In order to meet performance requirements of polypropylene (PP) for various applications, it must be modified based on original polypropylene resin. Property modification methods include chemical modification and physical modification. Chemical modification includes introduction of segment copolymerization modification and graft modification, physical modification mainly includes filling modification and blending modification. This article introduces polypropylene filling modification for first time, in hope of providing certain technical guidance for technicians.
1. The purpose of modifying filling of PP
Modification of PP filler consists in adding a certain amount of inorganic or organic fillers with a certain shape and particle size during processing. It has following advantages;
1) Improve physical and mechanical properties of base polypropylene material and increase temperature of thermal deformation;
2) Maintain dimensional stability of polypropylene products and reduce their shrinkage;
3) Reducing costs of enterprise and increasing competitiveness of products.
Second, classification of fillers
2.1 Inorganic filler
2.2 Organic filler
Adding a certain amount of fillers to PP can provide lower investment and faster results, but when adding fillers, it will also degrade some properties of PP and have a negative impact on some products. Therefore, in real work, according to complex characteristics of product, strong promotion method should be used. sides and avoiding weaknesses to make full use of role of fillers.
Thirdly, effect of talc on mechanical properties of polypropylene
According to proportion of each raw material in table, prepare 5kg of powder, use a twin screw pelletizing extruder, and then inject it into a standard sample with an injection molding machine to test performance.
Table 3.1 Table of raw material proportions
Among them, calcium stearate is a kind of medium strong base stearate, and polarity of calcium stearate is slightly higher than that of ordinary organic weak acid stearic acid. In addition, hydrogen bonds will form between stearic acid molecules, further weakening polarity of stearic acid. 1010 is main antioxidant of hindered phenol, and 168 is auxiliary antioxidant of phosphite. The main function of hindered phenol is to chemically react with oxidized free radicals generated by oxidation in main polypropylene material, interrupting growth of active chain of polypropylene. PP;168 The main function of PP is decomposition of highly active oxides in PP into low-active molecules by changing valency of the phosphorus atom in its own molecule.
Table 3.2. Physical and mechanical properties
It can be seen from comparative experiments that as amount of talc increases, tensile strength, flexural strength, and modulus of polypropylene tend to increase, while elongation and impact load decrease. This experiment aims to test effect of various talc additives on mechanical properties of polypropylene, and then use surface treatment agents (such as KH-550) to treat surface of powder in large-scale production, so as to improve relationship between powder and polypropylene base. Resin material compatibility can optionally improve mechanical properties of modified polypropylene.
Mineral-filled modified polypropylene has a relatively mature formula. When considering product characteristics, most technicians must also consider impact of manufacturing technology on product. Different mixing modes affect homogeneity of material. Various screws The combination differs in shear rate and material dispersion. Competitive products can only be produced if formula and process are perfectly matched.
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