CN113185821A

CN113185821A - High-toughness heat-resistant biodegradable composite material for tableware and preparation method thereof

Info

Publication number: CN113185821A
Application number: CN202110540332.9A
Authority: CN
Inventors: 江作富; 刘若纳; 王舜; 尹德武; 金辉乐; 高军昌
Original assignee: Wenzhou University
Current assignee: Wenzhou University
Priority date: 2021-05-18
Filing date: 2021-05-18
Publication date: 2021-07-30

Abstract

The invention discloses a high-toughness heat-resistant biodegradable composite material for tableware and a preparation method thereof. According to the technical scheme, 30-65 parts by mass of polylactic acid (PLA) and 35-70 parts by mass of polybutylene succinate (PBS) are used as raw materials, and the high-toughness heat-resistant biodegradable tableware is prepared by uniformly mixing 30-65 parts by mass of the PLA, 35-70 parts by mass of the PBS, 0.1-0.5 part by mass of modified maleic amide polylactic acid (PLA-g-MAH), 4-12 parts by mass of inorganic materials, 0.4-1.3 parts by mass of chain extender, 0.1-0.7 part by mass of compatilizer and 0.1-0.5 part by mass of heat stabilizer. The technical scheme of the invention enhances the mechanical property and the hydrophilic property of the blending system, also enhances the thermal stability of the PBS and PLA blending system, avoids the thermal decomposition process of the blending system in the processing process, and meets the requirements of the current catering industry on tableware.

Description

High-toughness heat-resistant biodegradable composite material for tableware and preparation method thereof

Technical Field

The invention relates to the field of tableware and materials thereof, and discloses a high-toughness heat-resistant biodegradable composite material for tableware and a preparation method thereof.

Background

Tableware is inseparable from the catering industry, the traditional tableware material is mainly prepared from petroleum base (such as polypropylene, polyethylene and the like) as a raw material, and the tableware prepared from the material is discarded in nature after use and is difficult to degrade, so that the serious environmental pollution problem is caused.

Polylactic acid (PLA) is lactic acid formed by fermenting starch, lactic acid is dehydrated to obtain lactide, and the lactide is subjected to ring-opening polymerization to finally obtain polylactic resin. The polylactic acid is safe and harmless, the raw material source is renewable, and the polylactic acid can be completely decomposed into carbon dioxide and water after being discarded, so that the polylactic acid is an internationally recognized green high-molecular environment-friendly material at present. In addition, polylactic acid has some characteristics such as high strength, high modulus, high transparency and the like which are not possessed by other biodegradable materials, but on one hand, the heat distortion temperature of pure polylactic acid is only about 61 ℃, so that the polylactic acid cannot be directly applied to tableware with higher heat resistance requirement; on the other hand, the polylactic acid is hard and brittle and has poor toughness, so that the requirement of tableware on toughness is not met, and even the conventional transportation requirement cannot be met.

The polybutylene succinate (PBS) has excellent mechanical property and good heat resistance, and the synthetic raw material source of the polybutylene succinate (PBS) can be petroleum resources and can also be obtained by fermentation of biological resources, so that the polybutylene succinate (PBS) is the biodegradable plastic with the best comprehensive performance which is generally recognized in the world at present. But the strength of PBS is not enough, the flexibility of PLA is enhanced by adding PBS into PLA, meanwhile, the strength of PBS is enhanced by PLA, so that the blend has excellent breaking strength and breaking elongation, but the interface bonding between PBS and PLA matrix is weak, and the thermal stability is not good, so that the combination of PBS and PLA matrix can not meet the requirement of tableware materials.

Disclosure of Invention

The invention aims to overcome the defects and shortcomings of the prior art and provide high-toughness heat-resistant biodegradable tableware and a preparation method thereof.

In order to achieve the aim, the technical scheme of the invention is to provide a high-toughness heat-resistant biodegradable composite material for tableware, which comprises the following components in parts by mass:

30-65 parts by mass of polylactic acid;

35-70 parts by mass of polybutylene succinate;

0.1-0.5 parts by mass of a maleic anhydride-polylactic acid graft copolymer;

4-12 parts of inorganic materials;

0.4-1.3 parts by mass of a chain extender;

0.1-0.7 parts by mass of a compatibilizer;

0.1-0.5 parts by mass of a heat stabilizer;

the inorganic material is at least one of calcium carbonate, glass beads, barium sulfate, silicon dioxide, asbestos, mica, wood powder, attapulgite, clay, carbon black and argil.

