Additional Studies on the Softening of Rigid PVC by Aqueous Solutions of Organic Solvents

This study examined whether an aqueous solution that contained 18 organic chemicals that are either solvents or good swelling agents of PVC are able to cause softening when combined in a solution, with each solute at an activity of 0.05. This activity was selected because there is no evidence that an individual organic solute with an activity of 0.05 can soften PVC. However, we found that this combined test solution rapidly softened PVC. We also examined whether organic chemicals that are either solvents or good softening agents of PVC and are also totally miscible in water are able to soften PVC when mixed with water. Four chemicals (tetrahydrofuran, acetone, dimethylformamide and pyridine) were tested in a study that ran for 20 weeks. Tetrahydrofuran, a PVC solvent, caused a significant change in the hardness readings of samples exposed to concentrations as low as 0.01% (w/v). Acetone, a good swelling agent of PVC, caused a significant change in the hardness readings of samples exposed to a 10% concentration but not a 5% concentration. Dimethylformamide, a poorer swelling agent of PVC, did not cause any measurable signs of softening at concentrations below 60%. The lowest concentration of pyridine tested (20%) was found to have a significant effect on the hardness readings. A preliminary short-term study (seven days) showed that n-butylamine was intermediate between pyridine and dimethylformamide in its ability to soften