Phase structure of polyvinyl chloride (PVC) and PVC/polymer blends

Abstract

Commercial PVC is considered as a largely amorphous glassy polymer containing a small fraction of crystalline (ordered) structure. Based on the unique strength of plasticized PVC the presence of a three dimensional network of crystallites is generally accepted. The crystallites consist of a small number of syndiotactically ordered monomer units. The exact size, order and amount of crystallites in PVC is still an open question. The morphology of 'as polymerized" PVCis characterized by free-flowing grains (about lOO,um) containing aggregates of primary particles (about 1 ,um). The existence of subprimary particles are often claimed but the evidence is still controversial. A remaining microheterogeneity after plasticizing with diallylphtalate or ethylene-vinylacetate copolymer with 63 wt-% vinylacetate is, however, indicating the presence of unplasticized nodules or crystallites.The phase structure of PVC blends with acrylo-nitrile-butadiene rubber (NBR), ethylene-vinylacetate copolymer (EVA) and chlorinated polyethylene (CPE) have been elucidated with special reference to the formation of a network structure. The phase structure is shown to depend on compatibility, method of blending and processing temperature at mechanical blending. Thus at increasing compatibility i.e. by increasing the content of acrylonitrile, vinylacetate and chlorine in NBR, EVA and CPE, respectively, the phase inversion of PVC to rubber as continuous phase, is shifted from about 15 to about 2% content of rubber. Increasing the mechanical processing temperature from below to above the critical temperature of primary particle fusion shifts the phase inversion to higher rubber contents (about 30% for non-compatible rubber). At solution blending the inversion is shifted to still higher rubber contents (about 50%). The phase structure of blends with ABS-type of polymers are briefly reported and the possibility of network structure formation is discussed. Finally, blends with crystallizable polymers like polycaprolactone (PCL) and Hytrel (a thermoplastic poyester-ether rubber) are reviewed. The amorphous segments of these polymers are compatible with PVC. PHASE STRUCTURE OF PVCIntroduction PVC has been produced and processed in large volumes for a long time on account of its versatile properties in relation to its low price. Nevertheless, the polymer is still considered "difficult" and its basic properties to a large extent unexplored (1). These problems can be discussed in terms of structure on a molecular,intermolecular and supermolecular level.

Styrene-co-acrylonitrile resin modifications of PVC/CPE blends

“…can form a continuous network embedding Figure 4 contains SEM photographs of impact sections of PVC/CPE and PVC/CPE/AS blends. the primary particles of PVC when the amount of impact modifiers and processing conditions are The root whiskers on the impact section of the PVC/CPE blend are fewer and shorter than that proper, [5][6][7] on the impact section of PVC/CPE/AS blend; the obvious increase of impact strength (see Fig. 3), which shows that AS promotes the brittle-ductile former mainly shows a brittle feature and the latter a typical ductile feature.…”

“…7 Its melt plasticizing and flow behaviors are relative to both processing conditions and additive materials, and these will further affect their physical and mechanical properties. Figure 6 shows that the PVC/CPE blend itself cannot plasticize well without plasticizers, but AS can accelerate the plasticizing of the PVC/CPE the toughening effect cannot be obtained or is low compatibility among the components.…”

Why ferroelectric polyvinylidene fluoride is special

“…Polyvinyl chloride (PVC), forms a polar all-trans molecular structure of the form -CH 2 -CHCl-CH 2 -CClH-where the chlorine atoms alternate left and right. It doesn't crystallize well, and appears to have a nonpolar structure when it does [64]. PVC is readily stretched and poled to make an electret with good piezoelectric and pyroelectric properties [10,65], more so with plasticizer added [66].…”

Chitosan withPVC Polymer for Biomedical Applications: A Bibliometric Analysis

“…CS is a polysaccharide gotten from chitin; chitin is the second most bountiful polysaccharide on the planet, after cellulose [7]. The presence of amino gatherings in the CS structure may be protonated-giving solvency in weakened acidic watery arrangements, a few amazing properties of chitosan offered novel occasions to the advancement of biomedical applications [8], [9]. CS is biocompatible, biodegradable and non-poisonous, so it tends to be utilized as clinical applications as antimicrobial and wound mending biomaterials [10].…”