Preparation of biodegradable packaging materials based on modified starch

Degradable plastics based on starch are a very important part of degradable plastics. Plastics that use natural starch as a filler or natural starch and its derivatives as a blending system belong to this category and can be mainly divided into filled type and Whole starch type two.

Filled starch plastic

The so-called filled starch plastic, strictly speaking, starch in plastics does not only play a filling role, but under certain conditions, activates the hydroxyl groups in starch and plastics to form a high polymer blend. In the early days of the study of starch-based biodegradable plastics, the researchers blended unmodified natural starch or simply physically modified starch with general-purpose resins to formulate early starch-based biodegradable plastics due to starch. Many advantages have prompted people to continuously strengthen the research and promotion of starch-based plastics. In the ongoing research and use, researchers have discovered that the compatibility of starches that have not been modified or simply physically modified with general-purpose resins is poor, and the mechanical properties of the degraded plastics that are prepared are relevant to people’s daily lives. There is a large gap between the use of polymer plastics. Due to the compatibility between starch and general-purpose resins, there are certain problems. In the degradation process of degradable plastics, the starch part of the degradable plastics is more easily degraded in the natural environment, while the part of the general-purpose resin is still hard to be degraded, resulting in the final "Disintegration" occurs, and the disintegration of plastic debris creates certain difficulties, so the damage to the natural environment is still great.

The use of chemically modified starches blended with general purpose resins can greatly improve this situation. Since plastic packaging products are widely used in people's daily life, the use of modified starch-based biodegradable plastics in plastic packaging products is of great significance for environmental protection and natural resource conservation.

The process of filling starch plastics is simple, it can use general plastic processing technology and equipment, the production cost is low, and it has certain degradation performance. To a certain extent, it is a practical technical means to ease the pressure of plastic products on the environment. It is currently degraded in China. The plastic market mainly uses such plastics.

All-starch plastic

As the filled plastics still have some limitations in the degradation performance, all-starch plastics are expected by people. All-starch plastics belong to the category of natural polymers containing more than 90% starch, and other components added are also completely degradable, while starches need to change their molecular structure so as to form thermoplastics. Research work to study the plasticizing effect of water and polyols on starch and made some progress.

Among the varieties of fully degradable plastics that are currently available, the most cost-reducing plastics are entirely starch plastics, because the raw starch they require is a renewable resource, and its unit price is far lower than conventional plastic materials and degradable resins. However, due to the immature production process, the cost of starch plastics is still high. In addition, the full-starch plastics still have certain defects in mechanical strength and other properties. The focus of future research is to further improve the performance of products, broaden their application areas, reduce product production costs, and achieve industrial production.

Preparation of biodegradable packaging materials

The use of modified starch can improve the degradation performance of packaging materials to some extent, but in order to meet the special requirements of packaging materials, the material must also meet the breathability, moisture permeability, antibacterial and preservation, and the packaging of fruits and vegetables must also meet the anti- Dew condensation and other requirements. Because of the better film forming ability of the modified starch, it can meet the requirements of ordinary packaging materials in both air permeability and moisture permeability after being blended with the general resin.

Antibacterial properties of packaging materials

A large part of the contents of packaging materials is fruits and vegetables and foods that people eat daily. Antibacterial properties of packaging materials are an important indicator. The corruption of fruits and vegetables after harvest can be as high as 20% to 40%. The safe and effective antibacterial ingredients are polymerized into the film or coated in the film during the blending, so that they are released slowly after being packaged to produce antibacterial effect. Silver zeolite: Ag+ replaces Na+ in the porous zeolite crystal structure to obtain silver zeolite, which has broad antibacterial spectrum and strong effect. It has good effect at the content of 10-50mg/kg. Fruit and vegetable preservatives: Nisin, imazalil, etc. can also be added to the film substrate; antibacterial Chinese herbal powder mixed in oxidized starch, and then applied to the inside of the Paper Bag, or can be added to the film with chitosan, hinokitiol, etc. Inside, all have bactericidal antiseptic effect. The rate of drug release and release must be controlled.

Anti-condensation function of packaging materials

The water vapor generated in the life of fruits and vegetables will condense when the temperature fluctuates. Sucrose ester, polyethylene glycol, monoglyceride, and other surfactants are properly added to the film or applied to the inside to make the surface of the film wet uniformly to form water. The film no longer dew, preventing the film from becoming cloudy.

Conclusion

Biodegradable plastics are of great significance for environmental protection and saving of petroleum resources. Starch is widely sourced and inexpensive, and it is an ideal raw material for biodegradable plastics. Packaging materials are widely used in daily life. After the starch is modified, compatibility with general-purpose resins is further improved, and supplements such as preservatives and rust inhibitors can be used to prepare ideal biodegradable packaging plastics.

Reprinted from: China Zhejiang Online Technology Market