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Polymers and Polymer Composites

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Title: Experimental study on the mechanical properties of basalt fibres and pultruded BFRP plates at elevated temperatures
Page Range: p.277-284
Author(s): Zhongyu Lu; Guijun Xian; Hui Li
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 23
Issue No: No.5

Abstract
Basalt fibre reinforced polymer (BFRP) composites have been widely used for structural strengthening and reinforcement in civil engineering recently. Since fire risk is unavoidable for most civil structures, the degradation of BFRP at elevated temperatures needs to be known for the safe design of its strengthened or reinforced structures under fire risk. In this study, the mechanical properties of basalt fibre roving and pultruded basalt fibre reinforced epoxy plates were investigated at elevated temperatures. As the temperatures increasing from room temperature to 200 deg C, the tensile strength and modulus of the fibre roving were reduced by 8.3% and 9.7%, respectively. Meanwhile, the Weibull shape parameter (m) of the fibre roving decreased by 20.5%. As regards the BFRP plates, however, the elevated temperatures show more adverse influence. The tensile strength and modulus of the BFRP plates is reduced by 37.5% and 31% as temperature rising to 200 deg C. Compared to the tensile properties, the short beam shear strength (SBS) was reduced by around 90%, more susceptible to the elevated temperatures. The glass transition temperature (~93 deg C) plays a key role on the inflexion of the variation of the mechanical properties, especially for the tensile strength. In a wide temperature range, the relationship between the tensile strength and the SBS showed a good linearity, indicating the reduction of the tensile strength comes from the deterioration of the interlaminar shear strength at elevated temperatures. 22 Refs.

Title: Dispersibility of hydrophilic and hydrophobic nano-silica particles in polyethylene terephthalate films: evaluation of morphology and thermal properties
Page Range: p.285-296
Author(s): Mazeyar Parvinzadeh Gashti; Siamak Moradian; Abosaeed Rashidi; Mohamad-Esmail Yazdanshenas
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 23
Issue No: No.5

Abstract
The development of polyethylene terephthalate (PET) nanocomposites with different nano-fillers has been an especially intense area of research due to an enhancement in thermal and physical properties of nanocomposites compared to pure PET. In this regard, the surface properties of nano-particles and their interactions with PET chains have a critical role on different properties of prepared nanocomposites. The aim of this paper is to study the influence of the type of nano-silica particles with different surface properties on the dispersibility, the interfacial adhesion, surface morphology, nucleation and thermal properties of the resultant PET/silica nanocomposites. For this purpose, PET composites containing hydrophilic or hydrophobic nano-silica were prepared by melt compounding. Different properties of nanocomposites were investigated using polarised optical microscopy (POM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), dynamical mechanical thermal analysis (DMTA) and contact angle measurements (CAM). POM images indicated that nano-silica tended to increase the number of spherulites in the PET composite structure depending on the type of particles. The thermal studies of the nanocomposites showed a slight decrease in the melting temperature compared to the pure PET. 65 Refs.

Title: Pullout performance of common construction fasteners from long fiber thermoplastic composites
Page Range: p.297-304
Author(s): Kaliberov D; Uday Vaidya
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 23
Issue No: No.5

Abstract
The recent increase in cyclone activity in the last 20 years has pressured the construction industry to look for alternative materials for roof construction. Although plywood is a cheap material, its mechanical properties are highly dependent on moisture content. Long fibre thermoplastics are an emerging type of plastic materials that feature enhanced mechanical properties due to high aspect ratio discontinuous fibres in a tough polymer matrix. The present study focuses on comparing the pullout strength of commonplace fasteners from plywood and long fibre thermoplastic composite panels. Specimens were tested according to ASTM standards D176188 and D6117-97 for mechanical fasteners in wood and long fibre thermoplastic (LFT) composites. Common construction nails like 6D, 10D and 16D and a #8 screw were used to compare the performance in terms of withdrawal. The data showed that LFT composites had withdrawal strength on average two to three times that of plywood for all tested fasteners types. Experimental data was analytically verified by APA TT-109 guidelines. 25 Refs.

