LDPE/EVA/graphene nanocomposites with enhanced mechanical and gas permeability properties

In the present work, graphene oxide (GO) and reduced graphene oxide (RGO) were incorporated at low‐density polyethylene (LDPE)/ethylene vinyl acetate (EVA) copolymer blend using solution casting method. Monolayer GO with 1‐nm thickness and good transparency was synthesized using the well‐known Hummers's method. Fourier transform infrared and X‐ray photoelectron spectroscopy data exhibited efficient reduction of GO with almost high C/O ratio of RGO. Scanning electron microscopy showed the well distribution of GO and RGO within LDPE/EVA polymer matrix. The integrating effects of GO and RGO on mechanical and gas permeability of prepared films were examined. Young's modulus of nanocomposites are improved 65% and 92% by adding 7 wt% of GO and RGO, respectively. The tensile measurements showed that maximum tensile strength emerged in 3 wt% of loading for RGO and 5 wt% for GO. The measured oxygen and carbon dioxide permeability represented noticeably the attenuation of gas permeability in composite films compared with pristine LDPE/EVA blend. Copyright © 2015 John Wiley & Sons, Ltd.     

POM／EVA共混物的研究

用力学测试、扫描电镜（ＳＥＭ）、热分析（ＤＳＣ）等手段研究了聚甲醛（ＰＯＭ）与乙烯－醋酸乙烯酯共聚物（ＥＶＡ）共混物（ＰＯＭ／ＥＶＡ）的力学性能及其微同形态；用聚甲醛与马来酸二丁酯（ＤＢＭ）的接枝物（ＰＯＭ－ｇ－ＤＢＭ）作相溶剂，能改变共的两相间的粘结力，从而提出了共混物的力学性能，ＳＥＭ观察表明接枝物的加入改变了ＰＯＭ／ＥＶＡ共混物的断裂方式，微观形态及结晶性能，对其热性能影响不大；通过改变ＰＯ     

利用~1H-NMR研究HDPE/PET/EVA共混体系的酯交换反应

本文在选用EVA作为HDPE/PET共混体系增容剂的基础上 ,通过双螺杆反应挤出熔融加工过程 ,促使EVA侧基上的酯基官能团与PET组分主链上的酯基在适当催化剂———有机金属化合物存在的条件下发生酯交换反应 .1H NMR结果表明 ,酯交换反应的产生在共混体系界面原位形成接枝或交联的PET EVA共聚物 ,且主要是以生成接枝共聚物的反应为主 .     

Influence of mechanical properties,toughness, and barrier properties of PMMA‐EVA‐organoclay nanocomposites with and without in situ crosslinking

Poly methyl methacrylate (PMMA)‐ethylene vinyl acetate (EVA)‐organoclay nanocomposites were prepared with and without in situ crosslinking using tetrapropoxysilane (TPOS) as a crosslinking agent and dibutyl tin oxide (DBTO) as a catalyst. Brabender Plasticorder experimental results suggest that in situ crosslinking transforms the EVA from a liquid to a viscoelastic solid. Transmission electron micrographs analysis indicates that most of the organoclay was clustered in the crosslinked EVA phase. X‐ray diffraction and morphology indicate that the PMMA‐EVA‐organoclay nanocomposites were intercalated and incompatible. Dynamic mechanical analysis (DMA) results indicate some interaction between PMMA‐EVA‐clay nanocomposites. The in situ crosslinked of EVA and the addition of organoclay increased the modulus properties of PMMA. However, in situ crosslinking slightly reduced the barrier properties of PMMA‐EVA‐organoclay nanocomposites. Copyright © 2009 John Wiley & Sons, Ltd.     

Crystallization Kinetics of Functionalized Fe3O4/Ethylene-vinyl Acetate Copolymer Nanocomposites Adhesives

In the present paper, the crystallization behaviors of six different functional Fe₃O₄/ethylene-vinyl acetate (EVA) copolymer nanocomposite adhesives were studied. Crystal structures of the nanocomposite adhesives were characterized by wide-angle X-ray scattering, and the results showed that both functionalized and non-functionalized Fe₃O₄ nanoparticles had only a small influence on the crystal structure of EVA. The cystallization kinetics was investigated through differential scanning calorimetry. The Ozawa and Mo methods were applied to analyze the crystallization behaviors, and the nucleating effect was estimated through the Dobreva and Gutzow method. Finally, the crystallization energy barrier was studied by the Kissinger method.     

