阅读说明：本技术 一种可降解塑料降解性能的快速检测方法 (Method for rapidly detecting degradation performance of degradable plastics ) 是由 李林林 周经纶 许士明 姜传兴 张维 李效平 张圣斌 尚吉光 王微山 于 2021-09-17 设计创作，主要内容包括：本发明涉及塑料检测技术领域,具体涉及一种可降解塑料降解性能的快速检测方法,所述检测方法为通过测试可降解塑料降解过程中的生物活性碳转化率来测试可降解塑料的降解性能,本发明的可降解塑料降解性能的快速检测方法通过与在堆肥环境下降解产物生物分解率测试对照,证明降解产物生物分解率和其本身生物活性炭含量具有一致性关系,并且验证了在不同的降解阶段生物活性炭转化率与分子量下降率,羰基指数的增大变化规律一致,该方法既能够动态的研究聚烯烃类材料降解过程的有效性,还能鉴定该类材料在一定的老化条件结束后终产物的生物分解性能,方法准确,快速,高效,并且不需要昂贵的仪器设备,易于在企业和第三方实验室推广应用。(The invention relates to the technical field of plastic detection, in particular to a method for rapidly detecting the degradation performance of degradable plastic, which tests the degradation performance of the degradable plastic by testing the conversion rate of bioactive carbon in the degradation process of the degradable plastic, proves that the biodegradation rate of a degradation product has a consistent relation with the content of the bioactive carbon per se by comparing with the test of the biodegradation rate of the degradation product in a composting environment, verifies that the conversion rate of the bioactive carbon, the molecular weight reduction rate and the increase and change rule of carbonyl index are consistent in different degradation stages, can dynamically research the effectiveness of the degradation process of polyolefin materials, and can also identify the biodegradation performance of a final product of the materials after certain aging conditions are finished, and the method is accurate, the method is rapid and efficient, does not need expensive instruments and equipment, and is easy to popularize and apply in enterprises and third-party laboratories.)

1. A rapid detection method for degradation performance of degradable plastics is characterized in that the degradation performance of the degradable plastics is tested by testing the conversion rate of bioactive carbon in the degradation process of the degradable plastics.

2. The method for rapidly detecting the degradation performance of the degradable plastic according to claim 1, wherein the sample is subjected to aging treatment according to the GB/T16422.2 standard;

respectively adding a potassium dichromate standard solution and a sulfuric acid solution into the samples before and after degradation, heating the samples in a boiling water bath, taking out the samples for cooling, adding water and a phenanthroline indicator, and titrating the samples by using a ferrous sulfate standard titration solution; meanwhile, silica is used for replacing a sample, the same analysis steps are adopted, and a blank test is carried out;

the degradation performance of the degradable plastic is expressed by the release conversion rate of the biological activated carbon, and the release conversion rate of the biological activated carbon is as follows: the ratio of the difference between the total organic carbon content of the sample after degradation and the total organic carbon content of the sample before degradation to the total organic carbon content of the sample before degradation;

the total organic carbon content X of the test sample before and after degradation is measured as follows: the ratio of the product of the volume difference of the ferrous sulfate standard solution consumed by the blank solution and the sample, the concentration of the ferrous sulfate standard solution and the molar mass of the quarter carbon atom to the mass of the sample.

3. The method for rapidly testing the degradation performance of a degradable plastic according to claim 2, wherein the sample is cut into a rectangular shape of 5cm x 20cm before the sample is aged.

4. The method for rapidly detecting the degradation performance of the degradable plastic according to claim 2, wherein the specific steps of aging the sample according to the GB/T16422.2 standard are as follows: black standard temperature 65 ℃ ± 0.5 ℃, relative humidity 65% ± 0.5%, further, water spraying period: each time of water spraying is 18min +/-0.5 min, the interval of two water spraying periods is 102 +/-0.5 min, and the cumulative irradiation amount is 26MJ/m²。

5. The method for rapidly detecting degradation performance of degradable plastics according to claim 2, wherein the concentration of the standard solution of potassium dichromate is 0.8 mol/L.

6. The method for rapidly detecting degradation performance of degradable plastics according to claim 2, wherein the concentration of the ferrous sulfate standard titration solution is 0.2 mol/L.

7. The method for rapidly detecting degradation performance of degradable plastics according to claim 2, wherein the sulfuric acid solution is concentrated sulfuric acid.

8. The method for rapidly detecting degradation performance of degradable plastics according to claim 2, wherein the solution is changed from green to dark green by titration with ferrous sulfate standard titration solution, and then is added dropwise until the solution becomes brick red.

