Use of maleic anhydride-grafted polyethylene as compatibilizer for HDPE-tapioca starch blends: Effects on mechanical properties

Tapioca starch in both glycerol-plasticized and in unplasticized states was blended with high-density polyethylene (HDPE) using HDPE-g-maleic anhydride as the compatibilizer. The impact and tensile properties of the blends were measured according to ASTM methods. The results reveal that blends containing plasticized starch have better mechanical properties than those containing unplasticized starch. High values of elongation at break at par with those of virgin HDPE could be obtained for blends, even with high loading of plasticized starch. Morphological studies by SEM microscopy of impact-fractured specimens of such blends revealed a ductile fracture, unlike blends with unplasticized starch at such high loadings, which showed brittle fracture, even with the addition of compatibilizer. In general, blends of HDPE and plasticized starch with added compatibilizer show better mechanical properties than similar blends containing unplasticized starch. (C) 2001 John Wiley & Sons, Inc.

Evaluation of physico-mechanical properties and in vitro biocompatibility of compression molded HDPE based biocomposites with HA/Al2O3 ceramic fillers and titanate coupling agents

The present article demonstrates how the stiffness, hardness as well as the cellular response of bioinert high-density polyethylene (HDPE) can be significantly improved with combined addition of both bioinert and bioactive ceramic fillers. For this purpose, different amounts of hydroxyapatite and alumina, limited to a total of 40 wt %, have been incorporated in HDPE matrix. An important step in composite fabrication was to select appropriate solvent and optimal addition of coupling agent (CA). In case of chemically coupled composites, 2% Titanium IV, 2-propanolato, tris iso-octadecanoato-O was used as a CA. All the hybrid composites, except monolithic HDPE, were fabricated under optimized compression molding condition (140 degrees C, 0.75 h, 10 MPa pressure). The compression molded composites were characterized, using X-ray diffraction, Fourier transformed infrared spectroscopy, and scanning electron microscopy. Importantly, in vitro cell culture and cell viability study (MTT) using L929 fibroblast and SaOS2 osteoblast-like cells confirmed good cytocompatibility properties of the developed hybrid composites. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

In vitro cytotoxicity and in vivo osseointergration properties of compression-molded HDPE-HA-Al2O3 hybrid biocomposites

The aim of this study was to investigate the in vivo biocompatibility in terms of healing of long segmental bone defect in rabbit model as well as in vitro cytotoxicity of eluates of compression-molded High density polyethylene (HDPE)hydroxyapatite (HA)-aluminum oxide (Al2O3) composite-based implant material. Based on the physical property in terms of modulus and strength properties, as reported in our recent publication, HDPE-40 wt % HA and HDPE-20 wt % HA-20 wt % Al2O3 hybrid composites were used for biocompatibility assessment. Osteoblasts cells were cultured in conditioned media, which contains varying amount of composite eluate (0.01, 0.1, and 1.0 wt %). In vitro, the eluates did not exhibit any significant negative impact on proliferation, mineralization or on morphology of human osteoblast cells. In vivo, the histological assessment revealed neobone formation at the bone/implant interface, characterized by the presence of osteoid and osteoblasts. The observation of osteoclastic activity indicates the process of bone remodeling. No inflammation to any noticeable extent was observed at the implantation site. Overall, the combination of in vitro and in vivo results are suggestive of potential biomedical application of compression-molded HDPE- 20 wt % HA- 20 wt % Al2O3 composites to heal long segmental bone defects without causing any toxicity of bone cells.

Estudio de la desactivación en el proceso de pirólisis de plásticos (HDPE) y reformado en línea para la producción de hidrógeno

La producción de hidrógeno a partir de residuos plásticos es un proceso interesante y viable, teniendo en cuenta el aumento significativo del actual consumo de hidrógeno. Sustituyendo así, la producción a partir de fuentes fósiles las cuales emiten grandes cantidades de CO2. El interés principal de este proyecto es avanzar en la valorización del plástico, HDPE, a través de la pirólisis y posterior reformado con vapor en línea para la obtención de hidrógeno, producto de alto valor añadido. Para ello se ha propuesto una primera etapa de pirólisis en un reactor spouted bed cónico y una segunda etapa catalítica de reformado con vapor en un lecho fluidizado en línea. Partiendo de unas condiciones de operación óptimas para el proceso, se pretende conocer cómo afecta la desactivación del catalizador al proceso a medida que la reacción avanza.