Title: Qualifying dispersion and distribution of carbon nanotubes in polyamide matrix during melt-mixing by flow simulation
Page Range: p.305-316
Author(s): Loux C; Prashantha K; Roger F; Lacrampe M F; Krawczak P
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 23
Issue No: No.5

Abstract
This work aims at numerically simulating the flow of nanocomposites in a twin-screw mixer so as to develop a prediction tool of nanofiller dispersion and distribution in a polymer matrix during processing. The rheological behaviour of polyamide 6 / carbon nanotubes blends (PA6/MWCNT) containing from 1 to 5 wt.% of MWCNT was investigated over a large range of shear rates (0.1 to 100 s-1) and temperatures (230 to 245 deg C). The macroscopic dispersion of the nanotubes was assessed by dynamic rheometry. Viscosity laws of the nanocomposites were characterised and implemented in a finite element software package to compute the velocity, pressure and temperature fields during the mixing process. A good agreement was founded between the calculated and measured torques. The dispersive and distributive capability of the flow was numerically evaluated and compared to the nanotubes dispersion quality experimentally qualified by oscillatory rheometry. Experimental and numerical results are complementary and allow better understanding the mixing capability of the twin-screw mixer used to compound nanocomposites. 35 Refs.

Title: Toughening polystyrene by core-shell rubber particles: analysis of the internal structure and properties
Page Range: p.317-324
Author(s): Chao Zhou; Shuting Wu; Bowen Yang; Yunxia Gao; Guangfeng Wu; Huixuan Zhang
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 23
Issue No: No.5

Abstract
A series of polybutadiene-graft-polystyrene (PB-g-PS) core-shell structural rubber particles has been prepared by grafting styrene onto polybutadiene seeds via emulsion polymerisation. All the PB-g-PS particles were designed with the same chemical composition and similar grafting degree but different internal structures. The difference in internal structure was realised by controlling the allocation of 'external grafting' and 'internal grafting' of styrene. Three different internal structures: rare sub-inclusion, small size sub-inclusions and large-scale subinclusions in the rubber phase were observed by transmission electron microscopy. Slight aggregation of rubber particles of PB-g-PS with large-scale sub-inclusions was found in PS/ PB-g-PS blends. The results of dynamic mechanical analysis showed the PB-g-PS with small size sub-inclusions had lower glass transition temperature than the others. Izod test results showed that the PB-g-PS with large-scale sub-inclusions could toughen the PS matrix more effectively. The deformation mechanisms responsible for these effects are discussed. 27 Refs.

Title: Chitosan/cellulose/halloysite membranes produced using solvent casting method
Page Range: p.325-332
Author(s): Kavitha Govindasamy; Muhammad Hafiz Ramli; Pooria Pasbakhsh; Vengidesh Pushpamalar; Babak Salamatinia
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 23
Issue No: No.5

Abstract
Polymer biocomposites have attracted a lot of attention due to the increasing requirements for biomaterials to replace conventional materials. This replacement is due to the remarkable properties of biomaterials, including their biocompatibility, biodegradability and non-toxicity. Chitosan (CS) is a renowned abundantly-available biopolymer that is furnished with such properties. However chitosan is known to be unstable in acidic conditions, and it has fairly low mechanical strength and requires further improvement for various applications. This study aims to improve the properties of chitosan by making composites of CS reinforced with carboxymethyl cellulose (CMC), microcrystalline cellulose (MCC) and halloysite nanotubes (HNTs). These composites were prepared through solvent casting method and were investigated for their mechanical, chemical and morphological properties. The mechanical testing results showed that the CS/MCC membranes had the best mechanical properties, with a tensile strength (s) of 79.98 plus/minus 8.12 MPa and a Young's modulus (E) of 2.44 plus/minus 0.21 GPa. Scanning electron micrographs confirmed that the high mechanical strength of CS/MCC membranes is attributed to better dispersion of MCC in chitosan. Infrared spectroscopy compared the chemical interactions between the main functional groups of the matrix and fillers. A surface wettability test was performed and revealed that chitosan membranes reinforced with 10 (w/w%) of CMC had the lowest (88.45 deg ) and chitosan membrane with 5 (w/w%) HNT and 5 (w/w%) had the highest contact angle (130.83 deg ). Addition of both CMC and MCC led to an improvement of the mechanical properties over the pure chitosan membrane, which was attributed to a significant interaction between chitosan and cellulose through hydrogen bonding. 34 Refs.

