Design,Preparation And Performance Research Of Thermal Viscosity Reducing Pressure Sensitive Adhesives

With the development of the information industry,semiconductor components and electronic components have become smaller and thinner,and it is very easy to cause damage for these electronic components during processing and transportation.Pressure sensitive adhesive can temporarily fix and protect these electronic components.As a pressure sensitive adhesive with adjustable peel strength,the pressure sensitive adhesive can be easily removed after processing without damaging the electronic components.the viscosity reduction pressure sensitive adhesive has become a subject with great industrial value.Among them,thermal viscosity reduction pressure sensitive adhesive has advantages of wide application range,simple operation method,high safety,which has become the focus of the research.In this paper,through the method of doping long chain polyacrylate or liquid crystal polymer in UV curing pressure-sensitive adhesive matrix,preparation of heat reducing pressure sensitive adhesives.First,using isooctyl acrylate(EHA),butyl acrylate(BA),stearyl acrylate(SA)and acrylic acid(AA)as comonomers,high molecular weight and low glass transition temperature polyacrylates were synthesized by solution radical polymerization,combine it with other photocurable monomers to form photocurable pressure-sensitive adhesive matrix.Secondly,the thermotropic liquid crystal monomer with acrylate double bond was designed and synthesized,and the thermotropic liquid crystal polymer was prepared by the method of solution radical polymerization,and the liquid crystal monomer structure and the thermotropic phase transition of the liquid crystal polymers were characterized.Liquid crystal polymer as a hightemperature viscosity reduction functional component was added to the pressure sensitive adhesive matrix to construct a thermal viscosity reduction photocurable pressure sensitive adhesive system.The effect of the amount of liquid crystal polymer on the initial adhesion,holding adhesion,and peel strength of the pressure-sensitive adhesive system at different temperatures was explored.When the liquid crystal polymer content in the pressure sensitive adhesive is 20%,the peel strength at 20°C is 9.89 N/25 mm,the peel strength at80°C is 0.56 N/25 mm,the peel strength drop ratio is 94.3%,and its thermal viscosity reduction performance is the best.Finally,a series of long chain polyacrylates with different molecular weights and different melting points,including poly(hexadecyl acrylate),poly(octadecyl acrylate)and poly(behenyl acrylate),were synthesized through solution radical polymerization.The effect of initiator concentration on molecular weight,polydispersity coefficient and melting point of long chain polyacrylate was studied.Because these three long chain polyacrylates melt upon heating to appropriate temperature,its melting temperature is around 35°C,47°C,and 60°C,respectively.They can be added to the pressure sensitive adhesive matrix as high-temperature viscosity reduction functional components to construct different response temperature thermal viscosity reduction photocuring pressure sensitive adhesive systems.The effect of the molecular weight and content of long chain polyacrylates,the content of photoactive monomers on the initial adhesion,holding adhesion and peel strength at different temperatures of the prepared pressure-sensitive adhesive were explored.When the molecular weight of poly(octadecyl acrylate)in the pressure sensitive adhesive is 71,000,the content is 20%,and the ratio of acrylate copolymer: reactive diluent is 4:6,the peel strength at 20°C is 6.95 N/25 mm,and the peel strength at 60°C is 0.81 N/25 mm,the peel strength drop ratio is88.3%.As a thermal viscosity reduction pressure sensitive adhesive system,its comprehensive performance is the best.