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Polymers and Polymer Composites

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Title: Solvent effect on the fabrication and mechanical behavior of sandwich structured poly(vinyl alcohol)/ carbon-nanofiber buckypaper composite
Page Range: p.624-632
Author(s): Lu M; Sun S C; Bu Z X; Wang L S; Sun L
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.8

Abstract
A solution-casting method has been developed to fabricate polymer/carbon nanofibre (CNF) buckypaper composite/polymer sandwich structures. Such layered nanocomposites can take advantage of the buckypaper's mechanical reinforcement effect and to introduce multi-functionalities including dynamic damping, electrical/ thermal conductance and electromechanical responses. By controlling the solution chemistry, the structure, morphology and thus the performances of the composite samples were effectively manipulated. Dimethyl sulphoxide (DMSO) as a solvent was found to greatly enhance the wettability of polyvinyl alcohol (PVA) to carbon nanofibre as compared to water, and it increased polymer penetration in the buckypaper. It was also observed that PVA formed a surface coating layer surrounding individual CNF which behaved differently from bulk polymer. This intermediate layer played a critical role in determining the static mechanical reinforcement effect of buckypaper and further affected the composite dynamic damping characteristics. Incorporating carbon nanofibre buckypaper not only strengthened the PVA static mechanical performance but also lowered the loss modulus and tan m. By introducing the controlled structure of such composite sandwiches, it is possible to tailor the multi-functionalities targeting specific applications. 21 Refs.

Title: Preparation, characterization and application of polyaniline/silk fibroin composite
Page Range: p.633-642
Author(s): Sharique Ahmad; Adil Sultan; Waseem Raza; Muneer M; Faiz Mohammad
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.8

Abstract
We report the electrical properties and photocatalytic activity of polyaniline (Pani) and polyaniline/silk fibroin (Pani/SF) composite. The Pani/SF composite has been synthesised first time by chemical oxidative in-situ polymerisation method by using potassium persulphate (K2S2O8) in an acidic medium. Thus prepared Pani and Pani/SF composite were characterised by using Fourier-transform infrared spectroscopy, x-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The stability in terms of the DC electrical conductivity of Pani/SF composite and Pani was investigated under isothermal and cyclic ageing conditions. Results indicated that the electrical properties of the composite were significantly influenced by the loading of SF to Pani and observed to be more thermally stable than those of Pani. As-prepared Pani and Pani/SF composites were studied for the degradation of methylene blue (MB) and Rhodamine B (RhB) under UV-light irradiations. The results showed that 91.4% and 85.4% degradation of RhB and MB takes place respectively after 90 min over Pani/SF composite. The decomposition rate of composite was 1.8-2.2 times greater than that of Pani. The improvement of photocatalytic activity of composite may be attributed to the electron-sink function of silk fibroin which increases the optical absorption property and separation of photogenerated charge carriers than Pani alone. 32 Refs.

Title: Thermal crosslinking of maltodextrin and citric acid. methodology to control the polycondensation reaction under processing conditions
Page Range: p.643-654
Author(s): Castro-Cabado M; Parra-Ruiz F J; Casado A L; San Roman J
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.8

Abstract
This paper presents an affordable methodology for the analysis of the crosslinking, by polycondensation reaction, between maltodextrin and citric acid under thermal processing. This methodology is based on three complementary analytical techniques: Fourier Transform Infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and rheometry. FTIR has been found to be a powerful technique for the characterisation of both the esterification reaction and other non-covalent interactions between maltodextrin and citric acid. TGA has been mainly applied to quantify the progress of the polycondensation reaction. Rheometry has been extensively used to understand the crosslink formation resulting from the polycondensation process between maltodextrin and citric acid, allowing the determination of the gel time. Furthermore, these techniques have revealed added value when used as complementary techniques. For instance, the FTIR results supported the conclusions from the study of polycondensation reaction progress by TGA. Similarly, the TGA results about the polycondensation reaction temperature are consistent with the rheology study. Overall, the insightfulness and accuracy of the methodology presented in this paper make it very useful as a tool to optimise industrial processing of materials which apply binding systems based on maltodextrin and citric acid. 37 Refs.

Title: Physical properties of UV-cured epoxy nanocomposite films
Page Range: p.655-662
Author(s): Eun Ho Lee; Dae Su Kim
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.8

Abstract
Cationic UV-curing of a cycloaliphatic epoxy proceeds efficiently at room temperature, resulting in a highly crosslinked polymer network exhibiting the same excellent physical properties as obtained by thermal curing. However, the highly crosslinked rigid polymer network generally shows undesirable brittleness. Therefore, in this study, three kinds of reactive diluents, one epoxy and two polyols, were tested to prepare a cycloaliphatic epoxy film with reasonable physical properties by cationic UV-curing. Also, effects of nanosilica on the physical properties of the epoxy film were investigated. FTIR spectroscopy was used to investigate the UV-curing behaviour of the epoxy resin systems. Amongst the diluents enhanced UV-curing rate and final conversion levels, the epoxy diluent was the most effective. The tensile properties of the epoxy films were investigated by UTM. At a fixed diluent content of 30 phr, the film with the epoxy diluent showed best tensile strength. The film with the epoxy diluent 40 phr showed optimum tensile properties. The film with the epoxy diluent 40 phr showed further enhanced tensile properties at the nanosilica content 0.05 phr. 13 Refs.

