Continuous dosing of fast initiator during vinyl chloride suspension polymerization: Thermal stability of PVC resin

Abstract

Thermal stability of poly(vinyl chloride) (PVC) produced using continuous dosages of a fast initiator method was investigated in terms of morphological and microstructural characteristics. The results were compared with the properties of the PVC prepared by conventional polymerization method. The Brabender V R Plastograph and DSC results showed a lower fusion time, higher stable time, and greater degree of fusion for PVC obtained by polymerization using initiator continuous dosage method. Also, chemical analysis indicated that the PVC produced under an initiator continuous dosage system have lower structural defects, that is, branch numbers, internal double bonds, labile chlorine, and tacticity index, thereby improving the thermal stability of PVC resin. The results obtained from dehydrochlorination and thermogravimetry analysis confirm the improvement of thermal stability of PVC chains synthesized with continuous dosages of a fast initiator. Moreover, it was found that the concentration of microstructural defects and the dehydrochlorination rates of the PVC samples prepared by both processes increase with monomer conversion, particularly after critical conversion. V C 2016 Wiley Periodicals, Inc. J.Appl. Polym. Sci. 2017, 134, 44480.

The Effects of Initiators Mixture on Suspension Polymerization of Vinyl Chloride and its Comparison with other Productivity-Enhancing Procedures

“…Comparison of our results with the data provided by Bijanmanesh et al [13] show that the continues fast initiator dosage system provide the most rapid formation of three-dimensional network of the primary particles and the lowest CoV. The higher the initiation rate, the smaller the primary particle size and the earlier the aggregation take place, thereby resulting in more uniform size distribution of smaller primary particles.…”

“…Bijanmanesh et al [13] reported that continuous dosing of a fast initiator during suspension polymerization of vinyl chloride enhanced productivity by 40%. According to the results reported here, it seems that the best approach to reduce the polymerization time of a typical VCM suspension polymerization is continuous dosage of a fast initiator.…”

“…An appropriate temperature trajectory which can adjust the final MW to the predefined value produces only less than half as much average reaction rate as possible maximum reaction rate (corresponding to maximum cooling capacity of the reactor) [15][16][17].This is while the averge reaction rate can reach up to 80% as much as possible maximum reaction rate using continous dosage of fast initiator [13]. The Cok process represents the second most significant strategy for enhancing the productivity of VCM suspention polymerization.…”

“…For the first time, Akzo Nobel Company (Netherlands) suggested the process of fast initiator dosage system to enhance the productivity. Recently, Bijanmanesh et al [13], have applied continuous dosage of a fast initiator during polymerization reaction and had success in reduceing time reaction by 40%.…”

“…Polymer phase is changed from the aggregation of the precipitated macro-radicals to nano-domains and then domain and finally to a three-dimensional network of primary particles which are surrounded in a rigid skin. The process variables such as polymerization temperature, the type and concentration of initiator and the method of initiator addition have been found to have a significant influence on the internal structures and molecular characteristics of PVC resin [1,[8][9][10][11][12][13][14]. In other word, the final characteristics of final PVC is influenced by the conditions governed by the strategy implemented to enhanced productivity.…”