Application and method of terahertz broadband spectrum to determine the final aerobic biodegradability of polylactic acid-based degradable materials

Abstract

The invention belongs to the technical field of determination of polylactic acid degradation materials, and specifically relates to an application and method of terahertz broad spectrum determination of final aerobic biodegradability of polylactic acid degradation materials. A Fourier transform infrared spectrometer is used to test the terahertz broad spectrum of a sample at different degradation stages, and the rupture of ester bonds and the transformation of polymers into oligomers in the degradation process are reacted to the changes in the effective areas of certain specific characteristic peaks in the spectrum. It is found that there is a significant correlation between degradation performance data and the effective areas of certain specific characteristic peaks in the spectrum. A linear regression equation is then established, and sharp characteristic peaks with sample characteristic information can be obtained without destroying the original form of a polylactic acid degradation material product. The detection is fast, convenient and efficient, and the detection cost is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of determination of polylactic acid-based degradable materials, and specifically relates to an application and method of terahertz broad spectrum determination of the final aerobic biodegradability of polylactic acid-based degradable materials. Background Art

[0002] In the future, packaging materials will develop towards more environmentally friendly, recyclable and degradable ideas. The traditional plastic products industry will face great changes, and many fields such as healthcare, aerospace, fashion and food will be greatly affected.

[0003] Plastic restriction and ban have become important measures in the global process of promoting sustainable development. Degradable plastics are mainly divided into three categories according to the source of raw materials: petroleum-based, bio-based and coal-based. Petroleum-based degradable plastics include polybutylene terephthalate / adipate (PBAT) and polybutylene succinate (PBS). Bio-based degradable plastics include starch-based, cellulose, polylactic acid (PLA), polyhydroxyalkanoate (PHA), etc. Coal-based degradable plastics include polyglycolic acid (PGA). At present, starch-based, PLA, and PBAT are mainstream products, with a total production capacity of nearly 90%, of which polylactic acid accounts for more than 1 / 3. Biodegradable plastics are renewable resources and are the development direction of the field of degradable materials in the future. Single degradable materials have their own advantages and disadvantages, and generally need to be modified to give full play to their respective advantages and be used in specific fields.

[0004] Biodegradable materials are in the early stages of rapid development, and the original testing methods can no longer meet the market's demand for fast and flexible testing. For example, the current national standard GB / T19277.1 stipulates, "Determination of the ultimate aerobic biodegradability of materials under controlled composting conditions, using the method of measuring the released carbon dioxide." There are problems such as long time for product inspection and report issuance (each sample requires 3-6 months), cumbersome process, and high price.

[0005] More importantly, due to the need to accurately collect the amount of carbon dioxide released during the degradation process, only one sample can be composted and tested each time, which greatly limits the development of the industry.

[0006] Traditional mid-infrared spectroscopy technology requires mixing the material with potassium bromide and diluting it to obtain sharp characteristic information. When characterizing the degradation performance of the material, the original form of the material needs to be retained, and most of the characteristic peaks in the infrared spectrum are flattened, losing their analytical value. Furthermore, the mid-infrared spectrum can only reflect changes in molecular structure, and cannot obtain information on molecular configuration or crystal changes from spectral information. In addition, the biodegradation process is complex and cannot be characterized by changes in one or several characteristic peaks in the mid-infrared spectrum. Therefore, it is urgent to develop new detection methods to solve the current dilemma. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide an application and method of terahertz wide spectrum determination of the final aerobic biodegradability of polylactic acid-based degradable materials in view of the above-mentioned defects. The sharp characteristic peaks with sample characteristic information can be obtained without destroying the original form of polylactic acid-based degradable material products. The detection is fast and convenient, which greatly reduces the detection cost. There is no need to collect carbon dioxide released during the degradation of the materials. Multiple samples can be composted at the same time, which greatly improves efficiency. With the upcoming plastic ban, the industry can be promoted to develop rapidly.

[0008] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0009] Application of terahertz broadband spectrum to determine the ultimate aerobic biodegradability of polylactic acid-based degradable materials.