Title: Bamboo fibre-reinforced self-compatibilizing functionalized polypropylene composites by palsule process
Page Range: p.663-674
Author(s): Kishor Biswas; Sanjay Palsule
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.8

Abstract
Bamboo fibre (BMBF) reinforced chemically functionalised polypropylene (CF-PP) composites (BMBF/ CF-PP) with in-situ fibre/matrix interfacial adhesion have been processed by Palsule process without using any compatibiliser and without any fibre treatment by co-rotating twin screw extruder and injection moulding machine using raw, untreated bamboo fibres as reinforcement and chemically functionalised polypropylene (i.e., polypropylene grafted with 1.8% maleic anhydride) as the polymer matrix. Mechanical properties of the 10/90, 20/80 and 30/70 BMBF/CF-PP composites have been found to be higher than those of the CF-PP matrix and increase with increasing amounts of reinforcing BMBF in the composites. In-situ fibre/matrix interfacial adhesion resulting in the formation of BMBF/CFPP composites has been established by Field Emission Scanning Electron Micrograph (FE-SEM) and Fourier Transform Infra-Red (FTIR) spectroscopy. 28 Refs.

Title: Study of in-plane fatigue failure and life prediction of weave composites under constant and variable amplitude loading
Page Range: p.597-608
Author(s): Qinghui Ji; Ping Zhu; Jiahai Lu; Zhao Liu
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.8

Abstract
The fatigue behaviour of two-dimensional weave composites under constant and variable amplitude loading was discussed in this article. The theories of life prediction methods were represented, including cycle counting, S-N formulation, constant life diagrams (CLD), damage accumulation rule and stress analysis. Special focuses on CLDs were studied through the interpolation method known as the kriging model. Fatigue tests under constant amplitude loading were carried out utilising the servo-hydraulic Shimadzu testing machine. Tension-tension, tension-compression and compression-compression loading patterns were investigated in fatigue testing. The macro-failure mode was obviously different between tensile and compressive loading. Micro-failure surfaces were observed in micro-mechanism with scanning electron microscopy (SEM). The Basquin equation and the linear Palmgren-Miner (P-M) rule were employed to characterise the fatigue properties under random loading conditions. A new constitutive relation was introduced which took into account the tensile-compressive asymmetry of composites. Finally, the benchmarking for the stochastic loading case was executed using proposed methodology and variable amplitude fatigue experiments. Through the contrast between prediction and the experimental data, it was inferred that the proposed prediction method under any loading conditions (stress ratios and ranges) gave an accurate life prediction. 21 Refs.

Title: Improving mechanical properties of glass fibre reinforced PBT waste for its recycling as a product of pipe system elements
Page Range: p.609-616
Author(s): Varga C; Bartha L
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.8

Abstract
PBT [poly(butylene terephthalate)] is an important engineering thermoplastic having several advantageous properties; however, its brittle behaviour is a disadvantage. Blending with a polymer or applying various types of commercial additives are the two methods widely used for taking advantage of PBT while improving its poor impact properties. In our experimental work, different types of commercially available additives have been applied for improving the mechanical properties of glass fibre-reinforced PBT. Blending a cyclic oligomer with GF/PBT samples made them much more elastic, which was shown by better resistance against tensile, flexure, dynamic and cyclic tensile stresses. 34 Refs.

Title: Investigation of thermal and ablative properties of modified epoxy resins
Page Range: p.617-623
Author(s): Bakar M; Kucharczyk W; Stawarz S
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.8

Abstract
The present work investigates the ablative and thermal properties of epoxy resins modified with silicon carbide (SiC) and tungsten carbide (WC). The properties of two epoxy resins (Epidian 52 cured with triethylenetetraamine and Epidian 112 cured with polyaminoamide) were investigated in this study. Statistical methods for planning experiments were used, and the effect of components on thermal protective properties of epoxy composites established. It was shown that the best thermal protective properties, i.e. the lowest temperature of the rear surface area and the lowest ablative weight loss (the highest thermal stability) were exhibited by the composite based on Epidian 112 containing 56% of silicon carbide SiC and 14% of tungsten carbide WC. A more stabilised ablative layer and limited erosion were obtained with higher SiC content. Moreover, the type of polymer matrix had the most significant effect on the value of the maximum temperature of the rear surface area. 26 Refs.

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