聚乙烯醇/明胶/纳米羟基磷灰石复合材料热塑加工性能研究

结合固相剪切碾磨技术(S3M),以胶原纤维(Col)在熔融挤出过程中原位降解成明胶(Gel),通过Gel与聚乙烯醇(PVA)分子间形成氢键复合增塑PVA,改善聚乙烯醇/纳米羟基磷灰石(PVA/n-HA)复合材料的热塑加工性能.采用扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FTIR)、示差扫描量热仪(DSC)、热重分析仪(TGA)、X射线衍射仪(XRD)和高压毛细管流变仪等研究了复合材料的结构与热塑加工性能.结果表明,通过S3M技术实现了n-HA在PVA基体中的均匀分散;FTIR表明Gel与PVA间形成了氢键作用和部分接枝反应;Gel和PVA分子间的氢键作用使PVA/Gel/n-HA复合材料的初始分解温度提高到287.6℃,改善了PVA的热稳定性,PVA的结晶度由纯PVA的58.2%降低到复合材料中的24.5%,使其熔点降低至130.5℃,拓宽了PVA/n-HA复合材料的加工范围,获得超过140 K的热塑加工窗口.Gel有效降低了PVA/nHA复合材料表观黏度,改善了PVA/n-HA复合材料的热塑加工性能.     

PVA微晶交联和SA/PAA双网络协效增强增韧SA纤维

为了提高海藻酸钠(SA)纤维的断裂强度和断裂伸长率, 以丙烯酸(AA)为化学交联组分, SA为离子交联组分, 聚乙烯醇(PVA)为微晶交联组分, 采用湿法纺丝和冻融循环方法制备含有PVA微晶交联点和海藻酸钠/聚丙烯酸(SA/PAA)双网络结构的海藻酸钠/聚丙烯酸/聚乙烯醇(SA/PAA/PVA)复合纤维. 通过流变性能、 力学性能、 红外光谱、 X射线衍射仪(XRD)和扫描电子显微镜(SEM)测试研究了交联剂N,N-亚甲基双丙烯酰胺(MBA)含量和PVA微晶交联对SA/PAA/PVA纺丝原液和复合纤维的结构与性能的影响. 结果表明, 当MBA质量分数为0.5%时, 纺丝原液的损耗模量(G″)最小, 可纺性最好, 复合纤维的断裂强度达到2.83 cN/dtex, 断裂伸长率达到9.38%, 比再生SA纤维分别提高了15.98%和38.96%; PVA冷冻之后形成微晶交联点并且PAA和PVA已经复合到体系中; PAA和PVA的加入提高了复合纤维的结晶度; 复合纤维的表面形貌趋于光滑和规整, 纤维断面更加致密.     

PVA/PEG/Mg(OH)_2复合材料体系的非等温结晶行为

采用熔融共混法,以聚乙二醇(PEG)为增塑剂、Mg(OH)2为稳定剂制备了聚乙烯醇(PVA)/PEG/Mg(OH)2复合材料。利用差示扫描量热仪(DSC)考察了PVA/PEG/Mg(OH)2复合体系中PVA的非等温结晶行为。结果表明:在熔融过程中PEG与PVA大分子形成的分子间氢键,破坏了PVA分子内或分子间的氢键,改善了PVA的热塑性能,使研究其熔融结晶行为成为可能。     

Papain/HA-Phe自组装复合纳米粒子及乳化性能

用L-苯丙氨酸乙酯(L-Phe)改性透明质酸(HA)双亲性生物大分子(HA-Phe)负载生物活性分子木瓜蛋白酶(papain),HA-Phe和Papain通过静电、氢键和疏水相互作用自组装形成生物基Papain/HA-Phe复合纳米粒子.用动态光散射(DLS)和透射电镜(TEM)对复合纳米粒子的尺寸和形貌进行表征.结果显示,形成的复合纳米粒子为球形结构,粒径约308 nm.以此复合纳米粒子为颗粒乳化剂稳定白油,形成水包油型Pickering乳液.乳液的扫描电镜(SEM)显示,复合纳米粒子吸附在油水界面,形成复合纳米粒子的吸附层以稳定乳液.详细研究了pH和盐浓度对复合纳米粒子性质和复合纳米粒子乳化性能的影响.结果表明,随着pH增加,复合纳米粒子在油滴表面的吸附数目减少,乳化性能降低;随着盐浓度增加,复合纳米粒子的形变能力增强,乳化性能提高.进一步研究了乳液中木瓜蛋白酶的活性及美白效果.研究表明,制备的乳液保留了一定的活性,且具有一定的美白效果.     

