Preparation of MPS (mercaptopropyltrimethoxysilane)-coated SiO2 nanoparticle and its effect on mechanical properties of surface treated SiO2/EVA nanocomposite

SiO₂ nanoparticles were synthesized from different three precursors, namely, TEOS (tetraethyl orthosilicate), sodium metasilicate and sodium silicate. First, SiO₂ nanoparticles were prepared by a controlled hydrolysis of TEOS. In another method, SiO₂nanoparticles were prepared by precipitation in an emulsion medium from sodium metasilicate and hydrochloric acid solution. Finally, SiO₂ nanoparticles were also synthesized from sodium silicate by an emulsion method. In this study, we concentrated on dispersion and compatibility between nanosized SiO₂ particles and EVA (ethylene vinyl acetate). Therefore, surface modification of synthesized SiO₂ nanoparticles was accomplished with MPS (3-mercaptopropyl trimethoxysilane) to enhance homogeneous dispersion and compatibility between the obtained SiO₂ nanoparticles and EVA. Finally, nanocomposites of surface treated SiO₂ nanoparticles and EVA were prepared. By inserting the MPS-coated SiO₂ nanoparticles into EVA, abrasion resistance and hardness were increased remarkably. On the other hand, insertion of SiO₂ nanoparticles barely decreased original tensile strength and elongation of EVA. Consequently, MPS-coated SiO₂/EVA nanocomposite can have an improved abrasion resistance and hardness compared with raw EVA, without decrease tensile strength and elongation. The characterization of synthesized SiO₂ nanoparticles and their nanocomposite with EVA was conducted by TEM, SEM, FTIR photography and mechanical property tests such as abrasion, hardness, tensile strength and elongation.     

Multifractal analysis of fracture morphology of poly(ethylene-co-vinyl acetate)/carbon black conductive composite

In this paper, based on scanning electron microscope (SEM), the fracture morphology of poly(ethylene-co-vinyl acetate)/carbon black (EVA/CB) conductive composite with various cross-linkers 2,4-di(2-phenylisopropyl) phenol (DCP) contents were analysed by multifractal analysis. The relationship among the multifractal spectrum, cross-linker DCP content, the fracture morphology, fracture process and some mechanical property were discussed. The results showed that the larger the width Δα (Δα = α_max − α_min) of the multifractal spectra f(α), the more nonuniform the fracture surface morphology, in other words, the more the roughness. Moreover, the width Δα (Δα = α_max − α_min) of the multifractal spectra f(α) is the result of competition between ductile fracture and brittle fracture. Also, some mechanical property will correspondingly change when various cross-linker DCP contents were added. Multifractal analysis showed that the spectrum width Δα (Δα = α_max − α_min) of the multifractal spectra f(α) could be used to characterize the surface morphology and mechanical property of EVA/CB conductive composite, quantitatively.     

Influence of the Particle Size of CaCO3 on the Adhesion of Filled EVA Materials

A surface treatment with corona discharge was used to improve the adhesion properties of ethylene vinyl acetate copolymer (EVA) containing small amounts of four CaCO₃ with different particle size. The nature of the surface modifications produced by the corona discharge treatment and the adhesion to a polychloroprene adhesive were assessed. Treatment of CaCO₃ filled EVA with corona discharge produced a decrease in water contact angle value, irrelevant to the different particle size of the calcium carbonates. The corona discharge treatment created C-O and C=O moieties on the EVA surface and also increased the peel strength, more markedly as the CaCO₃ particle size increased. In general, a mixed (adhesion + cohesive in the EVA) failure in the filled EVA material was produced (assessed by IR-ATR spectroscopy and SEM micrographs of the failed surfaces), but the failure was more cohesive in the EVA containing higher particle size CaCO₃. The durability of the joints was also studied.     

Polymer Layered Silicate/Carbon Nanotube Nanocomposites: Morphological and Rheological Properties

Morphological and rheological properties of new ternary nanocomposites based on ethylene vinyl acetate copolymers (EVA), commercial organo-modified clays (organoclays) and purified multi-walled carbon nanotubes (MWNTs), prepared via direct melt blending, have been evaluated. For sake of comparison, the corresponding binary compositions, i.e., EVA filled with either organoclays or MWNTs, have been investigated as well. While extensive exfoliation can be observed for binary EVA/clay nanocomposites, the addition of MWNTs appears to limit clay exfoliation. Rheological properties show that both clay and MWNTs increase the elastic modulus of the nanocomposites, reflecting the high degree of nanoparticle interconnectivity that can be found in these materials.     

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.     

用减差红外光谱分峰法测定EVA共聚物的总支化度及支化度分布

对EVA大分子链上出现的支链结构,可选用无规聚丙烯的支链甲基峰1378cm~(-1),2-乙基己烷的支链乙基峰780cm~(-1)和聚α-己烯的支链丁基峰730cm~(-1)作为测定总支化度、乙基和丁基支化度的量度,并得到1000C中各支化度的分布公式:(L.B为长支链)n_3/1000C=0.50564 A_(1378)/dt-1.01966 n_(C_2H_5)/1000C=1.27161 A_(780)/dt-7.67873nC_(4H9)/1000C=0.09113 A_(730)/dt-6.41352 n_(L.B)/1000C=0.50564 A_(1378)/dt-1.27161 A_(780)/dt-0.09113 A_(730)/dt+13.07259由于EVA共聚物中,测定峰会发生重叠,故先用减差FTIR光谱分峰法,扣除干扰峰对测定峰的影响后,对测定峰进行峰面积积分,再计算支链的数均支化度,其测定结果与~1H-NMR结果一致。     

聚乙烯醇衍生的聚离子复合物的研究——Ⅳ.聚离子复合物膜的力学行为及透过性能

聚离子复合物(PICs)膜对水、小分子电解质和低分子物质具有很高的透过性,而高分子物质则不易通透,因此,作为血液透析用的半透膜而受到很高的评价。然而,普通的PICs,如由聚苯乙烯磺酸钠和聚乙烯基苄基三甲基氯化铵形成的所谓“IOPLEX101”,     

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。