Abstract
Polyvinyl acetate emulsion adhesive has been widely used due to its good bonding performance and environmentally friendly properties. Indeed, the bonding performance can be further improved by copolymerizing with other monomers. In this study, the effect of the adjunction of redox initiator (hydrogen peroxide–tartaric acid, H2O2–TA) on the properties of the poly (vinyl acetate-butyl acrylate) (P (VAc–BA)) emulsion adhesive was investigated. With increasing dosage, the reaction became more complete and the obtained film was more compact, as identified via SEM. The core-shell structure of the emulsion particles was confirmed via TEM. Results indicate that while the initiator content increased from 0.5 to 1.0%, a clearer core-shell structure was obtained and the bonding strength of the plywood improved from 2.34 to 2.97 MPa. With the further incorporation of H2O2–TA (i.e., 1.5%), the bonding performance deteriorated. The optimum wood bonding strength (2.97 MPa) of the prepared P (VAc-BA) emulsion adhesive was even better than that (2.55 MPa) of a commercial PVAc emulsion adhesive, suggesting its potential application for the wood industry.
Highlights
With improvements in living standards, further application of green products is advocated, which certainly includes adhesives
The wood-adhesive industry is currently dominated by petrochemical-derived resins, such as urea formaldehyde (UF), phenol formaldehyde (PF), and melamine urea formaldehyde (MUF) [1,2,3], which are all harmful due to the presence of formaldehyde
Owing to the fascinating properties of polyvinyl alcohol (PVA), it was used as a protective colloid to provide the initial stage of the emulsion polymerization and could be grafted by other monomers [5]
Summary
With improvements in living standards, further application of green products is advocated, which certainly includes adhesives. VAc and BA are copolymerized with a chain transfer reaction initialized via hydrogen abstraction at the BA backbone tertiary C-H bonds by the highly-reactive VAc-ended chain radicals [15]. Due to their excellent mechanical properties and water resistance, VAc–BA copolymers can be used as interior glues, exterior architectural coatings, and adhesives for the aqueous phase [16,17,18]. H2 O2 –TA was applied as an initiator to form the “core-shell” structure of emulsions via semi-continuous seed emulsion polymerization with the hydrophilic monomer VAc and hydrophobic monomer BA [20]. The emulsion particle surface could be modified by tuning the ratio of VAc to BA monomers
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