Research, development and application of controllable degradable mulch films. The main types of controllable degradable mulch films currently developed and applied at home and abroad include: photodegradable mulch films, biodegradable mulch films and light and biodegradable mulch films.
Photodegradable mulch film. The method of adding photosensitizer to synthetic resin is mainly used to degrade it. This technology was developed by British G. SC0tt and Israel D. Pioneered by Gilead and used in the UK, Israel and South Africa. The former Soviet Union and Japan have also carried out this research. my country began to develop photodegradable mulch films in the early 1980s, adopting a process route similar to that of foreign countries, and has now reached the level of large-scale production. However, because the part of the photodegradable mulch film buried in the soil does not degrade; after degradation, the fragments cannot easily continue to be pulverized or assimilated into the soil, and the problem of contaminated soil has not yet been fundamentally solved. In addition, the cost is higher than that of ordinary membranes, which limits the promotion and application.
Biodegradable mulch. Mulch that can be degraded by microbial action (lower level biodegradable mulch). This kind of mulch film is mainly made of natural polymers. For example, Japan uses aqueous solutions of cellulose and chitin to make films. Germany uses amylose or high amylose and other natural polymer materials to make films. my country has also used cellulose to make films. However, although these films can be degraded, they all have problems such as difficult processing, poor mechanical properties and water resistance, and they cannot be promoted and applied at all.
Light and biodegradable mulch film (also known as double degradable mulch film). Microbial sensitive substances (such as starch) are mixed with synthetic resin, and a photosensitizer is introduced into the system. After the induction period, the synthetic resin is degraded into low molecular compounds through the sensitization effect of the photosensitizer. The added microbial sensitive substances are naturally degraded by microorganisms. At the same time, because the microorganisms gathered on the product can act on the generated low molecular compounds, the polymer is eventually assimilated into the soil. The low-density polyethylene-starch-plasticizer-photochemical degradation agent mulch film launched by Griffin in the UK in 1988 falls into this category. Several companies in the United States and Canada have successively started industrial production based on this patent. The photo- and biodegradable mulch film is completely degradable, which not only ensures photodegradation of the illuminated part, but also allows the buried part to be degraded through the combined effects of biodegradation and thermal degradation to a level that does not affect farming in the next season, and can be used in the next successive season. Annual degradation into non-polluting substances. Compared with ordinary mulch films and photodegradable mulch films, photo- and biodegradable mulch films have made great progress in reducing the hazards of residual films, but this technology, like other new technologies, should be further improved in application.