The effect of phosphorus containing polyamide Mg(OH)2 nanocomposite coating on the thermal stability of PVC

Polyvinylchloride (PVC) as a thermoplastic polymer has been known for many industry usages such as food packing, biomedical, piping [1] and many other applications. Chemical resistance, low cost and high processability can be mentioned as outstanding advantages of PVC [2]. The presence of chlorine in PVC made it flame retardant polymer, but one of the most important PVC disadvantages were known as low thermal stability. This instability would be because of releasing HCl and dehydrochlorination process which will cause convert to unsaturated polyolefin [3].Investigates have shown there some methods for improving thermal stability of PVC such as making blending, adding thermal stable additives e.g. nitrogen rich additives and phosphorus additives, adding organo-modified nano material and dip coating.In dip coating process, coating layer can be consisting of polyamides due to their special properties such as thermal stability [4].In this work, for increase thermal stability and combustion resistance, the surface of the thin PVC film was modified with phosphorous based polyamide coating and its related Mg(OH)2 nanocomposite coatings. For this purpose, a new phosphorous based aromatic polyamide as organic coating was synthesized by direct polycondensation reaction. On the other hand, phosphorous based dicarboxylic acid was used for surface modification of Mg(OH)2 nanoparticles . ATR-IR and EDX from surface of PVC coated films with phosphorous based polyamide and corresponding nanocomposites as well as FE-SEM micrograph from cross section of coated PVC films indicated that surface modification via phosphorous based polyamide and organo-modified Mg(OH)2 nanocomposites coating was successfully occurred. Thermal properties of PVC coated films have been improved compared to the neat PVC. Furthermore, it is interesting to mention that, incorporation of 10 mass% of organo-modified nanoparticle into the polyamide coating solution led to enhanced significantly char residue and two main degradation temperatures of PVC. By microscale combustion calorimeter (MCC) results found that PVC film coated with phosphorous based polyamide containing 10 mass% of organo-modified nanoparticles, exhibited synergistic effect to decrease peak heat release rate (pHRR), the total heat release (THR) and the heat release capacity (HRC) compared to the neat PVC. From tensile test studies, it was concluded that the phosphorous nanocomposite coating had good effect on increasing the tensile strength and Young s modulus of PVC film. The most effects of polymer nano composite coating in the tensile test parameters observed in 5 mass% of organo-modified nanoparticles. All of these results revealed that the phosphorous based polyamide coating along with organically surface modified Mg(OH)2 nanoparticles have been a good candidate for protecting of PVC against thermal degradation and this materials have been able to improve the combustion resistance properties.

کلیدواژه ها:

PVC ، organic coating ، Polyamide ، nanocomposite ، Mg(OH)2 nanoparticles ، thermal stability