Research on Thermoplastic Starch

Starch is a kind of biodegradable natural polymer, which exists in a large number of agricultural products. It has the advantages of wide source, low price, renewable, and pollution-free. However, the disadvantages of starch due to its own crystalline structure, such as processing performance, physical and mechanical properties, and insufficient water resistance, severely restrict its application, and need to be modified to enable them to be used in certain fields. The starch content in thermoplastic starch plastics is more than 90%, which can be completely degraded. It can greatly alleviate the problems of energy shortage and environmental pollution by replacing petroleum-based plastics. It is the development direction and goal of starch-based plastics.

Starch is composed of amylose and amylopectin. It contains a large number of hydroxyl groups and is highly hydrophilic. There are a large number of intramolecular and intermolecular hydrogen bonds to form crystals, resulting in difficulty in the movement of molecular chains and high glass transition temperature. At the decomposition temperature, it does not have thermoplasticity. Thermoplastic starch is under the action of small molecule plasticizers or other conditions, it destroys the internal hydrogen bond structure of starch, makes the arrangement of starch molecules tend to be disordered, reduces its glass transition temperature, and makes it thermoplastic. Starch-based plastics. The key to making starch thermoplastic is to reduce the glass transition temperature of starch. Physical or chemical methods can destroy the crystalline structure of natural starch, which can make the starch molecules as disordered as possible and achieve the goal. Although thermoplastic starch has the advantages of renewable raw materials and easily degradable products, it also has disadvantages such as poor water resistance, insufficient mechanical properties, and high production costs, which limit its further development and application. Selecting a plasticizer with superior performance, non-toxic and harmless, and pretreatment of the starch raw materials before plasticization can significantly improve the thermoplasticity of the starch, and at the same time enhance the water resistance of the material to a certain extent. Adding reinforcement to enhance the thermoplastic starch material can make it have better processing performance and higher mechanical strength. These methods expand the application range of thermoplastic starch materials, help increase production scale, reduce production costs, and gradually replace traditional petroleum-based plastics.