Degradable materials are materials that degrade both thermodynamically and kinetically over a period of time. According to the external factors of degradation, it can be divided into: photodegradable materials, biodegradable materials, etc. The main influencing factors are temperature, molecular weight and material structure.
Polylactic acid (PLA), also known as polylactide, is chemically synthesized from the microbial fermentation product lactic acid. It can be degraded automatically after use without polluting the environment.
Polylactic acid can be processed into fibers and films with excellent mechanical properties, and its strength is generally comparable to that of nylon fibers and polyester fibers. Polylactic acid can be hydrolyzed into lactic acid and acetic acid in the body and metabolized to CO2 and H2O by enzymes, so it can be used as a medical material. Japan and the United States have processed polylactic acid plastic into surgical sutures, artificial bones, and artificial skin. Polylactic acid is also used in the production of packaging containers, agricultural mulch films, fiber sportswear and bedding. More than 90% of starch is added, and other components added can be completely degraded. At present, Sumitomo Corporation of the United States, Wamer-Lamber of the United States, and Ferrizz of Italy claim that the research has a successful starch content of 90% to 100%. Starch plastics, completely biodegradable (January to 1 year) without leaving any traces, no pollution, can be used to manufacture a variety of containers, bottles, films and garbage bags.
The principle of production of all-starch plastics is to make the starch molecules deform and disorder, forming a starch resin with thermoplastic energy, so it is also called thermoplastic starch plastic. Its molding process can follow traditional plastic processing equipment.
The potential advantage of developing biodegradable plastics from starch is that starch has complete biodegradability in various environments; after degradation or ashing of starch molecules in plastics, carbon dioxide gas is formed, which does not poison soil or air; The appropriate process enables the starch to be thermoplasticized to achieve the mechanical properties of the plastic material; starch is a renewable resource, and the use of pioneering starch is beneficial to the development of the rural economy.
It should be noted that most of the starch plastics currently produced in China are filled starch plastics, that is, a certain proportion of starch is added to the non-biodegradable polymer materials, and the physical properties of the whole material collapse due to the biodegradation of starch. A large number of end groups are exposed to cause oxidative degradation, but PE, PVC, etc. in the remaining part after this "crash" are unlikely to be degraded and remain in the soil, which will of course cause pollution. Therefore, such products are classified as eliminated in foreign countries. type. Photodegradable plastic refers to a plastic that can degrade under the action of light.
1. Examples of photodegradable plastics
Photodegradable plastics can be classified into synthetic degradable plastics and additive degradable plastics according to the manufacturing method.
(1) Synthetic degradable plastic
a, ethylene / carbon monoxide copolymer (E / CO)
Photodegradation is characterized by backbone breaks. The photodegradation rate and degree of E/CO are related to the amount of ketone groups contained in the chain. The higher the content, the faster the degradation rate and the greater the degree. Scientists in Texas, USA, have conducted outdoor exposure experiments on E/CO. In sunny June, E/CO can be degraded in as little as a few days.
b, vinyl / vinyl ketone copolymer (Ecolyte)
The ketone group on the side chain of the Ecolyte molecule can be decomposed by the action of natural light. Ecolyte's photodegradation performance is better than E/CO, but the cost is also higher.
A disadvantage of such polymers is that degradation begins to occur once the light is visible, with little induction period, and an antioxidant is required to achieve the purpose of regulating the induction period.
(2) Addition type photodegradable plastic
Addition type photodegradable plastic is a small amount of photosensitizer added to the polymer. At low concentration, it is a photooxidation degradation catalyst, which is reacted by sunlight (ultraviolet light) to cause the polyolefin polymer to break.
Adding photosensitizers such as ketones and amines to polymers such as PE and PP can achieve better photodegradability.
The added photodegradable plastic has low cost, simple production process, and good coverage of the mulch film. However, its degradation characteristics are that the degradation of the exposed surface is relatively thorough, and the part buried in the soil is poorly degraded. The degradation induction period of such photodegradable plastics can be controlled for more than two months. However, the degradation time is less controllable.
Many of our customers have adopted raw materials of PLA materials. We also support customers' choice of environmental protection. In addition, the company is in the process of certification of the internationally recognized degradable standard DIN EN13432, and it is expected that it will be certified in May next year.