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Polymers and Polymer Composites

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Title: EFFECTS OF MOULDING CONDITION AND CURING ATMOSPHERE ON THE FLEXURAL PROPERTIES OF VINYL ESTER
Page Range: p.61-64
Author(s): Nouranian S; Lee J; Torres G W; Lacy T E; Toghiani H; Pittman Jr C U
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.2

Abstract
The effects of moulding condition and curing atmosphere on the flexural properties of a neat 33 wt.%-styrene epoxy vinyl ester (VE) were investigated. Specimens were prepared using either open or closed moulds, and thermally cured under either air or nitrogen atmosphere. Four-point bending tests were performed with both the top ('air-side') and the bottom ('mould-side') surfaces of the cured specimens in tension. The mean flexural moduli for nitrogen-cured and closed-mould specimens were 3% and 9% higher than for air-cured specimens, respectively. However, the mean flexural strength for open-mould air-cured specimens with their air-sides loaded in tension were 65% lower than the mean flexural strengths of open-mould nitrogen-cured or closed-mould specimens. This likely resulted from partial VE resin curing inhibition due to oxygen diffusion into the free surface region of the open-mould air-cured specimens. This creates gradients in the local stiffness and strength in the near-surface region due to lower crosslink density. This effect may be particularly important for thin specimens. These results underscore the significance of exposure to air during open-mould curing on the cured VE flexural properties. Such assessments are crucial for composite part manufacturing utilizing VEs. 26 Refs.

Title: THERMAL, TENSILE AND DYNAMIC MECHANICAL PROPERTIES OF SHORT CARBON FIBRE REINFORCED POLYPROPYLENE COMPOSITES
Page Range: p.65-72
Author(s): Chuanbao Wang; Sanjiu Ying
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.2

Abstract
Short carbon fibre (SCF) reinforced composites have made great progress in the last few decades due to their useful properties, and have been used in many areas. In this paper, carbon fibres were cut into short ones with the length from 40 (mu)m to 100 (mu)m and mixed with polypropylene (PP) fibres at the high speed of 105 rpm by HighSpeed Dispersator in reference to the way of papermaking. Three concentrations of SCF, 5, 15 and 25 w%, were used. Composites with good uniform dispersion of SCF in PP matrix were prepared via melting compounding in a twin-screw extruder followed by injection moulding. The effect of SCF content on the thermal and dynamic mechanical properties was studies by using differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA). The SCF dispersed uniformly and aligned along a direction in PP matrix according to the SEM photographs and the incorporation of SCF enhanced the nucleation process, which was confirmed by DSC results. The heat of fusion and crystallinity of the composites also decreased with increasing CFs concentration. In addition, the stiffness of SCF/PP composites increased as the content of SCF increased. Finally, DMA results showed that an increment of SCF could improve the damping properties. 31 Refs.

Title: NANOFLAKE PATTERNING OF SELF-ASSEMBLED MULTILAYER FILMS
Page Range: p.73-78
Author(s): Qunwei Tang; Benlin He; Lei Chu
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.2

Abstract
Nanopatterning has attracted much attention because of its growing use in designing nanoelectronic and optoelectronic devices. Development of a facile route to nanopatterning is a persistent goal in nanotechnology. Originating from positively charged polyethyleneimine (PEI) and negatively charged poly(4-styrenesulfonate) (PSS), we successfully designed separable nanoflake patterning using layer-by-layer self-assembly technique by sequential adsorption of PEI and PSS. The morphology and size of the nanopatterning can be controlled by adjusting the number of bilayers in the film. Electrochemical measurements reveal that the (PEI/PSS)n nanoflakes have good electroactivity and permeability for the electrolytes undergoing redox reaction. By controlling the distribution of surface charges on substrates, nanopatterning can be facilely achieved by self-assembly method. 10 Refs.

