电纺聚乙烯醇超细纤维膜的性能研究

由电纺制备聚乙烯醇(PVA)超细纤维膜,以扫描电镜观察纤维的微观形貌,用X射线衍射研究超细纤维膜的结晶行为,并测定了PVA超细纤维膜的力学性能和吸水性.结果表明,PVA超细纤维的平均直径为(184±26)nm,超细纤维中PVA的结晶度和晶体有序程度较浇铸膜低.超细纤维膜的拉伸强度、模量和断裂伸长率均较浇铸膜差,吸水率在300%以上,高于浇铸膜.     

二氧化硅/聚乙烯醇杂化电纺纤维膜的制备与结构形态

用溶胶-凝胶(Sol-Gel)法制备了不同二氧化硅含量的PVA/SiO2杂化纺丝液,将其电纺成纤维膜.XRD结果表明,杂化电纺纤维膜的结晶度较纯PVA电纺纤维膜小;FTIR证实了PVA的羟基与正硅酸乙酯水解后的羟基发生了缩合反应,杂化电纺纤维膜是以网络结构形式相结合的;FESEM表明,PVA/SiO2质量比为4∶1时,纤维光滑,分散比较均匀.随着二氧化硅含量的增加,纤维直径变细,纺锤形珠节结构增多.加入金属盐NaCl和MgCl2后,纤维直径变细,圆形珠节增多.从理论上分析了纤维膜结构形态的形成机理.     

大豆分离蛋白的酶水解

大豆分离蛋白的酶水解;大豆分离蛋白;水解作用;光散射     

大豆分离蛋白改性的研究进展

首先介绍了大豆分离蛋白的基本组成与结构,然后分别从化学改性、酶改性和物理改性三个方面对大豆分离蛋白改性进行了综述.其中,在化学改性方面,针对大豆分离蛋白中含有的氨基、羧基、巯基等不同活性基团的改性原理及研究现状进行了介绍.在酶改性方面,主要介绍了谷胺酰胺转胺酶、木瓜蛋白酶等对大豆分离蛋白的改性作用.在物理改性方面,介绍了共混、加热改性等目前研究较多的方法.通过化学、物理和酶等方法等来引起分子结构的微变化,可使人们获得各种符合预期的性能优良的产品,开发其在医药、化工等领域的应用潜力.     

液相色谱法测定大豆分离蛋白中的三聚氰胺

建立了大豆分离蛋白中三聚氰胺的液相色谱方法。大豆分离蛋白经过1%三氯乙酸和饱和乙酸铅溶液提取后,经过阳离子交换固相萃取柱净化处理,用5%氨化甲醇洗脱,洗脱液用高效液相色谱紫外检测器检测,外标法定量。三聚氢胺的质量浓度在0.4~40 mg/L范围内与色谱峰面积呈良好的线性关系,相关系数为0.9990。方法的检出限为0.6 mg/kg,定量限为2 mg/kg。2,4,20 mg/kg 3个浓度水平的加标回收率在78.82%~92.95%范围内。该方法分析成本低,测定结果准确,能满足常规检测及食品安全监控的需要。     

大豆分离蛋白甲基丙烯酸接枝共聚物的合成与表征

以过硫酸铵为引发剂、2-巯基乙醇为蛋白质变性剂,在浓度为8mol／L尿素溶液中进行了大豆分离蛋白与甲基丙烯酸的接枝共聚反应;傅里叶红外光谱和核磁共振谱证明,甲基丙烯酸成功地接枝到了大豆分离蛋白上;相关影响因素的单因数实验研究表明,各因数的最佳值分别为：引发剂浓度16mmol／L,单体浓度2．4mol／L,反应温度80℃,反应时间4h,巯基乙醇浓度0．05mol／L。     

大豆分离蛋白风味物质的气相色谱-质谱分析

采用顶空固相微萃取技术通过气相色谱一质谱联用分析了两种大豆分离蛋白的风味成分。在未经乙醇处理的样品中共检测到己醛等14种风味物质，而经乙醇处理的样品仅检测到5种风味物质；豆粕经乙醇处理后制备的大豆分离蛋白，主要异味成分之一——1-辛烯-3-醇未被检测到；且己醛、乙酸乙酯、1-己醇、辛酸乙酯及苯甲醛等5种风味成分的含量明显减少，不及对照样品的10％。证明经乙醇处理后的大豆分离蛋白，其风味已得到了明显的改善。     

大豆分离蛋白接枝改性与应用研究进展

随着人们对环保问题和新材料发展的日益重视,大豆分离蛋白由于其生物可降解性、营养价值高、对人体与环境无害、来源广泛等特点而倍受关注.本文介绍了大豆分离蛋白的接枝改性方法及在食品添加剂、包装膜和医用外敷膜材料的基料以及化妆品中的应用,并综述了国内外在改善膜的应用特性方面取得的研究进展.     