The chain extender is further provided to comprise one or a mixture of more of peroxide compounds, isocyanate compounds, ester compounds and amide compounds.

It is further provided that the compatibilizer comprises a mixture of one or more of maleic anhydride, carboxylic acid type, epoxy type, and oxazoline.

The heat stabilizer is one or more of polyethylene wax, zinc stearate, calcium stearate, magnesium stearate, oleamide, erucamide and titanate coupling agent.

In a second aspect of the invention, there is provided a method for preparing a composite material as described, comprising the steps of:

s1, weighing polylactic acid, polybutylene succinate, maleic anhydride-polylactic acid graft copolymer, inorganic material, chain extender, compatilizer and heat stabilizer according to the formula dosage;

s2, uniformly mixing the formula weighed in S1 according to the sequence of polylactic acid, polybutylene succinate, a chain extender and a compatilizer, adding a heat stabilizer, an inorganic material and a maleic anhydride-polylactic acid graft copolymer into the mixture according to the sequence of the heat stabilizer, the inorganic material and the maleic anhydride-polylactic acid graft copolymer, uniformly mixing, and sealing and standing the mixture;

s3, adding the mixed material of S2 into a double-screw extruder, and extruding and granulating at 170-200 ℃, wherein the rotating speed of the extruder is 100-400 r/min;

s4, drying the material particles obtained in the step S3 in a vacuum oven, wherein the temperature of the oven is set to be 70-90 ℃, and the time is set to be 7-15 hours;

s5, performing injection molding on the pellets obtained in the step S4 in an injection molding machine to obtain a product, wherein the injection molding temperature is 170-200 ℃.

The invention has the beneficial effects that: (1) the PBS has good tensile property, flexibility and high temperature resistance, but the strength is not high; while PLA is relatively rigid, but hard and brittle. Thus, PBS and PLA blends have a synergistic effect, with PBS enhancing the flexibility of PLA, while PLA also enhances the strength of PBS, resulting in blends with excellent strength and elongation at break. (2) By adding some modifiers, a good interface combination effect can be formed between the PBS and the PLA matrix, the mechanical property and the hydrophilic property of the blending system are enhanced, the thermal stability of the PBS and PLA blending system is enhanced, and the thermal decomposition process of the blending system in the processing process is avoided. (3) The PLA and the PBS are all biodegradable materials, are environment-friendly and accord with the green chemical concept. (4) The preparation method is simple in preparation process, easy to control, suitable for large-scale production, available in raw materials and low in cost.

The experimental results are described in detail in the examples.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.

FIG. 1 is a graph of the elastic modulus of a sample of an embodiment of the present invention;

FIG. 2 is a graph showing the test results of the fracture rate of the sample according to the embodiment of the present invention;

FIG. 3 is a graph showing the bending strength of a sample according to an embodiment of the present invention;

FIG. 4 is a graph of strength tests of samples according to an embodiment of the present invention;

FIG. 5 is a graph showing tensile strength tests of samples of examples of the present invention;

FIG. 6 is a Vicat softening point temperature test chart of a sample of an embodiment of the present invention;

FIG. 7 is an infrared spectrum of a sample of an embodiment of the present invention;

FIG. 8 shows a first temperature-lowering DSC curve obtained by DSC data analysis of a sample of an embodiment of the present invention;

FIG. 9 shows a second temperature-lowering DSC curve obtained by DSC data analysis of a sample according to an embodiment of the present invention;

FIG. 10 TG plots of PLA, B1 and B6 composites compared with examples of the present invention;

FIG. 11 thermogravimetric analysis of PLA, B1 and B6 composites according to an embodiment of the present invention;

FIG. 12 SEM images of fracture planes of B1 and B6 composites after impact testing according to an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.

The materials used in this example: polylactic acid (PLA), polybutylene succinate (PBS), a chain extender, TBC, erucamide, white talc and a maleic anhydride-polylactic acid graft copolymer (PLA-g-MAH).

