Proper Addition of Silicone Powder to Improve Composite Tensile Strength
Silicone powder particles have a small particle size and act as heterophase nucleating agents for the resin matrix, forming many fine spherical crystals, which improves the crystalline state of the material and increases crystallinity, thereby enhancing the tensile strength (hardness) of the composite material.
After reaching the maximum tensile strength, if the amount of silicone powder is further increased, the tensile strength and elongation at break (toughness) of the composite material will decrease. With the continuous increase in silicone powder content, there will be varying degrees of agglomeration of the powder in the melt, leading to weak interfaces and poor stress transfer. Additionally, as the amount of silicone powder further increases, it constrains the movement of the base material’s molecular chains, introducing more microscopic defects into the material.
To further improve the performance of the composite, a certain amount of compatibilizer must be added to the composite. The compatibilizer increases the solubility of the base material and silicone powder. The compatibilizer helps to disperse the silicone powder more evenly within the base material, reducing filler agglomeration and improving the interface between the silicone powder and the base material, thus further increasing the tensile strength, but excessive amounts can cause a sharp decline. The increase in compatibilizer leads to an increase in the content of small molecules in the base material, which is detrimental to the enhancement of compatibility between the base material and the silicone powder, thus lowering the mechanical properties of the composite.
Due to the small particle size of silicone powder and its heterophase nucleating effect, it can reduce the cooling rate of the base material, improving the material’s thermal stability and degradation temperature to some extent, without altering the inherent degradation mechanism of the base material.
Flowability: Silicone can accelerate the fragmentation of the base material particles and crosslink into the molecular chains of the base material. Due to the flexibility of siloxane molecular bonds, friction between molecular chains is reduced, providing lubrication. However, with increased usage, the balance torque of the composite system increases, and the flowability of the system worsens. The severe agglomeration of silicone powder in the base material due to increased dosage results in uneven distribution and larger dispersed particle sizes, making the frictional lubrication effect less apparent and restricting the motion of molecular chains.
Since the masterbatch method ensures more uniform dispersion and reduces the agglomeration of silicone powder particles, the performance of composite products made using the masterbatch method is better.
