Development Of Novel Water-based High Performance Pressure-sensitive Adhesive Of SBAS Via RAFT Emulsion Polymerization

It has been nearly two decades since the breakthrough of controlled/living radical polymerization(CLRP).However,the large-scale industrial application of CLRP has not been realized yet.This thesis focused on the preparation of a new kind of water-based high performance pressure-sensitive adhesive(PSA)via reversible addition-fragmentation chain transfer(RAFT)emulsion polymerization.A series of latex of homopolymer of butyl acrylate(PnBA)and styrene-butyl acrylate-styrene triblock copolymer(SBAS)were synthesized by design as the basic components of the water-based PSA.The formulation of the water-based PSA was developed.The relationship between structure and properties was also studied in detail,as well as the relationship between viscoelasticity and properties of the PSA.The followings were the main achievements:1.The basic formulation of the water-based PSA was developed.A series of homopolymer PnBA and triblock copolymer SBAS were synthesized via RAFT emulsion polymerization as the basic components of the water-based PSA.By mixing SBAS and PnBA,well-balanced cohesion and adhesion could be achieved.With the help of 0.12 wt%wetting agent surfynol 104E,3 wt%ethanol and 3 wt%glycol,a latex film with good adhesive properties could be formed under room temperature.2.The relationship between structure and properties was studied in detail.Loop tack was mainly affected by the mobility of polymeric chains.When the molecular weight of PnBA homopolymer decreased or its PDI became narrower,the molecular weight of SBAS increased,or the weight fraction of PnBA increased in the formulation,loop tack increased.Shear time,which mainly reflected the cohesive strength of an adhesive,always showed an opposite changing trend to loop tack.Peel strength was affected by both loop tack and shear time.Once cohesion was high enough,the increase in loop tack would increase peel strength.A mixture of SBAS latex with 20.0 wt%rosin emulsion also showed excellent adhesive performance.3.The relationship between viscoelasticity and properties of a PSA was studied.The introduction of PnBA latex or rosin emulsion into SBAS led to decrease in storage modulus.Accordingly,loop tack of the PSA increased in agreement with the theoretical prediction.However,in the ases of using PnBA with different molecular weight,the storage modulus of PSA was not correlated with the loop tack,conflicting with the well accepted theory.4.The adhesive performance of a PSA could be finely tuned to tailor-make high performance PSA according to its applied fields via adjusting the compositions in a formulation.For example,the triblock copolymer SBAS could be used as an excellent protecting film for it could not be peeled off for about one month in a shearing test.Half-half blends of triblock copolymer SBAS and homopolymer PnBA,showed 50%higher peel strength and 170%higher shear time,compared with a typical commercial permanent PSA.The PSA of mixing the triblock copolymer SBAS with 20.0 wt%rosin emulsion showed 70%higher loop tack and 130%higher shear time than those of a typical commercial permanent PSA.