Polypropylene (PP) is the lightest general-purpose plastic. Due to its excellent comprehensive performance and low production cost, it is widely used in household appliances, packaging, chemical and automotive industries. Its output ranks second in general-purpose plastics; Low temperature impact resistance, easy aging, and poor antistatic, weathering and dyeing properties, so the material industry and industry are very concerned about the modification of polypropylene.
Xiao Bian briefly introduces several common modification methods of polypropylene, and hopes to communicate with peers and help each other.
1. Polypropylene / Inorganic Nanocomposites
Rigidity and toughness are two important indicators for examining the properties of plastics. How to make plastics have good rigidity and toughness at the same time is the goal that people have been pursuing. Inorganic nano-example modification is one of the ways to solve this contradiction.
The inorganic nanoparticle-filled modified polymer has more excellent mechanical properties than the large-diameter filler-modified polymer. In order to disperse the inorganic nanoparticles as uniformly as possible in the polymer matrix, it is necessary to surface-modify the inorganic nanoparticles, and the surface-modified inorganic nanoparticles can improve the bonding strength of the interface layer with the matrix resin, and fully exert the rigid inorganic The enhanced toughening effect of particles on the polymer.
Taking nano-scale calcium carbonate as an example, nano-calcium carbonate can simultaneously enhance toughening, and the toughening effect is better than micron-sized calcium carbonate. At the same time, it is found that the morphology of nano-CaCO3 is different, and the mechanical properties of the composite are also very different. The cubic nanometer calcium carbonate is beneficial to improve the impact properties of the composite material, while the fibrous nano calcium carbonate can significantly improve the tensile properties of the material, and the nano calcium carbonate can significantly refine the PP spherulites.
Second, polypropylene microcellular foam material
When the polypropylene material is modified by microcellular foaming, its strength is not lowered, which is interesting because the material contains a pore size much smaller than the original defect or fine crack, because of the existence of such a pore diameter, The tip of the original crack in the plastic is passivated without reducing the strength of the plastic.
The microcellular foamed material has high toughness, long fatigue life, high specific strength, high thermal stability, and low dielectric constant. In addition, it is characterized by light weight, heat insulation, shock absorption, sound insulation and low price. Therefore, microporous expanded polypropylene has been strongly developed in the fields of automobiles, aerospace, and various other transportation vehicles.
Third, nucleating agent modified polypropylene material
PP is a general-purpose plastic that is not completely crystallized. Its crystallization rate is slow, and it is easy to form larger spherulites, resulting in poor gloss and transparent modification of the product. The appearance of the product lacks aesthetics, which limits its transparency in transparent packaging. Applications in fields such as daily necessities.
The use of a nucleating agent to modify polypropylene is a simple and effective method for preparing a polypropylene material having high transparency and excellent mechanical properties, and thus is widely used in the modification of polypropylene.
PP transparent nucleating agents are currently common in talc, silica, mica, aryl phosphates, etc. Generally speaking, the addition amount is not more than 0.8%. The effect is better. The specific application should be analyzed according to the site conditions.
Fourth, long glass fiber reinforced polypropylene material
Long glass fiber reinforced polypropylene composite is one of the fastest growing plastics in the thermoplastics market, especially in automotive plastics. In order to better enhance the fiber, the fiber length in plastic is greater than Lc, both critical length, Lc value is directly related to the type of plastic. If the length of the fiber is less than Lc, the reinforcing effect is not much different from that of a general powder filler. For example, in glass-reinforced PP, the critical length of glass fiber is 3.1 mm, while in another chemically modified PP, Lc may fall below 0.9 mm. For ordinary short-wave fiber reinforced plastics, the fiber length in the product is generally only 0.2 to 0.6 mm, which limits the performance of the finished product. In the long glass fiber reinforced plastic parts, the residual length of the glass fiber can reach more than 3 mm, which greatly improves the physical and mechanical properties of the product.
Due to the long fiber residual length in long glass fiber reinforced thermoplastic products, its impact strength is about 4 times higher than that of ordinary fiber reinforced materials; the specific strength (17.2%) is higher than that of aluminum materials (9.8%). In addition, the processing fluidity of the material is good, the appearance of the product is bright, there is no pit and other defects, and the molding shrinkage rate of the product is also small.
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