The compatibility of the blends of PUs with PVC and the adhesion behavior of PU to PVC

Three series of polyurethane adhesives—polyethyleneadipateurethane (PEAU), polybuthyleneadipateurethane (PBAU), and polyhexyleneadipateurethane (PHAU)—with the same MW and hard/soft segment ratio, based on the three polyesters polyethyleneadipate (PEA), polybuthyleneadipate (PBA), polyhexyleneadipate (PHA), with 4,4′‐diphnylmethane diisocyanate (MDI), and butendiol were synthesized by solution polymerization. The crystallinity of these polyesters and polyurethanes (PUs) and the compatibility of blends of PUs with PVC were studied by means of wide‐angle x‐ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic thermomechanical analysis (DMA), testing of solubility, and phase contrast microscopy. The results indicated that PBAU/PVC and PHAU/PVC were compatible systems, but PEAU/PVC was incompatible. The adhesive strengths of the three adhesives were quite different from one another, in the order of PBAU ≥ PHAU ≫ PEAU. The influences of crystallinity and compatibility on adhesion were discussed, and the Diffusion Theory for PU‐PVC systems was recommended.