Comparison the properties of PVA/Na+‐MMT nanocomposite hydrogels prepared by physical and physicochemical crosslinking

A novel physicochemical crosslinked nanocomposite hydrogel based on polyvinyl alcohol (PVA) and natural Na‐montmorillonite (Na⁺‐MMT) was synthesized by chemical crosslinking of nanocomposite hydrogel followed by a freezing‐thawing process. The effects of physical crosslinking, as well as physicochemical crosslinking, on the structure, morphology, and properties (thermal, mechanical, swelling, and deswelling) of nanocomposite hydrogels were investigated and compared with each other. The structure and morphology of nanocomposites were studied by Fourier transform infrared, X‐ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy techniques. The thermal and mechanical properties of nanocomposites that were affected by physical and physicochemical crosslinking were evaluated by thermogravimetric analysis, differential scanning calorimeter, dynamic mechanical analysis, hardness test, and Water vapor transmission rate (WVTR) experiments. The results showed that the physicochemical crosslinking of a PVA nanocomposite leads to a reduction in crystallinity and melting temperature, as well as an increase in the Hardness and WVTR compared to a physically crosslinked PVA nanocomposite hydrogel. The swelling and deswelling experiments were performed using a gravimetric method, and it was shown that controlled crosslinking of PVA nanocomposite hydrogel with glutaraldehyde causes the swelling ratio to increase and the cumulative amount of water loss to decrease. The swelling (sorption) and deswelling (desorption) kinetics data for physically and physicochemical crosslinking of nanocomposite hydrogels were fitted with a fickian model. It is concluded that through control crosslinking of PVA nanocomposite can lead to a hydrogel with higher swelling capacity than that is in conventional PVA nanocomposite hydrogel. POLYM. COMPOS., 37:897–906, 2016. © 2014 Society of Plastics Engineers     

Harmless hydrogels based on PVA/Na+‐MMT nanocomposites for biomedical applications: Fabrication and characterization

A series of nanocomposite hydrogels were prepared by a freeze‐thaw process, using polyvinyl alcohol (PVA) as polymer matrix and 0–10 wt% of hydrophilic natural Na‐montmorillonite (Na⁺‐MMT), free from any modification, as composite aggregates. The effect of nanoclay content and the sonication process on the nanocomposite microstructure and morphology as well as its properties (physical, mechanical, and thermal) were investigated. The microstructure and morphology were investigated by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and X‐ray diffraction technique. The thermal stability and mechanical properties of nanocomposite hydrogels were examined using thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis; moreover hardness and water vapor transmission rate measurements. It was concluded that the microstructure, morphology, physical (thermal) and mechanical properties of nanocomposite hydrogels have been modified followed by addition of nanoclay aggregates. The results showed that Na⁺‐MMT may act as a co‐crosslinker. Based on the results obtained, the nanocomposite hydrogel PVA/Na⁺‐MMT synthesized by a freeze‐thaw process, appeared to be a good candidate for biomedical applications. POLYM. COMPOS., 38:1135–1143, 2017. © 2015 Society of Plastics Engineers     

Innovative preparation of bacterial cellulose/silver nanocomposite hydrogels: In situ green synthesis,characterization, and antibacterial properties

In this study, an innovative in situ green strategy was applied to prepare bacterial cellulose/silver nanocomposites using green tea as a substrate for the fermentation of Acetobacter xylinum bacteria and a reducing agent for the in situ synthesis of silver nanoparticles. The samples were analyzed by different characterization tests including field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), UV–vis spectroscopy, atomic absorption spectroscopy, and ATR. The results indicated the excellent antibacterial activities with 100% bacterial reduction percentage and inhibition zones of 2.6 and 2.8 cm against S. aureus and E. coli, respectively. Moreover, water absorption percentage and vertical wicking measurements supported the hydrogel properties of the prepared bio-cellulose/silver nanocomposites. Finding of this research suggested the potential of the proposed green route for preparing antibacterial BC which can be regarded as a candidate for future wound healing applications.     

