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Polymers and Polymer Composites

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Title: FILM MORPHOLOGY AND ELECTROLUMINESCENCE OF POLY[9,9-DI-(2'-ETHYLHEXYL) FLUORENYL-2,7-DIYL] BLENDED WITH A HOLE TRANSPORTING POLYMER
Page Range: p.469-476
Author(s): Qiushu Zhang
File size: 365K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.9

Abstract
This paper reports on the phase-separated film morphology and electroluminescence (EL) of a polyfluorene, poly[9,9-di-(2'-ethylhexyl)fluorenyl-2,7-diyl], blended with the hole transport material, poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(N,N'-bis(4-butylphenyl -1,1'-biphenylene-4,4'-diamine))]. The film morphology changes remarkably with the blend ratio. Other factors like polymer solution concentration, substrate and film thickness could also influence the film morphology. The addition of the hole-transporting polymer to the host polymer improved device properties of light-emitting diodes (LEDs). The maximum luminance achieved was 884 cd/m2. The maximum external quantum efficiency of the blended polyfluorene devices was 0.1%, which is more than three times higher than that of the pristine polyfluorene LEDs. The introduction of the hole-transporting polymer also modifies the EL spectrum. For the blend-based devices, the EL peaked at 504 nm, having a blue shift of 33 nm compared to that of the single polymer based devices. Phase-separated domains, or interactions at their interfaces, may play a role in the improved device performance. 28 Refs.

Title: LIQUID SILICONE RUBBER VULCANIZATES: NETWORK STRUCTURE PROPERTY RELATIONSHIP AND CURE KINETICS
Page Range: p.477-488
Author(s): Rajesh G; Maji P K; Mithun Bhattacharya; Anusuya Choudhury; Nabarun Roy; Anubhav Saxena; Bhowmick A K
File size: 709K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.9

Abstract
Liquid silicone rubber (LSR) vulcanisates have been prepared from vinyl-end capped polydimethylsiloxane (PDMS) and polymethylhydrogenosiloxane (PMHS) in presence of platinum catalyst using solution casting technique. The science involving synthesis of usable silicone rubber by curing with polymethylhydrogenosiloxane has been studied in details. The effects of vinyl content of PDMS and the ratio of hydride crosslinker to vinyl concentration on crosslink density, mechanical, dynamic-mechanical and thermal properties have been discussed. It has been found that at optimum level of crosslinker, the LSR vulcanisate shows a maximum crosslink density with highest improvement in mechanical and thermal properties. The amount of crosslinker required, depends upon the number of vinyl functionality per unit length of the polymer chain and the chemical composition of the hydride crosslinker. This study makes a novel attempt to determine cure kinetics of PDMS by using Fourier Transform Infrared spectroscopy. Measurements have been done at three different temperatures and found to follow the first order reaction with respect to consumption of vinyl (C=C) and silyl hydride groups (Si-H). The activation energy and kinetic parameters have been determined as well. 48 Refs.

Title: ELECTRICAL AND DIELECTRIC PROPERTIES OF MULTI-WALLED CARBON NANOTUBE FILLED POLYPROPYLENE NANOCOMPOSITES
Page Range: p.489-494
Author(s): Prashantha K; Soulestin J; Lacrampe M F; Krawczak P; Dupin G; Claes M; Tewari A
File size: 373K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.9

Abstract
Different concentrations of multi-wall carbon nanotubes (MWNTs) filled polypropylene (PP) nanocomposites were prepared through PP/MWNT masterbatch dilution process by melt compounding with a twin-screw extruder. Prepared nanocomposites were characterized for their electrical resistivity and dielectric properties. The experimental results revealed that incorporation of MWNTs in PP matrix had decreased the electrical resistivity and increased the dielectric constant at low dielectric loss. The electrical conductivity and dielectric constant of PP/MWNT nanocomposites increased significantly near the percolation thresholds, which is equal to 2 wt.% of MWNTs. The PP nanocomposite containing 5 wt.% MWNT exhibited a high dielectric constant under wide sweep frequencies attended by low dielectric loss. Its dielectric constant is >110 under lower frequency, and remains the same in the entire frequency range. Interestingly, dielectric constant values of the prepared nanocomposite systems have weak or nil frequency dependence in the entire frequency range. Morphological characterisation was done using scanning electron microscopy (SEM) and it was observed that nanotubes are distributed reasonably uniformly indicating a good dispersion of nanotubes in the PP matrix. The obtained results indicate that a common commercial plastic with good comprehensive performance, which exhibited the potential for applications in advanced electronics, was obtained by a simple industry benign technique. 47 Refs.

