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Polymers and Polymer Composites

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Title: The low velocity impact response of nano modified composites manufactured using automated dry fibre placement
Page Range: p.233-240
Author(s): Umer R; Rao S; Zhou J; Guan Z; Cantwell W J
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.4

Abstract
The low velocity impact response of composite materials manufactured from dry fibre tows using the automated fibre placement technique has been investigated. Following fibre placement, the dry preforms were infused with an epoxy resin. The influence of incorporating graphene oxide (GO) nanoparticles into the matrix was investigated, and the impact response of these samples was compared to that of its plain resin counterpart. Flexural and low velocity impact tests were undertaken in this study to understand the influence of GO nano-filler loading on mechanical behaviour of the unreinforced epoxy resin. The introduction of GO into the resin showed nearly 50% increase in ductility compared with that of the neat polymer at a mere 0.1 wt% filler loading. However, GO had a negligible effect on the impact response of these novel composites. There was no observable difference between the load-displacement traces or the resulting damage in the plain and unmodified composites. It is possible that the polymer's ability to undergo larger non-linear deformation at lower rates of strain is suppressed when it is subjected to impact rates of loading. 18 Refs.

Title: Thermal conductivities of 2.5 dimensional woven composites
Page Range: p.241-248
Author(s): Leilei Song; Wei Geng; Yufen Zhao; Xiaoming Chen; Jialu Li
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.4

Abstract
The thermal conductivities of 2.5 dimensional (2.5D) woven composites were measured by using transient hot-wire method (THWM) in this study. The results showed that the THWM could also be used to measure the thermal conductivity of 2.5D woven composites, which were considered to be homogeneous materials. Heat diffusion models of the samples were simulated. The thermal conductivities of 2.5 dimensional woven composites increased with the warp fibre volume fraction when the hot wire was perpendicular to the warp direction. It was important that the thermal conductivity of 2.5 dimensional woven composites was found to be affected by the yarn size. Thermal conductivities also increased with the effective yarn size. Finally, thermal conductivities of 2.5 dimensional woven composites increased with the temperature from 288.15K to 298.15K, although the enhancement was not great. These conclusions indicated that the thermal conductivity of 2.5 dimensional woven composites was affected by the internal structure and the external environment. 39 Refs.

Title: A novel approach for fabricating poly-l-lactide materials by onestep bulk polymerization
Page Range: p.249-254
Author(s): Zhiyuan Peng; Zhiping Li; Fan Zhang; Xiaochun Peng
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.4

Abstract
Poly-L-lactide (PLLA) is one of the most significant members of a group of bioabsorbable polymers. A new approach for fabricating PLLA material was investigated by one-step bulk polymerisation. The focus of this paper was on the effect of reaction temperature and reaction time on the weight-average molar mass, the polydispersity index (PDI), and the flexural strength and modulus. Gel permeation chromatography (GPC), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and mechanical properties measurements were used to characterise the products. It was found that the optimal reaction conditions were at 140 degC for 24 h, under which the highest (5.02 x 105 Da) and the lowest PDI (1.16) were reached. In addition this material had the highest flexural strength and modulus, 74.58 plus/minus 2.35 MPa and 1.62 plus/minus 0.14 GPa, respectively. 19 Refs.

Title: A study of the friction coefficients of unidirectional and woven carbon fibre/epoxy composites
Page Range: p.255-264
Author(s): Cheng B; Kortschot M
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.4

Abstract
The friction coefficients of unidirectional carbon fibre/epoxy composites (with the fibres parallel and antiparallel to the sliding direction) were measured under severe abrasive conditions. Aluminium oxide sandpapers with three different grits (36, 80, and 120) were used as the counter surfaces. Three different applied loads (5, 10, 22N) and two different sliding speeds (2 m/s, 4 m/s) were selected as the testing parameters. Under these conditions, composites with fibres parallel to the sliding direction had a significantly lower friction coefficient. Using the measured friction coefficients of unidirectional composites, a modified rule of mixtures equation was developed to predict the friction coefficients of woven carbon fibre/epoxy composites under the conditions. The model is based on the hypothesis that the more wear resistant regions of the weave (fibres that are parallel to the sliding direction in this case) would protect the less wear resistant regions (fibres that are antiparallel to the sliding direction), and that the load is redistributed to yield equal wear rates for the two zones. It was found that the model was able to accurately predict the friction coefficients of the woven composites for the abrasive conditions tested in this study. 17 Refs.

