Improving the bond strength of a new polyvinyl chloride (PVC)-based adhesive

Polyvinyl chloride (PVC) is among the three polymers with the largest production worldwide. Its main use is in pipes to transport liquid waste and water, hence the need to improve the adhesives to join them. This work relates to a new polyvinyl chloride (PVC) adhesive, its composition, and its preparation. The adhesive composition comprises: PVC resin (Inovyn 375MD, Inovyn 373ND, Ecolvin A74 or Formolon KVH), methyl ethyl ketone as fixed solvent, one co-solvent (cyclohexanone, tetrahydrofuran or 1,2-dichloroethane) and a filler (MgO, CaCO3, Na2CO3 or NaHCO3). PVC resins must be the main component of an adhesive; thus, the resulting bond will have the same properties as the pipe itself. The shear stress using 1,2-dichloroethane exceeds cyclohexanone by 28.15%, and the lowest values were obtained with tetrahydrofuran. If resin concentration is less than 15%, it generates adhesives with few functional groups available to anchor to PVC substrates, and concentrations greater than 15% produce viscous adhesives, preventing surface impregnation and decreasing adhesion. Unfilled adhesives generate the best adhesion, exceeding by 31.44% the shear stress of adhesives containing 5% CaCO3 as a filler, but the importance of the filler lies in the reduction of the economic cost. The adhesive synthesized with 15% of the Inovyn 373ND resin, dissolved in 25% methyl ethyl ketone and 60% of 1,2-dichloroethane, without filler, presented the highest bond strength.