聚乙烯醇/海藻酸钠互穿网络水凝胶结构与性能研究

采用天然高分子海藻酸钠(SA)与聚乙烯醇(PVA)复合,通过化学交联法制备PVA/SA互穿网络水凝胶。SA的加入减弱了PVA分子间的氢键作用,而随SA含量增加,SA分子与PVA分子间的氢键作用增强。同时凝胶网络由致密变得疏松,网孔增大,出现微相分离的"核壳"结构。由于交联后的SA与PVA分子的Tg较接近,水凝胶仅有一个Tg,两相仍为部分相容。应变及频率扫描曲线中低应变区的储能模量远大于损耗模量,其网络松弛因子n值接近0,证明该凝胶具有较完整的网络结构,并表现为弹性。适量的SA可提高凝胶的力学及溶胀性能。     

甲基丙烯酸正丁酯/甲基丙烯酸β羟乙酯共聚吸附功能纤维的制备及表征

以过氧化苯甲酰(BPO)为引发剂, 合成了甲基丙烯酸正丁酯/甲基丙烯酸羟乙酯(BMA/HEMA)二元共聚树脂, 采用冻胶纺丝技术制备了低分子量有机液体吸附功能纤维, 利用傅里叶变换红外光谱(FTIR)和13C核磁共振波谱(NMR)、广角X射线衍射仪(WAXD)和综合热分析仪以及环境扫描电子显微镜(SEM)研究了共聚物的交联结构、纤维的结晶性能以及纤维的表面形貌, 同时研究了共聚合阶段HEMA与BMA投料比对纤维饱和吸附量的影响. 研究结果表明, 树脂大分子间不存在化学交联结构, 大分子内和大分子间存在氢键作用, 有利于物理交联结构的形成; 纤维结晶性能随着HEMA质量分数增加而减弱, 且HEMA质量分数对纤维表面形貌有较大影响; 纤维对甲苯和三氯乙烯的饱和吸附量随着HEMA质量分数增加而增大, HEMA质量分数相同时所得纤维对三氯乙烯的吸附量明显高于对甲苯的吸附量.     

高温高矿化度条件下驱油剂中聚合物分子结构形态及其在中低渗油层中的渗流特性

利用动态光散射(DLS)、电镜扫描(SEM)和岩心驱替实验等方法, 对高温高矿化度条件下聚合物溶液和“聚合 物/表面活性剂”二元复合驱油体系中聚合物分子线团尺寸及其影响因素和在中低渗油藏环境下的渗流特性进行了实验研究, 并对其渗流规律进行了机理分析. 结果表明, 在高温高矿化度条件下, 随聚合物浓度增加, 聚合物溶液和“聚合物/表面活性剂”二元复合驱油体系中聚合物分子线团尺寸D_h都呈现“先增大后减小”的变化规律. 非离子型表面活性剂以胶束聚集体形式吸附在聚合物分子链上, 造成二元复合驱油体系中聚合物分子线团尺寸D_h大于聚合物溶液. 在溶剂水矿化度较高和岩心渗透率较低条件下, 后续注入水的冲刷和稀释作用造成岩心内滞留聚合物浓度降低, 聚合物分子线团尺寸D_h增加, 最终导致聚合物溶液和“聚合物/表面活性剂”复合体系的残余阻力系数大于阻力系数.     

