凹凸棒土杂化粒子改性聚乙烯醇/壳聚糖复合膜的结构与性能研究

采用表面引发接枝聚合法制备凹凸棒土接枝聚丙烯酰胺杂化粒子(ATP-g-PAAm),以此改性聚乙烯醇/壳聚糖复合膜(PVA/CS).采用傅里叶红外光谱(FTIR)、差示扫描量热(DSC)、热失重分析(TG)等对三元复合膜(PVA/CS/ATP-g-PAAm)进行了表征,考察了杂化粒子含量对复合膜力学性能、热性能、吸湿率和...     

高体分SiCp/Al复合材料新型制备工艺研究

系统简要地介绍了低成本无压浸渗近净形制备加工高体分SiCp/Al复合材料的新技术。以碳化硅颗粒体分约为45％的制备态材料为例，对其基本力学性能、热物理性能及阻尼性能进行了测试。通过对比和分析，揭示了这种技术的优势所在，以及该结构／功能一体化复合材料最具前景的几个应用方向。     

Silicon carbide particle reinforced mullite composite foams

Silicon carbide particle reinforced mullite composite foams were produced by the polymer replica method using alumina and kaolin to form in situ mullite matrix. Up to 20 wt.% silicon carbide particles (SiCp) were added to aqueous ceramic slurry to explore its effect on the rheological behaviour of ceramic slurries and also properties of as sintered products. By means of solid loading optimisation and sintering enhancement by silicon carbide, mullite based ceramic composite foams of higher strength were obtained. The strength of the as sintered foams was found to depend greatly on the phase composition, relative density of the structures and the amount of SiCp addition. By studying the effect of the additive concentration, on the mechanical properties of the ceramic matrix, it is found that the optimal silicon carbide addition is 20 wt.%.     

Dynamic mechanical properties of particle‐reinforced EPDM composites

The dynamic mechanical property of particle‐reinforced ethylene–propylene–diene monomer (EPDM) matrix composites has been studied by using a dynamic mechanical thermal analyzer (DMTA). The individual composite has been reinforced with the various reinforcing particles as follows: silicon carbide particles (SiCps) of 60 μm in average diameter with various volume fractions (i.e., 10–40%); copper (Cu) and aluminum (Al) particles with 20 vol %; and SiCps with 6 and 36 μm in different average diameters with 20 vol % over the total composite volume. It is shown from the experimental results that the dynamic elastic modulus values increase and the composites with 40 vol % SiCps exhibit higher tan δ values through the entire rubbery phase after the glass transition region compared with the composites with lower particle volume percentages. This shows that the composites with 20 vol % Cu particles have the higher dynamic elastic modulus but the lower peak tan δ value than the composites with other particles of 20 vol % do. Scanning electron microscopy results show that the effective particle volume in the composite with Cu particles is higher than the other composites, although the same particle volume fraction of 20% has been used. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1595–1601, 2003     

Efficient cage structured polyhedral oligomeric silsesquioxane embedded poly(vinyl alcohol) membranes: Thermal degradation and mechanical stability in hydrated condition

In this work, the thermal degradation of functionalized cage structured polyhedral oligomeric silsesquioxane (POSS) incorporated poly(vinyl alcohol) (PVA) and poly(vinyl alcohol)-poly (ethylene oxide) (PEO) blend membranes were discussed. PVA-PEO/POSS and cross-linked PVA/POSS systems exhibited excellent improvement in thermal stability at lower loading of POSS as compared to pure PVA and uncross-linked PVA/POSS system. Uncross-linked PVA and PVA/POSS systems exhibited mainly two degradation steps. However, cross-linked PVA/POSS systems showed more degradation steps due to the formation of 3-dimentional network structure in the polymer. The mechanical stability of PVA/POSS and PVA-PEO/POSS systems at hydrated state were analyzed and observed a remarkable stability even in the wet condition.     