Desenvolvimento e avaliação de nanocompósitos à base de polietileno de alta densidade (hdpe-vERDE)/poli(ácido lático) (pla) e nanocarbonato de cálcio para fabricação de embalagens

Este trabalho traz como proposta a obtenção de nanocompósitos (PLA/HDPE-g-AM/HDPE-Verde/n-CaCO3) com propriedades mecânicas e de fluxo adequadas para aplicação no setor de embalagens. A produção desses nanocompósitos ocorreu por meio de uma mistura de PLA e polietileno proveniente de fonte renovável (HDPE-Verde), viabilizada pela ação do agente compatibilizante polietileno enxertado com anidrido maleico (HDPE-g-AM) e do aditivo carbonato de cálcio nanoparticulado (n-CaCO3), através do estudo das condições ótimas de processamento e composição, realizado por meio do Planejamento Fatorial Delineamento Composto Central Rotacional (DCCR). A obtenção deste balanço ótimo se deu ao se avaliar a influência dos fatores de estudo velocidade de rotação (100-400rpm), teor da fase dispersa PLA 2003D (0-35%) e teor da nanocarga mineral - n-CaCO3 (1-4%) sobre as propriedades mecânicas, térmicas, morfológicas e de fluxo dos nanocompósitos, através das variáveis de resposta - módulo de Young, resistência ao impacto, grau de cristalinidade (c) e índice de fluidez (MFI).Avaliações preliminares conduziram à escolha do PLA como fase dispersa dos compósitos. As variáveis de resposta do planejamento indicaram que a viscosidade dessas amostras é diretamente proporcional à concentração de n-CaCO3 e a velocidade de processamento, por promoverem, respectivamente, maior resistência ao escoamento e dispersão da carga. As composições apresentaram como característica resistência ao impacto similar ao comportamento do PLA puro e em contrapartida, módulo de Young similar a matriz de HDPE-Verde. A cristalinidade dos polímeros foi melhorada, observando-se uma ação mútua do HDPE-Verde e do PLA para este aumento, havendo ainda colaboração do n-CaCO3 e da velocidade de mistura. A morfologia dos compósitos foi função da velocidade que favoreceu maior dispersão e distribuição da fase dispersa e ainda por maiores teores de n-CaCO3 que ocasionaram a formação de gotas de PLA de menores dimensões, favorecendo uma estrutura mais homogênea. Maiores teores de PLA alteraram a morfologia dos compósitos, ocasionando a formação de grandes domínios dessa fase na forma de gota que atribuíram ao material maior rigidez. A avaliação individual do efeito do n-CaCO3 sobre o PLA e o HDPE-Verde individualmente apontaram que a ação da carga mineral em geral é benéfica para a melhoria das propriedades, com exceção da resistência ao impacto. Além disso, os resultados mostram que a compatibilizante HDPE-g-AM também minimiza a atuação da carga. Em relação à influência do HDPE-g-AM sobre a mistura HDPE-Verde/PLA é possível observar que a compatibilização da mistura tende a ocorrer, porém não de forma eficiente como o esperado

Studies on the suitability of HDPE material for gill nets

The suitability of HDPE yarn and HDPE twine in place of nylon for gill nets has been studied. As regards total catch nylon gill net is found to be better than HDPE nets. However, statistical analysis of the catch in respect of quality fishes shows that HDPE yarn nets are equally efficient as nylon nets.