[0010] According to the above application, the terahertz wide spectrum measures the specific characteristic peaks corresponding to polylactic acid in different degradation stages of polylactic acid-based degradation materials, and the final aerobic biodegradability of polylactic acid-based degradation materials is determined based on the significant correlation between the effective area of ​​the characteristic peaks and the degradation performance data.

[0011] The method for determining the final aerobic biodegradability of polylactic acid-based degradable materials by terahertz broad spectrum comprises the following steps:

[0012] 1) Obtain the degradation performance data of the polylactic acid degradation material standard

[0013] Under the composting method specified in the national standard GB / T19277.1, obtain the degradation performance data of pure polylactic acid products or modified polylactic acid products (only for PLA and PBS blends): degradation time DAY, biodegradation rate BR, total carbon dioxide release CDE;

[0014] 2) At room temperature, infrared spectroscopy equipment was used to test the degradation of polylactic acid materials at different degradation stages in the range of 30 to 680 cm -1 The terahertz broad spectrum (0.9-20.4THz) is used to determine the specific characteristic peaks corresponding to polylactic acid in polylactic acid degradation materials according to the terahertz broad spectrum;

[0015] 3) Calculate the specific peak effective area CPA;

[0016] 4) Pearson correlation analysis of bivariate was performed on the degradation time DAY, biodegradation rate BR, total carbon dioxide release CDE and specific peak effective area CPA, and the significant correlation between the degradation time DAY, biodegradation rate BR, total carbon dioxide release CDE and the characteristic peak effective area CPA was obtained;

[0017] 5) According to the significant correlation, the linear regression equation was established with degradation time DAY as the independent variable and biodegradation rate BR, total carbon dioxide release CDE and specific peak effective area CPA as the dependent variables:

[0018] BR=a*DAY+b,

[0019] CDE=c*DAY+d,

[0020] CPA=e*DAY+f,

[0021] BR=g*CPA+h,

[0022] a, b, c, d, e, f, g, and h are regression coefficients. The regression coefficients are corrected to achieve the determination of the ultimate aerobic biodegradability of polylactic acid-based degradable material products.

[0023] Furthermore, the calculation formula for the specific peak effective area CPA in step 3) is:

[0024]

[0025] Among them, (X 1 ,Y 1 ) is the coordinate value of the starting point of the characteristic peak, (X n ,Y n ) is the coordinate value of the end point of the characteristic peak.

[0026] Furthermore, in step 2), a Bruker v80v Fourier transform infrared spectrometer is used to test the terahertz broad spectrum.

[0027] The beneficial effects of the present invention are:

[0028] 1. Convenient sampling and quick testing, without destroying the original form of polylactic acid degradable plastic products, significantly reducing testing costs;

[0029] 2. The determination and calculation methods of biodegradability are simple;

[0030] 3. It is not limited by laboratory environment and can be used to test the degradation performance of polylactic acid-based degradable plastic products in any composting environment, solving industry problems and facilitating the entire industry chain of degradable plastic product production, transportation, use and recycling;

[0031] 4. The degradation performance of multiple samples can be tested at one time;

[0032] 5. It has good scalability and can be developed to detect other biodegradable materials;

[0033] 6. Terahertz spectroscopy technology reflects the collective vibration of molecules. It can obtain sharp characteristic peaks with sample characteristic information without destroying the original form of polylactic acid-based degradable material products. The detection is fast and convenient, which greatly reduces the detection cost. It does not need to collect carbon dioxide released during the degradation of materials. Multiple samples can be composted and detected at the same time, which greatly improves efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0035] Figure 1 Schematic diagram of the comparison of biodegradation rates between material 1 and reference material (microcrystalline cellulose).

[0036] Figure 2 Schematic diagram of the comparison of biodegradation rates between material 2 and reference material (microcrystalline cellulose).

[0037] Figure 3 Schematic diagram comparing the total carbon dioxide release of material 1 and reference material (microcrystalline cellulose).

