The solvent used with PVC adhesives is Methyl Ethyl Ketone. It penetrates and softens plastomer raft coatings, allowing the adhesive to get a better grip. It also thins PVC glue, which is usually necessary so you can be sure that you apply the adhesive in thin enough layers. MEK is highly toxic, so use it only in a well-ventilated area, and wear protective gloves, since it’s absorbed through the skin.