“PP-PE”聚合合金结构与性能的关系及PP/HDPE共混体系增容改性的新途径

试图澄清“PP-PE”结构与性能的关系，并以此为指导寻求增容改性PP/HDPE体系的新途径是本工作的主要内容。在本工作中，考虑到分子量、EPC组分和共混均匀性因素之后发现，“PP-PE”与相同条件下合成的均聚物样品构成的共混物之间在应力-应变行为、抗冲击性能和动态力学行为上并没有明显差别。在结合文献中有关现象详尽讨论了关于活性链寿命报导值和“（PP-PE）_(200)"的C~(13)NMR谱支持嵌段结构观点的可靠性之后，得到的结论是，现有实验现象不中以证明“PP-PE”具有嵌段结构，尽管四十年来这一观点已被普遍接受。通过TEM观察到，“PP-PE”与PP/HMWPE共混物结晶结构相同，“PP-PE”中的PE部分明显具有HMWPE的片晶特征，应力-应变和SEM实验的结果显示，“PP-PE”与HMWPE具有完全相同的增容PP/HDPE的作用。结合有关共混物结构和性能的实验结果，发现“PP-PE”主要是一个共混物，其中的HMWPE和EPC组分是决定其性能行为的主要因素。尽管在理论和实验上都已确认，分子量的增大不利于共混物组分间的相容，但通过应力-应变实验和形态结构的观察发现，虽然均聚物HMWPE的加入使PP/HDPE体系中PE组分平均分子量增大，但是体系中分散相尺寸却随HMWPE含量的增加大幅度减小，力学性能全面提高。HMWPE这种同接枝和嵌段共聚相似的增容作用既不能用“相似相容”，也不能用所谓“特殊相互作用”来阐明。为此，在本工作中提出了一个新的增容机制——“缠结作用”。应力-应变实验表明，PP/HMWPE体系的力学性能明显优于PP/HDPE体系。前者强度和断裂伸长率都高于后者，其差别尤以断裂伸长率为甚，而模量相差不大。SEM形态结构的观察发现，虽然PP/HDPE体系中的分散相尺寸随其量的增加而增大，并且界面清晰，但PP/HMWPE中的缠结作用使得组分间界面模糊，甚至消失。这种较强的组分间相互作用使得材料由脆性断裂转变为韧性断裂。PP/HMWPE的性能特点进一步证实了非理想换气条件下制备的“PP-PE”结构与性能的关系。

Characterization of the Microstructure of Bimodal HDPE Resin

In this work, two industrial bimodal high density polyethylene resins, resin A and resin B having similar molecular weight (M-w), molecular weight distribution (M-wD), and short-chain branching (SCB) content but different mechanical properties, were fractionated through cross-fractionation. The fractions were further, characterized by GPC, C-13 NMR, DSC AND FT IR techniques. These two resins were firstly fractionated into two franctions, i.e. high-temperature and low temperature fractions, via preparative solution crystallization fractionation. Resin A with much better mechanical properties contains more high-temperature fractions with longer crystalizable sequences. The SCB content in the low temperature fraction of resin A is lower than the of resin B. Both low-temperature fractions were then further fractionated using solvent gradient fractionation (SGF). The characterization of SGF fraction indicates that most of the branches fall into the high molecular weight chain in both low-temperature fractions.

Nanostructure and mechanical measurement of highly oriented lamellae of melt-drawn HDPE by scanning probe microscopy

Scanning probe microscopy was used to simultaneously determine the molecular chain structure and intrinsic mechanical properties, including anisotropic elastic modulus and friction, for lamellae of highly oriented high-density polyethylene (HDPE) obtained by the melt-drawn method. The molecular-scale image of the highly oriented lamellae by friction force microscopy (FFM) clearly shows that the molecular chains are aligned parallel to the drawing direction, and the periodicities along and perpendicular to the drawing direction are 0.26 and 0.50 nm, respectively. The results indicate that the exposed planes of the lamellae resulting from the melt-drawn method are (200), which is consistent with results of transmission electron microscopy and electron diffraction. Because of the high degree of anisotropy in the sample, coming from alignment of the molecular chains along the drawing direction, the measured friction force, F, determined by FFM is strongly dependent on the angle, theta, between the scanning direction and the chain axis. The force increases as theta is increased from 0 degrees (i.e., parallel to the chain axis) to 90 degrees (i.e., perpendicular to the chain axis). The structural anisotropy was also found to strongly influence the measurements of the transverse chain modulus of the polymer by the nanoindentation technique. The measured value of 13.8 GPa with transverse modulus was larger than the value 4.3 GPa determined by wide-angle X-ray diffraction, which we attributed to anisotropic deformation of the lamellae during nanoindentation measurements that was not accounted for by the elastic treatment we adopted from Oliver and Pharr. The present approach using scanning probe microscopy has the advantage that direct correlations between the nanostructure, nanotribology, and nanomechanical properties of oriented samples can be determined simultaneously and simply.