聚乙烯醇/蒙脱石支架用作生物催化剂的研究

PVA/MMT复合材料制备组织工程支架包衣片,用作新型的生物催化剂,同时以面包酵母作为模型细胞,对新型催化剂的各种性能进行了考察研究。结果表明,碟状三维多孔支架孔隙率达90%以上,细胞载量可达45 mg/cm3gel,具有很好的连通性。采用PVA/OMMT纳米复合材料作为包衣材料,多次使用后无细胞泄露现象。亲水与疏水分子在新型生物催化剂中都表现出很好的扩散性,同时包衣还可以降低底物和产物对细胞毒害作用。新型的生物催化剂具有很好的储存稳定性,储存30 d后残余活力为75.4%。     

Preparation and characterization of wood/styrene‐acrylonitrile copolymer/MMT nanocomposite

Wood polymer nanocomposite (WPNC) was prepared by impregnating Simul (Salmalia malabarica) wood with styrene‐acrylonitrile copolymer (SAN), glycidyl methacrylate(GMA), and a reactive polymerizable surfactant modified montmorillonite (MMT). The physical and mechanical properties of WPNC were investigated by using XRD, tensile tester, SEM, and FTIR. The polymer loading, dimensional stability, water uptake, mechanical property, and thermal stability were found to improve due to inclusion of MMT. SEM micrographs showed the presence of polymer and MMT into cell wall and cell lumen. FTIR analysis confirmed the presence of MMT and SAN in WPNC. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

PET/MMT纳米复合材料的制备

采用烷基季铵盐对蒙脱土(MMT)进行有机化处理,采用插层聚合法制备PET/MMT纳米复合材料。探讨了不同的MMT来源、添加量及聚合条件对PET/MMT纳米复合材料耐热性能的影响。结果表明: MMT的添加质量分数为2.5%,缩聚反应终温250℃时,PET/MMT纳米复合材料具有较好的综合性能。     

HES-HEMA nanocomposite polymer hydrogels: swelling behavior and characterization

Organophilic sodium montmorillonite (Na-MMT) and Laponite-RD clays were incorporated into photopolymerizable hydroxyethyl starch (HES) modified with 2-hydroxyethyl methacrylate (HEMA). Swelling, mechanical properties and thermal stability of obtained crosslinked nanocomposite polymers were evaluated. A camphorquinone-amine system was used as photoinitiating system in visible light. The interaction between nano-sized filler particles and polymer hydrogel was evaluated by FT-IR spectroscopy and the platelet distribution was investigated by SEM. An increased thermal stability of nanocomposite polymers upon addition of clay was observed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicating interaction between the clay platelets and the polymer chains. The crosslinking density for HES-HEMA/MMT nanocomposite hydrogels as investigated by swelling measurements increases with increasing the organo-clay content. The mechanical properties of virgin hydrogels were improved by the introduction of organo-clay as evidenced by oscillation rheology measurements. Whereas, the increase in crosslink density and storage modulus with clay content for laponite was found to be increasing for all concentrations investigated, for MMT there is an optimum content of ca. 1.5 wt%.     

Chitosan/clay nanocomposite film preparation and characterization

Nanocomposites of chitosan and nanoclays (MMT‐Na⁺ and Cloisite 30B) were prepared by solvent casting. The structural properties, thermal behaviors, and mechanical properties were characterized using X‐ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy, differential scanning calorimetry, thermogravimetry analyses, and an Instron universal testing machine. XRD and TEM results indicated that an exfoliated structure was formed with addition of small amounts of MMT‐Na⁺ to the chitosan matrix. Intercalation along with some exfoliation occurred with up to 5 wt % MMT‐Na⁺. Micro‐scale composite (tactoids) formed when Cloisite 30B was added to the chitosan matrix. Surface roughness increased with addition of a small amount of clay. Tensile strength of a chitosan film was enhanced and elongation‐at‐break decreased with addition of clay into the chitosan matrix. Melt behavior and thermal stability did not change significantly with addition of clays. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1684–1691, 2006     

Preparation and characterization of nylon‐6/PPy/MMT composite of nanocomposite

Series of composites consisting of polypyrrole/montmorillonite nanocomposites in the matrix of Nylon6 has been synthesized and characterized in this work. The composites were processable, so that test samples were prepared by compression‐molding of the materials for electrical property measurements. Intercalated structures were confirmed by wide‐angle X‐ray diffraction and TEM studies for PPy/MMT nanocomposites. A two‐phase structure was determined for the fused samples consisting of two separated N6 and PPy phases by using scanning electron microscopy analyses. A conductivity threshold was measured at 15%(w/w) loading level of PPy in the composites. Electrical resistivity–temperature behavior of the samples was investigated and a resistivity peak was observed at 100°C for the samples. It was proved that the glass transition temperature of PPy around 100°C should be the responsible factor for the observed resistivity peak, as studied by thermogravimetic analysis and differential scanning calorimetry thermal methods. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

