Preparation And Properties Of Silica / Acrylate Pressure-sensitive Adhesive Composites

Acrylic polymers with high molecular weight and low glass-transition temperature are widely designed as pressure-sensitive adhesives (PSAs). By providing its excellent adhered property, balance elastic-viscosity performance and chemical stability, acrylics is widely used into pressure sensitive adhesive or PSAs tape application with low toxic and relative low manufacturing cost. Commercially main monomers used for this purpose are ethyl, butyl acrylates, acrylic acid and also hundreds of tailor made functional acrylate which gives designed property. The major research work focus on acrylate monomer ratio define, polymerization process optimization, chemical modification like polyurethane, epoxy or SBS, SIS graft copolymer or cross-linkage, tackifier modification and it thermodynamic miscibility selection. However, for its given chemical structure and limited process window at rheology stand point, some problems are associated with the performance of these softer grade acrylic PSAs with its poor cohesive strength and heat resistance limit. Therefore, it is necessary to reinforce the acrylic polymer matrix with keeping its adhesive performance.Meantime, polymer/inorganic nano-composites have attracted extensive research interests due to their unique properties. Rigid inorganic filler particles have been widely used to improve the physical properties of polymers for specific applications. In general, the addition of rigid inorganic filler particles into polymers leads to an increase in stiffness and thermal stability. They can even bring some special properties, which is different with the single material and conventional composites material. Nano-silica is one of the most commonly used inorganic components in organic/inorganic nano-composites, which has positive effect on heat resistance, mechanical properties, fluid control and so on.Based on above research background, we select common acrylic copolymer with solution polymerization and commercialized fumed silica as the components, try to make acrylic/nano silica composite material with basic mechanical dispersion. Rheology character and adhesion performance are checked after nano particle modification. The major work includes two aspects as below:(1) A series of acrylic terpolymers from 2-Ethylhexyl (2-EHA), Butyl Acrylate (BA) and Acrylic Acid (AA) were synthesized by solution polymerization with AIBN as initiator, and also charactered by DMA, GPC. Adhesion performance was indicated with standard continues peel strength, static shear and dynamic shear strength, relative effect of monomer ratio, reaction condition were investigated as the facts of adhesive mechanical property(2) Nano composite adhesives based on these acrylic polymers with commercialized fumed silica were prepared by solution blending techniques, respectively. The effect of nano particles on the performance of the hybrid adhesives was investigated by measuring peel strength, dynamic shear strength or static shear resistance against Stainless Steel (SUS304). The results showed significant improvement in peel strength of SUS joints with increase in polarity of the polymer matrix and nano filler concentration. Both the dynamic shear strength and static shear resistance of the hybrid nano composites also gradually increased with nano silica loading. As the comparison, hydrophobic silica has better dispersion ability and obvious improved adhesion performance with increased loading. The solution dispersion method is very simple for manufacture replication and the positive composite performance can be reference to further silica modified adhesive study with different hybrid method.