1. PE Polyethylene
PE polyethylene is primarily made from polyethylene resin with small amounts of additives such as stabilizers. Polyethylene is an odorless, non-toxic, waxy solid with a milky white surface. Packaging bags made from it have a glossy surface but low transparency.
(1) Excellent barrier properties: effectively prevents the penetration of water and moisture, but has poor air barrier properties.
(2) Strong chemical stability: Does not react with acids or alkalis at room temperature, but has poor oil resistance.
(3) Mechanical properties: Good tensile strength, tear strength, and flexibility.
(4) High and low temperatures: Good low-temperature resistance, suitable for food refrigeration, but poor high-temperature performance, cannot be frequently exposed to high temperatures.
(5) Hygiene and safety: Complies with food safety standards and can directly contact food.
2. PP Polypropylene
PP polypropylene is primarily composed of polypropylene resin, featuring high gloss and transparency. Its heat-sealing properties are inferior to PE but superior to other plastic materials.
(1) Barrier properties are superior to PE, with higher strength, hardness, and stiffness than PE.
(2) Hygiene and safety are superior to PE
(3) Excellent high-temperature performance, capable of long-term use at temperatures between 100°C and 200°C, but inferior low-temperature performance compared to PE, becoming brittle at temperatures below -17°C.
Polypropylene is primarily used to manufacture food packaging bags made from film materials. It has better water resistance and moisture resistance than PET, is transparent and tear-resistant, but has poorer printability than PET. It is cost-effective and suitable for twist packaging of candies and cookies. Additionally, it can be used to produce heat-shrinkable films for food heat-shrink packaging, such as composite packaging bags for food vacuum packaging.
3. PET Polyester
PET is a milky white or light yellow highly crystalline polymer with a smooth and glossy surface.
(1) It has excellent mechanical properties, with impact strength 3–5 times that of other films and good fold resistance.
(2) It is resistant to oil, fat, dilute acids, dilute alkalis, and most solvents.
(3) Pure PET has low heat resistance, with a heat deflection temperature of approximately 85°C, but this is significantly improved after reinforcement. PET reinforced with glass fiber has mechanical properties similar to engineering plastics like PC and PA, with a heat deflection temperature reaching 225°C; PET has good heat aging resistance, with a brittle temperature of -70°C, and retains some flexibility at -30°C.
(4) Low permeability to gases and water vapor, with excellent barrier properties against gases, water, oil, and odors.
(5) Non-toxic, odorless, and hygienically safe, suitable for direct use in food packaging.
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