[0038] Figure 4 Schematic diagram comparing the total carbon dioxide release of material 1 and reference material (microcrystalline cellulose).

[0039] Figure 5a This is the terahertz broad spectrum of material 2 at different degradation stages.

[0040] Figure 5b This is a schematic diagram of the enlarged effective area of ​​the characteristic peak of Material 2 located at 7.15 THz in the spectrum.

[0041] Figure 6a This is the terahertz broad spectrum of material 1 at different degradation stages.

[0042] Figure 6b This is a schematic diagram of the enlarged effective area of ​​the characteristic peak of Material 1 located at 6.99 THz in the spectrum.

[0043] Figure 7 Schematic diagram of calculation of effective area of ​​characteristic peaks. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with the accompanying drawings.

[0045] The application of terahertz wide spectrum to determine the final aerobic biodegradability of polylactic acid-based degradable materials. Specifically, the specific characteristic peaks corresponding to polylactic acid in different degradation stages of polylactic acid-based degradable materials are determined by terahertz wide spectrum, and the final aerobic biodegradability of polylactic acid-based degradable materials is determined based on the significant correlation between the effective area of ​​the characteristic peaks and the degradation performance data.

[0046] This application technology can obtain sharp characteristic peaks with sample characteristic information without destroying the original form of polylactic acid-based degradable material products. It is not restricted by laboratory composting conditions, and the detection is fast and convenient. It does not need to collect carbon dioxide released during the degradation of materials. Multiple samples can be composted at the same time, which greatly improves efficiency and greatly reduces detection costs. It solves industry problems and helps the entire industry chain of biodegradable plastic product production, transportation, use and recycling. With the upcoming plastic ban, it can promote the rapid development of the industry.

[0047] The method for determining the final aerobic biodegradability of polylactic acid-based degradable materials by terahertz broad spectrum comprises the following steps:

[0048] 1) Under the composting method specified in the national standard GB / T19277.1, obtain the degradation performance data of pure polylactic acid products or modified polylactic acid products (only for PLA and PBS blends), including: degradation time DAY, biodegradation rate BR, total carbon dioxide release CDE, and the biodegradation rate BR and total carbon dioxide release CDE at different days before degradation and after composting.

[0049] As a preferred embodiment, the following two types of polylactic acid degradation materials are selected for sampling:

[0050] Material 1: modified polylactic acid product (straw, numbered 4386, made by mixing PLA and PBS in a mass ratio of 1:1);

[0051] Material 2 - pure polylactic acid product (cup lid, made of pure PLA material, numbered 1921), degradation performance data refer to Figure 1-Figure 4 shown.

[0052] 2) At room temperature, the two materials were tested at different degradation stages in the range of 30 to 680 cm using a Bruker v80v Fourier infrared spectrometer with a 6-micron beam splitter. -1 The terahertz broad spectrum (0.9-20.4THz) is obtained as Figure 5a , Figure 6a shown.

[0053] according to Figure 5a , 5b , the specific characteristic peak corresponding to material 2 is at 7.15THz in the spectrum. Figure 5a The samples in the middle (Beforecomposting, 10DAYs, 21DAYs, 31DAYs and 48DAYs) are taken at different days before degradation and after composting. Figure 5a *3 and *10 in the figure indicate that the intensity is amplified by 3 times and 10 times respectively.

[0054] according to Figure 6a , 6b , the specific characteristic peak at 6.99THz in the spectrum corresponds to the polylactic acid in material 1, Figure 6a The middle (Before composting, 10DAYs, 21DAYs, 31DAYs and 48DAYs) are samples taken at different days before degradation and after composting. Figure 6a *15 in the middle means that the intensity is amplified by 15 times, among which the characteristic information of 31DAYs is not obvious, so it is not considered;

[0055] 3) Calculate the specific peak effective area CPA

[0056] Reference Figure 7 The effective area of ​​the characteristic peak CPA is the closed area A enclosed by the tangent line between the troughs at both ends of the peak and the peak envelope: (X 1 ,Y 1 ) as the starting point, (X n ,Y n ) is the end point, and CPA can be calculated by the following formula:

[0057]

[0058] After calculation, we can get Figure 5a and Figure 6a The effective area of ​​the characteristic peak of material 2 at 7.15THz and the effective area of ​​the characteristic peak of polylactic acid at 6.99THz in material 1 are calculated as shown in Table 1: Table 1 shows the biodegradation rate, total carbon dioxide release and effective area data of the characteristic peaks of samples at different degradation periods during the composting degradation process.