Title: A study of bubble electrospinning of ethylcellulose ultrafine fibres
Page Range: p.265-272
Author(s): Ketankumar Vadodaria; Stylios G
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.4

Abstract
Bubble electrospinning (BE) is a recently-invented simple needleless concept to produce nanofibres. The bubble electrospinning method is not yet well established and there is a need to study the effects of different parameters on the fibre morphology. In the present work, ethylcellulose (EC) was successfully electrospun from 15% EC solution in toluene:ethanol (60:40) by bubble electrospinning. The effects of different parameters such as solution surface to collector distance and applied voltage on the morphology of bubble electrospun EC nanofibres were studied and are discussed below. Bubble electrospun EC fibres showed an increase in diameter as the distance between solution surface and collector increased. However, when the applied voltage was increased, the EC fibre diameter was initially reduced but then increased. The results are discussed in detail in the paper. FTIR analysis of EC powder, solution and fibres were also studied. 47 Refs.

Title: Electrical conductivity studies of conducting polymer nanocomposites in ambient conditions
Page Range: p.273-280
Author(s): Shahid Pervez Ansari; Faiz Mohammad
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.4

Abstract
Nanocomposites of conducting polymer (polyaniline, PANI) nanoparticles with zinc oxide (ZnO) nanoparticles as inorganic filler and cellulose acetate (CA) as supporting matrix were prepared by a solution-casting method using N-methyl-2-pyrrolidone (NMP) as solvent. The nanocomposites were studied for their DC electrical conductivity and stability in terms of electrical conductivity retention by isothermal accelerated ageing and cyclic accelerated ageing techniques using a four-in-line probe instrument. The nanocomposites were also characterised by FTIR, SEM, TEM, TGA and XRD. All the nanocomposite formulations followed an Arrheniustype temperature dependence of electrical conductivity, which supported a semiconducting nature for their HCl doped state. The electrical conductivity of the as-prepared HCl doped nanocomposites was also found to be in the semiconducting region. The studied nanocomposite formulations showed good stability towards retention of their electrical conductivity up to 90 deg C. X-ray diffractometry (XRD) data suggested the uniform incorporation of zinc oxide nanoparticles in the polymer matrix. 23 Refs.

Title: Numerical solution of penetration into woven fabric target impregnated with shear thickening fluid
Page Range: p.281-288
Author(s): Naser Kordani; Ali Sadough Vanini; Hosein Amiri
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.4

Abstract
In this paper, yarn pull-out testing was performed to estimate the pulling-out force and the friction coefficient. Fabrics were impregnated with Shear Thickening Fluid (STF) of two types. Single fibre tensile tests were performed to determine the resistance of each fibre. The speed of pulling out was 500 mm/min and the samples were placed horizontally in a tensile device. The results indicated that the fabric impregnated in STF needed more force in order to get out of the fabric. Friction coefficients of three fabric types of raw fabric, fabric with dissolved fluid and fabric with STF were entered into an explicit dynamics finite element model along with the mechanical characteristic of a yarn. Ballistic range velocity was extracted for samples by the software and was compared with experimental results. The effects of the shear thickening fluid (STF) were considered as frictional effects. 21 Refs.

Title: Recent advanced technologies in the processing of hybrid reinforced polymers for applications of membranes
Page Range: p.289-306
Author(s): Savita Dixit; Sandhya Pal
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.4

Abstract
This review presents a comprehensive introduction to recent advances in the field of blends of the natural and synthetic polymers as new material for biodegradable membranes. These materials and several blends have attracted industrial attention because they exhibit improvements in properties which are required in membrane technology. In the current review, the structure, preparation coating method and properties of the blends of natural and man-made polymer are discussed. We focus on the applications of blend materials for membrane technology like fuel cells, membrane electrolytes and ultrafiltration membranes for water treatment. From the literature, it is found that the most common natural polymers: collagen, chitosan, chitin, cellulose, starch and poly(lactic acid) are used as components of blends with man-made polymers. We have also studied the introduction of nano-fibrous and nano-particles to improve the mechanical properties of these membranes. 117 Refs.

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