Corn starch is one of the main sources of starch in humans, and it is also the main raw material for industrial starch and deep processing industry with starch as raw material.
The so-called corn starch is a mixture of amylose and amylopectin. High amylose corn starch refers to the amylose content of corn starch is as high as 55% to 85%, while the content of amylose in ordinary corn kernel is only 22%. %~27%.
Amylose is a polymer in which glucose is linked by α-1,4 bonds, and has a degree of polymerization of 100 to 6000 glucose units, and has a chain structure. Its aqueous suspension does not produce dextrin when heated, but dissolves in colloid to form an unstable solution with low viscosity. After standing at 50 ° C ~ 60 ° C for a long time, a crystalline precipitate will precipitate, and the reaction is reversible. The reaction with iodine is blue.
Amylose has similar fiber properties, and has unique application value compared with general starch. Especially the physicochemically modified amylose function is further strengthened, which provides new raw materials for exploring the application of starch in industrial production.
The film made of amylose has good transparency, flexibility, tensile strength and water insolubility, and is non-toxic and non-polluting. It is widely used in sealing materials, packaging materials and water and pressure resistant materials.
Due to the high shear resistance and strength of amylose, as well as good water resistance, it is also used in the wrinkle and adhesive industries. Amylose can be used in the manufacture of a variety of films and various strips. Films made with amylose have outstanding clarity, elasticity, tensile strength and water resistance.
White pollution has brought immeasurable losses to the human living environment, which has caused the whole society and all human beings to attach great importance to environmental protection. In the face of increasingly depleted oil resources, biodegradable materials that conform to the trend are becoming a research and development hotspot as high-tech environmentally friendly products. To enter the market for degradable plastics, the following requirements must be met:
1 Practicality, with similar application performance to similar ordinary plastics;
2 Degradability, after being used, can degrade faster in the natural environment, become a fragment that is easily absorbed by the environment, and eventually return to nature;
3 Safety, residues in the degradation process and after degradation are harmless or not harmful to the natural environment;
4 Economical, the price is close to or flat with similar ordinary plastics.
However, the price of biodegradable plastics is too high, and the price of degradable plastics is more than 50% higher than that of similar plastic products. Among them, the degradation can be completely 4 to 8 times higher, which is the biggest obstacle to its promotion and application. In order to reduce costs and ensure the degradation performance of products, starch biodegradable plastics have become a hot product in the country.
Starch is currently the most widely used type of fully biodegradable polysaccharide natural polymer. It has the advantages of wide source of raw materials, low price and easy biodegradation. It plays an important role in the field of biodegradable materials. The mechanical properties of various grades of starch plastics published at home and abroad can generally be compared with the traditional plastics of similar applications, but their performance is often unsatisfactory. One of the main drawbacks is that the degradation resistance of starch-containing degradation plastics is not good. The wet strength is poor, and its mechanical properties are seriously reduced in the case of water, and water resistance is precisely the advantage of traditional plastics in use. High amylose starch has good water resistance, shear resistance and film forming property compared with ordinary starch, so it has great development potential in the plastics industry.