聚乙烯醇/淀粉/MMT纳米复合材料的制备与性能研究

以蒙脱土（MMT）为增强填料,采用熔融加工的方法制备了聚乙烯醇（PVA）/淀粉/MMT纳米复合材料,通过X射线衍射、差示扫描量热法、扫描电子显微镜、热失重法以及力学性能测试等方法研究了MMT含量对复合材料结构与性能的影响。结果表明,在熔融加工过程中,淀粉、PVA分子破坏了MMT片层结构;MMT提高了复合材料中PVA组分结晶温度,阻碍PVA分子排入晶格,降低了复合材料熔融焓值及结晶度;MMT有效提高了材料的拉伸强度、弹性模量,同时降低了复合材料的吸水速率、平衡吸水率,提高了耐水性能。     

PVA/MMT纳米复合材料的化学改性研究

通过溶液插层-流延成膜法制备了四硼酸钠和戊二醛化学交联改性的聚乙烯醇/蒙脱土纳米复合材料薄膜。用扫描电子显微镜(SEM)和力学性能测试对复合材料的结构和性能进行了表征。结果表明:蒙脱土含量为5．0%时,含有不同质量改性剂的复合薄膜的拉伸强度、湿拉强度和耐水性能都得到了提高。     

Gamma irradiation synthesis and characterization of AgNP/gelatin/PVA hydrogels for antibacterial wound dressings

An antibacterial hydrogel wound dressing was successfully synthesized by the gamma irradiation method. A gelatin solution was mixed with a poly(vinyl alcohol) (PVA) solution of similar concentrations at different weight ratios of 100 : 0, 80 : 20, and 60 : 40 w/w, and irradiated at 30, 40, or 50 kGy. The testing of physical properties showed that the addition of PVA could improve both durability and mechanical integrity. The 60 : 40 hydrogels irradiated at 30 kGy were optimal, and chosen to add silver nitrate at 0.25, 0.50, 0.75, or 1.00 wt % (based on the solid content) to improve the antibacterial properties. After gamma irradiation, silver nanoparticles (AgNPs) were formed. The AgNP/gelatin/PVA hydrogels were characterized for physical properties, cytotoxicity, and antibacterial activity. The AgNP/gelatin/PVA hydrogels could be used as antibacterial wound dressings because they exhibited appropriate physical properties, noncytotoxicity, and could inhibit the growth of tested bacteria. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41138.     

Synthesis and characterization of PVA/YBCO nanocomposite for improvement of solar energy conversion

The development of nano‐metal oxide materials with unique optoelectronic properties such as highly solar energy absorption and generation of dense amount of electrons is one of the hottest topics now days. The incorporation of these nanomaterials into polymers results in an improvement of the properties of these polymers. Therefore, the understanding of their electronic properties is an essential demand to introduce these nanocomposites into service life. In this work, Yttrium barium copper oxide (YBCO) nanopowders with a uniform particle size of around 11 nm was prepared, sintered, and blended with polyvinyl alcohol (PVA) by casting technique. The characteristics of the structure and morphology of PVA/YBCO nanocomposite films are studied using X‐ray diffraction and transmission electron microscopy. The influence of YBCO nanoparticles on the thermal stability of PVA showed that the YBCO enhanced the thermal stability and reduced the rate of thermal degradation of PVA nanocomposites. Current–voltage behavior of PVA/YBCO nanocomposite films was measured at different temperatures. An explanation for the charge carrier concentration in the conduction band with the calculation of the barrier height, activation energy, and conversion and their dependence on temperature and applied field is presented.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Syntheses,characterization, and antibacterial activity of chitosan grafted hydrogels and associated mica‐containing nanocomposite hydrogels

Chitosan (CS) grafted poly[(acrylic acid)‐co‐(2‐hydroxyethyl methacrylate)] (CS‐g‐poly(AA‐co‐HEMA)) at different molar ratios of AA and HEMA, and the associated nanocomposite hydrogels of CS‐g‐poly(AA‐co‐HEMA)/mica were synthesized by radical copolymerization. The grafting positions at the amino or hydroxyl groups in the CS were identified by Fourier transform infrared spectroscopy. CS‐g‐poly(AA‐co‐HEMA) hydrogels were intercalated in the mica and the amount of hydrogel insertion did not affect the spacing of the silicate layers in mica. The higher mica loadings produced a rougher surface of the nanocomposite hydrogel. The water absorbency of the CS‐g‐poly(AA‐co‐HEMA)/mica nanocomposite hydrogels decreased with increasing levels of mica loading to a lower level than those of the CS‐g‐poly(AA‐co‐HEMA) hydrogels. Both CS‐g‐poly(AA) and CS‐g‐poly(AA‐co‐HEMA)/mica nanocomposite hydrogels exhibited a higher antiproliferative activity against Staphylococcus aureus than did the neat CS hydrogel with CS‐g‐poly(AA) revealing a very pronounced minimum inhibition concentration (MIC) of 1.56 mg mL^?1. The extent of mica loading in the CS‐g‐poly(AA‐co‐HEMA) nanocomposite hydrogels did not affect the MIC (12.5 mg mL^?1). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

