What are the characteristics and uses of films for food packaging?

Classification 1. Antibacterial mechanism of photocatalytic inorganic antibacterial film: At present, the main photocatalytic antibacterial agent is TiO2, which can produce a large number of hydroxyl vinyl groups and oxyvinyl groups on the surface under the action of light. These two vinyl groups have strong chemical activity and can decompose various microorganisms organically, so they are antibacterial. Application of photocatalytic inorganic antibacterial membrane. Since 1995, photocatalytic preparation was first listed in Japan, and now it is widely used in food packaging. 2. Natural and polymer antibacterial membranes Other antibacterial membranes include natural antibacterial membranes and polymer antibacterial membranes. Their antibacterial mechanism is that the charge on the molecular chain interacts with microorganisms, thus inhibiting microbial reproduction and playing an antibacterial role. At present, chitosan, sorbic acid and curcumol are mainly used in food packaging. 3. The function of composite antibacterial membrane is mainly reflected in the following aspects: prolonging the antibacterial cycle; Can produce antibacterial performance at low concentration; Broaden the antibacterial spectrum and inhibit more microorganisms than any single antibacterial membrane. 4, inorganic antibacterial agent Thin inorganic antibacterial agent is an antibacterial agent made of silver, copper, zinc, titanium and other metals and their ions, with bactericidal and bacteriostatic capabilities. In the early 1980s, Japanese scientists began to directly add silver compounds to resin, and made antibacterial plastic film with inorganic antibacterial agent for the first time. Antibacterial mechanism: Because inorganic antibacterial agent belongs to dissolution contact antibacterial agent, the antibacterial effect of inorganic antibacterial agent film is passive. At present, there are two explanations for the antibacterial mechanism of metal ions. One is the contact reaction mechanism. The metal ions in the inorganic antibacterial membrane contact with microorganisms, which destroys the protein structure of microorganisms and leads to the death or dysfunction of microorganisms. One is the active oxygen mechanism. Trace metal ions distributed on the surface of inorganic antibacterial film can absorb energy in the environment, activate oxygen adsorbed in air and water on the surface of packaging film, and produce hydroxyl vinyl and active oxygen ions. They have strong redox ability, can destroy the reproductive ability of bacterial cells, inhibit or kill bacteria, and produce antibacterial effect. 5. Antibacterial mechanism of organic antibacterial agent membrane: The main mechanism of organic antibacterial agent is to destroy the synthesis system of protein and cell membrane by combining with anions on the surface of microbial cell membrane or reacting with sulfhydryl groups on the surface of cell, thus inhibiting microbial reproduction and gradually entering cells. There are many methods to prepare food antibacterial packaging film. One is to make antibacterial agent into antibacterial master batch, and form antibacterial composite membrane by single-layer extrusion or salivation of antibacterial agent or antibacterial master batch with resin, or coextrusion with other layers as surface layer. The other is obtained by coating or evaporating an antibacterial agent on a resin film. For the antibacterial film made of antibacterial masterbatch, the film itself is thin, so it is required that the particle size of antibacterial particles is small, the particle size distribution is narrow or organic antibacterial agents soluble in resin are used. Adding general antibacterial agents or antibacterial masterbatch has no obvious effect on the mechanical properties of the film and has no adverse effect on the printing properties of the film. However, it has some influence on the barrier properties of some films. Therefore, when selecting antibacterial agent and antibacterial master batch, we should pay attention to the influence of the addition amount of antibacterial agent and antibacterial master batch on the film performance, and choose the appropriate antibacterial agent to ensure the packaging performance meets the requirements. Generally selected packaging materials are LDPE, LLDPE, EVA, cellulose film, edible film and so on. For the method of coating or evaporating antibacterial agent on film, the barrier properties of different plastics are very different. If the substrate is not damaged during coating and coating, the quality of the final product can still be affected. The surface properties, polarity, surface roughness and the percentage of oxygen atoms and nitrogen atoms on the surface of plastic film will affect the bonding strength between the film and antibacterial agent, thus affecting the antibacterial performance. In addition, before coating or evaporating antibacterial agent on the film, the surface of the film substrate should be pretreated in advance to improve its surface energy and adhesion. Packaging film substrates used for coating or evaporation generally include PET, PA, PVC, BOPP, LDPE, etc. Food antibacterial packaging film not only meets the necessary properties of packaging materials, such as mechanical properties, printing properties and display properties, but also has high requirements for the hygienic properties of food packaging materials all over the world. China's national standard