PBAT (poly (butylene adipate-co-terephthalate)) foam material, preparation method and compressive property prediction method

Abstract

The invention discloses a PBAT foam material, a preparation method and a compressive property prediction method, and belongs to the technical field of high polymer materials. The preparation method comprises the following steps: by taking 60-80 parts by weight of PBAT, 20-40 parts by weight of PLA, 0.3-0.5 part by weight of a chain extender, 0.2-0.4 part by weight of a nucleating agent and 0.1-2 parts by weight of an antioxidant as preparation raw materials, firstly carrying out melt blending on the raw materials to obtain a granular product, then carrying out extrusion molding on the granular product, and carrying out foaming by using supercritical fluid to obtain the PBAT foaming material. The whole operation is simple, industrial production is easy, the obtained foaming material has high compressive strength, the durability of the foaming material can be improved, and the application scene of the material is widened; meanwhile, the invention further provides a method capable of rapidly and accurately predicting the compressive strength of the foaming material prepared through the method, a tedious testing process is not needed, a scientific basis can be provided for design, preparation and application of the material, and progress of material science is promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and in particular relates to a PBAT foam material, a preparation method and a method for predicting the compressive properties of the foam material. Background Art

[0002] With the rapid development of the industrial industry, plastic products can be seen everywhere in daily life. Plastic products are popular among the public because of their light weight and durability. However, ordinary plastic products generally have problems such as low reuse rate and difficulty in degradation. Large accumulation in the environment will cause serious pollution problems and threaten human health. In order to solve the corresponding problems, biodegradable plastics have entered people's field of vision.

[0003] PBAT (polybutylene terephthalate-adipate) is a biodegradable plastic with great application prospects, which is widely used in packaging, agricultural films and other disposable products. Further foaming of PBAT can effectively increase the porosity of the material, make the material lightweight, and give the material good energy absorption and heat insulation properties. It can be effectively used in cushioning packaging, aerospace and other fields. There are two main foaming methods: physical foaming and chemical foaming. Supercritical CO 2 (Carbon dioxide) / N 2 Physical foaming methods such as (nitrogen) have the advantages of being non-toxic, harmless and non-flammable. Through autoclave foaming, injection molding foaming and extrusion foaming processes, low-density polymer foaming materials with uniform pore size distribution can be obtained.

[0004] However, compared with amorphous polymers, PBAT, as a linear semi-crystalline polymer, faces two main problems when preparing foaming materials using conventional methods: (1) low melt strength, which makes it easy for cells to collapse, break and merge during cell growth and shaping; (2) narrow processing temperature window and poor foamability. These problems lead to unstable foaming effects. During the foaming process, the size, uniformity and stability of the cells are often difficult to control, especially in large-scale production.

[0005] In order to effectively improve the foaming performance of PBAT, technicians in this field usually choose to blend it with other polymers (such as polyethylene, polypropylene, polylactic acid, etc.) or modify it with additives such as plasticizers and fillers, which can improve the fluidity, thermal stability and foaming of PBAT. However, different additives, formulas and process conditions have different effects on the improvement of cell uniformity. This difference will ultimately affect the mechanical properties and appearance of the material, and it is often difficult to ensure that it has good physical properties such as compressive strength. As a result, although the foaming material can be degradable, it becomes not durable due to its own insufficient strength, which seriously deviates from the original intention of product design. Therefore, when preparing foaming materials, we cannot blindly pursue high foaming ratios, because high foaming ratios usually mean that the density of the material is reduced, which is very likely to lead to insufficient strength and toughness of the foaming material.

[0006] Therefore, how to make the foamed material have sufficient mechanical properties (such as tensile strength, impact toughness, etc.) without significantly affecting the foaming of the material is a difficult problem. In order to achieve this effect, the prior art focuses on improving the foaming process, which makes the production process of PBAT foamed materials more complicated, involving precise formula control and complex additive addition, and ultimately makes the production cost not well controlled, violating the economic principle of industrial production.

[0007] In addition, there is no method in the prior art that can quickly and accurately predict the compressive properties of foamed materials. The characterization of material properties often requires related equipment and complex testing processes to complete, which is extremely inefficient and difficult to quickly provide a reliable basis for material design and optimization. Summary of the invention

[0008] In view of the above-mentioned problems, the present invention aims to provide a PBAT foam material, a preparation method and a method for predicting its compressive properties.

