Wollastonite powder, as an inorganic needle shaped silicate mineral, mainly plays a role as a reinforcing filler in plastic composite materials. Its unique needle like structure and excellent physical and chemical properties enable it to significantly enhance the mechanical strength, thermal stability, dimensional stability, and processability of composite materials.
Specific manifestations of enhancing effect
-Improvement of mechanical properties: The addition of wollastonite powder can significantly enhance the tensile strength, flexural strength, and flexural modulus of the plastic matrix. For example, adding 30% wollastonite to polyamide (PA6) significantly enhances both bending strength and bending modulus, while tensile strength also increases with increasing content. This enhancement effect originates from the needle like morphology of wollastonite forming a network structure in the matrix, effectively transmitting stress and limiting the movement of polymer chains.-Improvement of thermal performance: The addition of wollastonite can significantly increase the thermal deformation temperature of composite materials. The increase in the hot deformation temperature of PA6/wollastonite composite material from 105 ℃ to 177 ℃ enhances its potential for application in high-temperature environments.
-Dimensional stability and processability optimization: Wollastonite can reduce the molding shrinkage rate of plastics (to 1-2%), reduce product warping and deformation, and improve processing flowability due to its low viscosity characteristics, making the molding process more stable.
-Durability and appearance improvement: The needle like structure endows the composite material with better scratch resistance and wear resistance, extending its service life. In addition, wollastonite can improve the surface glossiness of products and avoid problems such as exposed glass fibers.
The key role of surface modification in enhancing the effect
The compatibility between wollastonite powder and polymer matrix is poor, and direct addition can easily lead to uneven dispersion. Therefore, surface modification is a prerequisite for fully exerting its reinforcing effect. Common modification methods include:-Coupling agent treatment: Silane coupling agents (such as silane SCA1113) form Si-O-Ca bonds through chemical adsorption, significantly enhancing the interfacial bonding strength. Under optimized conditions (such as a dosage of 0.8% and a temperature of 80 ℃), the tensile strength and thermal deformation temperature of PP/wollastonite or PA6/wollastonite composite materials can be significantly improved.
-Surface active agent modification: Low cost reagents such as stearic acid and polyethylene glycol can adjust the hydrophilicity and hydrophobicity of wollastonite. For example, when the amount of stearic acid is 1.5%, the tensile strength and bending strength of polypropylene composite material reach their optimal levels; Polyethylene glycol coating can improve low-temperature impact performance.
-Composite modification strategy: Combining coupling agents with surfactants (such as KH-550 and stearic acid composite), or introducing compatibilizers (such as maleic anhydride grafted polypropylene), can further optimize interfacial compatibility and balance the rigidity and toughness of the material.
Application advantages and precautions
The application of wollastonite powder can reduce the production cost of plastic products while avoiding performance degradation caused by water absorption, especially suitable for precision injection molded products such as lamps and heat-resistant parts. However, it should be noted that the modification process parameters (such as temperature, time, and modifier dosage) have an impact on the final performance. For example, excessive temperature during dry modification may damage the structure of the coupling agent.By selecting appropriate modifiers and processes, wollastonite powder can achieve efficient reinforcement in plastic composite materials, meeting the requirements of high-performance engineering plastics.