异相成核和拉伸诱导对生物基PHBV复合纤维结晶结构与力学性能的影响

采用熔融纺丝法制备了聚(3-羟基丁酸酯-co-3-羟基戊酸酯)(PHBV)/二硫化钨(WS_2)复合纤维.利用示差扫描量热仪(DSC)、热台偏光显微镜、二维广角射线衍射仪(2D-WXRD)、纤维强力仪研究了WS_2异相成核作用和牵伸诱导作用对纤维的结晶结构和力学性能的影响.研究表明,WS_2显著提高了PHBV的结晶温度,当使用2 wt%WS_2时,复合材料的结晶温度提高到115~130oC,比纯PHBV(99~105oC)提高了约25oC.WS_2不仅没有影响PHBV球晶的径向生长速率,且明显提高了PHBV/WS_2复合材料的晶核密度,熔体成核活性Φ由1.0降低为0.49.随着牵伸倍率和WS_2用量的增加,纤维的拉伸强度呈现出先增加后减小的趋势.当添加1 wt%WS_2并采用单向牵伸3.8倍时,纤维中的晶体取向产生了β晶结构,使复合纤维的拉伸强度由纯PHBV的37 MPa提高至155 MPa,断裂伸长率由2.4%增加至45%.     

静电纺丝法制备聚乳酸/纳米磷酸钙复合纳米纤维及其表征

首先合成了纳米磷酸钙(NCP),用扫描电镜(SEM)和X射线衍射(XRD)进行了表征.再利用静电纺丝法制备了PLA/NCP复合纳米纤维,对纤维进行了TEM,SEM,XRD以及单轴拉力测试的表征.TEM和XRD测试表明,NCP已成功掺杂到聚乳酸纤维中,获得的纤维为复合纤维.SEM测试表明,NCP在溶液中浓度较小时,复合纳米纤维的形貌变化不大;NCP浓度超过PLA质量的7%后,纤维表面出现粒状物;随着浓度继续增大,粒状物逐渐增多,最后很难成纤.拉伸实验结果表明,复合纤维拉伸强度先随着NCP浓度的增加而增大,但NCP浓度超过7%后拉伸强度随着浓度的增加反而减小.     

离子液体增塑改性玉米淀粉/聚丁二酸丁二醇酯共混材料的结构与性能

为考察离子液体对淀粉/聚丁二酸丁二醇酯(PBS)的作用效果,降低淀粉/PBS的脆性,以离子液体(1-丁基-3-甲基咪唑氯盐[BMIM]Cl)作为增塑改性剂通过熔融共混法制备了玉米淀粉/聚丁二酸丁二醇酯(PBS)共混材料,采用红外光谱(FTIR)、扫描电镜(SEM)、热重分析(TGA)、X射线衍射分析(XRD)及力学性能测试方法研究了[BMIM]Cl对淀粉/PBS共混材料结构和性能的影响.结果表明,[BMIM]Cl能与淀粉/PBS分子发生强相互作用,破坏淀粉/PBS共混物中原有的氢键与结晶结构,增强界面相互作用,改善相容性,进而改变淀粉/PBS共混材料的结构与性能;[BMIM]Cl的加入不影响淀粉/PBS的热稳定性,可使材料玻璃化转变温度(Tg)、结晶温度(Tc)、冷结晶温度(Tcc)及结晶度(Xc)降低.[BMIM]Cl具有显著降低淀粉/PBS脆性的作用,使其断裂伸长率大幅度增加,拉伸强度和弹性模量降低.     

Effect of aging time and salt on the viscosity behaviour of a Gemini cationic surfactant

Rheological properties of micellar solutions of a cationic Gemini surfactant, 2-hydroxypropyl-1,3-bis (dodecyldimethylammonium chloride), are studied as a function of aging time and salt addition. The results show that the self-aggregating behaviour in solution changes as a factor of time, probably due to intermolecular hydrogen bonds. The viscosity of the solution undergoes a series of visible changes so that the solution changes from a flow state to highly viscoelastic state, and finally, to a transparent solid, with a corresponding 4–6-fold increase in zero shear state viscosity. Rheology and freeze fracture transmission electron microscopy (FF-TEM) measurements show rod-like micelles at the beginning, which then change to wormlike micelles, and eventually to a quasi-gel-like network. Addition of an inorganic salt (NaCl) induces salting out, while the addition of an organic salt (NaSal) promotes micellar growth. At a fixed NaSal-to-surfactant molar ratio of 3:5, all solutions show Maxwell fluid behaviour and maximum zero-shear-rate viscosity; these trends can be attributed to the formation of a network structure between the cationic ions of the surfactant and Sal^– as the surfactant concentration increases. Crystal analysis further confirms the presence of structures linked by intermolecular hydrogen bonds.     