[0009] In order to achieve the above-mentioned object, the technical solution adopted by the present invention is as follows: a PBAT foaming material, which is made of 60 to 80 parts by weight of PBAT, 20 to 40 parts by weight of PLA, 0.3 to 0.5 parts by weight of a chain extender, 0.2 to 0.4 parts by weight of a nucleating agent and 0.1 to 2 parts by weight of an antioxidant as raw materials.

[0010] Furthermore, the foaming material is made of 70 parts by weight of PBAT, 30 parts by weight of PLA, 0.3-0.5 parts by weight of chain extender ADR4468, 0.2-0.4 parts by weight of nucleating agent BTD8808 and 0.1-2 parts by weight of antioxidant IRGANOX 1076 as raw materials.

[0011] The preparation method of the above-mentioned PBAT foam material is: mixing corresponding weight parts of PBAT, PLA, chain extender, nucleating agent and antioxidant and then performing supercritical fluid foaming to prepare the PBAT foam material.

[0012] Furthermore, the supercritical fluid foaming is to mix the raw materials and then melt-blend them to obtain a granular product, and then press the granular product into a sheet product and extrude it, and then use the supercritical fluid to foam it.

[0013] Furthermore, the melt blending process is carried out using a twin-screw extruder at an extrusion temperature of 145 to 165°C.

[0014] Furthermore, the sheeting process is completed by using a casting machine, the extrusion speed is 50-70 rpm, the extrusion temperature does not exceed 175° C., and the thickness of the extruded sheet is 3-4 mm.

[0015] Furthermore, the supercritical fluid is supercritical CO 2 / N 2 Mixed gas, the total pressure of the mixed gas is 12-18MPa, the pressure holding time is 1-3h, and the foaming temperature is 106℃-110℃.

[0016] This application proposes a method for predicting the compressive performance of the above-mentioned PBAT foam material, which is specifically calculated by the following calculation formula:

[0017] y1=-0.3097+0.0899x1+0.1517x2+4.1159x3;

[0018] Wherein, y1 is the compressive strength / MPa, x1 is the chain extender content / weight part; x2 is the nucleating agent content / weight part; x3 is the foam density / g / cm 3 .

[0019] The beneficial effects of the present invention are:

[0020] 1. This application uses blended PLA to improve the problem of insufficient mechanical properties of PBAT alone in making foaming materials, and at the same time, by adding chain extender ADR4468 and nucleating agent BTD-8808 to improve the melt strength of the polymer and broaden the processing window, it is a good breakthrough in the limitations of low melt strength and narrow processing window on material foaming;

[0021] 2. In the present application, PBAT, PLA, chain extender ADR4468 and nucleating agent BTD-8808 in corresponding weight parts are mixed and then subjected to supercritical fluid foaming to prepare a PBAT foam material. The obtained PBAT foam material has excellent compressive strength and Shore hardness, and excellent mechanical properties;

[0022] 3. This application improves the mechanical properties of the material by adjusting the dosage of the chain extender ADR4468 and the nucleating agent BTD-8808 and the foaming temperature, which can ensure smooth foaming of the material while having good mechanical properties. The overall operation is relatively simple, and no complex additives and sophisticated equipment are required. The production cost can be well controlled, and it has prospects for industrial application.

[0023] 4. This application proposes a method for predicting the compressive properties of PBAT foam materials, which can quickly calculate the compressive strength of the foam material with the help of a fitting equation with high accuracy. This provides a scientific basis for the design, preparation and application of subsequent materials, and can be used for material optimization to improve the mechanical properties and service life of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the multiple linear regression fitting curve obtained according to the data in Example 1.

[0025] Figure 2 This is the SEM image of the pore structure of the sample foamed 20 to 25 times after magnification 1000 times. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0027] The chain extender used in the following embodiments is BASF chain extender ADR4468; the nucleating agent BTD-8808 is a special nucleating agent for polylactic acid (PLA), which has good compatibility with polylactic acid resin, can remain stable at the processing temperature, and induces PLA molecules to crystallize during the cooling process of the PLA resin melt, thereby achieving the purpose of accelerating the crystallization rate, shortening the molding cycle, and improving the heat resistance, bending modulus and surface gloss of the product; the antioxidant is BASF antioxidant IRGANOX 1076.

[0028] Example 1

[0029] This embodiment adopts a supercritical fluid foaming method to foam the material. The supercritical fluid foaming is to mix corresponding weight portions of PBAT, PLA, chain extender ADR4468, and nucleating agent BTD-8808, and then melt blend them to obtain a granular product, and then extrude the granular product into a shape and foam it using a supercritical fluid.

