Studies On Thermoplastic Elastomers With Special Reference To Triblock Copolymers And Nbr/Pvc Blends

Thermoplastic elastomers are a relatively new class of materials which compete with thermoset rubbers in some areas and thermoplastic materials in other areas. The main thrust of the present investigation is a comparative study’ on commercially .available triblock. styrene thermoplastic elastomers and those derived from blends of acrylonitrile-butadiene rubber and poly(vinyl chloride). The styrene—based thermoplastic elastomers are gaining acceptance as a replacement for both natural and synthetic rubber‘ in many‘ applications. TPEs based on blends of elastomers and plastics ix: the fastest growing segment of the broad class of thermoplastic elastomers. Broad applicability and simple technology of production are the attractive features of this class of TPES. NBR/PVC thermoplastic elastomers were selected for this investigation due to the versatility of PVC, its number one position, low cost. ability to Ina compounded into various flexible and rigid form with good physical and chemical and weathering properties etc., which will be passed over to PVC blends especially NBR/PVC blends which are known to form miscible systems

Construction and demolition waste as a source of PVC for recycling

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

SURFACE MODIFICATION of SUGARCANE BAGASSE CELLULOSE and ITS EFFECT on MECHANICAL and WATER ABSORPTION PROPERTIES of SUGARCANE BAGASSE CELLULOSE HDPE COMPOSITES

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

UV exposure of polymeric geomembranes

The break of polymer chemical bonds may occur due to penetration of sun short wavelengths. In sanitary landfills for instance, ultraviolet radiation affects uncovered materials and can be dangerous during the installation of the liner and before the placement of the waste. Only the ultraviolet part of the light is harmful to the geosynthetic materials, moreover, each material is sensitive to a particular wavelength. This article evaluates the effects of UV degradation and condensation in black HDPE (1.0 and 1.5 mm) and white HDPE (textured - 1.0 mm) geomembrane that were tested in laboratory during 6 months. The tests were performed using a weatherometer assembled at EESC-USP in accordance to ASTM G154. The results have shown variations in punction and tear resistance after each period of exposure.

Evaluation of geomembrane UV degradation using melt flow index and oxidative induction time tests

Many factors such as the sunlight, intensity of radiation, temperature, and moisture may influence the degradation process of geosynthetics. UV stabilizers are used especially in polyolefin geomembrane to prevent the degradation process. In these geomembranes the service lifetime is initially governed by the consumption of antioxidants. Tests like MFI and OIT are a alternative to detect the oxidative degradation in polyolefins. This article evaluates HDPE geomembrane degradation after UV exposure through the results of MFI and OIT tests. Two kinds of geomembranes were evaluated: a black and smooth (0.8, 1.0, 1.5, 2.5 mm) and a white and textured (1.0 mm). MFI test showed some levels of superficial degradation (crosslink) in HDPE geomembrane.

Biodegradation of blend films in soil and soil with chorume. I. PVC/PCL

Blends of synthetic and biodegradable polymers can be important in attaining material plastic degradation in the environment. Biodegradation using soil and chorume (liquid waste from landfill) microorganisms is a promising area these days. This paper intends to study the PVC/PCL blend degradation in soil using aerobic biodegradation (Bartha respirometer). The morphology and structural changes of the blends were studied by FTIR, scanning electron microscopy, differential scanning calorimetry and contact angle measurements. Blend films prepared by the casting of dichloroethane solutions were buried in a Bartha respirometer containing soil and soil plus chorume and kept there for 120 days. During this time CO2 evolution was measured from time to time. The results showed that PCL films degrade faster than PVC/PCL and PVC films.

Biotreatment effects in films and blends of PVC/PCL previously treated with heat

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Immobilized cells of Acidithiobacillus ferrooxidans in PVC strands and sultite removal in a pilot-scale bioreactor

The biooxidation of ferrous ion into ferric ion by Acidithiobacillus ferrooxidans can be potentially used for the removal of H2S from industrial gases. In this work, Fe3+ ions were obtained through the oxidation of Fe2+ using the LR strain of At. ferrooxidans immobilized in PVC stands in a pilot-scale bioreactor, while H2S was removed in an absorption tower equipped with Rasching rings. At. ferrooxidans LR strain cells were immobilized by inoculating the bacterium in a Fe2+-mineral medium and percolating it through the support. After complete Fe2+ oxidation, which took around 90 h, the reactor was washed several times with sulfuric acid (pH 1.7) before a new cycle was started. Four additional cycles using fresh Fe2+ mineral medium were then run. During these colonization cycles, the time required for complete iron oxidation decreased, dropping to about 60 h in the last cycle. The batch experiments in the H2S gas removal trials resulted in a gas removal rate of about 98-99% under the operational conditions employed. In the continuous experiments with the bioreactor coupled to the gas absorption column, a gas removal efficiency of almost 100% was reached after 500 min. Precipitate containing mainly sulfur formed during the experimental trial was identified by EDX. (c) 2005 Elsevier B.V. All rights reserved.

