Preparation method and application of high-toughness polyglycolic acid material

Abstract

The invention belongs to the field of high polymer materials, and particularly relates to a preparation method and application of a high-toughness polyglycolic acid material. The preparation method of the high-toughness polyglycolic acid material comprises the following steps: S1, carrying out vacuum drying on polyglycolic acid of which the molecular weight is 100,000-500,000 and the melting temperature is 210-230 DEG C; s2, performing vacuum pressing on the polyglycolic acid material subjected to vacuum drying to obtain a plate; and S3, the prepared plate is rapidly put into water for cooling treatment, and the high-toughness polyglycolic acid material is obtained. The properties of PGA are changed, so that the toughness is improved, and meanwhile, the transparency is improved. The reason of high brittleness of the PGA is high crystallinity, and in the PGA processing process, the crystallization temperature interval of the PGA is omitted, crystallization of the PGA is inhibited, and the purpose of improving the toughness is achieved. According to the preparation method disclosed by the invention, the crystallinity of the PGA is reduced by 30%, the elongation at break is increased by nearly 80 times, and the strength is more than 35 MPa, so that the application market of the PGA is expanded, and the PGA replaces a traditional petroleum-based material in more fields.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and in particular relates to a preparation method and application of a high-toughness polyglycolic acid material. Background Art

[0002] Polyglycolic acid (PGA) is a biodegradable plastic with very high strength and modulus, but PGA has the defects of high brittleness and narrow processing window, which greatly limits the application range of PGA. Therefore, modifying PGA to improve its comprehensive performance is one of the key research and application areas.

[0003] In order to solve the problem of PGA brittleness, some elastomers or tough materials are usually added to PGA using melt blending technology, such as polybutylene adipate / terephthalate (PBAT), polycaprolactone (PCL), polyethylene oxide (PEO), polybutylene succinate (PBS), etc., to achieve toughening modification of PGA. However, these elastic materials themselves have low strength, and the intermolecular forces between these materials and PGA are weak and the compatibility is very poor. These problems will cause the modification of PGA with elastomers or tough materials to increase the reduction of PGA's strength, thereby causing the PGA material to lose its own strength advantage and the toughness will not be improved. Therefore, when preparing high-toughness PGA materials, how to ensure that the strength of PGA itself will not be lost too much is a major challenge currently faced in the preparation of high-toughness PGA materials. Summary of the invention

[0004] In view of the problems and shortcomings in the prior art, the object of the present invention is to provide a preparation method and application of a high-toughness polyglycolic acid material.

[0005] Based on the above purpose, the present invention adopts the following technical solution:

[0006] The first aspect of the present invention provides a method for preparing a high-toughness polyglycolic acid material, comprising the following steps:

[0007] S1: vacuum drying PGA with a molecular weight of 100,000 to 500,000 and a melting temperature of 210 to 230°C;

[0008] S2: vacuum pressing the vacuum-dried PGA material into a sheet;

[0009] S3: The prepared plate is quickly placed in water for cooling to obtain a high-toughness polyglycolic acid material.

[0010] Preferably, the temperature of the water used for cooling the plate in step S3 is 0-90°C.

[0011] Preferably, the vacuum drying in step S1 is carried out at a temperature of 30 to 80° C., a vacuum degree of 10 to 80 KPa, and a drying time of 6 to 24 hours.

[0012] Preferably, in step S2, the vacuum pressing temperature is 225-240° C., the pressure is 1000-5000 kg, the preheating time is 3-10 min, and the hot pressing time is 1-3 min.

[0013] The second aspect of the present invention provides a high-toughness polyglycolic acid material prepared by the method described in the first aspect.

[0014] The third aspect of the present invention provides the use of the high-toughness polyglycolic acid material described in the second aspect in agricultural films and degradable plastic products.

[0015] Preferably, the high-toughness polyglycolic acid material can be prepared into a film for agricultural film to solve the pollution problem of agricultural film, and can also be prepared into degradable garbage bags. It can also be prepared into disposable plastic products, such as straws, lunch boxes, etc., to solve the pollution generated in daily life.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention uses polyglycolic acid with a molecular weight of 100,000 to 500,000 and a melting temperature of 210 to 230° C. The polyglycolic acid has high melt strength, is easy to process, is easy to shape, and is not easy to degrade.

[0018] The present invention uses the method of rapidly cooling the material to below the crystallization temperature to inhibit crystallization, which can effectively improve the toughness of PGA, improve the crystallization of PGA, and improve its transparency.

[0019] The reason for PGA's high strength and hardness is its high crystallinity. Its mechanical properties are similar to those of metals. Abandoning the traditional concept of polymer toughening, PGA is viewed from the perspective of metals to make the best of its strengths and overcome its weaknesses. Therefore, the commonly used quenching method for metals to reduce crystallinity and increase toughness is used to modify PGA. By improving the processing technology, a leap in PGA toughening has been achieved.

