At present, most of the food plastic packaging on the market is mainly based on composite plastic film packaging, especially high barrier materials have become the main body of plastic packaging. Therefore, the quality, freshness and flavor requirements of the contents should be considered first when choosing. At the same time, when choosing plastic film (bag), it is necessary to fully understand the relevant performance of plastic packaging and make a reasonable choice. We should pay special attention to the hygiene standards for food packaging materials that meet the requirements for plastic molded products of the corresponding material.

Commonly used food plastic packaging materials are as follows:

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

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

3. Polyester (PET), high transparency, good gloss. It has excellent gas barrier, oil resistance, fragrance retention performance, good chemical stability, and resistance to enoic acid and alkali. Wide range of use temperature, room temperature range of -70 °C ~ 120 °C, can be used at 150 °C for a period of time, health and safety. Widely used in poultry packaging. Composite films based on PET can be used for cooking food packaging.

4. Polyamide (PA), commonly known as nylon, has strong gas resistance, but poor water vapor barrier and strong water absorption, and expands with the increase of water absorption, so that the gas barrier and moisture resistance drop sharply. The strength and dimensional stability of the packaging are also affected. Polyamide (PA) film (bag) has good toughness, wear resistance, cold resistance, heat resistance; Stable chemical properties, good printability, good puncture resistance. The material meets the hygiene and safety requirements of food packaging. Therefore, it is widely used in frozen packaging and retort packaging of food. Most of the rice on the market now uses nylon packaging bags.

Food plastic packaging material requirements:

1. Appropriate barrier, such as oily foods that require high oxygen and oil resistance; Dry foods that require a high moisture barrier; Aromatic foods that require high odor barrier; Fresh fruit and vegetable foods, on the other hand, require a certain amount of oxygen, carbon dioxide and water vapor permeability.

2. Good physical and mechanical properties, mainly including 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 food; It should also have high temperature resistance, suitable for high-temperature sterilization and low-temperature storage of food.