Study On Preparation And Properties Of Polyimide/Polysiloxane Composite Particles

Polyimide has very excellent heat resistance, wear resistance, resistance to radiation, chemical resistance, good electric insulation, toughness, but also with high gas permeability. It has been widely used in aviation, aerospace, electrical and electronic, locomotive cars, precision machinery and automated office machinery, and other fields due to the superior performance. It's curing temperature is too high and difficult to molding. Polyimide powder, may act as a material modification additive, which has broad application prospects.This paper used crosslinking polysiloxane and alkyl modified polysiloxane as hydrophobic component, tow corresponding polyimide polysiloxane hydrophobic compound particle were preparated by compound with polyamic acid respectively. The particles have good hydrophobicity and high thermal decomposition temperature, and with good prospects, can be used for material modification additives, blending with other materials to improve their surface hydrophobicity and their thermal resistance and so on.4, 4'-oxydianiline diamine(ODA) and pyromellitic dianhydride (PMDA) as monomer, N, N-dimethyl formamide(DMF) as solvent, crosslinking polysiloxane and alkyl modified polysiloxane as the hydrophobic components, dipping in distilled water to remove the solvent after the reaction completed, the polyimide/crosslinking polysiloxane composite particles and polyimide/alkyl modified polysiloxane composite particles were preparated after cyclicing at high-temperature. Infrared spectra show that the two polysiloxane have a good composite with polyimide. Two composite particles both have good thermal resistance and hydrophobicity. The hydrophobicity of the former is growing with the content of crosslinking polysiloxane increasing, it is very good on the hydrophobicity in the latter when the content is extremely litter, the increasing of the amount have little impact on the hydrophobicity. Both the panicle size mainly distribution in 1-50μm.Amino polysiloxane substituted ODA partially and reacte with PMDA, Polyimide polysiloxanes particle was obtained, the panicles have good hydrophobicity.ODA and PMDA as monomer, toluene and acetone as mixture solvent, alkyl modified polysiloxane as hydrophobic component, evaporate the solvent after the reaction completed(the solvent is reused), polyimide/alkyl modified polysiloxane composite microparticle was preparated after cyclicing at high-temperature. Infrared spectra indicate that polyimide have a good composite with alkyl modified polysiloxane. The particles is spherical and the size distribution is uniform, mainly in 1-10μm. The particles have excellent hydrophobicity, its hydrophobic degree reached 100% when the alkyl modified polysiloxane content is 5%; the particles have high thermal decomposition temperature and good heat resistance. The particles blend with the epoxy, the hydrophobicity, hardness, heat resistance have certainly improved. The tensile strength of the epoxy is decreasing with the composite particles' content increasing. The impact strength is lower than the pure epoxy, when composite particles content of 10%, with alkyl modified polysiloxane content increase, impact strength is increasing.