The following process for the preparation of high-toughness heat-resistant biodegradable tableware was carried out according to the claimed method, comprising the steps of:

s1, weighing polylactic acid (PLA), polybutylene succinate (PBS), PLA-g-MAH, inorganic materials, a chain extender, a compatilizer and a heat stabilizer according to the formula dosage.

S2, uniformly mixing the formula weighed by the S1 according to the sequence of PLA, PBS, the chain extender and the compatilizer, adding the heat stabilizer, the inorganic material and the PLA-g-MAH into the mixture according to the sequence of the heat stabilizer, the inorganic material and the PLA-g-MAH, uniformly mixing, and sealing and standing for a period of time.

And S3, adding the mixed material of S2 into a double-screw extruder, and extruding and granulating at 170-200 ℃, wherein the rotating speed of the extruder is 100-400 r/min.

S4, drying the material particles obtained in the step S3 in a vacuum oven, wherein the temperature of the oven is set to be 70-90 ℃, and the time is set to be 7-15 hours.

And S6, carrying out mechanical property test and temperature resistance test on the test sample obtained in the step S5.

Example 1(B1)

S1, weighing 35 parts by mass of PLA, 55 parts by mass of PBS, 6 parts by mass of inorganic material, 0.8 part by mass of chain extender, 0.4 part by mass of compatilizer and 0.1 part by mass of heat stabilizer according to the formula dosage.

And S2, uniformly mixing the formula weighed by the S1 according to the sequence of PLA, PBS, the chain extender and the compatilizer, adding the heat stabilizer and the inorganic material into the mixture according to the sequence of the heat stabilizer and the inorganic material, uniformly mixing, and sealing and standing for a period of time.

S5, performing injection molding on the pellets obtained in the step S4 in an injection molding machine to obtain a product, wherein the injection molding temperature is 170-200 ℃. The obtained modified material was named B1

Example 2(B2)

S1, weighing 35 parts by mass of PLA, 55 parts by mass of PBS, 0.18 part by mass of PLA-g-MAH, 6 parts by mass of inorganic material, 0.8 part by mass of chain extender, 0.4 part by mass of compatilizer and 0.1 part by mass of heat stabilizer according to the formula dosage

S5, performing injection molding on the pellets obtained in the step S4 in an injection molding machine to obtain a product, wherein the injection molding temperature is 170-200 ℃. The obtained modified material was named B2

Example 3(B3)

S1, weighing 35 parts by mass of PLA, 55 parts by mass of PBS, 0.25 part by mass of PLA-g-MAH, 6 parts by mass of inorganic material, 0.8 part by mass of chain extender, 0.4 part by mass of compatilizer and 0.1 part by mass of heat stabilizer according to the formula dosage

The obtained modified material was named B3

Example 4(B4)

S1, weighing 35 parts by mass of PLA, 55 parts by mass of PBS, 0.29 part by mass of PLA-g-MAH, 6 parts by mass of inorganic material, 0.8 part by mass of chain extender, 0.4 part by mass of compatilizer and 0.1 part by mass of heat stabilizer according to the formula dosage

S5, performing injection molding on the pellets obtained in the step S4 in an injection molding machine to obtain a product, wherein the injection molding temperature is 170-200 ℃. The obtained modified material was named B4

Example 5(B5)

S1, weighing 35 parts by mass of PLA, 55 parts by mass of PBS, 0.35 part by mass of PLA-g-MAH, 6 parts by mass of inorganic material, 0.8 part by mass of chain extender, 0.4 part by mass of compatilizer and 0.1 part by mass of heat stabilizer according to the formula dosage

S5, performing injection molding on the pellets obtained in the step S4 in an injection molding machine to obtain a product, wherein the injection molding temperature is 170-200 ℃. The obtained modified material was named B5

Example 6(B6)

S1, weighing 35 parts by mass of PLA, 55 parts by mass of PBS, 0.42 part by mass of PLA-g-MAH, 6 parts by mass of inorganic material, 0.8 part by mass of chain extender, 0.4 part by mass of compatilizer and 0.1 part by mass of heat stabilizer according to the formula dosage

S5, performing injection molding on the pellets obtained in the step S4 in an injection molding machine to obtain a product, wherein the injection molding temperature is 170-200 ℃. The obtained modified material was named B6

In all prepared modified materials, after mechanical property tests, the elastic modulus of B2, B3, B4, B5 and B6 is reduced compared with that of B1, the breaking rate, the bending strength and the hardness are obviously improved, and the tensile strength is not obviously changed. See fig. 1, 2, 3, 4 and 5.

