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Polymers and Polymer Composites

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Title: EFFECT OF PROCESS PARAMETERS ON LAYER-BY-LAYER SELF-ASSEMBLY OF POLYELECTROLYTES ON COTTON SUBSTRATE
Page Range: p.237-249
Author(s): Wazed Ali S; Rajendran S; Joshi M
File size: 255K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.5

Abstract
To our knowledge, the present study is the first attempt to evaluate the effect of different process parameters on the amount of polyelectrolyte adsorbed on a cotton textile substrate via sequential adsorption of negatively charged poly (styrene sulphonate) (PSS) and positively charged poly (allylamine hydrochloride) (PAH) using layer-by-layer (LBL) self-assembly nanocoating process. A considerably different polymer adsorption behaviour was observed from thick adsorbed layers to thin adsorbed layer with different degree of layer penetration and ionic pair formation over the pH range (2.5 – 9.0) studied. The amount of polyelectrolyte adsorption on cotton fabric was evaluated by measuring the colour value (K/S) of methylene blue absorbed cotton surface. Contact angle measurement revealed that the extent of binding of the oppositely charged polyions on the fabric depends on the pH of the polyelectrolyte solution and ‘zipped-up' structure with more ion pair formation was observed at the pH range 4.5 – 6.5. At higher temperature, the amount of polyelectrolyte adsorbed within the multilayers was higher. An increased deposition of PSS and PAH was observed with increase in electrolyte (NaCl) concentration. The amount of PSS and PAH adsorption increased up to 0.03 (M) of PSS and 0.01 (M) of PAH concentrations, respectively. A dipping time of 5 min was sufficient to have a maximum deposition of the polyelectrolyte multilayers. 26 Refs.

Title: EFFECT OF POLY(2-ETHYL-2-OXAZOLINE) ON MULTI-WALLED CARBON NANOTUBES REINFORCED POLY(VINYL ALCOHOL) COMPOSITES
Page Range: p.251-256
Author(s): Tan S H; Suk K L; Goak J C; Hong S C; Kim J-Y; Lee S-W; Kim S; Seo Y; Lee N
File size: 348K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.5

Abstract
The effect of poly(2-ethyl-2-oxazoline) (PEOX) as a surface modifier for multi-walled carbon nanotubes (MWCNTs) in a poly(vinyl alcohol) (PVA) composite was studied through a simple polymer wrapping and melt extrusion processes. MWCNTs were carboxylated in a reaction with HNO3, followed by mixing with 10 wt.% PEOX in ethanol to produce a MWCNT-PEOX complex. High resolution transmission electron microscopy identified a PEOX layer existing on the surface of MWCNTs. Compared with pristine MWCNTs, MWCNT-PEOX showed an improved dispersion in hydrophilic solvents such as water and ethanol. The PVA composite reinforced with 0.5 wt.% MWCNT-PEOX exhibited 54% higher Young's modulus than pure PVA. 20 Refs.

Title: THERMAL PROPERTIES OF HIGH DENSITY POLYETHYLENE-KENAF CELLULOSE COMPOSITES
Page Range: p.257-261
Author(s): Tajeddin B; Abdulah L C
File size: 148K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.5

Abstract
Biocomposites of high density polyethylene (HDPE) and kenaf cellulose (KC) with polyethylene glycol (PEG) have been prepared by melt blending and compression moulding. The optimum temperature and reaction period for blending KC with HDPE were 145 °C and 12 minutes with rotation speed of 30 rpm, respectively. The effects of composition on the thermal properties of HDPE-KC biocomposites were investigated using TGA and DSC. Each sample of HDPE-KC biocomposites was subjected to heating programs between 35-600 °C for TGA, and the DSC analysis was determined under heating cycles of 25-600 °C. The results from TGA and DSC indicated that by increasing the KC content, the thermal stability was slightly improved. The melting temperature for all the composites was less than the melting point of KC (148.70 °C), and almost the same as that of HDPE (130.38 °C). Therefore no significant change in the melting temperature resulted from adding KC to the HDPE matrix. However, HDPE's presence surrounding the KC fibres, prevented water from reaching the cellulose fibre particles, thus reducing the water content in the composite; hence a significant advantage of forming KC composites with hydrophobic HDPE is that it helps to make the cellulose hydrophobic instead of hydrophilic. 15 Refs.