Green nanocomposites filled with spent coffee grounds

This study evaluated physical properties of the nanocomposites reinforced by used coffee grounds. Coffee grounds were ball‐milled and filtered in an effort to secure nanoparticles for the fabrication of polyvinyl alcohol (PVA)/coffee nanocomposites. We analyzed the particle size distribution of coffee particles and investigated mechanical and optical properties of the prepared nanocomposites. Carbon black (CB)‐filled nanocomposites were also prepared to understand the physical behavior of the nanocomposites reinforced with coffee grounds and to explore the possibility of replacing CBs with nanosized coffee grounds used as a composite filler. It was found that the tensile strength and Young's modulus of PVA/coffee grounds nanocomposites were significantly enhanced compared with those of the PVA/CB nanocomposites. In addition, morphological observation for the nanocomposites was carried out using scanning electron microscopy (SEM). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42043.     

Development of Silicon Carbide Reinforced Jute Epoxy Composites: Physical,Mechanical and Thermo-mechanical Characterizations

The aim of the present study was to investigate the physical and thermo-mechanical characterization of silicon carbide filled needle punch nonwoven jute fiber reinforced epoxy composites. The composite materials were prepared by mixing different weight percentages (0–15 wt.%) of silicon carbide in needle punch nonwoven jute fiber reinforced epoxy composites by hand-lay-up techniques. The physical and mechanical tests have been performed to find the void content, water absorption, hardness, tensile strength, impact strength, fracture toughness and thermo-mechanical properties of the silicon carbide filled jute epoxy composites. The results indicated that increase in silicon carbide filler from 0 to 15 wt.% in the jute epoxy composites increased the void content by 1.49 %, water absorption by 1.83 %, hardness by 39.47 %, tensile strength by 52.5 %, flexural strength by 48.5 %, and impact strength by 14.5 % but on the other hand, decreased the thermal conductivity by 11.62 %. The result also indicated that jute epoxy composites reinforced with 15 wt.% silicon carbide particulate filler presented the highest storage modulus and loss modulus as compared with the unfilled jute epoxy composite.     

Electrospun polyvinyl alcohol/waterborne polyurethane composite nanofibers involving cellulose nanofibers

TEMPO‐oxidized cellulose nanofibers (TOCNs) were used as nanofillers in this work. Composite nanofibers of polyvinyl alcohol (PVA)/waterborne polyurethane (WPU) reinforced with TOCNs were produced by electrospinning. The reinforcing capability of TOCNs was investigated by tensile tests. Scanning electron microscopy (SEM), X‐ray diffraction, and thermogravimetry analyses were also carried out in order to characterize the appearance, crystallinity, and reinforcing effect of the cellulose nanofibers. SEM results showed that PVA/WPU/TOCNs composite nanofibers presented a highly homogeneous dispersion of TOCNs. The reinforced composites had about 44% increase in their mechanical properties with addition of only 5 wt % of TOCNs while about 42% decrease in elongation at break. The TOCNs reinforced composite nanofibers were more thermally stable than pure PVA/WPU nanofibers. The development of crystalline structure in the composite fibers was observed by XRD. Since PVA, WPU, and TOCNs are hydrophilic, non‐toxic, and biocompatible, and therefore, these nanocomposite nanofibers could be used for tissue scaffolding, filtration materials, and medical industries as wound dressing materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41051.     

ACS树脂粒径分布与性能的研究

详细研究了聚乙烯醇/活性磷酸钙(PVA/HAP)复合分散剂用量、氯化聚乙烯(CPE)含量及溶胀温度对ACS树脂的粒径分布、分子量、冲击性能及微观形貌的影响。结果表明:当复合分散剂用量为4.15%CPE含量为30%溶胀温度为40℃时,可以得到颗粒规整、粒径适宜、微观结构均匀、冲击性能良好的ACS树脂。     

Effect of dual reinforced ceramic particles on high temperature tribological properties of aluminum composites

