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Polymers and Polymer Composites

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Title: Determination of reactivity ratios of copolymerization of acrylamide (AM) and methacryloxyethyltrimethyl ammonium chloride (DMC) with ultraviolet initiation, and their sequence length distribution
Page Range: p.307-314
Author(s): Yonghong Wang; Xinru Zhang; Wanjie Li; Jialiang Cheng; Chengcen Liu; Jiajun Zheng
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.5

Abstract
The copolymer P(AM-DMC), one kind of cationic polyacrylamide, was synthesised by using acrylamide (AM) and methacryloxyethyltrimethyl ammonium chloride (DMC) as monomers with ultraviolet initiation. The copolymer was characterised by Fourier transform infrared spectroscopy. The composition of the copolymer was determined from the chlorine content by silver nitrate titration. The effects of monomer feed ratio and conversion on the composition of copolymer were discussed. Reactivity ratios were determined by the Fineman-Ross, Kelen-Tudos and Yezrielev-Brokhina-Roskin methods, indicating that their positive order calculation results were very different with those of reverse order, when the reactivity ratios were determined by Fineman-Ross. However, their positive order and reverse order calculation results were similar when the reactivity ratios were determined by the Kelen-Tudos and Yezrielev-Brokhina-Roskin methods. Therefore, the reactivity ratios were determined using the average results of the Kelen-Tudos and Yezrielev-Brokhina-Roskin methods. The reactivity ratios of AM and DMC were 2.3398 and 0.2285, respectively. This result showed that the copolymerisation of AM and DMC was a non-ideal random copolymerisation. Furthermore, the content of AM segments decreased with the increase of AM feed content, but the content of DMC segments increased. Moreover, the sequence length distribution was irregular and narrow, because AM was prone to homopolymerisation. 27 Refs.

Title: Anisotropic thermal characteristics of graphene-embedded polyimide composite sheets
Page Range: p.315-322
Author(s): Seong-Yeob Park; Jong-Seong Bae; Jin-Gyu Kim; Min-Wook Oh; Jungsoo Kim; Dae-Geun Nam; Jeong Hyun Yeum; Weontae Oh
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.5

Abstract
Polyimide-graphene (PIG) composites were prepared, and their thermal properties were characterised as films or sheets. Graphene loadings were controlled up to 8 wt.% or 12 wt.% in their composites. The graphenes used in this work were prepared by the chemical treatment of graphite. The as-prepared polyimide-graphene composites were thermally characterised in films or sheets. The thermal conductivities of the PIG sheets were separately analysed in both in-plane and out-of-plane directions. The thermal expansion coefficients (TECs) of the PIG composites slightly changed with the amount of graphene added to the composites. The in-plane thermal conductivities were higher than the out-of-plane thermal conductivities, and the thermal conductivities of both directions proportionally increased with the graphene loadings in the PIG composites. The temperature-dependent stresses of the composite films monotonically decreased with the graphene loadings. The experimentally obtained thermal characteristics of the polyimide-graphene composites were compared and discussed on the basis of the composite morphologies. 37 Refs.

Title: Morphology and thermal property of poly(l-lactide)/layered double hydroxides nanocomposites via melt intercalation
Page Range: p.323-330
Author(s): Mengqi Tang; Fei Qi; Man Chen; Yang Xu; Huan Li; Xiaolang Chen; Jun Qin; Shaoyun Guo; Ru Shen
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.5

Abstract
In this work, sodium dodecyl sulphate (SDS) was used to obtain organically-modified layered double hydroxide (OMgAl-LDH) by anion-exchange reaction. The PLLA/LDH nanocomposites were prepared via direct melt intercalation. The results from both XRD patterns and FTIR spectra showed that SDS entered into the layers of LDH successfully and the layer space was increased from 0.756 to 1.64 nm. For the PLLA/LDH nanocomposites, the increase of the layer space was verified by the good dispersion of LDH in the PLLA matrix from the SEM images. The rheological analysis showed that the typical Newtonian behaviour shifted to shear-thinning behaviour with the addition of LDH. In addition, DSC data illustrated that the glass transition temperature of the PLLA/LDH nanocomposites decreased and the crystallinity of PLLA increased due to the addition of LDH, which indicates that LDH acts as a heterogeneous nucleating agent and induces the crystallisation of PLLA. The modified LDH provided a better nucleating effect than the unmodified LDH. TGA results showed that OMgAl-LDH in the PLLA matrix caused earlier initial decomposition, suggesting that the presence of LDH decreased the thermal stability of the PLLA matrix. 28 Refs.

Title: The effect of montmorillonite modification on crystallization behaviour of polypropylene/montmorillonite composites
Page Range: p.331-340
Author(s): Zhihong Yang; Minghu Wu; Gang Chen; Shengjuan Li; Panpan Peng; Qiaolian Zhang
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.5

Abstract
This paper reports the preparation of organic montmorillonite (OMMT) modified by octadecylamine and polypropylene/montmorillonite (PP/MMT) composites produced by the method of melt compounding. The effect of MMT modification degree on the crystallisation behaviour of PP was emphasised by X-ray diffraction (XRD), polarising optical microscopy and differential scanning calorimetry (DSC). Interlayer d-spacings of 3.02 nm, 1.27 nm and 2.59 nm were detected for MMT modified by octadecylamine, Titivate coupling agent and commercial OMMT, respectively. The spherulite size and the crystallinity of the composite decreased and the number of spherulites increased with the interlayer spacing of OMMT. The values of t1/2 and F(T) for PP crystallisation decreased with the interlayer spacing at a given cooling rate or a given relative crystallinity degree, indicating that MMT with a larger gallery height could accelerate the crystallisation rate of PP more efficiently. Moreover, the composites containing OMMT modified by octadecylamine exhibited better mechanical properties in comparison to those incorporating OMMT modified by Titivate coupling agent and commercial OMMT, indicating that primary amine was one of the best potential surfactants for MMT modification. It was concluded that full modification of OMMT by octadecylamine was more beneficial to the crystallisation of PP and hence caused a positive effect on the mechanical properties of the composites. 42 Refs.