Salt-induced thickening and gelation of a poly(carboxylate) having three kinds of hydroxyl groups

A salt-induced physical gelation was found for the aqueous solution of poly(carboxylate)s having three kinds of hydroxyl groups, i.e., primary, tertiary and one on a hemiacetal ring. The gelation point (critical salt concentration) was positively correlated with the content of the hemiacetal component, while the previously confirmed hydrogen bond between the hemiacetal OH and –COO⁻ group does not seem to essentially contribute to the physical gelation. Above a critical polymer concentration, the solution viscosity was first decreased and then increased with increasing NaCl concentration, leading to gelation. However, below the critical polymer concentration, the viscosity decreased. These different behaviors of the solution viscosity depending on the polymer concentration were ascribed to a preferential promotion of intermolecular or intramolecular hydrogen bonds among the hemiacetal OH groups above and below the critical polymer concentration, respectively.     

Facile fabrication of chitosan active film with xylan via direct immersion

Chitosan film was immersed in NaOH solution with xylan to simply prepare active chitosan/xylan film. FT-IR, XRD, FE-SEM, AFM and XPS were used to evaluate the effects of xylan on the structure and morphology of chitosan film, and a wide variety of material characteristics of the chitosan/xylan composite films were investigated. The results showed that the xylan chains entered into the gap of chitosan film and became nodules, leading to strong hydrogen bonds and electrostatic interactions between chitosan and xylan. Moreover, the introduction of xylan not only resulted in stronger crystallinity and a more compact structure of chitosan film, but also had an important effect on the properties of chitosan film. The tensile strength, breaking elongation and anti-ultraviolet performance of the chitosan/xylan films were improved greatly with the increasing concentration of xylan; the water vapor transmission rate, water absorption rate and oxygen barrier property of chitosan/xylan composite films were higher than those of chitosan film; chitosan/xylan composite films still showed hydrophobicity when the xylan concentration was more than 1 %. The chitosan/xylan composite film has more potential to be used as food packaging than pure chitosan film.     

海藻酸盐/壳聚糖衍生物复合抗菌纤维

通过溶液纺丝法制备海藻酸盐/羧甲基壳聚糖（CMC）共混纤维,并用红外光谱,X射线衍射和扫描电镜对共混纤维进行了表征.结果表明：共混体系中的两种组分之间存在着较强的相互作用,有良好的相容性.当ωCMC=0.30时,共混纤维的干态抗张强度达到最大值,13.8cN/tex.当ωCMC=0.10时,纤维的干态断裂伸长率可达23.1%.纤维的湿态抗张强度和断裂伸长率随着CMC含量的增加而降低.CMC的引入,可显著提高纤维的吸水率.用壳聚糖季铵盐对纤维进行处理,可赋予纤维抗菌性.     

Computational study of structural and dynamical properties of formamide-water mixtures

A molecular dynamics simulation study of structural and dynamical properties in liquid mixtures of formamide and water is presented. Site-site radial pair distribution functions, local mole fractions, pair energy distributions, and tetrahedral orientational order are the quantities analyzed to investigate the local structure in the simulated mixtures, along with a review of the intermolecular structure in terms of the distribution of hydrogen bonds. Our results indicate that there is a substitution of formamide molecules by water in the hydrogen bonds and a formation of a common hydrogen bond network. By analyzing the extent of tetrahedral order in the liquid as a function of composition, it is observed that whereas the tetrahedral network of liquid water is progressively lost by increasing the formamide concentration, the water structure within the first coordination shell is preserved and somewhat enhanced. The hydrogen-bond mean lifetimes were estimated by performing a time integration of the autocorrelation functions of bond occupation numbers. The lifetimes associated with hydrogen bonds between water, formamide, and interspecies pairs are found to increase with increasing formamide concentration. The lifetimes of the water hydrogen bonds show the largest variations, supporting the picture of an enhancement of the water structure among the nearest neighbors within the first coordination shell. We have used two different force field models for water, SPC/E [J. C. Berendsen et al., J. Phys. Chem. 91, 6269 (1987)] and TIP4P/2005 [J. L. F. Abascal and C. Vega, J. Chem. Phys. 123, 234505 (2005)]. Our results for structural and dynamical properties yield very small differences between those models, the TIP4P/2005 predicting a slightly more structured liquid and, consequently, exhibiting a slightly slower translational and librational dynamics.     