Title: EVALUATION OF BIOLOGICAL PROPERTIES IN-VIVO OF POLY(L-LACTIDE-COGLYCOLIDE) COMPOSITES CONTAINING BIOACTIVE GLASS
Page Range: p.79-84
Author(s): Zhihua Zhou; Lihua Liu; Qingquan Liu; Tianlong Huang; Wennan Zeng; Qingfeng Yi; Zhongmin Yang; Dafu Cao
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.2

Abstract
To evaluate the biological safety of composite materials based on poly(L-lactide-co-glycolide) (PLGA) and bioactive glass (BG), which have a potential application in tissue engineering, the in-vivo biological properties were investigated by applying the micronucleus test, acute systemic toxicity test, haemolytic test and pyrogen measurement. The results indicated that the PLGA/BG composite showed no genetic toxicity; there was no toxicosis or death observed in the acute systemic toxicity test. The haemolytic test suggested that the PLGA/BG composite, with a haemolytic index of 0.281%, did not have an obvious haemolytic reaction. In addition, the PLGA/BG composite materials showed no pyrogen reaction. Therefore, PLGA/BG composite materials could be promising candidate biomedical materials for bone tissue engineering. 20 Refs.

Title: PREPARATION OF A RECOMBINANT SPIDER SILK PROTEIN/PCL BLEND SUBMICROFIBROUS MAT AND ITS CYTOCOMPATIBILITY
Page Range: p.85-92
Author(s): Liang Zhao; Denglong Chen; Meihong Wei; Qinghua Yao; Min Li
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.2

Abstract
With electrospinning technology, recombinant spider silk protein/PCL blend submicrofibrous mat was prepared. Its properties as a potential wound dressing material were evaluated by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). When the proportion of recombinant spider silk protein/ polycaprolactone (PCL) reached 1:20, the appropriate concentration of spinning solution was 30%. Also, the fibre diameter increased as the nozzle-to-ground distance decreased, or as the extrusion speed increased. The fibres tended to be non-uniform. As shown by FTIR, PCL and recombinant spider silk protein blended together without obvious molecular interaction. MTT assay analysis showed that, compared with PCL scaffold, the toxic level of pNSR16/PCL composite scaffold was below 1, which meets the criteria for biomaterials. NIH-3T3 cells cultivation on the composite scaffolds indicated that pNSR16/PCL composite scaffolds with RGD had better cell adhesion than PCL scaffolds. Immunohistochemical experiments proved that cells on the pNSR16/PCL composite scaffold materials had no effect on normal growth. pNSR16/PCL composite scaffold guaranteed good crawling capacity of cells. 22 Refs.

Title: EFFECT OF GRAPHITE AND CARBON BLACK FILLERS ON THE PROCESSABILITY, ELECTRICAL CONDUCTIVITY AND MECHANICAL PROPERTIES OF POLYPROPYLENE BASED BIPOLAR PLATES
Page Range: p.93-100
Author(s): Anett Kiraly; Ferenc Ronkay
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.2

Abstract
This study investigates the hybrid effect between graphite and carbon black in a polypropylene (PP) matrix, based on optical microscopy. PP sheets filled with various types of carbon black and graphite were prepared, and the effects of fillers on the flowability, electrical conductivity and mechanical properties were investigated. The effects of three kinds of carbon black with different specific surface areas (65, 770, 1400 m2/g) on the increase of conductivity in the polypropylene (PP) matrix were compared. The best performance was observed when the carbon black with the highest specific surface was used; therefore it was used for preparing the hybrid-filled (graphite - carbon black) materials by melt blending. Optical microscopic studies proved that the carbon black exerted not only a direct but also an indirect influence on the conductivity and on the mechanical properties of the hybrid composites, as it influenced the distribution of graphite significantly. At lower graphite contents the material became more flexible because of the better dispersion of graphite, but at higher carbon black contents the stiffness increased significantly. 23 Refs.

Title: RHEOLOGICAL BEHAVIOUR OF STYRENE-FREE UNSATURATED POLYESTER-CLAY NANOCOMPOSITES
Page Range: p.101-110
Author(s): Amir Masoud Rezadoust; Masoud Esfandeh; Mohammad Hosain Beheshty
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.2

