The plastic films used in composite materials are arranged in order of their dosage, including polyethylene, polypropylene, glass paper, polyester, nylon, co extruded film, ethylene and acrylic copolymer film, as well as polyvinyl chloride, polystyrene, ethylene and vinyl acetate copolymer, polyvinyl alcohol, etc.
Different plastic films have different properties and advantages and disadvantages. Composite materials are the combination of plastics with different properties, overcoming the shortcomings of individual film materials, concentrating their respective advantages, and allowing composite materials to fully exert their comprehensive excellent properties to meet people’s requirements for various packaging.
The general properties of commonly used plastics can be combined with two or more different films based on the properties listed in the table to produce packaging materials that meet the requirements.
- Polyethylene
Polyethylene (PE) is a polymer of ethylene monomers with a relative molecular weight of over 50000. Due to different manufacturing methods and control measures, it can not only synthesize products with different molecules, but also produce products with different properties such as low-density polyethylene, medium density polyethylene, high-density polyethylene, and cross-linked polyethylene
(1) Low density polyethylene (LDPE). Its density is about 0.92g/cm, which is lower than other polyethylene products, so it is called low-density polyethylene or high-pressure polyethylene.
(2) Medium density polyethylene (MDPE). Its density is approximately 0.93-0.94g/cm, between high-density polyethylene and low-density polyethylene, hence it is called medium density polyethylene.
(3) High density polyethylene (HDPE). Its density is between 0.9-0.96gm, which is the higher molecular weight among polyethylene, hence it is called high-density polyethylene, also known as low-pressure polyethylene.
(4) Cross linked polyethylene (CLPE). Cross linked polyethylene is a new type of polyethylene manufactured by radiation crosslinking method. Due to its higher heat resistance, barrier properties, tensile strength, and high thermal shrinkage rate compared to other polyethylene, it is currently mostly used as a heat shrinkable film for packaging.