From fig. 6, it can be obtained that the vicat softening point temperature of PLA is increased by about 50 ℃ by adding PBS, and B2, B3, B4, B5 and B6 have no significant change compared with B1, which shows that the vicat softening point of the material is not greatly affected by adding PLA-g-MAH.

As can be seen from fig. 6, by adding a certain proportion of PBS into PLA and adding a compatibilizer to compatibilize the polymer, the vicat softening point temperature of the prepared modified material after injection molding is increased by about 50 ℃ compared to pure PLA. PLA-g-MAH will generate acid anhydride bond and carbon-carbon double bond in the molecular skeleton of polylactic acid, and the property of the material must be changed because of the change of the structure: (1) due to the introduction of anhydride groups, the hydrophilic performance of the material is improved; (2) the introduction of carbon-carbon double bonds easily causes cross-linking between molecules, which is beneficial to improving the mechanical property of the material; (3) the branched chain formed on the polylactic acid molecular skeleton is beneficial to reducing the brittleness of the material at low temperature; (4) another advantage of the structural change is that the material has a molecular basis for continuing chemical reaction, and PBS can be introduced by using an acid anhydride bond and a carbon-carbon double bond in the molecular structure of the modified polylactic acid. The improved properties are just lacking in PLA, and the limitation of a PLA and PBS blending system on tableware is better solved.

Analysis was performed by infrared spectroscopy on B1, B2, B3, B4, B5 and B6, see fig. 7. As shown in FIG. 7, with the continuous addition of PLA-g-MAH content, 2922cm of PLA and PBS blended system main chain^-1C-H stretching vibration peak on saturated carbon, 1713cm^-1C ═ O stretching vibration peak, 1334, 1156 and 1014cm^-1The peak of-C-O-stretching vibration in the group of-O-C ═ O-, and 669cm^-1The C-H out-of-plane bending vibration peaks show strong enhancement or weakening of the peaks, but the positions of the peaks are basically not moved, which indicates that after the PLA-g-MAH is blended, the structures of the molecular main chains of the PLA and the PBS blended molecules are basically kept unchanged, and the interaction force between the PLA and the PBS blended molecules is shown as physical interaction. By comparing the maps of B2, B3, B4 and B5 and B6, it was found that 1334, 1156 and 1014cm were observed with the increase in the PLA-g-MAH content^-1The absorption intensity of the-C-O-stretching vibration peak in the-O-C ═ O-group is smaller and smaller, which is presumed to be because the addition of PLA-g-MAH in the PLA and PBS blending system can increase the number of acid anhydride (a hydrophilic group) in the material, which is beneficial to the improvement of the hydrophilic property of the material and simultaneously improves the biodegradation property of the composite material.

By performing DSC data analysis on B1, B2, B3, B4, B5 and B6, the obtained first-stage temperature-reducing DSC curve is shown in figure 8, the obtained second-stage temperature-increasing DSC curve is shown in figure 9, and the obtained crystallization temperature (T)_x) Enthalpy of crystallization (. DELTA.H)_x) Melting temperature (T)_m) Enthalpy of fusion (. DELTA.H)_m) Cold crystallization temperature (T)_cc) Enthalpy of cold crystallization (. DELTA.H)_cc) See fig. 8, 9; TABLE 1 according to the formula

(of pure PLA)

) The crystallinity (χ) of B1, B2, B3, B4, B5 and B6 is given.