Abstract
The rheological behaviour of styrene-free unsaturated polyester resin-organoclay (Cloisite 15A) nanocomposites at various clay contents, prepared by melt mixing, was investigated. Styrene-free resin was used to achieve high-shear mixing and to avoid viscosity changes due to solvent evaporation. In order to compare the effects of shear- and diffusion-induced phenomena on the intercalation of nanoclay; samples were prepared at two different temperatures of 40 degrees C (cold-mixed) and 150 degrees C (hot-mixed) and tested in the range of 40-120 degrees C using dynamic rheometry. Complex viscosity-temperature curves for cold-mixed samples showed a decrease in viscosity with increasing temperature followed by the formation of a plateau at a particular temperature, depending on the clay content. This behaviour is characteristic of systems with a network structure. The results of small angle X-ray diffraction and TEM analysis confirmed the intercalation of the nanoclay particles as well as a reduction in their thickness. TEM images revealed that the size reduction happened through bending fracture followed by shear delamination of the fractured clay layers. On this basis, a structure of the physical network was proposed to be formed by sticking several nanoclay stacks inside a polymer chain and more involvement of polymer chains with the delaminated layers' ends. A dispersion model was used to quantify and interpret the dispersion status of nanoclay particles in the resin system. 27 Refs.

Title: PHASE TRANSFER CATALYZED POLYMERIZATION OF STYRENE AND GRAFT COPOLYMERIZATION OF STYRENE ONTO GELATIN
Page Range: p.111-122
Author(s): Inderjeet Kaur A; Deepika Khanna N
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.2

Abstract
The use of tetrabutylammonium bromide (TBAB), as phase transfer catalyst during polymerisation of styrene in the presence of water-soluble radical initiator, potassium persulphate (KPS), and graft copolymerisation of styrene onto gelatin, a water soluble polymer, using a water-insoluble radical initiator, benzoyl peroxide (BPO), has been explored in a water-benzene biphasic system. The percentage conversion (Pc) of styrene to polystyrene and percent grafting (Pg) of styrene onto gelatin was studied as a function of various reaction parameters. Under optimum reaction conditions, maximum Pc (76%) was obtained at [KPS] = 12.9 x 10^-4 moles/L, [Sty] = 4.3 x 10^-3 moles/L, and maximum Pg (87%) was obtained at [BPO] = 4.6 x 10^-4 moles/L, [Sty] = 13.88 x 10^-3 moles/L using [PTC] = 2.89 x 10^-4 moles/L in 10 mL each of water and benzene in 120 min at 60 degrees C. The graft copolymer, Gelgpoly(Sty), was characterized by IR, Thermogravimetric Analysis, Scanning Electron Microscopy and swelling behaviour in different solvents. Metal uptake and degradation studies of the grafted sample were also carried out. The grafted sample showed maximum uptake for Cu2+ (88%), Ni2+ (80%) and Fe2+ (50%). Degradation studies of Gel-g-poly(Sty) were carried out by soil burial test and UV radiations. Photo-degradation showed better degradation (5.26% wt. loss) in 32 h of exposure to UV radiations as compared to soil burial degradation (8.46% wt. loss) in 30 days. Gelatin-styrene graft copolymers can thus be used as bio- and photo-degradable materials for environmental management. 18 Refs.

Title: STUDY ON CHLORINATION OF MALEIC ANHYDRIDE GRAFTED POLYPROPYLENE
Page Range: p.123-128
Author(s): Heqing Fu; Caibin Yan; Xiaoli Wei; Wei Deng; Lina Wang
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.2

Abstract
The non-polarity of polypropylene has restricted its use; therefore it needs to be modified. Maleic anhydride grafted polypropylene(PP-g-MAH) is such a kind of modified polypropylene; however its polarity is still low. In order to improve its polarity, chlorinated maleic anhydride-grafted polypropylene (Cl-PP-g-MAH) prepared by free radical polymerisation was carried out using PP-g-MAH as reaction material, carbon tetrachloride (CCl4) as solvent and benzoyl peroxide (BPO) as initiator. The products were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance Spectroscopy (NMR). The effects of the reaction temperature, reaction time, flow rate of chlorine and concentrations of PP-g-MAH and BPO initiator on the degree of chlorination were studied. The optimum technological conditions were obtained, and the surface tension, light transmission, particle size and tensile strength of chlorinated maleic anhydride grafted polypropylene were better than those of maleic anhydride grafted polypropylene. After modification by maleic anhydride and chlorine, PP could meet commercial needs in the fibre composites, adhesives, printing inks, coatings and plastics industries. 18 Refs.

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