Application of biodegradable materials in plastic film

Application of biodegradable materials in plastic film

Text/Polymer

As they say, "Food is most important thing for people." In order to expand sown area and increase productivity in field of agricultural production, technology of mulching with plastic film is widely used. Because PE material is easy to process and has excellent chemical resistance and physical properties, it has become main raw material for plastic mulch film. However, PE material has a large relative molecular weight, corrosion resistance, and is difficult to decompose under natural conditions. Environment. It can persist for hundreds of years and is harmful to environment. Causes serious "white pollution". Today we will learn about degradable mulch with same effect.

Application of biodegradable materials in plastic film

1. Biodegradable plastic film

In recent years, biodegradable mulch has been continuously developed using new material synthesis technology. Biodegradable mulch is a type of plastic that biodegrades in soil to form CO2 and H2O in natural environment and causes no harm. to environment Mulch. Sources of biodegradable polymer materials are shown in Table 1-1.

Application of biodegradable materials in plastic film

Table 1-1 Sources of biodegradable polymer materials

1.1 Starch Based Biodegradable Plastic Film

Starch is renewable, cheap, easily extractable and fully biodegradable. However, due to strong hydrogen bonds between molecules, starch-based materials have poor thermoplasticity and low mechanical properties. Therefore, it must be mixed with other polymeric materials to improve its technological characteristics and mechanical properties. Common blending systems include cornstarch/polyvinyl alcohol (PVAL)/PE blend film, starch/ethylene acrylate (EAA) blend film, starch/PCL blend film, etc.

The film based on modified starch with excellent complex characteristics cannot currently achieve 100% biodegradability, and residual non-biodegradable components pollute soil. Further improvement of mechanical properties and technological properties of films based on starch, provided that its complete biodegradation is ensured, may become a trend for future development.

1.2 PLA based biodegradable plastic film

Polylactic acid (PLA) has a high modulus of elasticity and strength. It is a biodegradable material with biorenewable characteristics. Its raw materials are derived from plants and have good biocompatibility. It is widely used in biological fields such as medicine and packaging.

Application of biodegradable materials in plastic film

Figure 1-1 Molecular structure and production method of polylactic acid

The biggest problem with PLA base film is its high brittleness and poor flexibility, so it needs to be strengthened and modified to fit film's requirements. Commonly used stiffness modifiers include low molecular weight plasticizers, inorganic nanoparticles, and flexible polymers. Among them, PLA is blended with flexible and degradable polyesters such as PHB and PCL, which can not only improve strength of PLA base film, but also ensure that PLA base film is completely degraded under natural conditions.

1.3 PBAT Biodegradable Plastic Film

PBAT is a new type of degradable aromatic copolyester that has characteristics of PBA and PBT and is composed of BT and BA. Therefore, PBAT not only has good ductility and elongation at break, but also has good heat and impact resistance, and has excellent biodegradability.

The advantage of PBAT is that conventional PE film processing equipment can be used to blow film, which is very suitable for production of film products. It is most popular biodegradable film material currently being studied. At this stage, thickness of the biodegradable film based on PBAT is 40-50 microns.

2. Some commercial biodegradable mulches

Application of biodegradable materials in plastic film

Table 2-1 Some commercial biodegradable mulches

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