[0059]

[0060] In the table, BR1 (biodegradation rate of pure polylactic acid products of material 2), BR2 (biodegradation rate of modified polylactic acid products of material 1), CDE1 (total carbon dioxide release of pure polylactic acid products of material 2), CDE2 (total carbon dioxide release of modified polylactic acid products of material 1), CPA1 (effective area of ​​the characteristic peak at 7.15 THz in the terahertz broad spectrum of pure polylactic acid products of material 2), CPA2 (effective area of ​​the characteristic peak at 6.99 THz in the terahertz broad spectrum of modified polylactic acid products of material 1). The bold data in the table are normalized data.

[0061] 4) Pearson correlation analysis of two variables was performed on the degradation time DAY, biodegradation rate BR, total carbon dioxide release CDE and specific peak effective area CPA. The results of the Pearson correlation analysis of two variables are shown in Table 2:

[0062] Table 2 shows the Pearson correlation analysis of the two variables.

[0063]

[0064] It can be seen from Table 2 that the biodegradation rates BR1 and BR2 are significantly negatively correlated with the effective areas of the characteristic peaks CPA1 and CPA2 located at 7.15 THz and 6.99 THz in the terahertz spectrum of material 2 and material 1, respectively, at the 0.01 level, indicating that the change in the effective area of ​​the characteristic peak representing polylactic acid in the terahertz spectrum can well describe the biodegradability of the material.

[0065] 5) According to the significant correlation and the normalized data in Table 1, the degradation time DAY was taken as the independent variable, and BR1, BR2, CDE1, CDE2, CPA1 and CPA2 were taken as the dependent variables, and linear regression was performed using IBM SPSS Statistics24 software to obtain the standardized coefficients in Table 3.

[0066] Table 3 shows the standardized coefficients

[0067]

[0068]

[0069] According to the standardized coefficients, the linear regression equation is established as follows:

[0070] BR1=0.022*DAY-0.092,

[0071] BR2=0.022*DAY-0.089,

[0072] CDE1=0.021*DAY+0.042,

[0073] CDE2=0.021*DAY+0.048,

[0074] CPA1=-0.023*DAY+1.108,

[0075] CPA2=-0.018*DAY+1.057,

[0076] BR1=-0.897*CPA1+0.927 Formula 2

[0077] BR2=-1.247*CPA2+1.229 Formula 3

[0078] The coefficients can be corrected using IBM SPSS Statistics24 software. For equation 2 and equation 3, the correction coefficients are -0.897 and -1.247, respectively.

[0079] It can be seen that the process and method of measuring the terahertz spectrum of material 1 and material 2 by terahertz spectrum technology and finally obtaining the biodegradation rate of material 1 and material 2 is feasible. That is to say, this determination method can measure the terahertz spectrum of material 1 and material 2 in the range of 30 to 680 cm -1 The terahertz wide spectrum (0.9-20.4THz) is used to determine the characteristic peaks corresponding to polylactic acid, and then the biodegradation rate can be obtained using formulas 1, 2, and 3. The terahertz wide spectrum technology can be used to replace traditional composting degradation and measure the released carbon dioxide to obtain the final aerobic biodegradability.

[0080] In summary, terahertz broadband technology can obtain sharp characteristic peaks with sample characteristic information without destroying the original form of polylactic acid-based degradable material products, and is not restricted by composting conditions. The detection is fast and convenient, greatly reducing the detection cost.

