| Hot melt adhesive is a kind of solid material at room temperature, it will melt into a kindof sticky liquid when heated to a certain temperature, and it will turned into a solid materialwhen cooled to room temperature, and it has strong adhesive property.One-component moisturecuring polyurethane adhesive does not contain water and solvent, its solid content is100%, soit is a kind of high performance and environmentally friendly adhesive.Comparing with ordinary hot melt adhesive, reactive one-component polyurethane hotmelt adhesive not only has excellent comprehensive performance of ordinary hot meltadhesive, such as no solvent, high initial adhesion, fast positioning speed, but also it has itsown good properties,such as good water resistant, heat resistant and cold resistant and so on.Its bonding process is simple and it will obtain good adhesive properties in short time.Thesizing temperature of one-component moisture-curing polyurethane adhesives is about80-120℃，it is lower than that of normal hot melt adhesive (150-180℃).Therefore,it ispreferred by modern automated assembly industryThe main material of the moisture curing polyurethane hot melt adhesive is polymercontaining isocyanate group,which made by polyester or polyether polyols and diisocyanate.The polyurethane hot melt adhesive will melt when heated to a certain temperature, then theisocyanate group in the polyurethane hot melt adhesive will react with water in the air orsubstances containing active hydrogen.Polyurethane hot melt adhesive can provide good initial adhesive strength and betterbonding strength. PET box adhesive has the following requirements:(1) the positioning speedis fast, it can satisfy the assembly line of the assembly process.(2)good transparency andultraviolet radiation resistance, invariant color.(3) high peel strength.In this paper,the fellowing experiments were studied:(1)In order to ensure transparencyand ultraviolet resistance, the main raw materials of synthesis of polyurethane prepolymerswere studied,and the light stabilizer was added to improve its yellowresistance.(2) in order tomeet the needs of assembly line fast positioning,the thermoplastic resin was added, anditsoptimum content was obtained by the dynamic thermodynamic analysis.(3) The effects ofthe type and content of the catalyst，isocyanate index (R) andresidual isocyanate groupcontenton the properties of the polyurethane hot melt adhesive were also studied and the optimumcontents were obtained.(4) The effect of latent wet curing agent on the curing time andmechanical properties of the film was studied, and its optimum content was got..Through a large number of experiments, one-component moisture-curing polyurethane hot melt adhesive was finally synthesized,and it could meet the market’s requirement. |
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