Title: INVESTIGATION ON FLAME RETARDANCY AND ANTIDRIPPING OF NEW INTUMESCENT FLAME RETARDANT POLYPROPYLENE FILM
Page Range: p.495-502
Author(s): Peng Bai; Bin Li; Suliang Gao; Mo Lin; Mi Wang
File size: 448K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.9

Abstract
A novel intumescent flame retardant (IFR) system consisting of a novel char forming agent (CFA), modified ammonium polyphosphate (MAPP), a synergistic agent (4A zeolite) and an antidripping agent (SN3300) was used in an intumescent flame retardant polypropylene film (IFR-PP film). The original ammonium polyphosphate (OAPP) was modified by octadecylamine to enhance its compatibility with the PP matrix. According to the results obtained from the flame retardancy tests, MAPP had a higher efficiency than OAPP, and the IFR-PP film without the antidripping agent reached a high limiting oxygen index (LOI) value, but it failed to pass UL-94 VTM-0 rating (0.2 mm). The reasonable loading of SN3300 was 0.10~0.15 wt.% (26 wt.% loading of IFR). Greater or smaller loadings did not help the samples to pass VTM-0 rating, and even deteriorated the flame-retardancy of the film. Based on thermogravimetric analytical data, the IFR enhanced the thermal stability of composites at high temperature and effectively increased the char residue. The cone results demonstrated that the IFR could reduce the flammability of PP films based on reduced heat release rate (HRR), total heat release (THR), smoke production rate (SPR) and total smoke production (TSP); also IFR containing MAPP became more effective in reducing smoke release than one containing OAPP. The mechanical properties test results showed that films containing MAPP had better tensile strength and tear strength. The morphological structures observed by scanning electron microscopy (SEM) showed that MAPP had much better compatibility with a PP matrix than OAPP, and it made the char layer become more homogeneous and dense. 34 Refs.

Title: EFFECT OF REACTIVE DILUENTS AND KAOLIN ON THE MECHANICAL PROPERTIES OF EPOXY RESIN
Page Range: p.503-510
Author(s): Bakar M; Szymanska J; Rudecka J; Fitas J
File size: 495K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.9

Abstract
Epoxy resin was modified using phenyl diglycidyl ether (PGE), xylene and kaolin. The impact strength (IS), critical stress intensity factor (KC), flexural strength and glass transition temperature (Tg) were evaluated as functions of the modifier content. It was found that the addition of diluents led to a significant reduction of both viscosity and Tg. A three-fold increase of IS was obtained with the addition of 2.5% PGE. Moreover, the addition of 15% PGE resulted in about 145% enhancement of the KC parameter. However, the addition of xylene had no significant effect on these properties. Furthermore, the addition of 10% kaolin to epoxy resin gave compositions with the highest fracture toughness. Maximum KC values were obtained with epoxy hybrid compositions containing 10% kaolin and 2.5% PGE and 10% kaolin and 5% PGE respectively. All tested compositions had higher energy at break than non-modified epoxy resin. SEM micrographs of fractured surfaces of modified epoxy compositions revealed the presence of plastic deformations, which can be considered as the main source of the mechanical properties enhancement. 13 Refs.

Title: PREPARATION AND CHARACTERIZATION OF PBMA/SIO2-TIO2 HYBRID FIBRES
Page Range: p.511-516
Author(s): Haihong Ma; Tiejun Shi
File size: 315K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.9

Abstract
Silica-titania (SiO2-TiO2) blend sols were prepared via a sol-gel method from tetraethoxylsilane and tetrabutyl titanate. Poly(butyl methacrylate) (PBMA)/SiO2-TiO2 hybrid sols were synthesised through in-situ polymerisation of butyl methacrylate (BMA) in the blend sol. After ageing treatment, PBMA/SiO2-TiO2 hybrid fibres were prepared by drawing from the hybrid sol. The mechanism of the hybrid reaction was studied carefully. The hybrid fibres were characterized by Fourier transform infrared (FT-IR) spectrometry, scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HRTEM), Fluorescence Spectrophotometry (FL), Ultraviolet Visible Spectrometry (UV-Vis) and Thermogravimetric Analysis (TGA). FT-TR results suggested that PBMA was linked to SiO2-TiO2 network through chemical bonds. SEM measurements indicated that the diameter of the fibres was about 50 micrometre, and the whole system was homogeneous. HRTEM images showed that the dimensions of the organic phase were about 50 nm, and the distributions of the organic phase were not very uniform. FL and UV-Vis measurements confirm the fluorescence of the hybrid fibres with improved shielding to UV. TGA measurements suggest that the hybrid fibres show better resistance to heat than pure PBMA. 15 Refs.

