Preparation Of Special Polyurethane Pouring Sealant

With the rapid development of electronic industry, pouring materials are put higher requirements to meet high-performance for electronic components. Polyurethane material has excellent water resistance, oil resistance, low temperature performance, vibration absorption, electrical insulation, anti-fungal, and adjusTablele mechanical properties, so they are widely used in the field of electronic pouring sealants.Electronic components may receive vibration, shock and high pressure during using process. So pouring sealant materials were need well properties, high strength, flexibility, high volume resistance and low friction when it suffer external force.In this paper, the mechanical properties, electrical insulation properties, dynamic mechanical properties, pouring technology for polyurethane pouring sealants were researched. The influence of polyol type, isocyanate type, isocyanate index, isocyanate content for products properties were discussed. Double pre-polymerization technology was put to greatly improve pouring properties. The reaction process was characterized by FI-IR and molecular weight of B component after reaction was measured by gel permeation chromatography (GPC).Polyurethane was synthesized by traditional pre-polymer technology. The experiment results showed that:the type of polyol was 80% polytetra methylene glycol (PTMG) and 20% polyester (PYZ) as polyurethane elastomer soft segment, then reacted with totylene diisocyanate (TDI) to prepare pre polymer with 6.5% NCO amount. Pre polymer reacted with methylene bis ortho chloroaniline (MOCA) in NCO index of 1.1, then heated in vacuum and cured. The polyurethane pouring sealant products were formed. The mechanical properties, electrical insulation properties, dynamic mechanical properties and aging properties were researched. The tensile strength, elongation at break, tear strength, surface resistance, volume resistance, internal friction peak high and ageing properties were 56 MPa, 581%,120 KN/cm,7.4×1012Ω·cm,4.8×1013Ω·cm, tanδ=0.224 and 28 years at room temperature.Double pre-polymerization synthesis technology was researched. Polyurethane pre polymer (A component) terminated with NCO was synthesized by PTMG and TDI. PTMG reacted with TDI first and then added PTMG as terminated. After then add curing agent-methylene bis ortho chloroaniline (MOCA). It was as B component.The two components were mixed in NCO index of 1.1 Polyurethane pouring sealant products were formed after heated in vacuum and cured.The properties of polyurethane pouring sealants were listed. The tensile strength, elongation at break, drawing time and tack-free time, respectively, were 42MPa,600%,50min and 2h. Compared to conventional pre-polymerization synthesis technology, the properties of double pre-polymerization were improved.