Study On The Preparation And Properties Of Water-Based Acrylic Pressure-Sensitive Adhesives

The preparation of three series of acrylic water-borne pressure-sensitive adhesives (PSAs) with structured particle morphologies was reported. The lattices were prepared with a solid content of 50% by two-stage sequential emulsion polymerization using the monomers, n-butyl acrylate (n-BA), methy methacrylate (MMA), acrylic acid (AA) and allyl methacrylate (ALMA). This process consisted of a batch seed stage giving a particle diameter of 110±3nm, which was then grown by the semi-continuous addition of monomer to a final particle diameter of 303±3nm. Photon correlation spectroscopy was used to monitor the particle diameters and showd that the particles had grown without the secondary nucleation.Adhesive properties were assessed by peel and tack adhesion and shear resistance testing. Peel adhesion values were measured as the force required to peel 25mm wide strips of adhesive at an angle of 180°from a stainless steel test plate at 300mm·min-1. Shear resistance values were measured as the time taken to complete failure of an overlap bond (25×25mm2 contact area) on a glass plate (held at 2o to the vertical) under a static shear force of 1kg.Emulsion polymerization was used to prepare three series of core/shell lateces: latex comprising of a rubbery seed polymer(PBA) and a rubbery shell polymer (P(BA-co-AA)), latex comprising of a rubbery seed polymer(PBA) and another rubbery shell polymer (P(BA-co-AA-co-MMA)) and latex comprising of a glassy seed polymer(P(MMA-co-ALMA)) and a rubbery shell polymer (PBA-co-AA). An increase in the level of chain transfer agent in the growth stage from 0.0 to 0.15% by weight to shell monomer caused the increase of tack force and peel strength, while the shear resistance decreases rapidly. The main part of the work consisted of an investigation of the structured polymer on adhesive properties. TEM and PCS measurements were used to monitor the latex particle sizes and its distribution, and showed the morphologies of the latexes. The core-shell structure was formed in the semi-continuous emulsion polymerization. For the latex with the hard core and soft shell, two Tg were measured by DMA.For (PBA) core and P(BA-co-AA) shell polymer, the effect of an increase in the level of CTA in shell layer was to increase the tack and peel force while decrease sheer resistance. For (PBA) core and P(BA-co-AA-co-MMA) shell polymer, the effect of an increase in the level of MMA in shell polymer was to increase sheer resistance dramaticly. And the effect of an increase in the level of PMMA core polymer over the range 5 to 50% was to decrease peel adhesion and for shear resistance to pass through a maximum.