Title: Processing routes for the preparation of poly(lactic acid)/cellulose-nanowhisker nanocomposites for packaging applications
Page Range: p.341-346
Author(s): Moran J I; Luduena L N; Vu Thanh Phuong; Cinelli P; Lazzeri A; Alvarez V A
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.5

Abstract
In this work, poly(lactic acid) (PLA)/cellulose-nanowhisker (CNW) nanocomposites were prepared by twinscrew extrusion followed by injection moulding. The CNW was dispersed in a plasticiser/compatibiliser (PL) before the melt mixing process. It was found that the PL not only improved the processability and reduced the fragility of PLA but also prevented the agglomeration of the CNW up to 12 wt.% of CNW content, obtaining well dispersed and distributed PLA/CNW nanocomposites. The prepared nanocomposites were injection moulded and their mechanical/thermal properties were evaluated. PLA/CNW nanocomposites showed better mechanical properties than those of the neat matrix but the material with the lower CNW content showed the best mechanical performance. 23 Refs.

Title: Techno-economic feasibility study of new concept for build-up of local load specific reinforced hybrid structures
Page Range: p.347-364
Author(s): Holschuh R; Becker D; Mitschang P
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.5

Abstract
This article describes a new process approach, based on a combination of thermoforming and in-situ tape placement for the build-up of locally load-related, reinforced multi-material-systems based on polymer-polymer-hybrids. The process is evaluated and compared with state-of-the-art technologies. A techno-economic analysis is presented for a case study, considering the cost-efficiency throughout the complete development in a process-based and stepwise differentiation approach. Compared to other competing concepts the novel concept offers the potential for reducing the unit costs at large-scale production scenarios. 46 Refs.

Title: Evaluation of the mechanical and radiopacity properties of poly(methyl methacrylate)/barium titanate-denture base composites
Page Range: p.365-374
Author(s): Elshereksi N W; Mohamed S H; Azlan Arifin; Ishak Z A M
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.5

Abstract
This study aimed to evaluate the flexural and hardness properties of poly(methyl methacrylate) (PMMA) denture base filled with barium titanate (BaTiO3). The BaTiO3 filler was treated with 3-trimethoxysilylpropyl methacrylate, which is a silane coupling agent. Curing was performed in a water bath at 78 deg C for 1.5 h. The samples were tested for tensile and flexural strength and surface hardness. The samples were also radiographed, and their optical densities were determined. Radiopacity values were compared with that of an aluminium (Al) plate with equivalent thickness. A reduction in the tensile and flexural strength of the PMMA composite was observed at high filler loadings. However, the surface hardness of the denture base composites was enhanced as a function of filler loading. The radiopacity of the PMMA/BaTiO3 composites was also improved. Adding 10 wt.% of BaTiO3 to PMMA resulted in a higher optical density (OD) (p< 0.07) compared with that of Al. 47 Refs.

Title: Thermal and mechanical properties of compression-moulded poly(lactic acid)/gluten/clays bio(nano)composites
Page Range: p.375-386
Author(s): Mohamed A A; Finkenstadt V L; Gordon S H; Alamri M S; Shahzad Hussain
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 24
Issue No: No.5

Abstract
Bio(nano)composites comprising agricultural-based polymers blended with biodegradable plant-based fillers and clays were produced to develop novel hydrophobic, yet biodegradable materials that have properties comparable to those of petroleum-based plastics. Poly(lactic acid) (PLA), vital wheat gluten (VG), and 3, 6, and 9% clays (NC1 or NC2) were mixed in a Haake Rheocord torque rheometer at 170 deg C for 10 min. Blends were compression-moulded and tested using modulated DSC (MDSC), thermogravimetric analysis (TGA), Instron, FTIR and HPLC. The DSC profile of neat PLA exhibited a glass transition (Tg) and exothermic (Cry) followed by endothermic (Mel) transitions. The profile showed a Tg of 0.46 J/g/ deg C, Cry with 29.6 J/g, whereas Mel exhibited 28.3 J/g. Vital wheat gluten displayed a single Tg (0.45 J/g/ deg C). Enthalpic relaxation of PLA was noted in the presence of clays, where the overall DSC profiles of PLA were different, especially during melting. The hydrophobic nature of NC1 clay created shoulders during PLA melting. The degradation kinetics of the blends followed a multistep mechanism, as shown by the TGA data. The tensile strength dropped because of processing and due to the addition of clay, whereas elongation was reduced by the presence of NC1. Higher Young's modulus value due to NC1 or NC2 indicated stiffer bio(nano)composites. Better biodegradability was indicated after proteinase-K enzyme treatment in the presence of NC1. Due to the hydrophobic nature of NC1, the amount of the acetic acid-extractable protein was reduced. FTIR analysis showed no evidence of chemical reaction between PLA, gluten and the clays, but suggested the occurrence of significant non-covalent intermolecular interactions. 18 Refs.

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