Novel acrylic/nanocellulose microsphere with improved adhesive properties

A synthesis of acrylic microsphere pressure sensitive adhesives with addition of nanocellulose filler is presented. In the first stage α cellulose was modified by acid hydrolysis and the produced nanocellulose suspension was added into the continuous phase of a suspension polymerization reaction mixture. The amount of nanocellulose varied in range from 0 wt% (reference synthesis) to 5 wt% calculated on monomer amount. The first part of the study was assigned to the characterization of the synthesized adhesive suspension. Particle sizes and particle size distributions were measured. Then, adhesives were coated via a transfer coating process and adhesive properties were evaluated. Additionally, polymer glass transition temperatures were determined and due to significant differences in measured adhesive properties, adhesive viscoelastic properties were examined using dynamic mechanical analysis (DMA). Results showed that it's possible to use nanocellulose as a nanofiller in microsphere adhesives. Suspensions were stable, mean particle sizes decreased with increasing nanocellulose content mainly due to a higher continuous phase viscosity. Adhesive properties testing revealed non typical behavior for the nanocomposite microsphere PSA material. All three measured adhesive properties increased with increasing nanocellulose content. A synergistic effect of lower particle sizes along with hydrogen bonding exhibited an increase in adhesive properties. DMA analysis showed that the storage modulus (G') increased with increasing amount of added nanocellulose. At the same time a decrease in maximal tan δ values was observed which concurred with improved cohesivity, hence higher shear strength.