[0020] Starting from the essence of PGA's mechanical properties, by taking advantage of its strengths and making up for its weaknesses, PGA achieves ultra-high toughness while increasing its transparency. Without losing too much stress, its toughness is increased by 60 times compared to raw materials, and the toughness of ultra-high toughness PGA composite materials is increased by nearly 100 times. This has expanded the application market for PGA and replaced traditional petroleum-based materials in more fields.

[0021] At the same time, the present invention solves the problem of poor toughness of PGA by quenching. By improving PGA, the transparency is also greatly improved. It is well applied to agricultural films and degradable plastic products, solving the pollution problems of agricultural films and pollution problems generated in daily life, and is green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope microscopic morphology of the polyglycolic acid material prepared in Comparative Example 1;

[0023] Figure 2 This is a scanning electron microscope microscopic morphology of the high-toughness polyglycolic acid material prepared in Example 1;

[0024] Figure 3 It is the DSC curve diagram of comparative example 1 and embodiment 1;

[0025] Figure 4 The transparency of the high-toughness polyglycolic acid material;

[0026] Figure 5 The transparency of the polyglycolic acid material;

[0027] Figure 6 2D-WAXD spectra of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below through embodiments in combination with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] 1. Sample preparation

[0030] The raw material PGA used in the embodiment comes from Shenzhen Boli, and the material information is: PGA-4, molecular weight is 100,000; PGA-5, molecular weight is 500,000. Unless otherwise specified, all are PGA-4.

[0031] Example 1

[0032] A method for preparing a high-toughness polyglycolic acid material comprises the following steps: vacuum drying PGA (molecular weight 100,000) at a drying temperature of 60°C, a vacuum degree of 80KPa, and a time of 12 hours, and preparing the vacuum-dried PGA material into a plate using a vacuum laminator at a temperature of 230°C, a pressure of 2000Kg, a preheating time of 5 minutes, and a hot pressing time of 1 minute. Then, the obtained plate is subjected to a cooling treatment, and after being taken out of the laminator, it is quickly placed in 30°C water for cooling, thereby obtaining a high-toughness polyglycolic acid material.

[0033] The microstructure of the prepared samples was observed under an electron microscope. Figure 2 As shown, the scanning electron microscope microscopic morphology of the high-toughness polyglycolic acid material shows that the material interface is relatively smooth and flat, which is due to the reduction in crystallinity and smaller crystals.

[0034] Example 2

[0035] The content of the preparation method of a high-toughness polyglycolic acid material is basically the same as that of Example 1, except that the water temperature used for cooling the plate is 0°C, that is, the cooling is carried out in an ice-water mixture.

[0036] Example 3

[0037] The content of the preparation method of a high-toughness polyglycolic acid material is basically the same as that of Example 1, except that the water temperature used for cooling the plate is 50°C.

[0038] Example 4

[0039] The content of the preparation method of a high-toughness polyglycolic acid material is basically the same as that of Example 1, except that the water temperature used for cooling the plate is 70°C.

[0040] Example 5

[0041] The content of the preparation method of a high-toughness polyglycolic acid material is basically the same as that of Example 1, except that the water temperature used for cooling the plate is 80°C.

[0042] Example 6

[0043] The content of the preparation method of a high-toughness polyglycolic acid material is basically the same as that of Example 1, except that the water temperature used for cooling the plate is 90°C.

[0044] Example 7

[0045] The preparation method of a high-toughness polyglycolic acid material is basically the same as that of Example 1, except that PGA is a material with a molecular weight of 500,000.

[0046] Comparative Example 1

[0047] The content of the preparation method of a high-toughness polyglycolic acid material is basically the same as that of Example 1, except that the plate is cooled by natural cooling.

[0048] The microstructure of the prepared samples was observed under an electron microscope. Figure 1 As shown, the cross section of the material is bumpy, which is caused by the high crystallinity of the material and the large crystals.

[0049] Comparative Example 2

[0050] The content of the preparation method of a high-toughness polyglycolic acid material is basically the same as that of Example 1, except that the plate is cooled by machine.

