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Polymers and Polymer Composites

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Title: THE EFFECTS OF GAMMA IRRADIATION ON MEDICAL GRADE POLY(METHYL METHACRYLATE)
Page Range: p.1-8
Author(s): Barton S J; Foot P J S; Miller Tate P C; Mariko Kishi; Baljit Ghatora
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.1

Abstract
Within developing countries the most cost-effective polymer used in the fabrication of rigid intraocular lenses (IOLs) is poly(methyl methacrylate) (PMMA), for which gamma irradiation is increasingly being used as the preferred method of sterilisation. Medical grade PMMA samples sterilised using a dose of 29kGy of gamma irradiation, were immersed in a simulated aqueous humour solution (SAHS) (pH 7.4, 35 degrees C), and periodically removed to assess changes in their thermal and structural properties with respect to control samples. Triple detection gel permeation chromatography indicated that substantial chain scission had occurred during gamma irradiation, an adverse effect that also resulted in a small increase in the rate of diffusion of the SAHS into the PMMA. The diffusion coefficient of SAHS into the gamma-sterilised PMMA was 2.7 plus/minus 0.6 x 10^-12 m2 s-1, and that for the control samples was 2.0 plus/minus 0.5 x 10^-12 m2 s-1. Thermomechanical analysis revealed a decreasing Tg with time for samples incubated in SAHS, showing that the solution caused plasticisation irrespective of irradiation; however, the i-sterilised PMMA had a Tg 7 degrees C lower than the control PMMA, which indicates the effect of the e-irradiation on the rigidity of the polymer. 27 Refs.

Title: EFFECT OF ALKALI TREATMENT ON PHYSICAL PROPERTIES OF BIO-BASED COMPOSITES
Page Range: p.9-20
Author(s): Williams T; Hosur M; Vaidya U; Jeelani S
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.1

Abstract
In the present study, bast kenaf natural fibres were alkali-treated to determine the effect of treatment on the physical properties of natural fibre-reinforced biocomposites. Both unsaturated polyesters and bio-polyester resins were used as matrices. Other resin systems were studied as well, including a resin made with low VOC, fatty acid-derived reactive diluents. After all the biocomposites had been fabricated via compression moulding, it was observed that the incorporation of alkali-treated fibres in the biocomposites decreased the flexural and thermo-mechanical properties of the biocomposites. It was also observed that mercerizing the kenaf aided in reducing the moisture absorption by 30% and increasing the compressive strength by ~30% compared to that of the untreated biocomposites. The property changes were believed to be the result of crystallinity changes in the kenaf as a result of the treatment. 36 Refs.

Title: SYNTHESIS AND ADSORPTION OF ORGANO-MONTMORILLONITE/POLY(ACRYLIC ACID) SUPERABSORBENT COMPOSITE
Page Range: p.21-26
Author(s): Linhui Zhu; Lili Zhang; Yaoji Tang; Jing Yang
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.1

Abstract
Organo-montmorillonite /poly (acrylic acid) superabsorbent composite was prepared by intercalation polymerisation of acrylic acid (AA) and organo-montmorillonite (OMMT). The composite was characterized by means of Fourier-transform spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Maximum absorbency of OMMT/PAA in distilled water and 0.9% NaCl was 1439 and 97 g/g, respectively. Water retention of the composite was also tested. The composite was used for removal of heavy metal ions from aqueous solutions. The maximum adsorption capacities for Pb2+, Cu2+ and Ni2+ were 1006.97, 280.56 and 165.67 mg/g, respectively, and the adsorption was consistent with the Freundlich model. It was found that the superabsorbent composite showed good re-use performance in wastewater treatment. 17 Refs.

Title: THE PROPERTIES OF MELT-BLENDED COMPATIBILIZED METALLOCENE POLYETHYLENE/CLAY NANOCOMPOSITES
Page Range: p.27-36
Author(s): Wen-Chih Chen; Sun-Mou Lai; Zi Way Wang; Rong Yu Qiu
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.1

Abstract
Although it is well known to employ compatibiliser to assist clay dispersion in thermoplastic/clay systems, the properties of compatibilisers have often been neglected. Metallocene polyethylene (mPE)/clay nanocomposites were prepared via a melt-blending approach to further investigate this compatibilisation effect. Maleated mPE (mPE-g-MA) was also prepared as a compatibiliser to improve the dispersion of commercial organoclay. The mPE/mPE-g-MA/clay compatibilised systems showed good dispersion of clay or swollen tactoids through X-ray diffraction (XRD) and transmission electron microscopy (TEM) assessments. The compatibilised cases showed slightly higher crystallisation temperatures at higher clay contents than their counterparts without any compatibiliser. The mechanical properties of the investigated systems were rather complex and unusual. The Young's modulus of compatibilised nanocomposites showed slightly higher values in all investigated cases, stemming from the more effective interfacial interaction. The tensile strength of mPE/clay systems increased with increasing clay content; however, that of mPE/mPE-g-MA/clay systems decreased with increasing clay content due to possible heterogeneous microgel (bound polymer) formation in the compatibilised clay. Lower tear strength for compatibilised cases was found, which was attributed to the low tear strength of the compatibiliser and microgel formation, along with the clay moiety serving as inorganic crosslinks to give less energy dissipation during deformation. The results indicated that high dispersion of clay did not guarantee high strength, and the mechanical properties should be carefully evaluated to exploit the reinforcement of nanocomposites. 32 Refs.