Title: PREDICTION OF PROCESS-INDUCED GEOMETRICAL DEFORMATIONS FOR STIFFENED THERMOSETTING COMPOSITE PANELS
Page Range: p.263-273
Author(s): Zhang B; Yue G
File size: 486K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.5

Abstract
Stiffened thermosetting composite panels are primary structure of aircraft and fabricated with co-curing processing. The process-induced residual stresses resulted in geometrical deformation when the stiffened composite panel was fully cured and removed from the tool. An investigation into the three-dimensional cure simulation of T-shape stiffened thermosetting composite panels was presented to predict the process-induced deformation during cocuring. And flexible tools and locating tools were considered in the cure simulation. Simulation examples were presented to demonstrate use of the present finite element procedure for predicting composite parts deformations. The T300/BMI structure was analyzed provide insight into the non-uniform curing process. The temperature was higher in the interface between web and flange during the entire cure cycle. And the distortions of skin and webs for T-shape stiffened thermosetting composite panel were remarkable. 23 Refs.

Title: COMPUTER SIMULATION OF RESIN FLOW THROUGH THE BLEEDER IN THE AUTOCLAVE CURING PROCESS
Page Range: p.275-282
Author(s): Xu P; Jing X
File size: 235K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.5

Abstract
In the autoclave curing process of phenolic resin composite at high pressure, uncured resin usually flows into the vacuum pipe through improperly used bleeder and blocks the vacuum orifice. Therefore, there are too many defects formed in the as-prepared composite because not all volatiles can be expelled from the laminate. In order to choosing or manufacturing the bleeder used in this special condition, the resin flow in the bleeder should be carefully investigated. However, the resin flow in the bleeder cannot be observed directly during the autoclave curing process, computer simulation is employed to describe the flow in the bleeder. The simulation results show that i) the resin flow near the vacuum orifice is quite different compared to that far away from the vacuum orifice, the resin can flow through the bleeder near the vacuum orifice within a shorter time; ii) a bleeder made from needle-punched nonwoven material with low porosity, small fibre diameter and small permeability could prevent the resin from flowing into the vacuum pipe in the autoclave curing process. 19 Refs.

Title: SYNTHESIS OF HYPER-BRANCHED 4A ZEOLITE AND ITS APPLICATION IN NATURAL RUBBER SYSTEMS
Page Range: p.283-290
Author(s): Wang J; Zheng X; Chen Y
File size: 442K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.5

Abstract
Hyper-branched 4A zeolite (HB-4A zeolite) was prepared by condensation reaction between 4A zeolite and the monomer we prepared. It was then characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). This HB-4A zeolite was then used in the preparation of natural rubber (NR)/HB-4A zeolite composite. Different types of NR/HB-4A zeolite composites were prepared with different amounts of HB-4A zeolite and compared with the composites directly incorporated with 4A zeolite. The cure characteristics of different 4A zeolite filled NR composites were studied. Then, the tensile and thermal properties were compared. Results revealed that the mechanical properties of NR/HB-4A zeolite, especially elongation at break, showed a remarkable enhancement compared with that of NR/4A zeolite and NR systems. SEM studies showed that hyper-branching modification might increase the compatibility between 4A zeolite and NR matrix. A reinforcing mechanism was proposed, assuming that the ‘anchor' effect caused by the hyper-branched polymer may reduce the amount and size of voids and increase the length of the crack spread path during tensile drawing. 16 Refs.

Title: THERMAL OXIDATION BEHAVIOUR AND DEGRADATION KINETICS OF POLYPROPYLENE WITH P-TERT-BUTYLCALIX[N]ARENES
Page Range: p.291-296
Author(s): Zhu L; Xu K; Chen J; Chen M
File size: 192K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 18
Issue No: No.5

Abstract
p-tert-butylcalix[4]arene (C4), p-tert-butylcalix [6]arene (C6) and p-tert-butylcalix[8]arene (C8) were synthesised and explored as antioxidants for polypropylene (PP). The structures of these compounds were characterized by 1H-NMR and FTIR, and their antioxidation efficiencies for PP were evaluated by rheology analysis, differential scanning calorimetry (DSC), melt flow index analysis, and thermogravimetric analysis (TGA). The rheology results from a Haake Polydrive mixer revealed that calix[n]arenes had little effect in preventing PP from degradation during the processing, and the DSC analysis showed that the antioxidation performance of the calix[n]arenes for PP was in the order of C4 greater than C6 greater than C8. The values of melt flow index indicated that calix[n]arenes, especially C4 and C6, could largely improve the thermal stability of PP, and the activation energies for degradation of PP with C4, C6 and C8 calculated with the data from TGA were 97.05, 84.60 and 53.69 kJ/mol, respectively. 22 Refs.

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