Study of the emissions from pyrolytic and oxidative thermal decomposition of PVC

Polyvinyl chloride (PVC) is one of the plastics most extensively used due to its versatility. The demand of PVC resin in Europe during 2012 reached 5000 ktonnes1. PVC waste management is a big problem because of the high volume generated all over the world and its chlorine content. End-of-life PVC is mainly mixed with municipal solid waste (MSW) and one common disposal option for this is waste-to-energy incineration (WtE). The presence of plastics such as PVC in the fuel mix increases the heating value of the fuel. PVC has two times higher energy content than MSW ‒around 20 MJ/kg vs 10 MJ/kg, respectively. However, the high chlorine content in PVC resin, 57 wt.%, may be a source for the formation of hazardous chlorinated organic pollutants in thermal processes. Chlorine present in the feedstock of WtE plants plays an important role in the formation of (i) chlorine (Cl2) and (ii) hydrochloric gas (HCl), both of them responsible for corrosion, and (iii) chlorinated organic pollutants2. In this work, pyrolytic and oxidative thermal degradation of PVC resin were carried out in a laboratory scale reactor at 500 ºC in order to analyze the influence of the reaction atmosphere on the emissions evolved. Special emphasis was put on the analysis of chlorinated organic pollutants such as polychlorodibenzo-p-dioxins (PCDDs), polychlorodibenzofurans (PCDFs) and other related compounds like polychlorobenzenes (PCBzs), polychlorophenols (PCPhs) and polycyclic aromatic hydrocarbons (PAHs). Another objective of this work was to compare the results with those of a previous work3 in which emissions at different temperatures in both pyrolysis and combustion of another PVC resin had been studied; in that case, experiments for PCDD/Fs emissions had been performed only at 850 ºC.

Construction and demolition waste as a source of PVC for recycling

Construction and demolition waste can contain considerable amounts of polyvinyl chloride (PVC). This paper describes a study of the recycling of PVC pipes collected from such waste materials. In a sorting facility for the specific disposal of construction and demolition waste, PVC was found to represent one-third of the plastics separated by workers. Pipes were sorted carefully to preclude any possible contamination by poly(ethylene terephthalate) (PET) found in the waste. The material was ground into two distinct particle sizes (final mesh of 12.7 and 8 mm), washed, dried and recycled. The average formulation of the pipes was determined based on ash content tests and used in the fabrication of a similar compound made mainly of virgin PVC. Samples of recycled pipes and of compound based on virgin material were subjected to tensile and impact tests and provided very similar results. These results are a good indication of the application potential of the recycled material and of the fact that longer grinding to obtain finer particles is not necessarily beneficial.

Maturação somática e desempenho físico em jovens futebolistas = : Somatic maturation and physical performance in young soccer players

Universidade Estadual de Campinas . Faculdade de Educação Física

Shear bond strength of self-etch and total-etch bonding systems at different dentin depths

The purpose of this study was to evaluate the dentin shear bond strength of four adhesive systems (Adper Single Bond 2, Adper Prompt L-Pop, Magic Bond DE and Self Etch Bond) in regards to buccal and lingual surfaces and dentin depth. Forty extracted third molars had roots removed and crowns bisected in the mesiodistal direction. The buccal and lingual surfaces were fixed in a PVC/acrylic resin ring and were divided into buccal and lingual groups assigned to each selected adhesive. The same specimens prepared for the evaluation of superficial dentin shear resistance were used to evaluate the different depths of dentin. The specimens were identified and abraded at depths of 0.5, 1.0, 1.5 and 2.0 mm. Each depth was evaluated by ISO TR 11405 using an EMIC-2000 machine regulated at 0.5 mm/min with a 200 Kgf load cell. We performed statistical analyses on the results (ANOVA, Tukey and Scheffé tests). Data revealed statistical differences (p < 0.01) in the adhesive and depth variation as well as adhesive/depth interactions. The Adper Single Bond 2 demonstrated the highest mean values of shear bond strength. The Prompt L-Pop product, a self-etching adhesive, revealed higher mean values compared with Magic Bond DE and Self Etch Bond adhesives, a total and self-etching adhesive respectively. It may be concluded that the shear bond strength of dentin is dependent on material (adhesive system), substrate depth and adhesive/depth interaction.

Aplicação de espectroscopias raman e infravermelho na identificação e quantificação de plastificantes em filmes comerciais de PVC esticável

This paper reports the use of Raman and infrared techniques for the qualitative and quantitative analysis of plasticizers in polyvinylchloride (PVC) commercial films. FT-Raman marker bands were indentified for di-2-ethyl-hexyl adipate (DEHA) and di-2-ethyl-hexyl phthalate (DEHP), allowing for the rapid identification of these species in the commercial film. Quantitative analysis by FT-IR resulted in plasticizers concentrations ranging from 11 to 27% (w/w). Considering the little sample preparation and the low cost of the techniques, FT-IR and FT-Raman are viable techniques for a first assessment of plasticizers in commercial samples.