Views: 0 Author: Site Editor Publish Time: 2021-04-21 Origin: Site
PE film is a thermoplastic polymer with variable crystal structure and a wide range of applications depending on the specific type. It is one of the most widely produced plastics in the world, producing tens of millions of tons worldwide every year. In the 1950s, two scientists, Karl Ziegler of Germany and Giulio Natta of Italy, developed the commercial process that made PE film so successful.
There are several types of PE film, and each PE film is most suitable for different applications. Generally speaking, high-density polyethylene (HDPE) is much more crystalline than low-density polyethylene (LDPE), and is usually used in completely different situations. For example, LDPE is widely used in plastic packaging, such as food bags or cling film. In contrast, HDPE has widespread applications in construction (for example, in the manufacture of drainage pipes). Ultra-high molecular weight PE film (UHMW) has high performance applications in medical equipment and bulletproof vests.
l Low-density PE film (LDPE) is a very soft material with unique fluidity, making it particularly suitable for shopping bags and other plastic film applications. LDPE has high ductility, but low tensile strength, which is obvious in the real world because it is easy to stretch when stretched.
l Linear low density PE film (LLDPE) is very similar to LDPE, but has more advantages. Specifically, the characteristics of LLDPE can be changed by adjusting the molecular formula, and the entire production process of LLDPE generally consumes less energy than LDPE.
l High-density PE film (HDPE) is a strong, medium-hardness plastic with a highly crystalline structure of polyethylene-hdpe-trashcan-1. PE film is often used in plastics for milk cartons, washing powder, trash cans and cutting boards.
l Ultra-high molecular weight PE film (UHMW) is a very dense PE film whose molecular weight is usually an order of magnitude larger than HDPE. It can be spun into a thread with a tensile strength many times higher than steel, and is often used in bulletproof vests and other high-performance equipment.
Now that we know the purpose of PE film, let us study some of the key characteristics of PE film. According to the way plastics react to heat, PE film is classified as "thermoplastic" (as opposed to "thermosetting"). The thermoplastic material becomes liquid at its melting point (110-130 degrees Celsius in the case of LDPE and HDPE, respectively).
A useful property of thermoplastics is that they can be heated to the melting point, cooled and reheated without significant degradation. Thermoplastics like PE film liquefaction will not burn, so they can be easily injection molded and then recycled. In contrast, thermoset plastics can only be heated once (usually during the injection molding process). The first heating will cure the thermosetting material (similar to a two-part epoxy), causing the chemical change to be irreversible.
If you try to heat the thermoset to a high temperature a second time, it will burn. This characteristic makes thermoset materials unsuitable for recycling. Different types of PE film show great variability in their crystal structure. The lower the crystallinity (or amorphous) of the plastic, the greater the tendency for it to gradually soften; that is, the greater the range between the glass transition temperature and the melting point of the plastic. In contrast, crystalline plastics exhibit a rather sharp transition from solid to liquid.