Study On The Synthesis And Properties Of Moisture-curable Polyurethane Hot Melt Adhesives Modified With Silane Coupler

Moisture-curable polyurethane hot-melt adhesive (PUR) has excellent early adhesion properties and the high end intensity sticky. Because of its solvent-free, no VOCs emissions, environmental compliance, it is developing rapidly. In China, the level of PUR both in theory and technology and equipment of products is lower than that of developed countries. The demand of high-performance PUR is strong in the domestic market, Therefore the application of PUR needs urgent study.The paper contained three parts mainly. In the first part, we researched synthesis technics of reaction between polymer polyols of PBA,PPG and MDI; The relationship between the structure and properties of PUR was studied by infrared (IR), Differential thermal analysis (DSC); Then the factors of influence on the mechanical properties, softening point, melt viscosity and the adhesion properties of PUR were researched; At last the influence to performances such as softening point, melt viscosity, adhesion strength of PUR modified with tackifier, EVA resin and minicrystal wax were discussed. The results showed that the synthesis of PUR should be controlled at 90±5℃and the reaction time was 2.5～3.5 hours; DSC indicated the more content of PBA, the higher the crystallinity of PUR, and the mechanical properties and bonding strength become higher quickly, then become smaller slowly as the increasing of crystallinity of PUR. When the mole ratio of NCO/OH was 2.2 and the mole ratio of PBA/PPG was between 8/2～4/6, PUR had lower melt viscosity, suitable softening point and better adhesion strength. The addition of tackifying resin could improve early adhesion strength and melting fluidity of PUR. Minicrystal wax could reduce melt viscosity, but it had bad compatibility with PUR and so induced the final cohesive strength.In the second part, the moisture-curing behavior of PUR was systematically investigated. The crystallinity of PUR was observed by X diffraction, the influences of humidity and temperature on the crosslinkage of PUR were discussed. The effects of the degree of humidity and the rate of moisture penetrative on the curing rate of PUR with different crystallinity were also discussed. The relationship between cured depth and adhesion strength was researched too. The results showed that the degree of humidity had no influence on the crosslinkage of PUR, and as temperature was raised, the crosslinkage is higher. The crystallinity of PUR had great influences on the cured time and the rate of moisture penetrative. The higher crystallinity of PUR, the lower moisture curing rate and the higher humidity induced the faster curing rate of PUR. The adhesion strength of PUR was increasing gradually as the increasing of cured degree.In the third part, the one component PUR modified with silane coupler (SPUR) was researched by solution polymerization. The synthesis technics of SPUR was studied firstly, the reaction Process between silane coupler and NCO was observed by IR too. The influences to the melt viscosity and mechanics performance of SPUR with silane coupler were studied, the relationships between surface contact angle and adhesion of SPUR were also researched, the TGA of SPUR was studied at last. The results showed that the reaction between silane coupler and NCO was quick, so the reaction should be under the condition of temperature 40℃and the silane coupler should be dropped into the toluene liquor of PUR. The yield of termination of silane coupler was higher, mechanics performance was better, and the melt viscosity of SPUR was higher. When the yield of termination was among15％～20％, SPUR has the highest surface contact angle, the bonding strength was better for its good soakage. A spot of silane coupler has no influence on the TG of SPUR.