Title: The effect of a novel intumescent flame retardant-functionalized montmorillonite on the thermal stability and flammability of EVA
Page Range: p.345-350
Author(s): Yan Liu; Qingli Yu; Zhengping Fang; Yan Zhang
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 23
Issue No: No.5

Abstract
A novel intumescent flame retardant-functionalised montmorillonite (PAB-MMT) was prepared by modification of sodium montmorillonite (Na-MMT) with an intumescent flame retardant (PAB) containing phosphorus-nitrogen structure. The results of X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) analysis indicated that PAB had intercalated into Na-MMT. The applications of this fact for improving the thermal stability and flammability of poly(ethylene-co-vinyl acetate) were investigated by thermogravimetric analysis (TGA), and microscale combustion calorimetry (MCC). Scanning electron microscopy (SEM) was carried out to learn the morphology of the char residue. The results showed that the addition of PAB-MMT into EVA could improve the flame retardancy of the EVA matrix. The peak heat release rate (PHRR) and total heat release (THR) were significantly reduced in comparison with those of other EVA composites. The TGA data showed higher char residue than other composites, which was the reason for the improved flame retardancy. 21 Refs.

Title: Manufacture of fibreglass nonwoven composites and study of the effect of different variables on their quality
Page Range: p.351-358
Author(s): Sheraz Hussain Siddique Yousfani; Gong R H; Porat I
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 23
Issue No: No.5

Abstract
A new technique of manufacturing thermoset composites using chopped fibreglass strands was investigated during this research work. This technique involved manufacturing of fibreglass nonwoven webs by the wet-laid method, these webs were then used as reinforcement for making composites. The wet-laying process allows the opening of the fibreglass strands to single fibres so that the fibres are dispersed more uniformly within the composite. The in-plane fibre orientation distribution in these nonwoven webs was random and the composites manufactured from these webs have more in-plane isotropic properties. The effect of key process variables i.e. dispersion, fibre length and multiple layering on the density, fibre content and void content of the composites was studied. It was found that layering increased the fibre content and decreased the void content. Dispersion and increase in fibre length also decreased the void content. 16 Refs.

Title: Manufacturing and performance evaluation of polyurethane composites using one-part and two-part resin systems
Page Range: p.333-344
Author(s): Mohamed M; Hawkins S; Chandrashekhara K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 23
Issue No: No.5

Abstract
Polyurethane (PU)-based composites show superior performance compared to polyester and vinylester composites. The demand for PU composites is increasing in high technology as well as conventional applications such as infrastructure and automobile. In this study, glass fibre reinforced composite laminates using one-part and two-part PU resin are manufactured using vacuum-assisted resin transfer moulding (VARTM) process. A new generation two-part thermoset PU resin system is investigated and compared with commercial one-part PU resin systems. The mechanical performance of glass fibre reinforced composites manufactured using two different PU resin systems is evaluated. Tensile and flexure tests are conducted on both neat resin and glass/PU composites. Low velocity impact tests are performed on both types of glass fibre reinforced PU composite specimens. Mechanical properties including strength and modulus were measured and analysed for the two resin systems. Differential scanning calorimetry (DSC) is used to study the cure behaviour of both resin systems. A Brookfield LVDV-II programmable rotational type viscometer is employed to study the viscosity profiles of the resin systems. The influence of resin properties on the overall performance of glass fibre reinforced composites is discussed. 18 Refs.

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