大豆分离蛋白与壳聚糖复合材料的制备

蛋白质与多糖的静电作用是生物体内一个基本医学-化学现象,是实现自组装的主要驱动力,可利用这种非共价作用设计和构筑理想的微结构。 以大豆分离蛋白(Soybean Protein Isolates,SPI)和壳聚糖(Chitosan,CS)为原料,采用浊度法考察了配比、溶液pH值、离子强度和温度对SPI与CS在溶液中相互作用的影响。 结果显示,由于pH值影响静电作用强度,从而成为影响SPI与CS相互作用的主要因素,其中,当pH值为5.5~6.6时,SPI与CS可以实现有效结合。在较低的离子强度下,有利于形成具有紧凑结构的CS/SPI聚集体,较高离子强度下聚集体发生解离。 蛋白质受热发生变性,多肽链上的疏水氨基酸残基暴露在溶液中,导致与壳聚糖链的疏水作用增强。 DLS结果显示,CS与SPI自组装形成了分布均一的纳米粒子,变性后的SPI与CS形成的纳米粒子粒径有所增大,分布均一;经戊二醛交联,粒径有所减小。 SEM显示,壳聚糖单层膜表面存在龟裂现象,与SPI形成双层膜后龟裂消失;同时,单层膜厚度约为300 nm,双层膜厚度约为500 nm。     

毛细管电泳检测奶粉中添加的大豆分离蛋白

采用毛细管电泳方法对乳蛋白和大豆分离蛋白进行检测。选择聚丙烯酰胺涂层毛细管,在紫外检测波长214 nm、分离电压25 kV条件下测出五种乳蛋白在不同线性范围内的线性相关系数均大于0.998,各乳蛋白的迁移时间和峰面积的相对标准偏差(RSD)分别小于0.34%和4.50%,奶粉样品加标回收率范围为88.07%~102%;通过对比大豆7S和11S组分、大豆分离蛋白及乳蛋白的电泳图谱,定性确定出大豆分离蛋白8个特征峰,各特征峰的迁移时间和峰面积的RSD分别小于0.36%和4.87%,方法重现性较好。建立了奶粉中添加大豆分离蛋白的半定量检测方法。     

Electrospinning and characterization of medium-molecular-weight poly(vinyl alcohol)/high-molecular-weight poly(vinyl alcohol)/montmorillonite nanofibers

Submicron fibers of medium-molecular-weight poly(vinyl alcohol) (MMW-PVA), high-molecular-weight poly(vinyl alcohol) (HMW-PVA), and montmorillonite clay (MMT) in aqueous solutions were prepared by electrospinning technique. The effect of HMW-PVA and MMT on the morphology and mechanical properties of the MMW-PVA/HMW-PVA/MMT nanofibers were investigated for the first time. Scanning electron microscopy, viscometer, tensile strength testing machine, thermal gravimetric analyzer (TGA), and transmission electron microscopy (TEM) were utilized to characterize the PVA/MMT nanofibers morphology and properties. The MMW-PVA/HMW-PVA ratios and MMT concentration played important roles in nanofiber's properties. TEM data demonstrated that exfoliated MMT layers were well distributed within nanofibers. It was also found that the mechanical property and thermal stability were increased with HMW-PVA and MMT contents.     

Study on morphology of electrospun poly(vinyl alcohol) mats

Submicron poly(vinyl alcohol) (PVA) fiber mats were prepared by electrospinning of aqueous PVA solutions in 6-8% concentration. Fiber morphology was observed under a scanning electron microscope and effects of instrument parameters including electric voltage, tip-target distance, flow rate and solution parameters such as concentration on the morphology of electrospun PVA fibers were evaluated. Results showed that, when PVA with higher degree of hydrolysis (DH) of 98% was used, tip-target distance exhibited no significant effect on the fiber morphology, however the morphological structure can be slightly changed by changing the solution flow rate. At high voltages above 10 kV, electrospun PVA fibers exhibited a broad diameter distribution. With increasing solution concentration, the morphology was changed from beaded fiber to uniform fiber and the average fiber diameter could be increased from 87 ± 14 nm to 246 ± 50 nm. It was also found that additions of sodium chloride and ethanol had significant effects on the fiber diameter and the morphology of electrospun PVA fibers because of the different solution conductivity, surface tension and viscosity. When the DH value of PVA was increased from 80% to 99%, the morphology electrospun PVA fibers was changed from ribbon-like fibers to uniform fibers and then to beaded fibers. The addition of aspirin and bovine serum albumin also resulted in the appearance of beads.     

