Aging Properties Of Starch-Based Bio-Based Degradable Plastics

At present, starch-based plastics are mainly made from modified starch and a small amount of vinyl alcohol solution and plasticiser as raw materials, which are mixed by boiling in a water bath to make resin, and then the resin is dried at 130°C to make starch-based plastics.

The study concluded that vinyl alcohol can make up for the defects of starch in terms of strength and plasticity and enhance the thermoplasticity of the plastic.

Moreover, the hydrogen bonds formed between the large number of hydroxyl groups contained in vinyl alcohol can build up into interconnection network polymers, which will likewise improve the strength and increase the elongation at break of the plastic according to the ductility and adhesive properties that vinyl alcohol has in the macroscope.

Plasticisers have also been found to increase the amount of polyhydroxy compounds in starch-based plastics, which increase the plasticity of starch agglomerates, thereby improving the strength of starch-based plastics and enhancing their ductility and elasticity.

In particular, when the mass fraction of the plasticiser is greater than 25%, the elongation at break exceeds 100%, thus weakening the hydrogen bonding between starch molecules and enhancing the miscibility between starch-basedplastic materials, thereby increasing the toughness and strength of the plastic.

To add to this, as the mass fraction of vinyl alcohol and plasticiser increases, the degree of right angle tearing of plastics tends to increase more rapidly at 16% and 20% respectively.

Plastic ageing refers to the combined effects of microorganisms, oxygen, light, heat, water and other factors in the natural environment, which contribute to the deterioration of plastic performance and thus shorten the life of the plastic.

Some studies have shown that the mass fraction of vinyl alcohol raw material in biodegradable starch-based plastics, depending on the direction of use, needs to be controlled in a range of less than 16% or more than 20%, and the mass fraction of plasticiser needs to be more than 25% for the plastic to have high toughness and biodegradable properties.