Morphology, thermal behavior, and mechanical properties of PA6/UHMWPE blends with HDPE-g-MAH as a compatibilizing agent

A functionalized high-density polyethylene (HDPE) with maleic anhydride (MAH) was prepared using a reactive extruding method. This copolymer was used as a compatibilizer of blends of polyamide 6 (PA6) and ultrahigh molecular weight polyethylene (UHMWPE). Morphologies were examined by a scanning electron microscope. It was found that the dimension of UHMWPE and HDPE domains in the PA6 matrix decreased dramatically, compared with that of the uncompatibilized blending system. The size of the UHMWPE domains was reduced from 35 mu m (PA6/UHMWPE, 80/20) to less than 4 mu m (PA6/UHMWPE/HDPE-g-MAH, 80/20/20). The tensile strength and Izod impact strength of PA6/UHMWPE/HDPE-g-MAH (80/20/20) were 1.5 and 1.6 times as high as those of PA6/UHMWPE: (80/20), respectively. This behavior could be attributed to chemical reactions between the anhydride groups of HDPE-g-MAH and the terminal amino groups of PA6 in PA6/UHMWPE/HDPE-g-MAH blends. Thermal analysis was performed to confirm that the above chemical reactions took place during the blending process. (C) 2000 John Wiley & Sons, Inc.

PA6/UHMWPE/HDPE-g-MAH共混物反应增容作用的研究

通过 DSC、SEM、Molau试验和力学性能测试 ,研究了 PA6/ UHMWPE共混过程中 HDPE- g- MAH对体系的增容作用、力学性能及结晶行为的影响。结果表明 ,共混体系为热力学不相容体系 ;在熔融共混过程中 ,PA6和 HDPE- g- MAH发生化学反应 ,生成的接枝共聚物对 PA6/ UHMWPE体系有增容作用 ,分散性和界面形态以及力学性能明显改善 ;共混体系中两相的结晶行为亦发生变化 ,尼龙组分的熔融热焓明显下降

Epitaxial crystallization of sPP on the (100) lattice plane of HDPE crystals

Crystallization behavior of syndiotactic polypropylene(sPP) on the (100) lattice plane of high-density polyethylene(HDPE) crystals was studied by means of transmission electron microscopy and electron diffraction. The results indicate that sPP crystals can grow epitaxially on the (100) PE lattice plane with their chain directions +/-37 degrees apart from the chain direction of the HDPE substrate. The contact planes are (100) lattice planes for both polymers. This kind of epitaxy is explained in terms of parallel alignment of HDPE chains along the rows formed by the {CH3, CH2,CH3} groups in the (100) lattice plane of the sPP crystals. This implies that in the epitaxial crystallization of sPP with fiber oriented HDPE substrate, not only the (110) but also the (100) HDPE lattice planes can act as the oriented nucleation sites. Furthermore, according to the poor matching between HDPE chains in the (100) lattice plane and the {CH3, CH2, CH3} group rows in the (100) lattice plane of the sPP crystals, it is concluded that the geometric matching is not the only controlling factor for the occurrence of polymer epitaxy.

Deformation process and mechanism of HDPE/LDPE blends

Blends of HDPE in more LDPE, with appropriate heat treatment, produce a dispersion of separate entities of HDPE in a matrix of LDPE. The system offered an especially favourable means of studying the deformation of melt-crystallized lamellae. It has been found that sheaf-like spherulites are transformed under tensile deformation into hourglass shapes i.e. a double cone aligned along the drawing direction with origin in the center of the object. This is a consequence of different modes of deformation according to the relation of an individual lamella to the tensile axis. The work shows that the lamellae have not undergone melting and recrystallization in the deformation process at room temperature.

HDPE、UHMWPE稀溶液成膜的形态结构研究

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HDPE/LDPE共混物形变过程中的结构变化及机理

聚合物熔体结晶由于链缠结等因素的影响，其形态结构非常复杂，这给研究结晶聚合物的微观结构，特别是聚合物在拉伸过程中的形态变化带来很大困难．本文将高密度聚乙烯（ＨＤＰＥ）和低密度聚乙烯（ＬＤＰＥ）两种不相容的组分进行共混，使少量ＨＤＰＥ分散在ＬＤＰＥ中，…