[0051] 2. Performance Test

[0052] The high-toughness polyglycolic acid (PGA) materials prepared in Examples 1 to 7 and the high-toughness polyglycolic acid (PGA) materials prepared in Comparative Examples 1 to 2 were prepared into standard samples using a dumbbell-shaped cutter, and the tensile strength of the standard specimens was tested using a tensile testing machine according to the ASTM D638-2014 standard, with a tensile rate of 5 mm / min. The test results are as follows:

[0053] Table 1 Comparative Example 1, Comparative Example 2, Example 1, Example 2 Sample Performance Test Data Table

[0054] Group Cooling method Tensile strength(MPa) Elongation at break (%) Comparative Example 1 Natural cooling 125±2.6 5.6±0.3 Comparative Example 2 Machine cooling 91±1.7 14.7±0.5 Example 1 30℃ water cooling 37.5+2.2 407.6±9.7 Example 2 Ice water mixture cooling 37.1±3.3 417.1±6.3

[0055] It can be seen from Table 1 that different cooling methods affect the mechanical properties of high-toughness polyglycolic acid (PGA) materials: the tensile strength and elongation at break of the high-toughness polyglycolic acid (PGA) material plate samples prepared by Comparative Example 1, Comparative Example 2, Example 1, and Example 2 are very different. With the acceleration of the cooling rate, the elongation at break of the PGA material increases and the tensile strength decreases. When the polyglycolic acid (PGA) material in the molten state quickly drops below the crystallization temperature, the effect is best, the mechanical properties are optimal, the elongation at break is increased by nearly 100 times, and a relatively balanced material toughness and strength are obtained.

[0056] Table 2 Performance test data of samples of Example 1, Example 2, Comparative Example 3 and Comparative Example 4

[0057] Group Cooling method Tensile strength(MPa) Elongation at break (%) Example 1 30℃ water cooling 37.5+2.2 407.6±9.7 Example 2 Ice water mixture cooling 37.1±3.3 417.1±6.3 Comparative Example 3 50℃ water cooling 39.7±1.9 403.2±5.1 Comparative Example 4 70℃ water cooling 42.3±0.7 399.6±6.3

[0058] It can be seen from Table 2 that the effect of cooling with different water temperatures at 70°C and below on the mechanical properties of high-toughness polyglycolic acid (PGA) materials is not obvious: with the increase of water temperature, the elongation at break of high-toughness polyglycolic acid (PGA) materials decreases, and the tensile strength increases slightly, but the change is not obvious.

[0059] Table 3 Performance test data of samples of Example 1, Example 5 and Example 6

[0060]

[0061]

[0062] It can be seen from Table 3 that when the cooling water temperature exceeds the PGA cold crystallization peak (80°C), the PGA crystallinity will increase. The increase in crystallinity will increase the tensile strength and reduce the elongation at break. However, the mechanical properties of PGA are still better than before the improved process.

[0063] from Figure 3 It can be seen that the crystallinity of the high-toughness polyglycolic acid material of Example 1 is greatly reduced, and a cold crystallization peak is shown at about 80°C. Figure 6 It can be seen from the 2D-WAXD spectrum that the sample prepared in Example 1 has one less crystal than the sample prepared in Comparative Example 1, and the brightness of the diffraction ring becomes lower and the width becomes larger, which indicates that the crystallinity of the obtained high-toughness polyglycolic acid material is reduced and the grain size is reduced.

[0064] Table 4 Performance test data table

[0065] Group raw materials Tensile strength(MPa) Elongation at break (%) Example 1 PGA-4 (100,000 molecular weight) 37.5+2.2 407.6±9.7 Example 7 PGA-5 (500,000 molecular weight) 34.1±3.1 411.1±5.3

[0066] It can be seen from Table 4 that PGA with different molecular weights has little effect on the experimental results. The elongation at break of materials with high molecular weight is relatively high, but the tensile strength is slightly reduced. Therefore, PGA with a molecular weight between 100,000 and 500,000 can be used to prepare high-toughness polyglycolic acid materials using this method.

[0067] In summary, the present invention improves the processing technology in the processing of materials. On the one hand, the toughness of PGA is greatly improved, and on the other hand, the transparency of PGA sheet is greatly improved. Figure 4 and Figure 5 As shown, by comparison, it can be seen that the high-toughness polyglycolic acid material exhibits better transparency properties.

Claims

1. A method for preparing a high-toughness polyglycolic acid material, characterized in that , including the following steps: S1: vacuum drying polyglycolic acid having a molecular weight of 100,000 to 500,000 and a melting temperature of 210 to 230°C; S2: vacuum pressing the vacuum-dried polyglycolic acid material into a sheet; S3: The prepared plate is quickly placed in water for cooling to obtain a high-toughness polyglycolic acid material.

2. The preparation method according to claim 1, characterized in that: The temperature of the water used for cooling the plate in step S3 is 0-90°C.

3. The preparation method according to claim 1, characterized in that: The vacuum drying in step S1 is carried out at a temperature of 30 to 80° C., a vacuum degree of 10 to 80 KPa, and a drying time of 6 to 24 hours.

4. The preparation method according to claim 1, characterized in that: In the step S2, the vacuum pressing temperature is 225-240° C., the pressure is 1000-5000 kg, the preheating time is 3-10 min, and the hot pressing time is 1-3 min.

5. A high-toughness polyglycolic acid material prepared by the method described in any one of claims 1 to 4.

6. Use of the high-toughness polyglycolic acid material according to claim 5 in agricultural films and degradable plastic products.

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