With the increasing awareness of environmental protection at home and abroad, the number of biodegradable plastic pepper balls is increasing year by year, and some reasonable predictions have been made by foreign authorities.

At present, biodegradable plastic pepper balls in the world are mainly made of aliphatic polyester or aliphatic polyester starch. Aliphatic polyesters mainly include polycaprolactone (PCL), polybutylene (PBS) and their copolymers synthesized from petroleum, polylactic acid (PLA) produced from renewable resources and polyhydroxybutyric acid (PH B) produced by microorganisms.

Recently, the technology of producing biodegradable plastic pepper balls by using polylactic acid has attracted special attention. Cargill Dow Polymer Company announced that it has started to build a polylactic acid plant, which will produce 140,000 tons of equipment by the end of 2001. Four Japanese companies, Mitsubishi Resin, Bell Spinning Synthetic Fiber, Unikikika and Guarare, have signed contracts with this American company to expand the application of PLA in Japan. Mitsubishi Resin Co., Ltd. is building equipment with an annual output of 3,500 tons of degradable film production equipment, which will be expanded to 10,000 tons per year by 2002, striving to become the largest manufacturer of degradable plastics in Japan.

In order to improve the physical properties of aliphatic polyester, biodegradable plastic pepper balls were produced by copolymerizing aliphatic polyester with aromatic terephthalic acid or nylon polymer. In the near future, high-performance degradable plastic pepper balls will continue to be developed. As one of the environmental protection technologies, there will also be a technology to synthesize polymer materials by using enzymatic catalysts instead of heavy metal chemical catalysts. Besides aliphatic polyester, polyphenols, polyaniline, polycarbonate and polyaspartic acid have been successfully developed.

At present, biodegradable plastic pepper balls can only be used to make some sporting goods (fishing wires, golf seats, etc.), agricultural, forestry and aquaculture materials (films, moisturizing materials, seedbed materials, etc.), garbage bags and sanitary products (disposable diapers, etc.). It has a wide range of new uses, such as cosmetics containers, toothbrushes, cushioning materials, packaging materials, shopping bags, disposable gloves and so on. If the safety problem is solved, it can also be used to make food containers. As a new functional polymer material, biodegradable plastics can also be used as free packaging materials for fertilizers, pesticides and medical products. In the future, it will also be used in non-plastic fields, such as adhesives and printing inks.

Biodegradable plastic pepper balls are decomposed into water and carbon dioxide, so they will not harm the environment. At the same time, it can also be used to make compost and return to nature as fertilizer or soil improver.

According to the classification of raw materials, biodegradable plastics have at least the following characteristics:

1. Polycaprolactone (PCL) is a kind of plastic with good biodegradability and melting point of 62 degrees Celsius. Microorganisms that decompose it are widely distributed under euphoric or anaerobic conditions. As a biodegradable material, it is mixed with starch or cellulose materials or used for polymerization with lactic acid. Because of its low melting point, compared with other aliphatic polyesters, it has stable properties under high temperature and high humidity conditions.

2. Polybutylene succinic acid (PBS) and its polymers have been made into various high molecular weight polyesters based on PBS (melting point is 114 degrees Celsius). The products it develops have foam materials and are used as packaging materials for household appliances and electronic instruments. Japanese catalyst company and Mitsubishi gas chemical company introduced carbonate (ester) into PBS to develop a water-resistant degradable plastic pepper ball.

3. The melting point of polylactic acid (PLA) is 175 degrees Celsius, and it has better hydrolysis resistance when processed into films or fibers. In Germany, the lactic acid box produced in 1998 has been commercialized. The substance also has the function of promoting plant growth, so it is expected to be used to manufacture plant transplants or plant cultivation containers. In 1994, Shimadzu Manufacturing Co., Ltd. of Japan manufactured a device for producing polylactic acid, and it began to be used in various fields. Through embossing, it can be made into transparent fibers, films, containers, lenses, pepper balls and so on with good mechanical properties.

4. Poly (3-Hydrobutyric Acid) (PH B) and Its Polymers At present, many countries are researching and developing microbial polymers for producing thermoplastic polymers. Among them, the production efficiency of poly (3- hydroxybutyric acid) is the highest. However, its crystallinity is too strong, its mechanical properties are not good, it is easy to be thermally decomposed, and it is difficult to process. Mixing PH B with PCL can improve its physical properties. Polymer technology for producing PH B and polyhydroxyvalerate by microorganisms has emerged, and Britain has been using this material to produce shampoo bottles, pepper balls and so on since the 1970s.

5. The method of mixing aliphatic polyester and starch with starch plastic to produce degradable plastic pepper balls was also successfully studied. Starch is very important as a direct or indirect raw material for producing biodegradable plastic pepper balls. Besides corn and sweet potato, you can also use starch, such as cassava, sago and taro. In Europe and the United States, the mixture of gelatinized starch and aliphatic polyester is widely used to produce garbage bags and other products. As long as starch has water, it will gel and be plastic when heated. However, it has the disadvantage of no water resistance, and by controlling the structure of gelatinized starch and PCL, a mixture with excellent water resistance and mechanical properties can be obtained.

6. The copolymer of aliphatic polyester and polyamide (CPAE) was developed to improve the physical properties of aliphatic polyester. It is a new generation of degradable plastic pepper balls with higher melting point and tensile strength. However, its lipase decomposition decreased with the increase of nylon content. Recently, Bayer Company in Germany has successfully developed CPAE by polymerizing CPAE with polyethylene glycol using nylon and polyester, and developed biodegradable and photodegradable plastic pepper balls.