Poly(vinyl chloride), Part II: Effect of polymerization temperature and molecular weight on the glass transition and melting point of poly(vinyl chloride)

Abstract

A detailed study was made of the thermal behavior of poly(vinyl chloride) (PVC) homopolymers, whose chain length and structure were independently manipulated. Normal PVC polymerizations are made at temperatures, the selection of which determines the polymer chain length. In the case of PVC, this choice of temperature also determines its syndiotacticity, and so, its glass transition temperature, and in many ways, its processibility. The ability to understand how to control chain structure and length in PVC is critical in designing polymers for selected specific end use conditions. The thermal spectrum is known to be one measure of how polymers will perform. This study reveals how such controlled chain length/structure PVCs are characterized by thermal methods, and how one can separate individually the effects of syndiotacticity and molecular weight on thermal properties of poly(vinyl chloride).

Poly(Vinyl chloride) processing morphology part II—molecular effects on processing in the torque rheometer

“…Also, it has been reported that the melting point (Tm) of PVC is strongly affected by syndiotacticity (crystallinity) and to some extent by molecular weight ofthe polymer (7). The higher the crystallinity and molecular weight, the higher is the Tm.…”

“…It is expected that the molecular weight and crystallinity of the polymer should have a pronounced effect on its processing characteristics. Indications of this effect were given by Daniels (7), Fordham (8), Reding (9), and Collins (10).…”

Utilizing Hybrid Plasmon Modes to Probe Nanoparticle-Polymer Interfaces

“…A polymer with different functional groups may have stronger or weaker inter-molecular interactions, which drastically changes properties such as melting point, melt viscosity and glass transition temperature. 52,[54][55][56] The arrangement of these pendant groups can also play a role in the final properties of the polymer. The tacticity of the polymer describes the relative stereochemistry of the chiral centers on the polymer backbone.…”

“…Thus, compounds such as PVC which have a large dipole due to the Cl-C bond will have a higher than expected Tg due to the stronger interactions reducing free movement. PVC has a bulk glass transition reported between 80-90 °C, 65,66 whereas, polyethylene has a Tg reported between -125 to 35 C, 67 with the variability being due to the challenges in controlling crystallinity. Side groups, or more often called pendant groups, raise the bulkiness of the polymer which reduces the free movement and increases the Tg.…”

“…An example of this is the phenyl group on polystyrene, which raises the bulk Tg to ~100 °C. 55,56,68 Another effect is the tacticity of the pendant groups if all the polymer chains are syndiotactic or isotactic the Tg will change depending on the nature of the pendant group. 69,70 Cross linking polymer chains also reduces the free rotation in a molecule which in effect reduces the free mobility of the polymer chains, increasing the Tg.…”