Title: STRUCTURES AND MECHANICAL PROPERTIES OF POLYURETHANE/CLAY COMPOSITES PREPARED BY DIFFERENT PRE-MIXING PROCEDURES
Page Range: p.517-526
Author(s): Jen-Taut Yeh; Maw-Cherng Suen; Yu-Ching Lai; Hsun-Tsing Lee; Cheng-Chi Chen
File size: 380K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.9

Abstract
A novel method for preparing polyurethane/nano-clay composites was used in this study. The nano-clay was pre-mixed with the various components, such as diphenylmethane diisocyanate (MDI), 2,2-bis(hydroxymethyl) propionic acid (DMPA) or polytetramethyleneglycol (PTMG), of polyurethane (PU) polymer to prepare the composites. The PU/clay composites prepared by this method revealed that the values of the tensile strength at break, the elongation at break, the modulus and the surface roughness for the composite prepared from the pre-mixture of clay and PTMG (PU/clay-PTMG composite) were higher than those for the composite prepared from the pre-mixture of clay and MDI (PU/clay-MDI composite), the composite prepared from the pre-mixture of clay and DMPA (PU/clay-DMPA composite) and PU. The thickness of the crystals for PU/clay-MDI and PU/clay-DMPA composites was larger than that for PU and PU/clay-PTMG; whereas the layer distance of the crystals for PU/clay-MDI and PU/clay-DMPA composites was smaller than those for PU and PU/clay-PTMG. The values of glass transition temperature (Tg) of soft and hard segments were in the order of PU/clay-MDI > PU/clay-DMPA > PU > PU/clay-PTMG. Among the three PU/clay composites prepared by the pre-mixing procedure, PU/clay-MDI and PU/clay-DMPA composites showed significant gathering of the nano-clay in the PU matrix. A possible mechanism of the structural changes under tensile stress was speculated to explain the reason for the higher tensile strength and elongation at break of PU/clay-PTMG composite. The pre-mixing of clay-PTMG was a good procedure for the manufacture of the PU/clay composite, which had higher values of tensile strength and elongation at break. 29 Refs.

Title: MECHANICAL PROPERTIES OF UNPLASTICISED PVC (PVC-U) CONTAINING RICE HUSK AND AN IMPACT MODIFIER
Page Range: p.527-536
Author(s): Mazatusziha Ahmad; Abdul Razak Rahmat; Azman Hassan
File size: 510K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.9

Abstract
The objective of this study was to investigate the effects of rice husk and acrylic impact modifiers on the mechanical properties of unplasticised poly(vinyl chloride) (PVC-U) composites. The composites were prepared using a two-roll mill at temperature 165 C before being hot pressed at 185 C. The incorporation of rice husk (RH) fillers from 10 to 40 per hundred resin (phr) has increased the flexural and tensile modulus of the unmodified and modified (8 phr impact modifier) PVC-U composite. The flexural strength for both unmodified and modified PVC-U composite was observed to increase until RH loading of 20 phr. However, the tensile and impact strength of PVC-U composite decreased with RH loading. The scanning electron microscopy (SEM) showed that the rice husk fillers agglomerated and unevenly distributed throughout the matrix. The result showed that the impact strength of the filled PVC-U composites (20 phr filler) increased but the tensile and flexural properties decreased with increasing impact modifier content. The formulation containing 8 phr of acrylic impact modifier and 20 phr of RH loading showed the best balance of stiffness and toughness properties. 18 Refs.

Title: PULTRUSION OF COMPOSITE PROFILES POLYURETHANE (PU) AS ALTERNATIVE MATRIX SYSTEM
Page Range: p.537-542
Author(s): Michaeli W
File size: 418K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.9

Abstract
For structural components with high specific mechanical properties frequently parts made of fibre reinforced plastics (FRP) with thermoset matrix systems, oriented reinforcement fibres and high fibre volume contents are used. An established manufacturing technique for the production of composite profiles is the pultrusion process. By custom-designed properties pultruded parts are used for example as load-bearing structures in the building sector or lining elements in the transportation industry1. The pultrusion process is characterized by high laminate qualities, a high degree of automation and an eminent economic efficiency. A further reduction of the production costs can be achieved by the use of alternative matrix systems with comparable material properties by reduced raw material costs and increased processing speeds. By the restricted reactivity of the most commonly used matrix systems the processing speeds are limited. 5 Refs.

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