The nature and distribution of hard ceramic particles in composite materials influences the properties to greater extent. In the present work, the role of hard ceramic reinforced particles on the tribological behaviour of aluminum metal matrix composites consisting of single (SRP) and dual reinforced particles (DRP) is studied at different temperatures. Zircon sand and silicon carbide particles of size 20–32 μm were used as reinforcement in commercial grade LM13 piston alloy. Composites of dual reinforced particles in aluminum matrix (DRP-AMCs) were developed by mixing 15 wt% reinforced particles by two step stir casting technique. The wear behaviour of DRP-AMCs and SRP-AMCs (single reinforced particles aluminum matrix composite) was investigated using a pin-on-disc method at high temperatures under dry sliding condition. The microstructural examination of developed composites shows globular and finely distributed eutectic silicon in the vicinity of the reinforced particles. Metallographic investigation revealed that the wear zone of the SRP composite consisted of a hardened layer, which is responsible for high wear loss observed in the SRP composite. The results further indicate a transition in the wear mode that occurs after 150 °C for all composites. Study reveals that the dual reinforcement of particles enhances the wear resistance as compared to single reinforced particles if mixed in a definite ratio. A combination of 3% zircon sand and 12% silicon carbide particle reinforced composite exhibits better wear resistance as compared to other combinations at all the temperatures for low and high loads both.     

The slurry abrasive wear behaviour and microstructural analysis of A2024-SiC-ZrSiO4 metal matrix composite

This paper mainly reports a comparative study of dual reinforcement particles with combination of numerous weight ratios of reinforcement on micro-structural topographies and slurry abrasive wear behaviour of A2024 alloy. Silicon carbide and zircon sand particles size between 37–44 µm and 20–35 µm are reinforced in the alloy respectively, by two-step stir casting method. Slurry abrasive wear study reveals enhancement for twin particle reinforcement of the abrasive wear resistance ratio (1:1) as compared to others (1:3, 3:1) weight percentage of twin particle reinforcement if mixed in a stoichiometric proportion. The wear behaviour was examined by the sample rotation technique using slurry abrasive tester. The effects of speed, slurry media and sand concentration on the slurry wear behaviour have been investigated. To observe the influence of both SiC and ZrSiO₄ particles dispersion matrix alloy was also characterized under similar conditions. Analysis suggests the addition of both SiC and ZrSiO₄ significantly improves the wear resistance of as-synthesized matrix alloy in marine industry and marine environments. However, slurry environment and speed consists to the combined effect on wear rate. The analysis also indicate the specific combination of reinforcement (12%) with zircon sand and silicon carbide particles in the composite A exhibits better erosive wear resistance as compared to other combinations.     

纤维素纳米纤丝/聚乙烯醇复合材料热性能与力学性能研究

通过溶液浇铸法制备了纤维素纳米纤丝(CNFs)/聚乙烯醇(PVA)复合材料,利用TG、DSC、DMA等方法考察了CNFs对PVA热性能与力学性能的影响。结果表明:CNFs的加入提高了PVA的结晶度与熔点,但随着CNFs含量的增加,由于CNFs与PVA之间存在较强的氢键作用,限制了PVA分子链的运动,使得PVA的熔点与结晶度略有下降;CNFs的加入使得PVA的玻璃化转变温度、拉伸强度与弹性模量提高,添加2%CNFs的PVA复合材料的拉伸强度与弹性模量均达到最大值,分别较纯PVA提升了28.9%与14.1%。     

Cross-linked electrospun polyvinyl alcohol/sodium caseinate nanofibers for antibacterial applications

In this study, the polyvinyl alcohol (PVA) and sodium caseinate (SC) nanofibers were produced by a single-fluid electrospinning method from their blends. Afterward, the cross-linking process with two different methods was applied to the PVA/SC (70/30, v/v) ratio, which was selected according to the surface and mechanical properties of the electrospun mat. In the first method, different ratios (15%, 20%, 25%, and 30%) of glutaraldehyde (GLA) cross-linking agents were added to the PVA/SC solution and then, PVA/SC/GLA nanofibers were obtained. In the second method (in-situ method), the nanofibers obtained from the PVA/SC solution were cross-linked by dipping into the cross-linking solution. After, PVA/SC/GLA/Zinc oxide nanoparticles (ZnO NP) mats were obtained by adding ZnO NP at different rates to the PVA/SC/GLA (7030-25GLA) solution, which was chosen according to the results of thermal, mechanical, and moisture test. In addition, performing tests, a cytotoxicity test for fibroblast cell line (L929), and in vitro antibacterial test for Escherichia coli and Staphylococcus aureus were also applied to them. Therefore, the usability of PVA/SC/GLA/ZnO NP nanofibers as an antibacterial effective wound dressing was investigated. Due to the high toxic effect of GLA, it was found that PVA/SC/ZnO cross-linked nanofibers are not suitable for wound dressing use. However, it was determined that the PVA/SC nanofiber cross-linked by the in-situ method had high cell viability according to the cytotoxicity test result and thus could be used as a fibroblast tissue scaffold.     

