Structural aspects of suspension poly(vinyl chloride): Influence of temperature on the macro‐ and microstructure

Abstract

The structural aspects of rigid suspension poly(vinyl chloride), PVC, have been investigated on the basis of two independent series of suspension PVC samples, polymerized at temperatures between 26 and 84°C. The reproducibility of the suspension polymerization process and the importance of the polymerization temperature with respect to the macro‐ and microstructure is demonstrated. Quantitative examination of the grain structure by small angle neutron scattering, Brunauer‐Emmett‐Teller absorption technique, and mercury porosimetry clarifies the gradual increase of the specific surface on lowering the polymerization temperature. A detailed WAXS study shows an increasing degree of crystallinity on lowering the polymerization temperature, which can be associated with the corresponding increase of the syndiotacticity. Furthermore, the presence of a polymerization history in the PVC powders with respect to the crystallinity is evidenced. This effect seems to be related to chain mobility restrictions during the polymerization process and is determined by the difference between the polymerization temperature and the glass‐transition temperature (Tg) of rigid PVC. This so‐called Tg effect is indicative of the fact that no appreciable swelling of PVC by its monomer occurs. © 1994 John Wiley & Sons, Inc.

Structural aspects of suspension poly(vinyl chloride). Small-angle neutron scattering of rigid and plasticized suspension PVC

“…The high scattering intensity at low Q-values originates from the presence of some residual porosity in the compressionmolded sample. 14 The intensity of the interference maximum is relatively low considering the degree of crystallinity (5-20%) and the scattering contrast of a simple crystalline/amorphous morphology. The existence of a very wide distribution of crystalline order in commercial PVC14-16 is most probably on the basis of the poor scattering contrast.…”

PVC Manufacture Technology

“…Pore diameter (Figure 2.7) 16 and porosity (Figure 2.8) 18 of particles decrease with conversion and/or polymerization time increasing. Similar is the case of specific surface area (Figure 2.9), which also decreases with conversion.…”

“…Increase in polymerization time under particular conditions increases monomer conversion ( Figure 2.13). 18 Increase in polymerization temperatures causes an almost linear decrease in the (Figure 2.14). 21 Monomer conversion has smaller influence on molecular weight than the polymerization temperature (Figure 2.15).…”

Analytical Methods

“…• determination of structural defects, [190][191][192][193][194][195][196][197][198] • high-field proton NMR is considered to be the only reliable technique of determination of internal and terminal double bonds in PVC, 193 • determination of stereochemical microstructure, [199][200][201][202][203][204][205] • 13 C NMR measurement of tacticity, [207][208][209][210][211][212] • 1 H NMR measurement of tacticity, 213 • good correlation between chemical shift and configurational sequence distribution, 214 • branch structure, 215,216 • branch length and chain branching (peak assignment of partially reduced PVC), 217 • study of PVC crystallinity by solid state deuterium NMR, 218,219 • configuration of PVC in crystallites, 220 • model studies of PVC degradation, 221 • Diels-Alder reaction studies, 222 • effect of microstructure on nucleophilic substitution, 202,223 • determination of stability of conjugated bonds in air, 224 • PVC modification by reaction with thiols, 225,226 • studies of structural changes caused by UV degradation, 217 • mechanism of phosphite action by 31 P NMR, 221 • studies of tin stabilizers by 1 H and 13 C NMR, …”