250 ℃, 500-1500psi, injection molding conditions are sufficient to perform 150-250 ℃, 1-15 minutes.

By performing these steps sequentially, biocomposites of compression-molded natural fiber / polypropylene with flexural strength up to about 100 MPa, flexural modulus up to about 5 GPa, tensile strength up to about 60 MPa, and modulus up to about 5 GPa can be obtained. have.

In addition, by performing these steps sequentially, injection-molded natural fiber / polypropylene biocomposites with flexural strength up to about 100 MPa, flexural modulus up to about 5 GPa, tensile strength up to about 60 MPa, and modulus up to about 5 GPa. You can get it.

According to the present invention, by incorporating the natural short fibers into the polypropylene through a double-axis extrusion technique, the mechanical properties and heat deformation temperature of the polypropylene alone is significantly enhanced. In addition, it was confirmed that the bending and tensile properties were more improved during the extrusion molding than the injection molding. This is believed to be because more desirable recrystallization behavior is performed at slow cooling rates during extrusion. However, the mechanical properties of the injection-molded biocomposites were also found to be much enhanced due to the natural fiber alignment through the injection nozzle during molding.

Furthermore, it was confirmed that the interfacial adhesion between the hydrophilic natural fibers and the hydrophobic polymer matrix substrate was enhanced by modifying the surface of the natural fibers with an electron beam.

material

1) Kenaf Fiber:

Low density (1.42 g / cm ³ ) consisting of 45-57% cellulose, 21-23% hemicellulose, 8-13% lignin and others (peptin, wax).

2) Polypropylene:

This product is supplied by Hyosung Corporation of Korea, and its brand name is J-640 PP.

Specific property values are as follows:

Melt Flow Index: 10 g / 10min

Melting Temperature: 161 ℃

Heat deflection Temperature: 108 ℃

Example 1 Preparation of Kenaf Fiber / Polypropylene Composites

First, Kenaf fibers were used with or without electron beam treatment at very low intensities of 20 kGy or less.

Due to the problem of feeding the kenaf fibers into the extruder in the state of receiving the electron beam treated or untreated kenaf fibers (straight fibers), the average length of about 10 mm was cut using a grinder.

The cut kenaf fibers and polypropylene were then mixed in a twin screw extruder (Modular Intermeshing, trade name LG (BT-30-S2-421, Ø 30 mm)).

At this time, the extrusion conditions were carried out a number of times the extrusion process in consideration of various variables such as various temperatures and fiber content to establish the optimum conditions as shown in Table 1 below.

Barrel temperature (℃) Screw speed (rpm) Feed rate (kg / hr) Side feed rate (kg / hr) Zone1 Zone2 Zone3 Zone4 Zone5 Head Die 50-250 0.5-10 3-100 130 150 160 180 180 180 180

For reference, the screw speed, feed rate and dripping amount per kenaf fiber content are as shown in Table 2 below.

The extruder combination uses three kneading disk block screw combinations to maximize melting and mixing behavior in the extruder, the properties of the blend and to reduce fiber damage. FIG. 1A shows three kneading disc blocks. (kneading disk block) is a cross-sectional view showing the extruder structure with the screw combination, Figure 1b is a partial enlarged view of the kneading disk block.

As shown in FIG. 1A, kenaf fibers were side-fed at a cylinder No. 4 position 72 cm away from the hopper at a total screw length of 132 cm using a side port. In this case, the pellet formability and the characteristics of each of the biocomposites obtained from the kenaf fibers were varied by varying the content of 10 wt%, 20 wt%, 30 wt%, and 40 wt%. The pellets thus prepared (Kenaf fiber content 30 wt%) are summarized in FIG. 2.

The kenaf / PP pellets fabricated in this way are most optimal to form a matrix after the PP fiber has been sufficiently melted for 30 minutes at 190 ° C and 1000 psi for compression molding. Judging. Compression molding machine structure and molding process used in the process are summarized in FIG.

In addition, in the case of injection molding (injection molding machine: manufactured by BAUTECH), the PP fiber was sufficiently melted at 190 ° C. for 8 minutes in the molding process of the kenaf / PP pellets produced at various temperatures, pressures, and time conditions. Was determined to be the most optimal. The injection molding machine structure and molding process used in the process are summarized in FIG. 4.

For reference, photographs of the compression-molded Kenaf / PP biocomposite and the injection-molded Kenaf / PP biocomposite were summarized as FIGS. 5A and 5B, respectively.

