Polypropylene is the largest single consumption of all plastics, and it is also the most widely used one. It can be classified according to different substrates, and specifications can still be set according to different melt flow rates within the classification. You can even add additional additives to use according to the needs of individual goods. For example, in a single polymer, MFR: 12 can be used for general injection finished products, and can also be used to produce multifilament fibers, and a wide molecular weight distribution can be specially made to improve the post-processing of fiber woven fabrics. At the same time, slip agents and anti-sticking agents can be added to increase the requirements of convenient plastic bag products. Therefore, many specifications have been expanded, but the general physical properties are similar, and they are all substituted for each other except for unintentional main uses. Here, we try to classify different substrates for reference and explain them one by one.
1. homopolymer, called homopolymerization in Chinese mainland, is the raw material of pure propylene polymerization.
2. Impact copolymer is a single polymer containing ethylene-propylene rubber. Impact strength mainly depends on rubber content, and cold resistance mainly depends on ethylene content. Different raw material manufacturers have different processes, and the maximum ethylene content is also different.
3. Random copolymer is a random polymer formed by polymerization of propylene and ethylene, and ethylene is randomly dispersed in the polymer, mainly to reduce the crystallinity of the polymer and improve the transparency.
4. High crystallinity or high crystallinity reduces the content of dislocation structure in PP polymer and relatively increases the content of regular structure, which also increases the crystallinity. Mainly improve the rigidity, thermal denaturation temperature, surface hardness, scratch resistance and luster of raw materials. Of course, adding nucleating agent will also contribute to the improvement of the above physical properties.
5. Terpolymer is an extension of random polymer. Generally, propylene contains ethylene (non-EPR) as high as 3.5%, but it can be added to 5% in some processes. The higher the ethylene content, the softer the product, and the lower the thermal deformation temperature, softening point and heat sealing temperature. Sometimes, in order to increase the ethylene content, butadiene or other third component will be used as trimer to meet the above physical requirements.
6. A high proportion of plastic raw materials with different alloy grades can be described as alloy grades. For example, adding LDPE to PP can improve softness and impact strength, reduce necking in processing, increase flatness and reduce blanking in molding. PP plus EPR plus HDPE can maintain rigidity, reduce whitening caused by high EPR content and improve impact strength.
7. Mixing different materials together is called composite material. For example, glass fiber, various inorganic mineral powders, organic wood powder, paper scraps or grain fragments are added to PP materials to improve various physical properties. Mineral powder also includes talcum powder, calcium carbonate, barium sulfate, mica, carbon black, carbon fiber and bromide.
8. Rubber rubber, TPR (thermoplastic rubber) and TPE (thermoplastic elastomer) are sometimes difficult to distinguish, but there are various definitions. Most rubber can be mixed with PP, except EPR series, it is difficult to define whether the mixing is in alloy or composite. Generally, the rubbers that are often mixed with PP are EPR and EPDM, and the brands that are suitable for direct mixing with PP are CATALLOY, PLASTOMER, ENGAGE, TAFMER, KRATON and SANTOPLENE.
9. Special specifications not covered in the above categories can be classified into this category. For example, high melt strength raw materials (HMS) can be used in foaming materials, which can improve the surface air tightness and foaming effect, and can also reduce the blanking phenomenon in sheet forming.