Isotropic polypropylene composition with low linear expansion coefficient and preparation method thereof

Abstract

The invention discloses an isotropic polypropylene composition with low linear expansion coefficient and a preparation method thereof, and belongs to the field of modified plastics. The isotropic polypropylene composition with low linear expansion coefficient, provided by the invention, is prepared from the following components by mass percent: 20-98% of polypropylene, 2-20% of crystal whiskers, 0-30% of mineral powder, 0-20% of a flexibilizer, 0-5% of a compatilizer and 0-5% of other auxiliary agents, wherein the crystal whiskers adopt three-dimensional tetrapod-like structures and are isotropic, and the length-diameter ratio of each crystal whisker in single direction can reach 50 above. According to the polypropylene composition, the linear expansion coefficients of the polypropylene composition in the transverse and longitudinal directions can reach 4.0*10<-5> below by virtue of the added crystal whiskers, and the purpose of isotropy can be achieved. The polypropylene composition prepared through the method can be applied to inner and outer decorative parts of automobiles.

Description

technical field [0001] The invention belongs to the field of modified plastics, and in particular relates to an isotropic low linear expansion coefficient polypropylene (PP) composition and a preparation method thereof. Background technique [0002] Polypropylene has become one of the most important general-purpose plastics because of its excellent comprehensive properties, wide range of sources, light weight and low price, and easy molding and processing. It is also the fastest-used plastic variety in recent years. The development and application of modified PP materials in automobiles has always been the focus of the automobile industry and the plastics industry. However, ordinary polypropylene has a large linear expansion coefficient. When it is used as a material such as a bumper, it will be deformed in a long-term alternating state of cold and heat, so it must be guaranteed to have an extremely low linear expansion coefficient. The reduction of the linear expansion coe...

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Problems solved by technology

However, ordinary polypropylene has a large linear expansion coefficient. When it is used as a bumper and other materials, it will be deformed in a long-term alternating state of cold and heat. Therefore, it must be guaranteed to have an extremely low linear expansion coefficient.

The reduction of the linear expansion coefficient of polypropylene materials for automobile bumpers is usually solved by adding talc powder, but to achieve a low linear expansion coefficient, a large amount of talc powder needs to be added, which will cause a sharp increase in the density of the material and a decrease in toughness

In recent years, some scientific and technological workers have also done a lot of work on how to reduce the linear expansion coefficient, such as adding wollastonite to reduce the linear expansion coefficient. The addition of wollastonite does greatly reduce the linear expansion coefficient in the flow direction. However, due to the large aspect ratio of wollastonite, the linear expansion coefficient of wollastonite-filled polypropylene material is very different in the transverse direction and longitudinal direction, which is easy to cause deformation such as warping of the material, which is not a very good reduction method. Fillers with coefficient of linear expansion

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