IR spectroscopy and X-ray diffraction analysis of industrial polyvinyl chloride suspension

In terms of the contemporary plastic industry, world production of polyvinyl chloride is second only to polyolefins. Recyclable by almost all known methods, polyvinyl chloride offers high strength, good insulating properties, as well as resistance to acids, oxidising agents and solvents. At the same time, the ability to process polyvinyl chloride into products is limited by its lack of stability at high melt viscosity temperatures, since hydrogen chloride released during its heating catalyses further process of polymer decomposition. Thus, due to the softening temperature of polyvinyl chloride being higher than its decomposition temperature, it cannot be processed in its pure form. Consequently, functional polyvinyl chloride-based materials tend to be composites. By varying the composition of mixtures, plastic masses characterised by either very soft (plastic compounds) or hard (vinyl plastics) structures can be obtained. The properties of polyvinyl chloride-based polymer products are largely determined by the structure and morphology of the polymer. In the present work, the properties of industrial suspension polyvinyl chloride (Sayanskkhimplast JSC, Irkutsk Oblast) were studied in detail for the first time. The molecular weight of the polymer determined by the viscometric method was 1.0 · 106. Thermogravimetric analysis showed that polyvinyl chloride mass loss started to occur at 160 °C. Following the complete IR band assignment of the polymer, the polyvinyl chloride under study was established to contain no foreign substances (impurities of stabilisers, emulsifiers and additives). The diffraction curve of the polymer was established to be qualitatively similar to equivalent partially crystalline polymers. Two amorphous halos were detected at 2θ of 24° 30′ and 39° 30′ below a group of crystalline peaks. The crystallinity degree of polyvinyl chloride was determined and mechanisms for the formation of its regular and irregular structure were proposed.

Features of some Polymer Building Materials Behavior at Heating

The problems of reducing combustibility and increasing fire resistance of some polymer building materials are considered. And the toxicity of the gaseous products of their thermal degradation was evaluated both individually and in various combinations with each other. The features of thermal degradation and the loss of mechanical properties under the influence of a flame of polymer building materials were studied. The following samples were used: water pipes based on polyethylene; Tarkett linoleum, Ondex roofing products, Rolvaplast PVC profile panels; structural panels of the company "Polygal"; facing tile based on phenol-formaldehyde oligomers. The processes occurring during pyrolysis and combustion are considered, the results of a study of the combustibility and mechanical properties of polymer building materials based on polyethylene, polyvinyl chloride, polycarbonate, phenol-formaldehyde and epoxy oligomers under the influence of a flame are presented. For the studied building polymer materials, the products of pyrolysis and combustion were studied; their ignition and self-ignition temperatures, and also the flame propagation velocity were measured. The data on the toxicity of the products of their combustion, both individually and under combined action, are summarized. Also, for the studied polymer building materials, the losses of heat resistance, toughness, and flexural strength under the influence of a flame were studied. Thermogravimetric analysis of Rolvaplast PVC panels and Poligal polycarbonate panels allowed us to determine the maximum temperatures and activation energies of the polymer decomposition process. It was concluded that if the material is recognized as non-combustible or slow-burning, it will not always be fire resistant, since its strength and thermal properties can sharply decrease already in the first seconds of flame exposure.

Preparation and Characterization of Alumina HDPE Composites

In this study, effects of two different types of porous alumina nanoparticles have been incorporated into high-density polyethylene (HDPE) to study their impact on the properties of the HDPE composite. The dispersion of fillers in the HDPE matrix was evaluated by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) integrated with Fourier transform infrared spectroscopy (FTIR) were applied to investigate the calorimetric behavior and thermal stability and to analyze the polymer decomposition, respectively. The dielectric properties were determined by a broadband dielectric spectroscopy. The effect of filler loading on the tensile properties and melt flow index was also examined. A homogenous distribution of the fillers was observed at low loading of alumina particles (below 5 wt. %). However, agglomerates of sub-micro size were formed extensively on samples with high loading of fillers (above 7 wt. %). A significant improvement of the thermo-oxidation stability of the composite was observed. The permittivity values of the prepared composites also increased with the addition of the fillers. The incorporation of fillers also increased the electrical conductivity values of the prepared composites at high frequencies.

Influence of model assumptions on charring polymer decomposition in the cone calorimeter

This article addresses the one-dimensional modeling of a charring polymer decomposition in the cone calorimeter used to reproduce at bench scale the radiative heating from a fire. The rate-controlling phenomena are first discussed in a preliminary analysis of dimensionless numbers. Then, the role of three critical assumptions is highlighted by simulations: (1) transport of the gaseous products within the material or instantaneous release of gaseous products, (2) volume variation or constant volume, and (3) absorption of applied heat flux at the exposed face or through the thickness. Their influence in thermally thick regime is shown in particular on mass loss rate and time to extinction. Under the conditions tested, the influence of internal transport by convection on mass loss rate and time to extinction is minor. The assumption of constant volume appears to have a moderate influence on the mass loss rate and time to extinction. Variations of optical properties affect the numerical results by an increase of the maximum peak of mass loss rate and a decrease of time to extinction. Finally, the effects of applied heat flux and initial material thickness on the mass loss rate and time to extinction are important. With a higher heat flux or a smaller thickness, the decomposition is earlier, faster, and more intense.

Microscopic Characterization and Analysis of Electrospun TiO2-PVP and TiO2-PVDF Fibers

Titanium dioxide (TiO2) is a suitable material to be used in the field of photocatalytic water treatment. In this research, TiO2 membrane fibers were synthesized using a combination of non-aqueous sol gel method and electrospinning technique. Titanium isopropoxide (TTIP) was used as the precursor for the TiO2 filler of the fibers. Both polyvinylpyrrolidone (PVP) and polyvinylidene fluoride (PVDF) were used as the polymer base to obtain the respective membrane fibers. The effects of weight concentration of TTIP as well as the type and molecular weight of the polymer on the morphology of the fibers were studied. Microscopic characterization using field-emission scanning electron microscopy (FESEM) and Energy Dispersive X-Ray (EDX) analysis was performed to obtain the morphology and elemental composition of the fibers. Sub-micron range fibers with a continuous network were generally obtained. Fibers that are subjected to post-electrospinning calcination have a lower fiber diameter. Polymer decomposition is shown to occur during calcination which yielded higher purity TiO2 fibers. The use of higher molecular weight polymers can produce a stronger fibre network for membranes.

“House-of-cards” structures in silicone rubber composites for superb anti-collapsing performance at medium high temperature

We have introduced a novel polymer nanocomposite with superb anti-collapsing performance after polymer decomposition.