Properties stability and biodegradation behaviors of soy protein isolate/poly (vinyl alcohol) blend films

The objective of this work was to investigate the color, transparency, water sensitivity and mechanical properties stability in air under photo-oxidative degradation influencing consumer acceptance and biodegradation behaviors in soil of soy protein isolate (SPI)/poly (vinyl alcohol) (PVA) blend packaging films during 30 days. The results showed that PVA could dilute the yellow color and make the SPI-based films less darkness in application and the transparency of SPI/PVA films at various stages of degradation was improved. The addition of PVA decreased the ability of SPI protein molecules to absorb water and enhanced the mechanical properties of blend films comparing to pure SPI film in 30 days. Aerobic biodegradation of films in soil proved that the PVA compound interacting with protein imposed negative effects on biodegradation of blend films prolonging their decomposing time. The SPI/PVA blend films decomposed into small fragments of less complex molecules along with surface completely digested after 30 days.     

聚乙烯醇/纳米羟基磷灰石复合材料微型注塑研究

结合固相剪切碾磨和分子复合技术制备了适合于微型注塑加工的聚乙烯醇/纳米羟基磷灰石(PVA/n-HA)复合材料,实现了n-HA含量达30%的PVA/n-HA复合材料的微型注塑加工。采用差示扫描量热法(DSC)、热重分析仪(TGA)和高压毛细管流变仪研究了PVA/n-HA复合材料的热性能和流变性能,结果表明:改性PVA/n-HA复合材料的熔点降低,热分解温度升高,获得120℃以上的热塑加工窗口;PVA/n-HA复合材料呈现剪切变稀特性,在高剪切速率下具有较低的熔体粘度,适合微型注塑加工,具有良好的充模性能。采用扫描电子显微镜(SEM)和X射线衍射(XRD)研究了PVA/n-HA微型注塑样品的结构与性能,结果表明n-HA均匀分散于PVA基体中,提高了复合材料的尺寸稳定性;受微型注塑过程中高剪切应力诱导结晶作用的影响,PVA/n-HA微型注塑样品的结晶度高于常规注塑样品的结晶度。     

Electrospinning and characterization of poly(vinyl alcohol)/chitosan oligosaccharide/clay nanocomposite nanofibers in aqueous solutions

Submicron fibers of the composite of poly(vinyl alcohol) (PVA), chitosan oligosaccharide [COS, (1→4)2-amino-2-deoxy-β-d-glucose], and montmorillonite clay (MMT) were prepared using electrospinning method with aqueous solutions. Scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), thermal gravimetric analyzer, and tensile strength testing machine (Zwick) were utilized to characterize the PVA/COS/MMT nanofiber mats morphology and properties. The PVA/COS ratio and MMT concentration play important roles in nanofiber mat properties. XRD and TEM data demonstrated that exfoliated MMT layers were well-distributed within nanofiber. It was also found that the mechanical property and thermal stability were increased with COS and MMT contents.     

Preparation of electrospun chitosan/poly(vinyl alcohol) membranes

Electrospinning of chitosan from its solutions in 2% aqueous acetic acid was studied by adding poly(vinyl alcohol) (PVA) as a “guest” polymer. Properties of the chitosan/PVA solutions including viscosity, conductivity, and surface tension were measured, and effects of the polymer concentration, chitosan/PVA mass ratio and processing parameters (applied voltage, flow rate, capillary-to-collector distance) on the electrospinnability of chitosan/PVA were investigated. Analyses of scanning electron micrographs and transmission electron micrographs suggested that the chitosan/PVA ultrafine fibers were often obtained along with beads, and chitosan was located in the elctrospun fibers as well as in the beads. Uniform chitosan/PVA fibers with an average diameter of 99 ± 21 nm could be prepared from a 7% chitosan/PVA solution in 40:60 mass ratio. Results of Fourier transform infrared spectroscopy and X-ray diffraction demonstrated that there were possible hydrogen bonds between chitosan and PVA molecules, which could weaken the strong interaction in chitosan itself and facilitate chitosan/PVA electrospinnability. The electrospun chitosan/PVA membranes showed higher water uptake and would have potential applications in wound dressings.     

