Study On The Preparation And Properties Of Core-shell Polyacrylic Pressure-sensitive Adhesives

Recent environmental policy concerns pushing many industries to develop pressure-sensitive adhesives (PSAs) prepared by emulsion polymerization. The nature of theparticles can influence on the adhesive properties of PSAs, and the control of particlecomposition or structure is particularly important. The special composition of thecopolymers has been achieved through semi-batch emulsion polymerization traditionallycarried out under starved conditions. On this study, we used n-butyl acrylate (n-BA),methyl methacrylate (MMA), allyl methacrylate (ALMA) as core monomers, and n-butylacrylate, methyl methacrylate and acrylic acid (AA) as shell monomers to prepare twokinds of polyacrylic latexes: P(MMA-co-ALMA)/P(BA-co-AA) multi-shell gradientcopolymers and PBA/P(BA-co-MMA-co-AA) multi-shell gradient copolymers. And thenwe used power feed monomer addition method to prepare P(MMA-co-ALMA)/P(BA-co-AA) continuous gradient copolymers. The overall and instantaneous monomer conversion,solid content and coalescence content were determined by gravimetric analysis, whichindicated that the latexes were prepared at a solid content of50wt%with high conversionand low coalescence content. Dynamic light scattering (DLS) was used to monitor theparticle diameters and proved that no new nucleation occurred during the growth stage.The adhesive properties, such as loop tack, peel force, and shear resistance, weremeasured according to the FINAT test methods No.9,1and8. The relationship betweenpressure-sensitive properties and the structures was evaluated. The results showed that thedifferent particle composition influenced the shear resistance greatly, while the tack andpeel force changed a little.For P(MMA-co-ALMA)/P(BA-co-AA) continuous gradient copolymers, weresearched the effect of gel content, soluble molecular weight and glass transitiontemperature (Tg) on the adhesive properties. It was shown that PSAs prepared using thepositive gradient power feed had the highest gel content and strongest core-shell interaction.So it had the highest shear resistance, and the lowest tack and peel force. Compared withother PSAs, they greatly increased the shear resistance while the tack and peel forcedecreased slightly.