Investigation of the effects of nonisothermal suspension polymerization of vinyl chloride on resin properties

Abstract

Molecular and morphological properties of suspension poly(vinyl chloride) produced by nonisothermal polymerization was experimentally investigated in a pilot-scale reactor. Although molecular weight and polydispersity index of the nonisothermally produced poly(vinyl chloride) is almost the same as the equivalent isothermal polymerization, there are differences in morphological characteristics. The cold plasticizer absorption of the resin produced nonisothermally is greater than that of the equivalent isothermal product. Scanning electron microscopy showed that nonisothermally produced particles are more regularly shaped, with a smoother surface, and had greater porosity compared with the product of isothermal polymerization reaction. Applying temperature trajectory produces particles with slightly wider particle size distribution relative to the particles produced isothermally. The evolution of particles with conversion is characterized by processing images obtained by scanning electron microscope. Applying a variable temperature trajectory accelerates the formation of a three-dimensional skeleton of primary particles relative to the isothermally produced particles. J. VINYL ADDIT. TECHNOL., 23:267-274, 2017.

Agitating transformation during vinyl chloride suspension polymerization: aggregation morphology and PVC properties

“…The mean size of the primary particles (Sauter mean diameter D32) was measured using the method reported by Darvishi. 5 2.3.4 Porosity and bulk density (BD). The porosity of the sample grains was characterized by cold plasticizer absorption.…”

“…When the conversion reached about 27%, the aggregation of the primary particles formed a three-dimensional network structure in the droplets, which prevented the primary particles from continuously growing. 5 The aggregation of primary particles was gradually hindered, and the size of the primary particles slowly increased until the reaction reached a conversion of about 60% (the motionless point). At the conversion of motionless point, the droplets were occupied by primary particles and the VCM lled in the interstitial spaces among the primary particles.…”

“…Poly(vinyl chloride) (PVC) is one of the four general plastic materials and widely applied in many elds. 1 Almost 80% of PVC is produced via suspension polymerization (S-PVC), [2][3][4][5][6][7][8] which offers many advantages including production of pure material and easy control of the reaction heat loss. The essential feature of suspension polymerization is the bulk polymerization of a large number of small droplets dispersed in aqueous media.…”

The influence of two‐stage variable temperature suspension polymerization on polyvinyl chloride resin: The molecular chain segment structure and thermal stability

“…Although structural defects in PVC chain caused by side reactions in early stage of VCM suspension polymerization has been known in many years, more attention has been paid to the influence of temperature on polymerization kinetics. The programmed temperature curve was designed from high to low or with a large temperature range, which could generate more structural defects in chain segments and a wider molecular weight distribution . The present study designed a simple two‐stage rising temperature polymerization process based on the actual industrial production, specifically those exhibiting a minimal change in the molecular weight and molecular weight distribution.…”

A Review on Enhanced Productivity Approachesin VCM Suspension Polymerization

“…This process uses mechanical agitation in conjunction with suspending agents to disperse the monomer in water as a continuous phase. The initiator dissolves in the monomer droplets and decompsed after adjusting the temperature, resulting in initiating free radical polymerization in the droplets [2]. Typically, The reaction takes place at a constant temperature.…”