Study on Degradation of Foamed Plastic Meal Boxes (1)

introduction

With the rapid development of economic construction, the pace of life of people is getting faster and faster, and the fast food industry has also been born. In the fast food industry, a large variety of disposable plastic lunch boxes are used. The degradability of these lunch boxes will directly affect the environment in which we live.

Abstract Disposable lunch boxes are widely used in human life, but they also bring considerable troubles while bringing convenience to people. Because of their large molecular weight, structural stability, strong hydrophobicity, and small surface area, these polymers generally degrade in nature at very low rates, and typically require 200 to 400 years to decompose. At present, the disposal of waste plastics is mainly landfill and incineration. Incineration of plastics can easily lead to dioxin pollution; long-term mixing of plastic debris in soil can also easily cause soil compaction, affect plant growth, and may contaminate groundwater.

The exploratory activity was conducted from 2004/8/7 to 2004/12/19, and the conditions for the degradation of disposable lunch boxes were mainly studied through chemical biodegradation and solid phase experiments.

1. Chemical biodegradation utilizes the principle of similar dissolution of organic matter. First, the polystyrene lunch box is dissolved in a non-toxic aqueous solution of raspberry ketone or vanillin, and whether or not the organic dispersion in the precipitation is observed and used in vivo is observed. In order to achieve the goal of degradation. Microorganisms were aerated for a period of two to three days with the sludge from the Tianshan Sewage Plant as the source of microorganisms. The supernatant was discarded and the gelatinous layer in the sludge was taken.

2. The solid-phase experiment , that is, the landfill experiment, is based on the weight loss and breakage of plastic fragments after landfilling for a certain period of time to evaluate the degradability. In this experiment, the solid phase was divided into soil buried and activated sludge landfill.

The current experiment of landfilling with activated sludge has made some progress. From the data and visual observations, white meal boxes have certain degradability in high-concentration and high-activity microorganisms, indicating the direction for future experiments.

Keywords: Disposable lunch boxes Degradation Landfill

one. Introduction;

1. The status quo;
Plastics are widely used in human life and production, and are tied to steel, timber and cement as the four pillar materials. However, it brings considerable trouble to people while it is convenient. Because of the large molecular weight, structural stability, strong hydrophobicity, and small surface area of ​​these polymers, the degradation rate is generally minimal in nature except for thermal degradation. Experiments show that the decomposition rate in soil varies with environmental conditions (such as rainfall, air permeability, temperature, etc.), but it usually takes 200 to 400 years to decompose. In 2002, the total output of plastics in the world was 150 million tons, while disposable plastic products accounted for about 30%, that is, 45 million tons (2).
At present, the disposal of waste plastics is mainly landfill and incineration, and the huge annual output has exerted great pressure on the already very tense urban landfill. The burning of plastics can easily lead to dioxin pollution. In addition, long-term mixing of plastic debris in the soil can also easily cause soil compaction, affect plant growth, and may contaminate groundwater. After dumping into the ocean, it will cause adverse effects on the marine ecosystem.

In response to this situation, the countermeasures adopted by some countries are 3R, namely Reduce, Reuse, and Recycle. To implement this countermeasure, governments of all countries are vigorously developing technologies for the recycling and recycling of waste plastics, such as incineration and pyrolysis. However, in some areas where recycling is difficult or requires much energy after recycling, the cost of plastic recycling is too high. Economically feasible, the most typical example is a disposable foam plastic lunch box. Therefore, biodegradable plastic products have become the first choice in these fields.

2. Degradable plastics;
The degradation of organic polymer materials such as plastics in the environment can be divided into physical degradation (thermal degradation, photodegradation, radiation degradation), chemical degradation and biodegradation, of which the greatest role is photodegradation and biodegradation, or light and microbiological Combined degradation. Developed countries began to study the photodegradable plastics in the 1970s, and their theory has become more mature. The research of biodegradable plastics began in the mid-1980s, and it has developed rapidly and there are industrial products. (2) (3) (4) (5)

3. Biodegradability;
The structure of the polymer has a great influence on the biodegradability of the polymer, including its chemical structure, physical structure and surface structure. Other factors that affect the rate of degradation are external environments such as temperature, enzymes, pH, microbes, electromagnetic, ultrasonic, and radiation. For example, the biodegradability in the soil is related to various factors such as pH, illuminance, temperature, humidity, and the composition and content of metal ions in the soil. (7) Since virtually any degradation material is not in a single form of degradation in the environment, it is simultaneously biodegradable, photodegradable, and thermally oxidatively degraded. Therefore, the degradation rate of the material may be affected by various factors. The quantitative relationship between structures is difficult to grasp. In general, however, some basic structural features that are conducive to biodegradation can be generalized, such as hydrophilicity, chemical groups that are sensitive to specific enzymes, low crystallinity, low molecular weight, linear structures, large surface areas, etc. (5 ) (6).

two. The feasibility of the experiment;
Various standards;
At present, all countries in the world are stepping up the research on the standardization of degradable plastics. The contents include the definition, classification, experimental evaluation methods and standards of degradable plastics. The American Society of Materials Experiments (ASTM) took the lead in the development of degradable plastics standardization. In 1989, the Subcommittee on Environmentally-Degradable Plastics was established. It began to study and formulate experimental evaluation methods for the degradation of plastics under various environmental conditions, and has published more than 20 times. Item related standards.

Japan and Germany have also conducted corresponding research. Japan established the Biodegradable Plastics Research Society in 1989. Since 1991, 22 points have been selected for 6 kinds of biodegradable plastics. The soil burial and fresh water immersion experiments were carried out respectively, and the JISK6950 standard for the testing methods of biodegradable plastics was established; Germany also A standard DIN V54900 for the biodegradability of biodegradable plastics has been developed for testing by composting.
In terms of international common standards, there are ISODIS14851, 14852, ISOCD14853, 14855, ISO486 and OECD301.

China's research in this area started relatively late. The relevant standards are: Technical requirements for environmental labeling products HJBZ12-1997, and 1999 “Test method for degradation performance of disposable biodegradable food and beverage” GB/T 18006.2-1999. (1)