Modification of poly(vinyl chloride). X. Crosslinking of poly(vinyl chloride) with a soft segment of an elastomer containing thiol groups

Abstract

AbstractTo obtain poly(vinyl chloride) (PVC) of excellent toughness, a new method of crosslinking PVC is proposed in which PVC is crosslinked with the soft segment in an elastomer such as liquid Thiokol. The reaction can be accomplished by immersing PVC–Thiokol blends in liquid ammonia at 20–30°C. A similar reaction occurs in aqueous ammonia when hexamethylphosphoramide is used as an activator. Characteristics of the crosslinked PVC thus obtained and of the controls of a similar uncrosslinked composition (PVC–Thiokol LP‐8, 100:5 by weight) were as follows: tensile strength, 7.3 and 4.8 kg/mm2; elongation at break, 30 and 2.5%; Young's modulus, 3.5 × 104 and 2.9 × 104 kg/cm2; tensile impact, 88 and 15 kg‐cm/cm3, respectively. The crosslinked PVC as plasticized with dioctyl phthalate (DOP) and the control blend (PVC–Thiokol LP‐8–DOP, 100:10:10 by weight), respectively, showed tensile strengths of 5.9 and 4.8 kg/mm2, elongations at break of 44 and 24%, Young's moduli of 2.5 × 104 and 1.6 × 104 kg/cm2, and tensile impact strengths of 62 and 120 kg‐cm/cm3. As the crosslinkage through the soft segments increases up to about 5%, the elongation at break, Young's modulus, and tensile impact, in addition to the tensile strength, are improved. This is different from the results so far observed with the crosslinked amorphous polymers and is characteristic of the products of crosslinking through the soft segment. The experimental results are discussed in this paper.