Classification and Application of PP Modified Materials
PP modified material, as its name implies, is based on PP raw materials to improve its performance and other aspects, such as strengthening the impact resistance, tensile strength, flexibility of PP materials, etc. Following is a brief introduction of the modification of PP plastic raw materials can be divided into several categories:
Chemical Modification of PP
1. Copolymerization Modification
Copolymerization is an important means of chemical modification. In addition to the copolymerization of propylene and ethylene monomers, propylene can also copolymerize with vinyl chloride, acrylic acid and other monomers. It can also be grafted onto the main chain of PP with polymer segments with completely different chemical structure from the main chain, which is called graft copolymerization.
2. Grafting modification
PP is a non-polar polymer. PP can be polarized by grafting modification, so as to improve the adhesion, finishing and ink printing of PP. After grafting, it can be used as the bonding layer and hot melt adhesive of extruded composite film, and also as compatibilizer of PP and various polar polymers such as PA. Grafting elastic segments onto PP molecular chains can improve the impact strength and low temperature properties of PP. If appropriate polar groups were grafted, the bonding properties of PP could be improved.
The crosslinking methods of PP include chemical crosslinking and radiation crosslinking. But for PP, the degradation of radiation cross-linking is also very serious, so the effect of radiation cross-linking is limited, so chemical cross-linking is generally used. The mechanical properties and heat resistance of PP can be improved by crosslinking.
1. Filling Modification
Filling modification is to add relatively inexpensive non-metallic mineral powder materials or other materials to plastics, which can reduce the cost of raw materials of products, and improve some properties of plastics materials, such as rigidity, hardness and heat resistance. The commonly used non-ore powder materials are calcium carbonate, talc powder, mica powder, kaolin, wollastonite powder, aluminium hydroxide, magnesium hydroxide or brucite powder, precipitated barium sulfate or barite powder, etc.
The distribution and dispersion of fillers in polypropylene matrix are also found in filling modification. At the same time, the surface of filler particles should be properly treated to have good affinity with non-polar polypropylene molecules. The selection of surface treatment method and treatment agent is the key to the success of filling modification.
It is called blending modification that mechanical method is used to add other polymers into the polymer which has been produced and make its performance change.
In blending modification, the compatibility of different polymers must be paid attention to. When two polymers with poor compatibility are blended, the third component, which has good compatibility with both polymers, is often needed to be added, which is called compatibilizer. In blending modification, it should be noted that only when incomplete compatible multiphase system is formed and two polymers can be evenly dispersed, the desired modification effect can be achieved.
3. Reinforcing Modified PP
Fibrous materials added to plastics can significantly improve the strength of plastic materials, so it is called reinforcing modification. Material with large diameter-thickness ratio can significantly improve the flexural modulus (rigidity) of plastic materials, which can also be called reinforcing modification.
Glass fiber is the main reinforcing material, which can significantly improve the tensile strength of PP plastics. As glass fiber reinforced PP can improve mechanical strength and heat resistance, and its water vapor resistance, chemical corrosion resistance and creep resistance are very good, it can be used as engineering plastics in many occasions, such as fan blades, heater grids, impeller pumps, lampshades, electric furnaces and heater shell, etc.
4. Nano-modified PP
In recent years, with the surface treatment technology of filler particles, especially the development and application of ultrafine filler particles, the filling modification of polymers has changed from the simplest incremental reinforcement to toughening and strengthening; from the simple emphasis on improving mechanical properties to the development of functional composites. Compared with traditional PP blends, nano-PP composites have better rigidity and good low-temperature impact properties.