TABLE 1

Fig. 9 shows second temperature-rising DSC curves of B1, B2, B3, B4, B5, and B6, and fig. 8 shows first temperature-falling DSC curves of B1, B2, B3, B4, B5, and B6 in order to eliminate the influence of the thermal expansion history on the crystalline performance of the composite material. It can be seen from fig. 9 that the melting temperature of B1, B2, B3, B4, B5 and B6 is about 112 ℃, and the cold crystallization temperature of B1, B2, B3, B4, B5 and B6 is about 104 ℃; it can be seen from fig. 8 that the crystallization temperatures of B1, B2, B3, B4, B5 and B6 are around 82 ℃; however, we can see that fig. 8 shows a small segment of cold crystallization, because in the process of cooling, the tail end of the PLA modified molecular chain is frozen without being arranged regularly, and when the temperature is raised again, the molecular chain starts to move, and the phenomena of temperature rise and crystallization occur at the same time, forming a cold crystallization peak, thereby confirming that PBS can effectively improve the crystallization capacity and the crystallinity of PLA.

It can be seen from table 1 that the addition of a certain amount of PBS into PLA increases the crystallinity of PLA much more than that of pure PLA (3%), because the PBS has a high crystallization rate, which can keep up with the cooling rate during injection molding, and the addition of PBS can significantly increase the density of crystal nuclei of PLA modified molecule fragments, thereby rapidly increasing the crystallization rate of PLA molecular chains, increasing the crystallinity, which is closely related to the heat resistance of substances, and the higher the crystallinity, the higher the heat resistance, and thus greatly improving the heat resistance of PLA modified molecules. However, we found that the addition of PLA-g-MAH had little effect on increasing the crystallinity of the PLA and PBS blended system, which also corroborates the data for Vicat softening temperatures of B1, B2, B3, B4, B5 and B6.

PLA was analyzed for thermal stability and compared to B1 and B6 composites. The TG diagram is shown in FIG. 10. Table 2 analyzes the material at 5% weight loss (T)_5％) Temperature at room temperature, 10% weight loss (T)_10％) Temperature at and weight loss at 50% (T)_50％) The temperature of (c). Three processes of material mass loss can be observed in the TG diagram: first, all compoundingThe water loss of the material is basically the same; the thermal decomposition processes of B1 and B6 substantially overlapped, and according to previous literature reports, a variety of chemical and physical reactions occurred during polymer processing, and as can be seen in fig. 10, the composite was relatively stable until 340 ℃. The composite material starts to decompose at temperatures around 340-445 ℃, and it can be found in fig. 11: the decomposition rate of polylactic acid was faster before 400 ℃ and at 410 ℃ the composite showed a second decomposition peak, probably due to the decomposition of the added PBS. It can also be seen in table 2 that the temperatures at which B1 and B6 lost 50% weight were higher than PLA, further indicating that the second peak of decomposition of the composite occurred due to PBS decomposition.

TABLE 2

Sample (I)	T_5％/℃	T_10％/℃	T_50％/℃
				PLA	358.504	367.004	388.008
B1	364.837	373.171	406.337
				B6	358.671	367.837	402.671

SEM images of fracture surfaces of the B1 and B6 composites after the impact test are shown in FIG. 12. It can be seen that the fractured surface of the B1 composite was entirely smooth and flat, whereas the addition of PLA-g-MAH changed the appearance of the fractured surface, and that the fractured surface of the B6 composite exhibited some fine lines and pinholes, which indicated that B6 had better interfacial adhesion than B1 and could be confirmed by analysis of mechanical properties.

The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.

Claims

1. A high-toughness heat-resistant biodegradable composite material for tableware is characterized by comprising the following components in parts by mass:

2. The high toughness, heat resistant biodegradable composite for tableware according to claim 1 characterized in that: the chain extender comprises one or a mixture of more of peroxide compounds, isocyanate compounds, ester compounds and amide compounds.

3. The high toughness, heat resistant biodegradable composite for tableware according to claim 1 characterized in that: the compatilizer comprises one or more of maleic anhydride, carboxylic acid type, epoxy type and oxazoline or a mixture thereof.

4. The high toughness, heat resistant biodegradable composite for tableware according to claim 1 characterized in that: the heat stabilizer is one or more of polyethylene wax, zinc stearate, calcium stearate, magnesium stearate, oleamide, erucamide and titanate coupling agent.

5. A method of preparing the composite material of claim 1, comprising the steps of: