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Polymers and Polymer Composites

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Title: Pull speed influence on fiber compaction and wetout in tapered resin injection pultrusion manufacturing
Page Range: p.419-434
Author(s): Masuram N B; Roux J A; Jeswani A L
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 25
Issue No: No.6

Abstract
In the resin injection pultrusion process (RIP), liquid resin is injected into the tapered injection chamber through the injection slots to completely wetout continuously pulled fibres. As the resin penetrates through the fibres, the resin also pushes the fibres away from the wall towards the centerline, causing compaction of the fibre reinforcements. The fibres are squeezed together due to compaction, making resin penetration more difficult; thus at low resin injection pressures, the resin cannot effectively penetrate through the fibres to achieve complete wetout. However, if the resin injection pressure is too high, the fibres are squeezed together to such an extent that even greater injection pressure is necessary to wetout the compacted fibres. The design of the injection chamber significantly affects the minimum injection pressure required to wetout the fibre reinforcements. A tapered injection chamber is considered such that wetout occurs at lower injection pressures due to the taper angle of the injection chamber. In this study, the effect of fibre pull speed on the fibre reinforcement compaction and complete fibre wetout for a tapered injection chamber is investigated. 16 Refs.

Title: Experimental studies of stiffness degradation and dissipated energy in glass fibre reinforced polymer composite under fatigue loading
Page Range: p.435-446
Author(s): Ospina Cadavid M; Al-Khudairi O; Hadavinia H; Goodwin D; Liaghat G H
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 25
Issue No: No.6

Abstract
In this work, tensile and compressive properties and fatigue performances of laminated glass fibre-reinforced polymer (GFRP) composite under constant amplitude sinusoidal load control at frequency of 5 Hz and at room temperature were investigated for three different types of loading: tension-tension at R=0.1 and 0.5, reverse loading tension-compression at R=-1 and compression-compression at R=2 and 10 in the fibre and normal-to-fibre directions. From these series of tests, the corresponding S-N diagrams were obtained. The dynamic stiffness during fatigue loading showed classical degradation of the GFRP laminates. It was observed that the dynamic modulus decreased with time, and the hysteresis loop area changed with some distortion according to the loading conditions. Finally hysteresis loops throughout fatigue testing were examined, and the variation of energy dissipated per cycle throughout the specimen lifetime was quantified. It was demonstrated that the dissipated energy during the fatigue lifetime is dependent on R-ratio and fibre orientation. However, in majority of the cases, the energy dissipated per cycle near the end of the fatigue lifetime increases as a result of an increase in the area captured by hysteresis loops. 25 Refs.

Title: Thermal diffusivity of copper/linear-low-density polyethylene composites
Page Range: p.447-452
Author(s): Carson J K; Mohamed Alsowailem
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 25
Issue No: No.6

Abstract
The thermal diffusivities of copper/linear-low-density polyethylene (Cu/LLDPE) composites were measured relative to the thermal diffusivity of pure LLDPE. The relative thermal diffusivities were similar to those obtained for copper/high-density polyethylene composites, but were noticeably different from estimated values derived from thermal conductivity, density and specific heat capacity data for Cu/LLDPE from the literature. The thermal diffusivity of the composite material initially decreased below that of the pure polymer with the addition of a small amount of copper, before increasing above it as more was added. There would appear to be marginal or no benefit from adding less than about 15 to 20% metal by volume to a polymer, since the relative increase in thermal diffusivity only becomes significant for greater volumes. 24 Refs.

Title: The mechanical and optical properties of injection-moulded PMMA, filled with glass particles of a matching refractive index
Page Range: p.453-462
Author(s): Wildner W; Drummer D
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 25
Issue No: No.6

Abstract
In this paper, the optical and mechanical properties of injection-moulded plates (thickness: 1 mm) made of poly(methyl methacrylate) (PMMA) and glass particles as filler with a matching refractive index are investigated. Tests show that the orientation resulting from the injection moulding process greatly affects the tensile strength and elongation at break, whereas the elastic modulus merely depends on the filling degree, which is investigated up to 13 vol.%. In terms of the optical properties, the specimens' haze depends on the difference in the refractive index between a glass and polymer. However, the absolute value of haze increases with increasing filling degree and decreasing particle size. Surface defects resulting from the injection moulding process were found to be the primary reason for this haze, even with identical RI between PMMA and glass. 29 Refs.

Title: Effect of sisal fibre hybridisation on static and dynamic mechanical properties of corn/sisal/polylactide composites
Page Range: p.463-470
Author(s): Honglin Luo; Dehui Ji; Guangyao Xiong; Lingling Xiong; Chuanyin Zhang; Yong Zhu; Yizao Wan
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 25
Issue No: No.6

Abstract
The relatively poor mechanical properties of corn fibre (CF) and its green composites have hindered its applications. In this work, sisal fibre (SF) was hybridised with CF to reinforce polylactide (PLA) composites (CF/SF/PLA). The static mechanical properties such as tensile, flexural and impact strengths and dynamic mechanical properties such as storage modulus (E'), damping behaviour (tan,), glass transition temperature (Tg) of the hybrid composites were determined and, for the first time, hybrid effects on both static and dynamic mechanical properties were evaluated. It is found that the tensile, flexural, impact strengths, and E' and tan peak height, as well as the hybrid effects change with hybrid ratio (SF:CF). It is demonstrated that a hybrid composite with desirable static and dynamic mechanical properties can be produced by optimising the fibre:hybrid ratio. 34 Refs.

Title: Auto-hybridization of polyethylene/maple composites: the effect of fiber size and concentration
Page Range: p.471-482
Author(s): Rodriguez-Castellanos W; Rodrigue D
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 25
Issue No: No.6

Abstract
This work investigated the effect of maple fibre size and content on the auto-hybridisation of linear low density polyethylene (LLDPE) composites. The samples were compounded by twin-screw extrusion and moulded by compression moulding. Different fibre loadings (5 to 20% wt.), fibre sizes (0-425 microns) and size ratios (30/70, 50/50, 70/30 of short, medium, and long fibres) were used to prepare the auto-hybrid composites with 3% of coupling agent (maleated polyethylene). Micrographs and impact strength results showed that the fracture in auto-hybrid composites is mostly dependent on the longer fibres. At 10% wt. the optimum ratio was 30/70 of shorter/longer fibres, which improved tensile strength (20%), tensile modulus (20%), and impact strength (13%) compared with composites with a single fibre size. But at 20% wt., tensile modulus increased by 30% and torsion modulus by 40% above the rule of hybrid mixtures (RoHM) at a 70/30 ratio of shorter/longer fibres. 68 Refs.

Title: Facile synthesis of core-shell structured CuS@PANI microspheres and electrochemical capacitance investigations
Page Range: p.483-488
Author(s): Chunnian Chen; Qi Zhang; Chengyang Peng
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 25
Issue No: No.6

Abstract
A core-shelled structure CuS@PANI composite microsphere was successfully synthesised via chemical oxidative polymerisation procedure and the electrochemical performance was investigated. The as-prepared composites were characterised by FE-SEM, TEM and XRD, and their particulate structure has been confirmed. Interestingly, the CuS microsphere was not a whole solid but composed of several sheet-like subunits, and the PANI was loosely-coated on the surface of spherical CuS particles. The advantage of this kind of core-shell structure is that PANI has better conductivity, which favours the electronic conductive channels to the CuS cores. Moreover, the loosely-attached PANI could buffer the disadvantages of the volume changes of CuS during the charge-discharge process. The galvanostatic charge/discharge profile shows a specific capacitance of 308.1 F g-1 at a current density of 0.5 A g-1 and the composite retained 71.6% of its initial capacitance after 1000 cycles at a current density of 1 A g-1. 19 Refs.

Title: Halloysite with iron oxide inclusions as a soft ferromagnetic filler for polymer composites
Page Range: p.489-494
Author(s): Stanislaw Frackowiak; Ludwiczak J; Leluk K; Kozlowski M
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 25
Issue No: No.6

Abstract
Natural mineral fillers for polymer composites have frequently been investigated as cheap and easily obtainable alternatives to carbon nanotubes or synthetic short fibres. In this paper we have investigated a natural product from a deposit located in Poland and containing halloysite clay and ferromagnetic particles as main components. In order to assess the homogeneity and possible application fields of polyethylene-based composites prepared from these materials, the composites were evaluated by studying their melt rheology, mechanical properties, wetting, magnetic properties and surface morphology. 13 Refs.

Title: Studies on crystallization and melting behaviors of UHMWPE/MWNTs nanocomposites with reduced chain entanglements
Page Range: p.495-506
Author(s): Guoyong Xu; Qingren Zhu
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 25
Issue No: No.6

Abstract
The nonisothermal crystallisation and melting behaviour of UHMWPE (ultra-high molecular weight polyethylene)/ MWNTs (multi-walled carbon nanotubes) nanocomposites with reduced chain entanglements was studied using differential scanning calorimetry (DSC) technique. The Ozawa approach failed to describe the crystallisation behaviour of nanocomposites, whereas the modified Avrami analysis could explain the behaviour of UHMWPE/ MWNTs nanocomposite to some extent. A novel kinetic model by Liu et al. was able to satisfactorily describe the crystallisation behaviour of UHMWPE/MWNTs nanocomposites. The Dobreva and Kissinger methods failed to calculate the nucleation activity and activation energy, respectively, for the UHMWPE/MWNTs systems. Also the Vyazovkin model-free kinetic method was applied to nonisothermal crystallisation to evaluate the dependence of the effective activation energy on conversion and temperature. 30 Refs.

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