Abstract

Adhesives containing microcapsules filled with active resin materials are considered intelligent and promising systems. In this work, dual-component polyurethane/urea-formaldehyde (PU/UF) microcapsules comprising 2-ethyl hexyl acrylate monomer (EHA) and benzoyl peroxide (BPO)-filled gelatin-gum-Arabic/polyurea-formaldehyde (Gel-GA/PUF) microcapsules were synthesized. PU/UF-microcapsules containing EHA were made in an oil-in-water emulsion via in-situ and interfacial polymerizations at 1000 and 1200 rpm agitation speeds and with core-to-shell ratios of 75:25 and 85:15. The Gel-GA/PUF microcapsules were prepared in the presence of a mixture of sodium dodecyl sulfate and polyvinyl alcohol (SDS/PVA), or polyethylene maleic anhydride (EMA) at stirring rates of 500 and 700 rpm with core-to-shell ratios of 55:45 and 65:35 via consecutive complex coacervation and in-situ polymerization. The results showed that the BPO-filled Gel-GA/PUF-microcapsules synthesized at stirring speeds of 1000 and 1200 rpm were spherical with no inter-adherence and with an average diameter (dm) of 135 and 94 µm, respectively. Similarly, EHA-filled PU/UF-microcapsules synthesized in the presence of SDS/PVA at stirring speeds of 500 and 700 rpm formed free-flow powders consisting of spherical particles with a dm of 242 and 165 µm, respectively. Furthermore, adhesive formulations containing neat and microencapsulated EHA with 2.0 wt% BPO showed the best shear strength of 2.23 MPa and 1.95 MPa, respectively. These results reveal the efficacy of the EHA and BPO filled dual-component microcapsules in a capsular adhesive formulation.

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