[0081] The detection object of the present invention is based on a pure polylactic acid product or a modified polylactic acid product (only for a blend of PLA and PBS). Under the composting method specified in the national standard GB / T19277.1, degradation performance data of the product standard is obtained, including degradation time, biodegradation rate and total carbon dioxide release, etc., and the data are used as comparison parameters. A Fourier transform infrared spectrometer is used to test the terahertz broad spectrum (in the range of 1-20 THz) of the sample at different degradation stages (before degradation and during degradation). The rupture of ester bonds and the process of polymer conversion into oligomer in the degradation process are reacted to the change of effective area of ​​certain specific characteristic peaks in the spectrum, so as to determine that there is a significant correlation between the degradation performance data and the effective area of ​​certain specific characteristic peaks in the spectrum. Based on this, a linear regression equation is established, and a simple coefficient correction is performed. Finally, the terahertz broad spectrum technology is used to replace the national standard GB / T19277.1 "Determination of the final aerobic biodegradability of materials under controlled composting conditions, using a method for measuring released carbon dioxide" for rapid determination of the final aerobic biodegradability of materials under controlled composting conditions. It does not destroy the original form of polylactic acid-based degradable material products, significantly reduces testing costs, is not limited by laboratory environment, and can be used to test the degradation performance of polylactic acid-based degradable material products in any composting environment. It solves industry problems and helps the entire industry chain of degradable plastic product production, transportation, use and recycling. It has good scalability and can be developed to the testing of other degradable material products.

[0082] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. Application of terahertz broadband spectrum measurement in the final aerobic biodegradability of polylactic acid-based degradable materials; This application uses terahertz broadband to measure the specific characteristic peaks corresponding to polylactic acid in different degradation stages of polylactic acid-based degradation materials, and obtains the final aerobic biodegradability of polylactic acid-based degradation materials based on the significant correlation between the effective area of ​​the characteristic peaks and the degradation performance data; The method for determining the final aerobic biodegradability of polylactic acid-based degradable materials by terahertz broad spectrum comprises the following steps: 1) Obtain the degradation performance data of the polylactic acid degradation material standard Under the composting method specified in the national standard GB / T19277.1, obtain the degradation performance data of pure polylactic acid products or modified polylactic acid products (only for PLA and PBS blends): degradation time DAY, biodegradation rate BR, total carbon dioxide release CDE; 2) At room temperature, infrared spectroscopy equipment was used to test the degradation of polylactic acid materials at different degradation stages in the range of 30 to 680 cm -1 (0.9-20.4THz) terahertz wide spectrum, and determine the specific characteristic peaks corresponding to polylactic acid in polylactic acid degradation materials according to the terahertz wide spectrum; 3) Calculate the specific peak effective area CPA; 4) Pearson correlation analysis of bivariate was performed on the degradation time DAY, biodegradation rate BR, total carbon dioxide release CDE and specific peak effective area CPA, and the significant correlation between the degradation time DAY, biodegradation rate BR, total carbon dioxide release CDE and the characteristic peak effective area CPA was obtained; 5) According to the significant correlation, the linear regression equation was established with degradation time DAY as the independent variable and biodegradation rate BR, total carbon dioxide release CDE and specific peak effective area CPA as the dependent variables: BR=a*DAY+b, CDE=c*DAY+d, CPA=e*DAY+f, BR=g*CPA+h, a, b, c, d, e, f, g, and h are regression coefficients. The regression coefficients are corrected to achieve the determination of the ultimate aerobic biodegradability of polylactic acid-based degradable material products; The calculation formula for the specific peak effective area CPA in step 3) is: Among them, (X1, Y1) is the coordinate value of the starting point of the characteristic peak, (X n ,Y n ) is the coordinate value of the end point of the characteristic peak.

2. The method for determining the final aerobic biodegradability of polylactic acid-based degradable materials by terahertz broad spectrum according to claim 1, characterized in that: In step 2), a Bruker v80v Fourier transform infrared spectrometer is used to test the terahertz broad spectrum.

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