1.1.2.1 Research status of biodegradable film materials

Biodegradable materials research began in the 1960s. The initial study was mainly to add natural polymers with biodegradable properties (such as starch, etc.) to generic plastic, then get the so-called biodegradable materials. St. Lawrence starch-company developed a starch — polyethylene or polypropylene blends in Canada (Qiu Weiyang, 2002). With human understanding of biodegradability of macromolecule, the research focus began to turn to biodegradable materials (Qiao Haijun, 2007), which can be classified as microorganism synthetic polymer, chemical synthetic polymer and natural polymer.

biodegradable film, it includes structural degradation film, biodegradable film containing inorganic salts and adding starch. (3) photo — biodegradable film; (4) plant fibre film.

In China, the major research was additive photo-degradation film and synthetic photo­degradation film. The research focused on using light stabilizers to control degradation period. Since 1997, 944-polymeric efficient light stabilizer, BW-6911 new light stabilizer were developed, which replaced the severe irritation and sensitization GW-504/2002 anti-aging system. American Dupont CO. , Ltd produced copolymers of ethylene and CO, American OCC and DOW CO. , Ltd had used this technology to produce film and develop industrial production (Xiong Hanguo, 2004). The disadvantages of photo-degradation film were susceptible to external environment, which was difficult to control the degradation period, and covering field, the part into soil can not be degraded, so its application was limited (Xu Xiangchun, 2006).

The degradation of biodegradable film was caused by microbes in natural environmental condition. It was divided into additive biodegradable film and completely biodegradable film according to degradation mechanism and damage style.

At present, additive biodegradable film was composed of plastic, starch, compatibility agents, self-oxidants, processing additives. Typical varieties were polyethylene starch biodegradable film (Liu Ming et al., 2008). There were institutes of physics and chemistry, Beijing University of Technology, Guangdong biodegradable plastic CO., Ltd more than 20 research institutes. The research focused adding starch or modified starch into PE.

The main varieties of completely biodegradable film were PLA, PCL, and PHB and so on. United States used PCL to produce synthetic polymer biodegradable film (KAM Abd I J — kader, 2002). Warner-Lambert developed a new type of resin, which was made of 70% amylopectin starch and 30% amylose starch (He Aijun, 2002). It had good biodegradability, was considered a significant development in material science.

Photo-degradation film was made of additive photo-sensitizer, auto-oxidants, and anti­oxidants as microbial culture medium in general polymer.

Plant fibre film has good ventilation, wet and dry strength and good biodegradability. Chinese academy of agricultural sciences successfully developed the environmentally — friendly hemp film (Fu Dengqiang, 2008). In addition, paper films composed of different materials were produced. South China Technology University used sugar cane and starch as materials to manufacture a kind of fully degradable film (Tan Chengrong, 2002). Japan manufactured biodegradable film with 1%-10% chitosan cloth softwood mechanical pulp original paper in 1990. The demand of environmental film increased in Washington State University, France, Germany, Italy, Canada, Netherlands and South Korea and other countries, leading to the environmentally-friendly film industry rapid development (Han Yongjun, 2008).