[0030] The specific process is as follows:

[0031] 1) Dry all raw materials in an oven at 60°C for 4 h;

[0032] 2) 70 parts by weight of PBAT, 30 parts by weight of PLA (LX175), 0 to 0.5 parts by weight of chain extender ADR4468, and 0 to 0.4 parts by weight of nucleating agent BTD-8808 were mixed and melt-blended to obtain a granular product. The melt-blending process was carried out using a twin-screw extruder at an extrusion temperature of 165° C.;

[0033] 3) Using a casting machine to extrude the pellet product, the extrusion speed is 60 rpm, the maximum extrusion temperature is 175°C, and the thickness of the extruded sheet is 3-4 mm;

[0034] 4) Using supercritical CO 2 / N 2 The mixed fluid is foamed to obtain a degradable PBAT foaming material. The foaming temperature is 108℃~120℃ and the total pressure of the mixed gas is 14MPa, wherein CO 2 The partial pressure is 7MPa, N 2 The partial pressure is 7MPa and the holding time is 1.5h.

[0035] According to the formula shown in Table 1, the dosage of chain extender ADR4468 and nucleating agent BTD8808, as well as the foaming temperature in the foaming process, were adjusted to obtain a series of PBAT foaming products. The mechanical properties of the products (such as compressive strength, maximum energy absorption efficiency, hardness, etc.) were tested, and the results are summarized in Table 1.

[0036] Table 1. Performance data of PBAT foam materials prepared with different formulations

[0037]

[0038]

[0039] From the data in Table 1, it can be seen that when the antioxidant content is fixed at 0.2 parts by weight and the foaming temperature is fixed at 108°C, and only PBAT and PLA are used for foaming, the foaming ratio of the obtained foamed material is relatively high (9.19), but the compressive strength of the material is low (0.32MPa), and the Shore hardness is only 58.6; on this basis, adding nucleating agent and chain extender and increasing the amount of nucleating agent BTD8808 (0.2-0.4) and chain extender ADR4468 (0.3-0.5) can significantly improve the compressive strength and Shore hardness of the material, and the maximum energy absorption efficiency is not significantly different; while in the case of the main component dosage unchanged, after increasing the foaming temperature, for example, after increasing the foaming temperature from 108°C to 113°C, the foaming ratio of the material is significantly improved, but the compressive strength of the material is significantly reduced, the maximum energy absorption efficiency is still not significantly changed, and the Shore hardness is also significantly reduced. Further increasing the foaming temperature, the mechanical properties of the product also show this trend of change.

[0040] In addition, based on the above data, a method for predicting the compressive strength of PBAT foam products is proposed.

[0041] The idea is to use a part of the experimental data as the modeling data, give the fitting equation and the fitting results, and then use the remaining part of the data for verification to examine the deviation between the results calculated in the verification process and the actual results.

[0042] Specifically, the data of the first 22 groups of samples in Table 1 (i.e., 75% of the data in the entire table) were used as the original data for modeling, and Matlab was used for multivariate linear regression fitting. The program code is as follows:

[0043] >>x1=[0 0.5 0.3 0.3 0.3 0.5 ...

[0044] x2=[0 0 0.2 0.3 0.4 0.2 0.3 0 0.2 0.3 0.4 0.2 0.3 0.2 0.3 0.2 0.3 00.2 0.2 0.3 0]'; Nucleating agent content (parts by weight)

[0045] x3=[0.133 0.206 0.180 0.251 0.226 0.235 0.230 0.121 0.110 0.139 0.142 0.144 0.162 0.132 0.135 0.095 0.113 0.108 0.099 0.108 0.114 0.090]';%Foam density (g / cm 3 )

[0046] y1=[0.32 0.49 0.38 0.82 0.67 0.72 0.88 0.28 0.19 0.34 0.33 0.35 0.440.31 0.33 0.18 0.27 0.17 0.110.21 0.26 0.11]';%Compressive strength(MPa)

[0047] >>figure(1);

[0048] hold on;

[0049] plot(x1,'bo');

[0050] plot(x2,'ro');

[0051] plot(x3,'go');

[0052] plot(y1,'mo','LineWidth',1);

[0053] >>legend('Chain extender content (weight parts)','Nucleating agent content (weight parts)','Density (g / cm 3 )','Compressive strength (MPa)')>>len=length(y1);

[0054] >>pelta=ones(len,1);

[0055] >>x=[pelta,x1,x2,x3];

[0056] >>[b,bint,r,rint,stats]=regress(y1,x,0.05);

[0057] >>y1_NiHe=b(1)+b(2).*x1+b(3).*x2+b(4).*x3;