MMT/PMMA和MMT/PBA/PMMA纳米杂化材料的制备和表征

利用十二烷基苯磺酸钠,钠基蒙脱土和丙烯酸酯类单体通过乳液聚合的方法制备了MMT/PMMA和MMT/PBA/PMMA纳米杂化材料。与钠基蒙脱土有机化后再进行乳液聚合比较发现,直接利用钠基蒙脱土进行乳液聚合同样可以制得与用有机蒙脱土进行乳液聚合结构相似的有机 -无机杂化材料。这样可以省去蒙脱土的有机化处理和烦琐的洗涤过程,大大降低生产成本,缩短工艺过程。通过TEM,XRD等分析手段对制备的杂化材料进行了表征,证明该乳胶粒子具有剥离型结构,并用DSC对该杂化材料的热性能进行了测试,其玻璃化转变温度和起始分解温度均提高 10℃以上,放热量减少约 50%。     

PVA/MMT纳米复合材料的制备方法研究进展

介绍了采用原位聚合插层、溶液插层及熔融插层法制备聚乙烯醇/蒙脱土复合材料的方法。蒙脱土纳米片层的存在延长了气体分子通过复合材料的通道,限制了聚乙烯醇分子的自由体积,减少了聚乙烯醇分子的溶胀及热运动,从而使聚乙烯醇/蒙脱土复合材料的耐水性、热稳定性、气体阻透性及力学性能等都得以提升。蒙脱土在聚乙烯醇基体中以插层或剥离的分散形态存在,剥离型材料力学性能较好,而插层型材料的热稳定性、气体阻透性较好。在PVA基体中,钠基蒙脱土的插层效果优于有机改性蒙脱土。     

Curing kinetics and thermal property characterization of o‐CFER/MeTHPA/O‐MMT nanocomposite

The kinetics of the cure reaction for a system of o‐cresol‐formaldehyde epoxy resin (o‐CFER), 3‐methyl‐tetrahydrophthalic anhydride (MeTHPA), N,N‐dimethyl‐benzylamine, and organic montmorillonite(O‐MMT) were investigated by means of X‐ray diffraction (XRD) and differential scanning calorimetry (DSC). The XRD result indicates that an exfoliated nanocomposite was obtained. The analysis of DSC data indicated the behavior was shown in the first stages of the cure for the system, which could be well described by the model proposed by Kamal. In the later stages, the reaction is mainly controlled by diffusion, and diffusion factor, f(α), was introduced into Kamal's equation. In this way, the curing kinetics was predicted well over the entire range of conversion. Molecular mechanism for curing reaction was discussed. The thermal degradation kinetics of the system were investigated by thermogravimetric analysis (TGA), which revealed that with the increase of O‐MMT content, TG curves shift to higher temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3023–3032, 2006     

蒙脱土/碳纳米管多维增强的聚乙烯复合材料的制备

引言聚烯烃是国民生活和现代国防不可或缺的基础原材料,但与ABS、PC等工程塑料相比,其刚性不足,低温脆性也较明显,因此很难作为结构材料使用。纳米技术的出现为聚烯烃材料性能的提高提供了广阔的空间[1],其中,纳米复合材料中存在纳米尺寸效应、超大的比表面积以及很强的界面相互作用,具有比强度高、可设计性强、抗疲劳性好等优点,因此,纳米复合聚乙烯中含少量纳米材料便能极大增强材料本身的性能,同时聚合物中纳米材料的低含量也大大减少了无机载体在聚合物中的灰分,有利于聚合物材料高性能的保持,这引起了研究工作者的广泛关注。     

Magnetically active nanocomposite aerogels: preparation,characterization and application for water treatment

Journal of Porous Materials - Magnetically active nanocomposite aerogels were prepared, characterized and used for water treatment. These materials were characterized by SEM, TEM, XRD, FT-IR and...