Example 2 Measurement of Flexural Strength, Tensile Strength and Flexural Modulus of Biocomposites

The 3-point flexural test was performed to measure the flexural strength and flexural modulus of the bio-composites thus prepared. Specific performance conditions are as follows:

ASTM D790M-86

Load Cell = 30 kN

Span-to-Depth Ratio = 16: 1

Crosshead Speed = 0.85 mm / min (Compression molding) and 1.2 mm / min (Injection molding)

UTM (Instron 4476)

In addition, the conditions for measuring tensile strength during compression molding are as follows:

DIN 53455

Load Cell = 30 kN

-Gage Length = 100 mm

Crosshead Speed = 10 mm / min

UTM (Instron 4476)

In addition, the measurement conditions of the tensile strength during injection molding are as follows:

ASTM D638M-89

Load Cell = 1 kN

-Gage Length = 7.5 mm

Crosshead Speed = 10 mm / min

UTM (Instron 4476)

The measurement results are summarized in FIGS. 6 and 7, respectively.

That is, as shown in Figure 6, the flexural strength of the compression-molded kenaf / PP biocomposite material has a flexural strength of PP of about 30 wt% at about 44 MPa due to the numerous cell structures constituting the kenaf fibers like other vegetable fibers The addition of kenaf fibers rather reduced to about 41 MPa. However, this value was significantly improved to 50 MPa when the electron beam treatment was performed at a strength of 10 kGy.

In addition, the flexural modulus of the compression molded kenaf / PP biocomposite was improved to about 1.2 GPa when the kenaf fiber was added at about 0.9 GPa due to the aspect ratio of the kenaf fiber. This also greatly increased up to about 3.1 GPa when the electron beam treatment was performed at an intensity of 10 kGy.

Furthermore, the tensile properties of compression-molded kenaf / PP biocomposites showed similar tendencies to flexural properties, depending on the electron beam strength treated on the kenaf fiber surface. When both the tensile strength and the tensile modulus were 10 kGy, the tensile strength was up to about 24 MPa, and the modulus of elasticity was up to about 2.3 GPa.

In addition, as shown in FIG. 7, the bending strength of the injection-molded kenaf / PP biocomposite is about 30 wt% at about 39 MPa at about 39 MPa as the kenaf fibers are oriented along the nozzle during injection molding. The addition alone increased to about 41 MPa. When the electron beam treatment was performed at an intensity of 10 kGy, the flexural strength was further improved to about 45 MPa due to the improvement of the interfacial bonding force.

In addition, the flexural modulus of the injection-molded kenaf / PP biocomposite was improved to about 1.6 GPa when the kenaf fiber was added at about 0.8 GPa due to the aspect ratio of the kenaf fiber. This also increased significantly up to about 2.2 GPa when electron beam treatment was performed at an intensity of 10 kGy.

Furthermore, overall mechanical properties of the kenaf / PP biocomposites made by injection molding were lower than those produced by compression molding, which not only applied the shear force to the material during injection molding but also cooled it slowly for about 1 hour. Unlike compression molding for producing a composite material, injection molding cools the composite material in a short time of several minutes, and thus the crystallinity of the PP resin as a matrix is different. That is, it is determined that the crystallinity of the PP matrix constituting the green composite material manufactured by injection molding is relatively lower than that produced by compression molding.

As a result, the tensile properties of the injection-molded kenaf / PP biocomposites showed similar tendencies to the flexural properties depending on the electron beam strength treated on the kenaf fiber surface. When both the tensile strength and the tensile modulus were 10 kGy, the tensile strength was up to about 22 MPa, and the modulus of elasticity was up to about 2.3 GPa.

Example 3: Dynamic Mechanical Characterization of Biocomposites

The dynamic mechanical characterization conditions of the biocomposite obtained in the present invention are as follows:

-DMA Q800, TA Instruments

-30 ℃ ~ 100 ℃, N2 Gas

Heating Rate = 5 ℃ / min

Frequency = 1 Hz

Oscillating Amplitude: 0.2 mm

The analytical results are summarized as storage modulus as 8a and tan δ as 8b.

As shown in Figure 8a, it was confirmed that the storage modulus of PP was greatly increased by the introduction of kenaf fiber, and further improved as the electron beam intensity of the natural fiber increases. As shown in 8b, it was confirmed that tan δ of PP was reduced by introduction of kenaf fibers, and further reduced by electron beam treatment of natural fibers.

Example 5: Thermal deflection temperature analysis of biocomposites

Thermal deflection temperature conditions of the biocomposite obtained in the present invention are as follows:

ASTM D648

Fiber Stress: 0.5 MPa (66 psi)

Nominal Test Load (g): 313

-Tinius Olsen Co., Model 603

The analysis results are summarized in Table 3 below.

