(1) Plastics directly processed from natural materials: mainly including starch-based biodegradable plastics, chitin and plant fiber molding;
(2) A polymer synthesized by microorganisms: mainly including polylactic acid (PLA), polyhydroxy alkanoate (PHA).
Starch is a kind of natural polymer, and it has a strong interaction between its molecules because of a large number of hydroxyl group (molecular structure is 2 and 3) the starch contains. The strong interaction makes starch difficult to melt processing, and have a poor compatibility with other polymers in blending processing. However, these hydroxyl groups can undergo chemical reactions such as esterification, etherification, grafting and crosslinking. These chemical reactions are used to modify starch. Corn starch cutlery can reduce the hydroxyl of starch and change its original structure, which thereby change the characters of starch, and shift the original starch into thermoplastic starch. Therefore, degradable cornstarch resin does not belong to cornstarch, but to modified natural polymer.
(1) Starch-based biodegradable plastic is generally a compound of modified starch and biodegradable polyester (such as PLA/PBAT/PBS/PHA/PPC). It can be completely biodegradable, compostable, and pollution-free to the environment. This plastic waste is suitable for composting and landfill.
(2) Bio-based plastic based on starch in corn starch eco friendly cutlery set is generally a compound of modified starch and polyolefin. It can reduce the use of petrochemical resources, carbon dioxide emissions, and the waste is suitable for incineration. So, the bio-based plastic is environmentally friendly.
These two kinds of materials can replace the traditional petroleum-based plastics, and are widely used as plastic packaging materials, shockproof materials, plastic film and plastic bags, disposable catering utensils, food containers, toys, etc.