芳纶纳米纤维增强聚乙烯醇复合膜的制备与性能

以芳纶纤维Kevlar@49为原料,在温和条件下制备了芳纶纳米纤维分散体(ANFS),并利用分散体制备了芳纶纳米纤维/聚乙烯醇(ANFs/PVA)复合膜。通过傅里叶红外光谱(FTIR)仪、差示扫描量热(DSC)仪、原子力显微镜(AFM)、扫描电子显微镜(SEM)、电子万能试验机及透光度/雾度测定仪等考察了复合膜的微观结构、热学、光学及力学性能。FTIR证明,复合膜中ANFs与PVA具有一定的分子间氢键作用,促进了ANFs在PVA基体中的分散。由AFM和SEM可以清晰观察到直径为20~30 nm的芳纶纳米纤维分散体,并且通过SEM观察到复合膜表面较为平整。当芳纶纳米纤维质量分数为6.0%时,复合膜的抗拉强度为17.86 MPa,断裂伸长率为442%;透光度为82.63%,雾度为27.56%;玻璃化温度,熔融温度和结晶温度分别为75.20、208.82和174.51℃,表明其透光性良好,力学和热学性能达到最佳。     

改性水滑石/聚乙烯醇复合膜的制备及性能

采用焙烧复原法将山梨酸(SA)插入水滑石(LDH)层间合成了纳米插层材料SA-LDH,将其与聚乙烯醇(PVA)共混,通过溶液流延法制备得到复合薄膜SA-LDH/PVA。采用傅里叶变换红外光谱(FT-IR)、X-射线衍射(XRD)、热重-差热分析(TG-DSC)和扫描电镜(SEM)对其结构、热稳定性以及形貌进行表征,并测试了复合薄膜的力学性能、溶胀率、溶解率和抑菌性能。结果表明:复合薄膜SA-LDH/PVA中SA-LDH含量为5 wt%时得到的LDH晶型最为完整,对应的SA-LDH片层在PVA薄膜中分散比较均匀;添加3 wt%SA-LDH可提高PVA膜的热稳定性;SA-LDH添加量为5 wt%和7 wt%时,提高了复合膜的抗拉性能和断裂伸长率;SA-LDH的添加提高了PVA膜的耐水性能;SA-LDH的添加量分别为5 wt%和6 wt%时,SA-LDH/PVA复合薄膜对金黄色葡萄球菌和大肠杆菌的抑菌效果最佳。制备的改性水滑石/聚乙烯醇复合抑菌膜,为食品包装领域提供一种广谱的抑菌材料。     

Fabrication of high strength PVA/SWCNT composite fibers by gel spinning

High-strength composite fibers were prepared from polyvinyl alcohol (PVA) (Degree of polymerization: 1500) reinforced by single-walled carbon nanotubes (SWCNTs) containing few defects. The SWCNTs were dispersed in a 10 wt.% PVA/dimethylsulfoxide solution using a mechanical homogenizer that reduced the size of SWCNT aggregations to smaller bundles. The macroscopically homogeneous dispersion was extruded into cold methanol to form fibers by gel spinning followed by a hot-drawing. The tensile strength of the well-oriented composite fibers with 0.3 wt.% SWCNTs was 2.2 GPa which is extremely high value among PVA composite fibers ever reported using a commercial grade PVA. The strength of neat PVA fibers prepared by the same procedure was 1.7 GPa. Structural analysis showed that the PVA component in the composite fibers possessed almost the same structure as that of neat PVA fibers. Hence a small amount of SWCNTs straightforward enhanced by 0.5 GPa the tensile strength of PVA fibers. The results of mechanical properties and Raman spectra for the SWCNT composites suggest the relatively good interfacial adhesion of the nanotubes and PVA that improves the load transfer from the polymer matrix to the reinforcing phase.     

