A molecular simulation analysis of influence of lignosulphonate addition on properties of modified 2-ethyl hexyl acrylate/methyl methacrylate/acrylic acid based pressure sensitive adhesive

A novel PSA formulation that incorporates a bio-sourced lignosulphonate has been proposed. A molecular dynamics simulation study is attempted to explore the effect of lignosulphonate addition on the adhesion, thermal and mechanical properties of a conventionally used acrylic PSA composed of 2-EHA, MMA and AA. A good agreement of conventional PSA density and glass transition temperature, T-g, with literature estimates confirmed the accuracy of the molecular simulations. It is observed that there is an increase in PSA-substrate interaction energy with an increase in lignosulphonate content despite an increase in T-g due to its addition. This is proposed to be primarily due to an increase in polar groups contributed by lignosulphonate. The availability of more polar groups in bulk and increased density of these groups due to significant migration to interface results in an increase in interfacial energy, and hence, improved PSA adhesion. The shear modulus is observed to increase with increase in lignosulphonate content indicating its effectiveness to resist PSA shear deformation. Simulations suggest that in order to form an industrially useful adhesive, that may work well under RT conditions possessing an optimum cohesive strength and surface adhesion, a PSA formulation with similar to 15 wt.% lignosulphonate may be used.