Characterization of irradiation-induced crosslink of epoxidised natural rubber/ethylene vinyl acetate (ENR-50/EVA) blend

The effect of irradiation on tensile, dynamic mechanical properties, thermal properties and morphology of ENR-50, EVA and ENR-50/EVA blend was investigated. All the samples were irradiated using a 3.0 MeV electron beam (EB) machine with doses ranging from 20 to 100 kGy. Results indicate that the gel fraction of ENR-50, EVA and ENR-50/EVA blend increases with irradiation dose. Concerning tensile properties, it can be seen that EB radiation increases the tensile strength of all the samples, increases the elongation at break of ENR-50 and ENR-50/EVA blend, reduces the elongation at break of EVA, increases M200 (modulus at 200% strain) of ENR-50 and EVA, while decreases M200 of the ENR-50/EVA blend. For dynamic mechanical studies, it was found that EB radiation increases the T_g of all the samples due to the effect of irradiation-induced crosslinking. The compatibility of ENR-50/EVA blend also found to be improving upon irradiation. In the case of thermal properties, it was detected that T_m, T_c and the degree of crystallinity of ENR-50/EVA blend increase with an increase in irradiation dose. This was due to the perfection in the crystal growth occurring upon radiation. Morphology changes play a major role in the changes of the properties of ENR-50/EVA blend. Finally, it can be concluded that ENR-50/EVA blend can be vulcanized by EB radiation.     

Grafting of polymethyl methacrylate from poly(ethylene-co-vinylacetate) copolymer using atom transfer radical polymerization

Atom transfer radical polymerization was employed for the first time to prepare graft copolymer having by ethylene-vinyl acetate (EVA) copolymer as backbone and poly(methyl methacrylate) (PMMA) as branches. The polymerization of MMA was initiated by EVA carrying chloropropionate groups as macroinitiator, in the presence of copper chloride (CuCl) and bipyridine (bpy) at 80 °C. The macroinitiator was prepared by esterification of partially hydrolyzed EVA with 2-chloropropionyl chloride. Successful graft copolymerizations were performed both in toluene/γ-butyrolactone mixed solvent and in toluene solution, with grafting efficiency of 12% and 6%, respectively. Molecular weight distribution of the PMMA segments around 1.2 has been achieved with pure toluene solution. The ATRP graft copolymerization was supported by an increase of the molecular weight of the graft copolymers, as compared to that of the macroinitiator and also by their monomodal molecular weight distribution.     

高密度聚乙烯／低密度聚乙烯／乙烯－醋酸乙烯共聚物共混体系的结晶行为

通过ＤＳＣ和ＷＡＸＤ研究了高密度聚乙烯／低密度聚乙烯／乙烯－醋酸乙烯共聚物（ＨＤＰＥ／ＬＤＰＥ／ＥＶＡ）三元共混体系的热行为和结晶性能。发现当ＨＤＰＥ含量小于４０％时，ＥＶＡ对ＬＤＰＥ起稀释剂作用，促进ＨＤＰＥ、ＬＤＰＥ的晶相分离，使ＨＤＰＥ、ＬＤＰＥ单独结晶．当ＨＤＰＥ含量高于４０％时，ＬＤＰＥ片晶进入ＨＤＰＥ晶相。形成与ＬＤＰＥ在片晶水平上的共晶。     

GPC-VIS-MALS study of EVA copolymers: Quantification and interactions of SCB and LCB

Long-chain branching (LCB) is a structural phenomenon that affects important properties in polyethylene (PE) and some copolymers. Quantification of LCB frequency (λ) can be carried out by gel permeation chromatography dotted with detector for viscosity (GPC-VIS) or light scattering (GPC-MALS) by calculating branching indexes against a linear reference. In copolymers, interactions between LCB and SCB (short chain branching) have been described and lead to errors in quantification.In this work, ethyl vinyl acetate (EVA) copolymers of composition ranging 3–20 wt% VA have been studied. A numerical method, developed for the reduction of GPC-VIS and GPC-MALS data of PE, was used for quantifying molecular weights, intrinsic viscosities and gyration radius, as well as the confident ranges. Reliable results were obtained despite the low LCB determined values.A low density polyethylene was also included and compared. Discrepancies in the scaling laws for gyration radius and intrinsic viscosity reveal a strong effect of SCB which was confirmed by the structure factor and its dependence on molecular weight and comonomer content. However, the recently designed gpcBR index revealed to be nearly independent on the short chain branching and allowed detecting differences between apparently similar samples.     

Structure–property relationship of octa‐substituted POSS in thermal and mechanical reinforcements of conventional polymers

In this article, we describe the structure–property relationships between the polyoctahedral oligomeric silsesquioxane (POSS) fillers and the thermomechanical properties of the polymer composites using polystyrene, poly(methyl methacrylate), and ethylene‐(vinyl acetate) copolymer. We used eight kinds of octa‐substituted aliphatic and aromatic POSS as a filler, and homogeneous polymer composites were prepared with various concentrations of these POSS fillers. From a series of measurements of thermal and mechanical properties of the polymer composites, it was summarized that the longer alkyl chains and unsaturated bonds at the side chains in POSS are favorable to improve the thermal stability and the elasticity of polymer matrices. It was found that phenyl‐POSS can show superior ability to improve the thermomechanical properties of conventional polymers used in this study. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5690–5697, 2009