Preparation and characterization study on maleic acid cross-linked poly(vinyl alcohol)/chitin/nanocellulose composites

In the quest on improving composite formulations for environmental sustainability, maleic acid (MA) cross-linked poly(vinyl alcohol) (PVA)-α-chitin composites reinforced by oil palm empty fruit bunch fibers (OPEFB)-derived nanocellulose crystals (NCC) had been successfully prepared. Based on the Fourier transform infrared (FTIR) spectroscopic analysis, it was proven that molecular interactions of the cross-linker to the polymeric networks was through conjugated ester linkage. Differential scanning calorimetry (DSC) showed that the influence of MA was minimal toward crystallization in the PVA/chitin/NCC composite. Maximum tensile strength, elongation at break and Young's modulus of the respective PVA/chitin/NCC composites were achieved at different content of MA, dependent on the PVA/chitin mass ratio. Among all compositions, a maximum Young's modulus was achieved at 30 wt% MA loading in PVA/chitin-30/NCC, amounting to 2,413.81 ± 167.36 MPa. Moreover, the mechanical properties and selected physicochemical properties (swelling, gel content, and contact angle) of the PVA/chitin/NCC composites could be tailored by varying the chitin content (10–30 wt%) and MA content (10–50 wt% based on total mass of composite). In brief, this chemically cross-linked PVA-based biocomposites formulated with sustainable resources exhibited tunable physicochemical and mechanical properties.     

聚乙烯醇/淀粉纳米晶复合膜的制备及表征

利用蜡质玉米淀粉通过硫酸酸解制备淀粉纳米晶（SN）,并采用溶液流延法制备聚乙烯醇（PVA）/SN复合膜,研究SN对复合膜结构和性能的影响。结果表明,制备的SN样品为盘状颗粒,平均直径为30～60 nm;随着SN含量的增加,PVA/SN复合膜的力学性能和阻隔性能均呈现先增后减的变化;在SN含量为10 %时,复合膜的拉伸和阻隔性能最好,拉伸强度由纯PVA膜的47 MPa提高至54 MPa,气体透过系数相对于纯PVA膜也降低了70 %。     

Polyvinyl alcohol thin film reinforced by green synthesized zirconia nanoparticles

The focus of this work is to prepare polyvinyl alcohol (PVA) thin film reinforced by green synthesized zirconia nanoparticles. In order to do so, firstly, zirconia nanoparticles were synthesized by the rosemary extract-assisted sol-gel process as both template and stabilizing agents. The results showed that the as-obtained sample with zirconium salt to rosemary extract ratio of 1:4 had a semi-spherical morphology with the mean particle size of 12–17?nm. This nanoparticle was added as reinforcement with different ratios to the polyvinyl alcohol matrix. The mechanical property of the as-prepared nanocomposites revealed that the elastic modulus of 1?wt% ZrO2-PVA sample was about 5.5 times higher than pure PVA thin film.     

Preparation of well‐dispersed reduced graphene oxide and its mechanical reinforcement in polyvinyl alcohol fibre

The current work reports the preparation and characterization of polyvinyl alcohol (PVA) composite fibres reinforced with graphene reduced from graphene oxide (GO) by using oligomeric proanthocyanidin (OPC) as a reductant. After reduction, most of the oxygen‐containing groups were removed from the GO and reduced graphene oxide (rGO) was prepared. As a result of combined OPC as a dispersant, rGO could be well dispersed in a dimethyl sulfoxide/H₂O mixed solvent and in PVA matrix, and the PVA/rGO dispersion was wet spun followed by hot drawing to prepare continuous PVA/rGO composite fibres. The PVA/rGO composite fibres exhibited a significant enhancement of mechanical properties at low rGO loadings; in particular the tensile strength and Young's modulus of the 2.0 wt% rGO and PVA composite fibre increased to 244% and 294% respectively relative to neat PVA fibre. Moreover, the storage modulus (?10 °C) and T_g increased to 300% and 7.2 °C, respectively. © 2016 Society of Chemical Industry