Poly(vinyl alcohol)/cellulose nanocrystal barrier membranes

In this study, barrier membranes were prepared from poly(vinyl alcohol) (PVOH) with different amounts of cellulose nanocrystals (CNXLs) as filler. Poly(acrylic acid) (PAA) was used as a crosslinking agent to provide water resistance to PVOH. The membranes were heat treated at various temperatures to optimize the crosslinking density. Heat treatment at 170 °C for 45 min resulted in membranes with improved water resistance without polymer degradation. Infrared spectroscopy indicated ester bond formation with heat treatment. Mechanical tests showed that membranes with 10% CNXLs/10% PAA/80% PVOH were synergistic and had the highest tensile strength, tensile modulus and toughness of all the membranes studied. Polarized optical microscopy showed agglomeration of CNXLs at filler loadings greater than 10%. Differential thermogravimetric analysis (DTGA) showed a highly synergistic effect with 10% CNXL/10% PAA/80% PVOH and supported the tensile test results.Transport properties were studied, including water vapor transport rate and the transport of trichloroethylene, a representative industrial toxic material. Water vapor transmission indicated that all the membranes allowed moisture to pass. However, moisture transport was reduced by the presence of both CNXLs and PAA crosslinking agent. A standard time lag diffusion test utilizing permeation cups was used to study the chemical barrier properties. The membranes containing ≥10% CNXLs or PAA showed significantly reduced flux compared to the control. The CNXLs were then modified by surface carboxylation in order to better understand the mechanism of transport reduction. While barrier performance improvements were minimal, the chemical modification improved the dispersion of the modified CNXLs which led to improved performance. Of special note was an increase in the initial degradation temperatures of both modified and unmodified systems, with the modified system showing an initial degradation temperature >100 °C higher than the cellulose alone. This may reflect more extensive crosslinking in the modified composite.     

聚乙烯醇/聚乙烯吡咯烷酮碱性复合膜的制备及其性能

通过在不同浓度KOH溶液中进行掺杂,制备出了聚乙烯醇/聚乙烯吡咯烷酮(PVA/PVP)碱性聚合物电解质膜.详尽考察了膜的组成、微观结构、热稳定性、离子电导率和甲醇吸收率.结果表明,PVA与PVP两者具有较好的相容性,当m(PVA)∶m(PVP)=1∶0.5时,膜断面致密、均匀,未发生大尺度相分离.PVP的混入可以极大提高复合膜的电导率和热稳定性.当m(PVA)∶m(PVP)=1∶1时,复合膜的电导率可达2.01×10-3 S.cm-1.PVA/PVP/KOH膜的甲醇吸收率随温度的升高没有明显变化,100℃时其甲醇吸收率仅为同条件下Nafion 115膜的1/4.这表明该复合膜有望作为一种新型的碱性直接甲醇燃料电池用固体电解质膜且可提高膜的使用温度.     

六水合硝酸镁增塑改性淀粉-聚乙烯醇复合膜的合成与性能

以六水合硝酸镁[Mg(NO₃)₂·6H₂O]为增塑剂, 采用流延法制备了增塑改性的淀粉-聚乙烯醇(PVA)复合膜, 并研究了改性后淀粉-PVA复合膜的性能. 研究结果表明, Mg(NO₃)₂·6H₂O与淀粉和PVA发生一定的相互作用, 破坏了淀粉和PVA中的结晶结构. 因此, Mg(NO₃)₂·6H₂O的加入可提高淀粉与PVA间的相容性, 改变了淀粉-PVA复合膜的力学性能, 使其拉伸强度下降, 断裂伸长率提高.     

聚乙烯醇-碘复合物在水溶液中的形成

聚乙烯醇(PVA)在碘-碘化钾混合水溶液中能形成蓝色复合物,该复合材料在人们日常生活中已广泛应用.本文综述了在稀溶液条件下聚乙烯醇-碘复合物的形成,并对其复合物形成的可能影响因素,如:PVA的分子量、链结构的规整度、1,2-羟基结构、支链以及浓度、添加其它物质和反应时间等,进行了系统论述.从聚集模型观点看,在复合物中,碘主要是以线性多聚碘负离子形式存在的,如:T3-和I5-等;而PVA链通过分子间氢键作用形成链间聚集将多聚碘负离子包裹在内而形成复合物.