At present, most of the food plastic packaging on the market is mainly composed of composite plastic film packaging, especially high-barrier materials have become the main body of plastic packaging. Therefore, the selection should first consider the quality, freshness and flavor requirements of the content. At the same time, when choosing a plastic film (bag), it is necessary to fully understand the relevant properties of plastic packaging and make a reasonable choice. We should pay special attention to the materials used for food packaging to meet the hygienic standards of plastic molded products that require corresponding materials.

Commonly used food plastic packaging materials are as follows:

1. Polyethylene (PE), polyethylene is not very transparent, has a certain degree of air permeability, tensile strength and tear strength, has a certain degree of flexibility and good moisture resistance. It has good chemical stability and is a non-toxic packaging material. Therefore, it is often used for heat-seal and moisture-proof coatings of composite materials.

2. Polypropylene (PP), polypropylene is polymerized from propylene. It is a very light plastic with good transparency and gloss. It has good tensile strength, hardness, toughness and other physical and mechanical properties, and good heat resistance. , It can be used continuously at a high temperature of 120℃, with stable chemical properties, and strong stability to acids, alkalis, salts and various solvents within a certain temperature range.

3. Polyester (PET), high transparency and good gloss. It has excellent gas barrier, oil barrier, fragrance retention performance, good chemical stability, and resistance to olefinic acid and alkali. The use temperature range is wide, the normal temperature range is -70℃～120℃, and it can be used at 150℃ for a period of time, which is hygienic and safe. It is widely used for poultry meat packaging. The composite film with PET as the base material can be used for retort food packaging.

4. Polyamide (PA), commonly known as nylon, has strong gas barrier properties, but has poor water vapor barrier properties and strong water absorption. It swells with the increase of water absorption, causing a sharp drop in gas barrier and moisture resistance. Packaging strength and size Stability is also affected. Polyamide (PA) film (bag) has good toughness, abrasion resistance, cold resistance, and heat resistance; stable chemical properties, good printability, and good puncture resistance. The material meets the requirements of food packaging for hygiene and safety. Therefore, it is widely used in frozen packaging and retort packaging of food. Most rice on the market now uses nylon packaging bags.

Requirements for food plastic packaging materials:

1. Appropriate barrier properties, such as oily foods with high oxygen and oil barrier properties; dry foods with high moisture barrier; aromatic foods with high odor barrier properties; and fresh fruit and vegetable foods require a certain amount of oxygen, carbon dioxide and water Vapor permeability.

2. Good physical and mechanical properties, mainly including the tensile strength, tear strength and impact strength of plastic materials.

3. It has good stability and should not have any chemical reaction with the food inside to ensure the safety of the food; it should also have high temperature resistance and be suitable for high temperature disinfection and low temperature storage of food.