As shown in Table 3, it was confirmed that the heat deformation temperature of PP improved from 30 wt% up to 11 ° C. with the introduction of kenaf fiber. This property was further increased by 10 ° C. after the electron beam treatment. In other words, the heat distortion temperature was improved to 130 ℃.

Example 5 Surface Cracking of Biocomposites

Surface crack observation conditions of the biocomposite obtained in the present invention are as follows:

-Scanning Electron Microscopy (SEM, JEOL, JSM 6380)

Voltage: 5 kV

-Gold coating

The obtained SEM photograph was put together in FIG. As shown in FIG. 9, in the biocomposites obtained by compression molding and injection molding, microstructure defects such as cracks and the like were not observed.

According to the present invention, the incorporation of natural fibers into polypropylene via a double screw extrusion technique significantly enhances the mechanical properties and heat deflection temperature of polypropylene alone. In addition, it was confirmed that the bending and tensile properties were more improved during extrusion molding than injection molding. This is believed to be because more desirable recrystallization behavior is performed at slow cooling rates during extrusion. However, the mechanical properties of the injection molded biocomposite material were also found to be much enhanced due to the natural fiber alignment through the injection nozzle during molding.

Furthermore, it has been confirmed that the interfacial adhesion between the hydrophilic natural fibers and the hydrophobic polymer matrix substrate is enhanced by modifying the surface of the natural fibers with an electron beam.

1 is a view showing a twin screw extruder used in the present invention, where 1a is a cross-sectional view showing an extruder structure having three kneading disk block screw combinations, and 1b is a partially enlarged view of the kneading disk block. to be.

FIG. 2 is a photograph of pellets prepared via a double extruder from an electron beam treated Kenaf / PP composite with a Kenaf content of 30% by weight.

3 is a view showing the structure of the compression molding machine and the molding process used in the manufacture of Kenaf / PP composite material as an embodiment of the present invention.

Figure 4 is a view showing the injection molding machine structure and molding process diagram used in the manufacture of Kenaf / PP composite material as another embodiment of the present invention.

FIG. 5 is a photograph of a kenaf / PP biocomposite, 3a is a compression molded kenaf / PP biocomposite, and 3b is an injection molded kenaf / PP biocomposite, wherein (a) is a poly Propylene, (b) untreated kenaf / PP and (c) EB treated kenaf / PP.

FIG. 6 is a graph showing measurement results of bending and tensile properties of the compression-molded kenaf / PP biocomposite of FIG. 5A, in which A is polypropylene, B is untreated kenaf / PP, and C is a 5 kGy electron beam. Treated kenaf / PP, D means 10 kGy electron beam treated kenaf / PP, E means 20 kGy electron beam treated kenaf / PP.

FIG. 7 is a graph showing the bending and tensile properties of the injection molded kenaf / PP biocomposite of FIG. 5B, where A is polypropylene, B is untreated kenaf / PP, and C is a 5 kGy electron beam. Treated kenaf / PP, D means 10 kGy electron beam treated kenaf / PP, E means 20 kGy electron beam treated kenaf / PP.

FIG. 8 is a graph showing dynamic mechanical characterization results of the Kenaf / PP biocomposite of FIG. 5, where 8a shows a storage modulus result and 8b shows a tan δ result.

FIG. 9 is an SEM photograph showing a surface crack observation result of the Kenaf / PP biocomposite of FIG. 5.

Claims (7)

In preparing natural fiber / polypropylene biocomposites, The natural fiber may be Kenaf, Jute, Coir, rice straw, Sisal, Flax, Hemp or Banana, but within 1-100 kGy. Using electron beam to modify the surface, The surface modified natural fiber and polypropylene composite material are mixed using a twin screw extruder, The mixed composite material is molded as a biocomposite material by compression molding or injection molding. delete The internal temperature profile of the extruder is 130, 150, 160, 180 ℃, rotation speed is 50-250rpm, feed rate is 0.5-10kg / hr, side feed rate of natural fiber is 3-100kg / hr and natural fiber content is 10-60 wt% The method of claim 1, wherein the compression molding conditions are performed at 150-250 ° C. and 500-1500 psi for 10-60 minutes. The method according to claim 1, wherein the injection molding conditions are performed at 150-250 ° C. for 1-15 minutes. Compression molded natural fiber / poly, obtained by the method of any one of claims 1 to 3, wherein flexural strength up to 100 MPa, flexural modulus up to 5 GPa, tensile strength up to 60 MPa, modulus up to 5 GPa Propylene Biocomposites An injection molded natural fiber / poly having a flexural strength of up to 100 MPa, a flexural modulus of up to 5 GPa, a tensile strength of up to 60 MPa, and an elastic modulus of up to 5 GPa, obtained by the method of claim 1. Propylene Biocomposites

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