9. The method for rapidly detecting the degradation performance of the degradable plastic according to claim 2, wherein when the degradable plastic is a degradable material containing inorganic calcium carbonate and starch, the sample is acidified to remove carbon dioxide before the test.

10. A method for rapidly detecting the degradation performance of polyolefin degradable plastics, which is characterized by adopting the rapid detection method for the degradation performance of the degradable plastics as claimed in any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of plastic detection, in particular to a rapid detection method for degradation performance of degradable plastic.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

The degradable materials in the prior art are divided into compostable degradable materials and environment degradable materials according to raw material sources and degradation performance, the compostable materials which are accepted by the market at present mainly comprise polylactic acid, PBAT, modified starch, PBS and the like, the degradable materials which can be decomposed in natural environment are prepared by compounding polyolefin materials (PE, PP) and degradation additives, the materials are superior in physical service performance and low in cost at present, can be degraded as required, and are particularly trusted by consumers such as broad farmers in the application aspect of PE degradable mulching films, and the market prospect is good. The appearance and the use performance of the product before degradation are not different from those of common PP and PE plastic products, so that the products in the market are mixed with fish and are difficult to monitor.

At present, the domestic standard method for detecting the degradation performance of the polyolefin degradable plastics has the breaking elongation retention rate, the molecular weight reduction rate and the molecular weight percentage content of which the weight average molecular weight is less than 10000, although the molecular quality and the mechanical strength of the product can be tested to be reduced by the method, whether the product can be further biodegraded by microorganisms cannot be determined, for example, a product obtained by compounding polyolefin and inorganic salt meets the index requirements after degradation, but the structure and the property are plastic, so that the micro plastic is more harmful. In a test method for testing the degradation performance of polyolefin degradable plastics in ASTM6954 and PAS9017:2020, index requirements such as carbonyl index and biological decomposition rate are increased besides various molecular weights, the oxidation degree of the material is verified by testing the carbonyl index, the biological decomposition rate proves that the material can be finally decomposed into carbon dioxide and water, and the problem that a degradation product is not a micro-plastic and cannot cause secondary damage to the environment is solved essentially. However, most spectrograms of degradation products are disordered when the carbonyl index is tested by using an infrared spectrum, so that inaccurate integral and large analysis error are easily caused, and the test results of different laboratories have poor reproducibility. In the testing environment of the biological decomposition rate, whether in soil or compost conditions, the testing time is at least half a year when the index testing time of the biological decomposition rate is more than 60%, so that a large amount of manpower and material resources are consumed in production, development and product inspection, and the supervision and control steps are difficult. Therefore, it is urgent to develop a method for rapidly detecting the degradation performance of polyolefin degradable plastics.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a method for rapidly detecting the degradation performance of degradable plastics, which is used for testing the degradation performance of the degradable plastics by testing the conversion rate of bioactive carbon; the invention provides a method for testing the conversion rate of bioactive carbon to test the degradation performance of the polyolefin degradable plastic for the first time, and the method is simple and accurate and can realize the rapid detection of the degradation performance of the polyolefin degradable plastic.

In order to achieve the above object, the technical solution of the present invention is as follows:

in a first aspect of the present invention, a rapid detection method for degradation performance of a degradable plastic is provided, wherein the detection method is to test the degradation performance of the degradable plastic by testing the conversion rate of bioactive carbon in the degradation process of the degradable plastic.

Specifically, the detection method comprises the following steps:

carrying out aging treatment on the sample according to the GB/T16422.2 standard requirement;

adding a potassium dichromate standard solution and a sulfuric acid solution into the degraded sample, heating the sample in a boiling water bath, taking out the sample for cooling, adding water and a phenanthroline indicator, and titrating the sample by using a ferrous sulfate standard titration solution; meanwhile, silica is used for replacing a sample, the same analysis steps are adopted, and a blank test is carried out;

the degradation performance of the degradable plastic is expressed by the release conversion rate w,% of the bioactive carbon, and the release conversion rate of the bioactive carbon is as follows: the ratio of the biochar content of the degraded sample to the total organic carbon content;

and testing the biochar content X of the degraded sample as follows: the ratio of the product of the volume difference of the ferrous sulfate standard solution consumed by the blank solution and the sample, the concentration of the ferrous sulfate standard solution and the molar mass of the quarter carbon atom to the mass of the sample;

the method for rapidly detecting the degradation performance of the degradable plastics can dynamically research the effectiveness of the degradation process of the degradable plastics and identify the biological decomposition performance of the final product of the material after a certain aging condition is finished, and is accurate, rapid and efficient, and expensive instruments and equipment are not needed.

