Preparation And Properties Of Polyacrylate Pressure-Sensitive Adhesives By UV Initiation

UV technology is widely used in coatings,adhesives,inks and other fields due to its high initiation efficiency,easy operation at room temperature,environmental-friendly,and low investment costs.UV technology is divided into two stages: UV initiation and UV curing.Most researchers only stay at the UV curing stage,but less research on the preparation of prepolymer via UV initiation.Moreover,the prepolymer is usually prepared by solution polymerization.Therefore,this paper presents a simple,environmentally friendly method for preparation of polyacrylate pressure-sensitive adhesives.Firstly,the prepolymer of polyacrylate PSAs is synthesized by bulk polymerization via UV initiation.Then,UV curing is performed to obtain a solvent-free,environmentally-friendly polyacrylate pressuresensitive adhesives.Polyacrylate pressure-sensitive adhesives were prepared based on butyl acrylate(BA),2-hydroxyethyl acrylate(HEA),and acrylic acid(AA).The effects of experimental factors in the two stages of UV initiation and UV curing on the photo-polymerization rate and adhesive properties were investigated firstly.Among them,the factors that affected the photopolymerization rate mainly included the initiation activity of photoinitiator,the concentration of photoinitiator,monomer structure,light intensity,and the method of antioxidation inhibition.The factors that affected the adhesive properties of the pressuresensitive adhesives were the composition structure(the ratio of soft and hard monomers,the content of functional monomers,the type and contents of cross-linking agents)and curing process conditions(curing time,coating film thickness).In order to improve the residues of pressure-sensitive adhesives,two different methods of chemical crosslinking were introduced via 1,6-hexanediol diacrylate(HDDA)photocrosslinker and difunctional diisocyanate(KL-1202)thermal-crosslinker.The molecular structure of PSAs was characterized by FTIR;Gel content in the crosslinked portion was examined by Soxhlet extraction;soluble molecular weight of PSAs was characterized by gel permeation chromatography(GPC);the viscoelastic properties of polymer films were determined by dynamic mechanical analysis(DMA).Finally,the influence of the contents of crosslinker on the adhesive properties was investigated from the micro-molecular structure and viscoelastic behavior of acrylic PSAs.Through above studies,it was determined that the ratio of soft and hard monomers BA:AA was 92:8,the content of HEA was 10wt%,the photoinitiator TPO content was 0.2wt%,the viscosity of prepolymer was 1200 m Pa.s and its solid content is about 29.83wt%.The total amount of photoinitiator added in the UV curing stage was 2wt%(TPO:1173 =1:1),the content of active amine was 1wt%,the curing time was 20 s,and the coating film thickness was 100μm.In addition,the effect of addition of 1,6-hexanediol diacrylate(HDDA)photocrosslinking agent to form an interpenetrating network structure was smaller than the addition of a difunctional diisocyanate(KL-1202)thermal crosslinker to form an intermolecular crosslinking structure on the decreasing of the loop tack force and the peel force of PSAs.However,the latter was more obvious in improving the shear resistance of PSAs.