Different excellent characteristics of vest bags made of plastic packaging materials
Release date:2019-10-07 11:40
With the sustained and rapid development of China's economy and the continuous improvement of people's living standards, people pay more and more attention to food safety and hygiene. Food packaging as an important part of food, its safety and hygiene has been widely valued. The selection of raw and auxiliary materials of food packaging materials, the structural design of packaging materials, the processing and manufacture of packaging materials and their packaging labels have a direct impact on the safety of packaged food. Food Safety > defines food packaging materials as: paper, bamboo, wood, metal, enamel, plastics, rubber, natural fibers, chemical fibers, glass and other products and coatings for food contact.
PE, which is most widely used in the market, is synthesized by ethylene polymerization. Due to the different polymerization methods and densities, it can be divided into low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE). PE has low transparency, certain permeability, good moisture resistance, certain tensile strength and tear strength, and good flexibility. Good chemical stability, insoluble in any organic solvent at room temperature, resistant to most acids and bases, not resistant to concentrated nitric acid. It has good low temperature resistance (- 70 C), easy forming and processing, good heat sealing, but poor printability. Corona treatment or chemical surface treatment are often used to improve its printability. PE is a non-toxic packaging material. Therefore, it is often used in thermal sealing and moisture-proof coatings of composites. LLDPE can also be made into thin film and thin film bags for packaging. Nowadays, most of the inner layers of food packaging are PE or CPP. It is non-toxic, good moisture resistance, good flexibility, good heat sealing performance and other advantages, used for the inner layer of food composite packaging materials. Most of the plastic film bags we use in our daily life are made of this kind of material.
PVC plastics can be roughly divided into three categories: hard products, soft products and pasty products. In hard products, plasticizers are generally less than 5%, and in soft products, plasticizers are more than 20%. Because rigid PVC contains no or little plasticizer, its products have no peculiar smell of plasticizer, and have excellent mechanical strength, light weight and stable chemical properties. At present, most of the fresh-keeping films and food packaging boxes used in supermarkets are made of PVC. However, the safety of PVC materials has always been a concern. Our country has formulated relevant hygienic standards for PVC moulding products and PVC resins for food packaging. The standard specifies the content of vinyl chloride monomer.
PP is polymerized from propylene. It is light in weight, transparent and glossy. It has excellent mechanical properties, tensile strength, hardness and toughness. It has good heat resistance. It can be used continuously in high temperature at 120 C and can be boiled in boiling water. Chemically stable, stable to acid, alkali, salt and many solvents in a certain temperature range. Pure PP material is hygienic and safe and meets the requirements of food packaging. PP has some gas resistance. Because of its good physical properties and relatively low price, this product has become the most widely used substrate for food packaging composite films.