Title: THERMAL AND MECHANICAL REINFORCEMENT OF POLY(METHYL METHACRYLATE) VIA INCORPORATION OF POLYHEDRAL OLIGOMERIC SILSESQUIOXANE
Page Range: p.37-42
Author(s): Benhong Yang; Meng Li; Yun Wu; Xingliang Wan
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.1

Abstract
A series of inorganic/organic nanocomposites were prepared by blending cage-like, hydroxyl-bearing polyhedral oligomeric silsesquioxane (HO-POSS) with poly(methyl methacrylate) (PMMA) in THF solvent. Fourier transform infrared spectrophotometry (FTIR) and 29Si-nuclear magnetic resonance (29Si-NMR) were employed to characterize the structures of the HO-POSS/PMMA nanocomposites. Scanning electron microscope (SEM) images showed that the as-prepared composite films were smooth, and no severe aggregation of HO-POSS was observed when POSS content was less than 1.0 wt.%. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results showed that the incorporation of small amount of nanosized HO-POSS reinforced the thermal stability of PMMA. When 1.0 wt.% of HO-POSS was incorporated into PMMA matrix, the Tg and Td increased by 28.8 degree C and 18.9 degree C, respectively, due to the strong interaction between POSS cages and PMMA chains. However, higher POSS contents (>2.0 wt.%) deteriorated the thermal and mechanical properties of the nanocomposites owing to the phase separation in the composite matrix caused by the aggregation of POSS cages. 21 Refs.

Title: IMPACT OF LINKAGE GROUP IN COMB-LIKE POLYMER ON DISPERSION PROPERTIES OF CEMENT PASTES
Page Range: p.43-50
Author(s): Min Qiao; Qianping Ran; Jiaping Liu
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.1

Abstract
The present study aimed to develop a full understanding of the effects of the linkage group type in comb-like polymers on dispersion and dispersion retention of concentrated cement pastes. Two comb-like copolymer dispersants with ester and ether linkage groups were produced. The effects of the linkage group type in the comb-like polymers on the adsorption, dispersion, dispersion retention of the concentrated cement suspensions were investigated systematically. The mechanism of dispersion retention was investigated using isothermal calorimetry measurements and structure stability analysis. The retention of dispersion had a close relationship with the hydration of cement and hydrolysis of side chains. 11 Refs.

Title: SURFACE FREE ENERGY MODIFICATION OF CRUDE RUBBER USING OXYGEN PLASMA AND UV LASER TREATMENT
Page Range: p.51-54
Author(s): Gorazd Golob; Marta Klanjsek Gunde; Kaplanova M; Mladen Lovrecek; Miran Mozetic
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.1

Abstract
A study has been made of the surface properties of nitrile-butadiene rubber and ethylene-propylene-diene monomer crude rubber, basic raw materials for offset lithographic printing blankets manufacturing. Increased surface free energy of the crude rubber was achieved by treatment with the low-pressure oxygen plasma. After plasma activation, samples were treated using a UV laser to deactivate the surface layer. The surface free energy was calculated on the basis of contact angles with different liquids. Plasma-treated samples had higher surface free energy, especially the polar component, and the effect was larger for nitrile-butadiene rubber samples. This surface free energy decreased after exposure to UV laser light. FTIR-ATR spectroscopy was used to detect possible changes in chemical structure of the surface, but no differences were obtained. Changes of surface free energy were thus most likely a consequence of changes in the surface structure. 16 Refs.

Title: PROPERTIES OF HYALURONAN/PVA-SBQ COMPOSITE FILMS PROCESSED BY CASTING
Page Range: p.55-60
Author(s): Jing Xu; Huiyu Bai; Miao Wang; Wenshui Xia; Xiaoya Liu
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.1

Abstract
In this report, a novel hyaluronan/PVA-SbQ composite film was prepared by casting method. The miscibility and morphology of the films were investigated by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The surface hydrophobicity and the thermal properties of the composite films were examined by contact angle (CA) and thermogravimetric analysis (TGA), respectively. The results showed strong hydrogen bonding interactions and molecular miscibility between the two polymers. A dimerisation reaction of SbQ pendant groups in PVA-SbQ chains induced by UV led to the crosslinking of the composite film. The film displayed enhanced tensile strength and slightly weakened elongation at break after being photo-crosslinked. Such film may be a promising material for food or drug packaging applications. 26 Refs.

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