In one or more embodiments, the sample is cut into a 5cm by 20cm rectangle before being subjected to the aging treatment;

in one or more embodiments, the specific steps of aging the sample according to the GB/T16422.2 standard are as follows: black standard temperature 65 ℃ ± 0.5 ℃, relative humidity 65% ± 0.5%, further, water spraying period: each time of water spraying is 18min +/-0.5 min, the interval of two water spraying periods is 102 +/-0.5 min, and the cumulative irradiation amount is 26MJ/m²。

In one or more embodiments, the concentration of the potassium dichromate standard solution is 0.8 mol/L;

in one or more embodiments, the concentration of the ferrous sulfate standard titration solution is 0.2 mol/L;

in one or more embodiments, the sulfuric acid solution is concentrated sulfuric acid;

in one or more embodiments, the solution changes from green to dark green as the titration of the ferrous sulfate standard titration solution approaches the endpoint, and is added dropwise until it turns brick red.

The degradation performance of the degradable plastic is expressed by the release conversion rate w,% of the bioactive carbon, w is 100X/X₀

X — mass fraction (%) of bioactive carbon in the sample:

c-ferrous sulfate Standard solution concentration (mol/L)

V,V₀Volume of ferrous sulfate Standard solution (mL) consumed for sample and blank solutions, respectively

m-sample quality (g)

3-number of molar masses of one quarter of a carbon atom (g/mol);

in one or more embodiments, when the degradable plastic is a degradable material containing inorganic calcium carbonate and starch, the sample is acidified to remove carbon dioxide before the test is carried out, so that the positive deviation of the organic carbon of the starch and the calcium carbonate before the degradation to the test result and the reliability of the result are avoided.

Considering that various sources containing organic carbon and inorganic carbon such as calcium carbonate, starch, carbon powder additives and the like exist in polyolefin degradable plastic raw material sources in the current market, in order to ensure the reliability of the method, a calcium carbonate sample is acidified to remove carbon dioxide before testing, and the content of the biochar of a degraded product is divided by the total organic carbon of the degraded product, so that the positive deviation of the organic carbon of the starch and the calcium carbonate before degradation to the testing result and the reliability of the result are avoided.

In a second aspect of the invention, a method for rapidly detecting the degradation performance of polyolefin degradable plastics is provided, and the method is used for detecting the degradation performance of the degradable plastics in the first aspect.

The specific embodiment of the invention has the following beneficial effects:

the method for rapidly detecting the degradation performance of the degradable plastics proves that the biodegradation rate of the degradation products has a consistent relation with the content of the biological activated carbon of the degradation products by comparing with the test of the biodegradation rate of the degradation products under the composting environment, and verifies that the conversion rate and the molecular weight reduction rate of the biological activated carbon at different degradation stages and the increase and change rule of the carbonyl index are consistent.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a graph showing the trend of the molecular weight decrease rate, the carbonyl index and the biochar content in the 14-day PE degradable film aging process in example 1 of the present invention;

FIG. 2 is a graph showing the trend of the molecular weight decrease rate, carbonyl index and biological carbon conversion rate of the 28-day PP degradation hard sheet of example 1 of the present invention during UV aging;

FIG. 3 is an IR spectrum comparison of an initial hot oxygen PE catalyzed geomembrane sample, intermediate process and end product of example 1 of the present invention;

FIG. 4 is an infrared spectrum comparison of an intermediate run of an initial photo-oxygen PE catalyzed geomembrane sample of example 1 of the present invention;

FIG. 5 is a graph showing the carbon dioxide release profile of example 1 of the present invention;

FIG. 6 is a graph showing the biological decomposition rate in example 1 of the present invention.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

Example 1

An organic carbon analyzer (German element), a xenon lamp aging environment test chamber, an electronic balance (0.1mg), a water bath and a burette; concentrated sulfuric acid (analytically pure), potassium dichromate (1/6K)₆CrO₄0.8mol/L ferrous sulfate (FeSO)₄0.2mol/L), o-phenanthroline indicator;

aging test: cutting the sample into a cm:5 × 20 rectangle according to the GB/T16422.2 standard requirement: black standard temperature 65 ℃ ± 0.5 ℃ relative humidity 65% ± 0.5%: water spraying period: each time of water spraying is 18min +/-0.5 min, the interval of two water spraying periods is 102 +/-0.5 min, and the cumulative irradiation amount is 26MJ/m²。

Respectively weighing 0.02-0.04 g (accurate to 0.1mg) of samples before and after degradation, placing the samples in a 300mL triangular flask, accurately adding 10.00mL of 0.8mol/L potassium dichromate standard solution, adding 10mL of sulfuric acid solution, adding a bent-neck funnel to the triangular flask, placing the triangular flask in a boiling water bath for 45min, taking out and cooling the triangular flask, adding water to about 80mL, adding 2-3 drops of phenanthroline indicator, titrating the solution with ferrous sulfate standard titration solution to the near end point, changing the solution from green to dark green, and then dropwise adding the solution to brick red; meanwhile, about 0.1g of silica was weighed instead of the sample, and the same analytical procedure was carried out to carry out a blank test.