GB-9687 stipulates the hygienic requirements of food packaging materials, which require that the materials have normal color, no odor, no odor and no foreign matter, and meet the corresponding requirements in evaporation residue, potassium permanganate consumption, heavy metal content and decoloration experiment. The FDA of the United States has also made specific provisions on the ingredients of food packaging materials, specifications of additives, conditions of use, dissolution requirements, chronic toxicity test requirements and subchronic toxicity test requirements of food packaging materials. At present, triazine antibacterial agent, a compound antibacterial agent used in food packaging in Japan market, is composed of organic antibacterial agent triazine mildew inhibitor and pyridine antibacterial agent, and its antibacterial effect has been improved by 34 times. The compound antibacterial agent of organic antibacterial agent and inorganic antibacterial agent developed by Helko National Engineering Research Center of Chemical Plastics overcomes the problem of single function of KFHS series antibacterial agents. In addition, nano-TiO2 _ 2 can be added to inorganic silver antibacterial agent in food packaging film to solve the problem of slow antibacterial effect of silver antibacterial agent. The choice of substrate requires a variety of methods to prepare food antibacterial packaging films. One is to make antibacterial agent into antibacterial master batch, and form antibacterial composite membrane by single-layer extrusion or salivation of antibacterial agent or antibacterial master batch with resin, or coextrusion with other layers as surface layer. The other is obtained by coating or evaporating an antibacterial agent on a resin film. For the antibacterial film made of antibacterial masterbatch, the film itself is thin, so it is required that the particle size of antibacterial particles is small, the particle size distribution is narrow or organic antibacterial agents soluble in resin are used. Adding general antibacterial agents or antibacterial masterbatch has no obvious effect on the mechanical properties of the film and has no adverse effect on the printing properties of the film. However, it has some influence on the barrier properties of some films. Therefore, when selecting antibacterial agent and antibacterial master batch, we should pay attention to the influence of the addition amount of antibacterial agent and antibacterial master batch on the film performance, and choose the appropriate antibacterial agent to ensure the packaging performance meets the requirements. Generally selected packaging materials are LDPE, LLDPE, EVA, cellulose film, edible film and so on. For the method of coating or evaporating antibacterial agent on film, the barrier properties of different plastics are very different. If the substrate is not damaged during coating and coating, the quality of the final product can still be affected. The surface properties, polarity, surface roughness and the percentage of oxygen atoms and nitrogen atoms on the surface of plastic film will affect the bonding strength between the film and antibacterial agent, thus affecting the antibacterial performance. In addition, before coating or evaporating antibacterial agent on the film, the surface of the film substrate should be pretreated in advance to improve its surface energy and adhesion. Packaging film substrates used for coating or evaporation generally include PET, PA, PVC, BOPP, LDPE, etc. Food antibacterial packaging film not only meets the necessary properties of packaging materials, such as mechanical properties, printing properties and display properties, but also has high requirements for the hygienic properties of food packaging materials all over the world. China's national standard GB-9687 stipulates the hygienic requirements of food packaging materials, which require that the materials have normal color, no odor, no odor and no foreign matter, and meet the corresponding requirements in evaporation residue, potassium permanganate consumption, heavy metal content and decoloration experiment. The FDA of the United States has also made specific provisions on the ingredients of food packaging materials, specifications of additives, conditions of use, dissolution requirements, chronic toxicity test requirements and subchronic toxicity test requirements of food packaging materials. At present, triazine antibacterial agent, a compound antibacterial agent used in food packaging in Japan market, is composed of organic antibacterial agent triazine mildew inhibitor and pyridine antibacterial agent, and its antibacterial effect has been improved by 34 times. The compound antibacterial agent of organic antibacterial agent and inorganic antibacterial agent developed by Helko National Engineering Research Center of Chemical Plastics overcomes the problem of single function of KFHS series antibacterial agents. In addition, nano-TiO2 _ 2 can be added to inorganic silver antibacterial agent in food packaging film to solve the problem of slow antibacterial effect of silver antibacterial agent. Antibacterial packaging of food is the most promising part of food active packaging. Choosing antibacterial film packaging is the most favorable, which can continuously release antibacterial agents to inhibit the growth of microorganisms, ensure the safety of food and extend the shelf life of food. Let our consumers enjoy a higher quality of life. The above is my personal opinion, I hope it will help you.