[0058] >>figure(2);

[0059] >>hold on;

[0060] >>plot(x1,'bo-');

[0061] >>plot(x2,'ro-');

[0062] >>plot(x3,'go-');

[0063] >>plot(y1,'mo-');

[0064] >>plot(y1_NiHe,'kx-','LineWidth',1);

[0065] >>legend('Chain extender content (weight parts)','Nucleating agent content (weight parts)','Density (g / cm 3 )','Compressive strength (MPa)','Multiple linear regression fitting curve');

[0066] >>R_2=1-sum((y1_NiHe-y1).^2). / sum((y1-mean(y1)).^2);

[0067] >>str = num2str(R_2);

[0068] >>disp(['Goodness of fit is:',str])

[0069] Goodness of fit: 0.94067

[0070] % is the fitting correlation coefficient R 2

[0071] The obtained multiple linear regression fitting curve can be found in Figure 1 , the fitting equation is:

[0072] y1=-0.3097+0.0899x1+0.1517x2+4.1159x3

[0073] Wherein, y1 is the compressive strength (MPa), x1 is the chain extender content (parts by weight); x2 is the nucleating agent content (parts by weight); x3 is the foam density (g / cm 3 ).

[0074] Fitting correlation coefficient R2=0.940667067918459

[0075] The overall significance test of the equation is F = 95.1242793758144

[0076] P value = 3.12444240824588e-11

[0077] The estimated value of the error variance is s2 = 0.00331137693269628

[0078] The remaining 25% of the experimental data were taken for verification to examine the deviation between the calculated results and the actual results. The obtained data are shown in Table 2.

[0079] Table 2. Deviations between validation data and true results

[0080]

[0081] According to the data in Table 2, the mean square residual MSR between the 25% experimental data and the fitting value is 0.00075, which shows that the use of the above equation to predict the compressive strength of the PBAT foam material has high accuracy and feasibility.

[0082] The above shows and describes the basic principles, main features and advantages of the present invention. However, the above is only a specific embodiment of the present invention, and the technical features of the present invention are not limited thereto. Any other implementation methods derived by any technician in the field without departing from the technical solution of the present invention should be included in the scope of the present invention.

Claims

1. A PBAT foam material, characterized in that: The foaming material is prepared from 60 to 80 parts by weight of PBAT, 20 to 40 parts by weight of PLA, 0.3 to 0.5 parts by weight of a chain extender, 0.2 to 0.4 parts by weight of a nucleating agent and 0.1 to 2 parts by weight of an antioxidant as raw materials.

2. A PBAT foam material according to claim 1, characterized in that: The foaming material is prepared from 70 parts by weight of PBAT, 30 parts by weight of PLA, 0.3-0.5 parts by weight of chain extender ADR4468, 0.2-0.4 parts by weight of nucleating agent BTD8808 and 0.1-2 parts by weight of antioxidant IRGANOX 1076 as raw materials.

3. The method for preparing the PBAT foam material according to any one of claims 1 to 2, characterized in that: The preparation steps are: mixing corresponding weight portions of PBAT, PLA, chain extender, nucleating agent and antioxidant and then performing supercritical fluid foaming to prepare PBAT foaming material.

4. The method for preparing the PBAT foam material according to claim 3, characterized in that: The supercritical fluid foaming method comprises the following steps: firstly mixing raw materials, melt-blending them to obtain a granular product, then extruding the granular product into a shape, and foaming the mixture using a supercritical fluid.

5. The method for preparing the PBAT foam material according to claim 4, characterized in that: The melt blending process is carried out using a twin-screw extruder at an extrusion temperature of 145 to 165°C.

6. The method for preparing the PBAT foam material according to claim 4, characterized in that: The sheet forming process is completed by using a casting machine, the extrusion speed is 50-70rpm, the extrusion temperature does not exceed 175°C, and the thickness of the extruded sheet is 3-4mm.

7. The method for preparing the PBAT foam material according to claim 4, characterized in that: The supercritical fluid is a supercritical CO2 / N2 mixed fluid, the total pressure of the mixed fluid is 12-18 MPa, the pressure holding time is 1-3 hours, and the foaming temperature is 106°C-110°C.

8. A method for predicting the compressive properties of the PBAT foam material according to claim 1, characterized in that: The compressive performance is calculated by the following formula: y1=-0.3097+0.0899x1+0.1517x2+4.1159x3; Wherein, y1 is the compressive strength / MPa, x1 is the chain extender content / weight part; x2 is the nucleating agent content / weight part; x3 is the foam density / g / cm 3 .

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