Simultaneously testing the total organic carbon content X of the sample before degradation₀

X-mass fraction of biologically active carbon in sample (%)

C-ferrous sulfate Standard solution concentration (mol/L)

V,V₀Volume of ferrous sulfate Standard solution (mL) consumed for sample and blank solutions, respectively

m-sample quality (g)

3-number of molar masses of one fourth of a carbon atom (g/mol)

The biological activated carbon release conversion rate w for degrading the plastic degradation performance, percent

w＝100X/X₀

Screening of oxidant and oxidation time:

the capacity analysis method belongs to redox reaction, and comprises the steps of oxidizing reductive bioactive carbon in polyolefin plastic by adopting a strong oxidant under an acidic condition, titrating the residual potassium dichromate solution by using ferrous sulfate, and indirectly calculating the content of the bioactive carbon after environmental degradation in the polyolefin material by calculating the volume of the consumed ferrous sulfate. At present, potassium permanganate oxidant is adopted for oxidation, oxalic acid solution is adopted for titrating residual potassium permanganate solution, and the same polyolefin degradation product is selected for testing and screening, and the result is shown in table 1;

TABLE 1 comparison of results of testing the content of bioactive carbon in two redox systems

The results show that the detection result of potassium dichromate/ferrous sulfate is generally higher than that of a potassium permanganate/oxalic acid redox system, the RSD is small, and the precision is better, so that the potassium dichromate/ferrous sulfate is selected as a redox reaction system for testing the biological activated carbon, in addition, the detection results of 15min, 30min, 45min and 60min are compared with the oxidation time and are shown in table 2, and the optimum oxidation time of 45min is found in table 2.

TABLE 2 comparison of results of bioactive carbon content testing at different reaction times in potassium dichromate/ferrous sulfate redox systems

In a potassium dichromate/ferrous sulfate redox system, a test result shows an increasing trend in the reaction process of the same polyolefin degradation product within 15min to 45min, and the result basically keeps unchanged after increasing to 1 hour, so that a water bath of 45min is selected as the optimal reaction time.

2. Corresponding bioactive carbon release amount and infrared spectrum of sample under different aging time and molecular weight contrast analysis

The degraded polyolefin films and rigid sheets were tested by simulating the ageing conditions of a natural environment in a laboratory xenon lamp, according to british standard PF: 9017-2021, the period of PE film test is 14 days, the period of PP hard sheet test is 28 days, and partial materials are taken out every quarter of the test period to carry out the tests of molecular weight, infrared test and conversion rate of biological organic carbon. The results of the carbonyl index, molecular weight, and bio-organic carbon conversion tests are shown in table 3 and fig. 1 and 2; the infrared test spectrogram of part of the sample is shown in figures 3-4, and the test results show that the molecular weight of the degradation product is reduced, the carbonyl index and the increase trend of the conversion rate of the biological activated carbon tend to be consistent along with the prolonging of the aging time, and the conversion rates of the biological activated carbon are respectively 91.2 percent and 89.7 percent after the degradation of hard materials is finished for 14 days in the membrane class and 28 days in the hard materials.

TABLE 3 carbonyl index, molecular weight and bioorganic carbon conversion test results for PP hard degraded sheets

TABLE 4 carbonyl index, molecular weight and conversion of bioorganic carbon test results for PE degraded film

3. Comparison of biological activated carbon content and biological decomposition rate test results of samples under the same aging conditions

In order to verify the consistency of the conversion rate of the bioactive carbon and the test result of the biological decomposition rate, the polyolefin degradation product (14-day degradation PE film) is used for testing the biological decomposition rate, the biological decomposition rate of the material is up to more than 60% in 151 days according to the GB/T19277.1-2011 compost standard test method, the result proves that the polyolefin degradation material oxidized to a certain degree has the test index requirements of the biological decomposition rate of the biological-based full-biological degradation material, and the specific detection data, the carbon dioxide release amount and the biological decomposition rate curve chart are shown in a table 5 and fig. 5 and 6. Therefore, the volumetric titration method can rapidly identify the biodegradability of the polyolefin degradable material, and is accurate in quantification, rapid and efficient.

TABLE 5 carbon dioxide Release amount

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.