Degradation mechanism and mechanical properties of PVC in PVC‐PE melt blends: Effects of molecular architecture, content, and MFI of PE

Abstract

Thermal degradation mechanism and mechanical properties of poly(vinyl chloride) (PVC) in PVC-polyethylene (PE) mixtures with varying types, contents, and melt flow indexes of the PE were studied. The degradation behavior was investigated in terms of decomposition temperature and glass transition temperature, polyene index, and morphology of the PVC in the mix. The results suggested that adding small amounts of PE (5 phr) in PVC-PE mixtures could thermally stabilize the PVC, as noted by an increase in its decomposition temperature. At higher PE loading, the PVC encountered more degradation as a result of a consumption of the heat stabilizer by PE radicals and the dehydrochlorination reaction. A radical transfer reaction was proposed to explain the degradation mechanism of the PVC in the PVC-PE melt, specifically a progressive increase of the glass transition temperature of the PVC in the mix as a result of increasing PE content. The PVC-PE blend using HDPE with high MFI exhibited more pronounced thermal and structural changes of PVC. The mechanical properties of the PVC-PE blend were very much dependent on the PE content, but slightly affected by the type and MFI value of the PE. The dispersion level of the PE in the PVC phase was found to play an important role in affecting the mechanical properties of the PVC-PE mixtures.

Mechanical, morphological, and thermal properties of poly(vinyl chloride)/low‐density polyethylene composites filled with date palm leaf fiber

“…The second step probably associated with the thermal degradation of the LDPE by scission of bonds along the long chain, producing shorter‐chain LDPE and more degradation of PVC, followed by the formation of long conjugated double bonds or polyene sequences. This is in line with the mechanism of macro‐radical generation and the macro‐radical cross‐recombination of PVC and LDPE proposed by Thongpin et al and Sombatsompop et al .…”

“…It is obvious that the tensile strength, elongation at break, and modulus vary noticeably and attain the optimum values (9.53 MPa, 86%, 193 N/cm 2 ), respectively, at about 80 wt% of LDPE. Thongpin et al [30] studied PVC/PE mixtures with different contents of PE which the contents of PE in PVC were varied from 0 to 30 wt% of PVC resin and suggested that as the PE was increased, the mechanical characteristics of PVC-PE mixtures progressively deteriorated due to the thermodynamic incompatibility, but our experimental results indicate that mechanical properties of the blend improved significantly by increasing the LDPE content to values above 50 wt% in accordance with Bataille et al [31] who studied a PE/PVC mixture for which the loadings of PE were varied from 0 to 100 wt%. The matrix with LDPE (80 wt%) content showed a significant improvement in the mechanical properties, this improvement can be attributed to the good adhesion between LDPE and PVC, this results was further confirmed by SEM micrographs (see below).…”

Study on lanthanum-pentaerythritol alkoxide as a thermal stabilizer for rigid polyvinyl chloride

“…Polyvinyl chloride (PVC) is one of the most popular plastic materials in the world because of its diverse properties and low cost [1,2]. However, at the processing temperature, unstabilized PVC releases gaseous hydrochloric acid (HCl), which gives rise to the formation of conjugate double bonds or polyene sequences -(-CH5CH-) n -, thereby causing a color change [3,4]. The color of PVC changes rapidly from white to yellow to brown to black [5].…”

A comprehensive review of the polyolefin composites and their properties

“…Thongpin et al. [ 65 ] explored the mechanical properties and melt flow indexes (MFI) of different content PVC-PE composites. By investigating the structure and thermal degradation of the composites, it has been recorded that the addendum of PE led to higher thermal stability for the neat PVC and raised the PVC decomposition temperature.…”