Synthesis and Characterization of Acrylic Based Pressure Sensitive Adhesives Reinforced by Organically Modified Montmorillonite.

Abstract

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Acrylic based pressure sensitive adhesives (PSA) were synthesized by changing the m onom er combinations and introducing hydroxyethyl acrylate (HEA) as a functional monomer. The im pact o f nano-fillers on mechanical properties o f the said adhesive was analyzed by incorporating different dosages o f m odified and unm odified grades o f montmorillonite. M onom er m ixture o f nbutylacrylate (BA), 2-ethylhexyl acrylate (2-EHA), Hydroxyethyl acrylate (HEA) and M ethacrylic acid (M AA) m onom er m ixtures w ere used to disperse the nano-clay. M echanical blending technique was used to disperse the nano-clay w ith the synthesized adhesives. Adhesive synthesized using the com bination o f BA /2EH A exhibit remarkable improved properties for tack and peel strength. However, shear strength o f synthesized adhesives was not up to the standard level. Adhesion perform ance o f w ater based PSAs m ainly depend on m onom er composition. Percentage o f HEA present in the adhesive was increased and the shear strength o f the adhesive samples increases accordingly. W hen w e consider the shear strength o f the adhesive series having nano-clay, all the adhesives displayed better im provem ent o f shear strength w ith the increase o f M M T and OM M T percentages. However, tack and peel values have gradually decreased. Adhesive with M M T showed better shear strength com pared to adhesives containing OM M T as a nano-filler. The optimized adhesion properties were obtained in the range o f 0.1 to 0.25% composition o f nano-clay. A t this range all three properties (peel, shear and tack) o f the adhesive w ere w ell balanced. IR data confirm the desired synthetic products. T g values obtained from DSC thermo grams are in the range o f -48 °C to -55 °C and therefore all the adhesives are soft polymers. Generally, soft polym ers are highly tacky in nature, w hen it is elastic and flexible. A ll the adhesive samples have only one Tg w hich indicate that all the adhesives are random copolymers.