Biodegradable plastics

Biodegradable plastics------The starch based plastics

    Biodegradable plastic refers to the type of plastics that the performance of their products can meet the use requirement, in the use and preservation period performance remains unchanged, and can be degraded to innocuous substance for environmental after using in the natural environment conditions .from the mid of 1980 s, China began to develop biodegradable plastic, but focus mainly on light degradable plastics research and development, in the early of 1990 s focused on the type of biodegradable plastic, mainly for polyolefin polymers adding and blending of starch,but these degradable plastic limited by environment condition, no matter in the garbage disposal system or in a natural environment can not be all degradation, therefore, in the late 1990s the market of this kind of biodegradable plastics were shrinking, so far, only a handful of biodegradable masterbatch production enterprises produce normally. Recently,biodegradable plastics gradually aroused people's concern again.

    Starch based plastics refers to the composition containing starch or starch derivative type plastic, starch added biodegradable agricultural film is made from corn grains and potato starch,the hydrophilization of the starch surface treated with abhorred hydration,then graft copolymerization or blending with polyolefin ,then proccessing blowing to agricultural film. after an agricultural cycle,the film production would occur degradation under the microorganisms erosion in the soil. starch molecular chain contains a large number of hydrophilic hydroxyl, and polyolefin is hydrophobic material, judging from the molecular structure of starch and polyolefin, they can not be compatible well, and the mixture of starch and polyolefin can not be a homogeneous system, therefore the starch must be treated with physical modification and chemical modification.

    Physical modified starch is starch surface treated,such as using siloxane mixed with starch and water suspended solution,then the solution sprayed dried under 80℃, then the powder mixed with autoxidation oleic acid ethyl ester and oleic acid,then blend with polyethylene and made into masterbatch;chemical modified starch plastics is to put the compatilizer that is made by graft copolymerization of starch and monomer of polyolefin,into the system of starch blending with polyolefin, forming a homogeneous dispersion system, increase the compatibility of the starch and polyolefin.Currently the biodegradable PE film is produced with the modified starch- ethylene- acrylic acid copolymer, or the blending extrusion of starch gel ,polyethylene,ethylene and acrylic acid copolymer, blowing into biodegradable thin film.

     Combination of starch granules is essential, because when the polymer is buried under the appropriate conditions in soil, the starch granules could promote microbial immersed

                                                                                    By Steven