Effect of degree of saponification on structural and property change of poly(Vinyl alcohol) fibers

To improve the drawability and finally the mechanical properties, poly(vinyl alcohol)s (PVA₈₆, PVA₉₃, and PVA₉₉) with respective degrees of saponification of 86, 93, and 99% were synthesized using solution polymerization. Following the synthesis dimethylsulfoxide (DMSO) solutions of the PVAs were gel-spun into methanol. After extraction of DMSO from the as-spun fibers the dried fibers were first drawn at 120 °C then at 180 °C. An analysis of the structure and properties of the fibers was performed using FT-IR, differential scanning calorimetry (DSC) and a fiber strength tester. The degree of saponification had an effect on the formation and intensity of the intermolecular hydrogen bonds, melting, drawability and strength of the PVA fibers. Low degrees of saponification weakened the intermolecular hydrogen bonds and interfered with the formation of crystallites, causing low melting points and low heat of fusion. Generally, drawing was easier to carry out at lower temperature, and higher draw ratios could be obtained, leading to higher fiber strengths. Copyright © 2003 John Wiley & Sons, Ltd.     

The colloidal behaviour of kraft lignin III. Swelling behaviour and mechanical properties of kraft lignin gels

Summary Kraft lignin gels have been synthesized by cross-linking kraft lignin (Indulin ATR) in water with varying amounts of epichlorohydrin under alkaline conditions. The effects of pH and salt concentration on the swelling behaviour and on the mechanical properties of these gels have been investigated.Swelling was determined gravimetrically and the mechanical properties of the gels were tested under uni-axial compressive creep in the time interval 1–900 s. The gels show a linear viscoelastic behaviour without viscous flow.The kraft lignin gels exhibit a swelling behaviour typical for polyelectrolytic networks, i. e. the degree of swelling increases with an increasing number of ionized groups and decreases with increasing salt concentration. The swelling behaviour and ion exchange capacity were found to be nonspecific towards type of alkaline solution (LiOH, NaOH, and KOH).The ability of the carboxylic groups to form intermolecular hydrogen bonds has a strong influence on the mechanical properties of the gels. Creep compliance and creep rate increase greatly when the carboxyl groups are dissociated. It is therefore concluded that the effective number of crosslinks in the networks in addition to chemical cross-linking is also dependent on the state of dissociation of the carboxylic groups.With 11 figures and 1 table     

Preparation and characterization of biodegradable poly(l-lactide)/chitosan blends

In order to improve the properties of chitosan and obtain new fully biodegradable materials, blends of poly(l-lactide) (PLLA) and chitosan with different compositions were prepared by precipitating out PLLA/chitosan from acetic acid-DMSO mixtures with acetone. The blends were characterized by Fourier transform infrared analysis (FTIR), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), ¹³C solid-state NMR and Wide-angle X-ray diffraction (WAXD). FTIR and XPS results showed that intermolecular hydrogen bonds existed between two components in the blends, and the hydrogen bonds were mainly between carbonyls of PLLA and amino groups of chitosan. The melting temperatures, cold crystallization temperatures and crystallinity of the PLLA component decreased with the increase in chitosan content. Blending chitosan with PLLA suppressed the crystallization of the PLLA component. Although the crystal structure of PLLA component was not changed, the crystallization of the blends was affected because of the existence of hydrogen bonds between two components, which was proved by WAXD results.     

Preparation and Properties of Alginate/Water‐Soluble Chitin Blend Fibers

Water‐soluble chitin (half‐deacetylated chitin) was prepared from chitosan by N‐acetylation with acetic anhydride. Alginate/water‐soluble chitin blend fibers were prepared by spinning their mixture solution through a viscose‐type spinneret into a coagulating bath containing aqueous CaCl₂ and ethanol. The structure and properties of the blend fibers were studied with the aids of infrared spectra (IR), X‐ray diffraction (XRD) and scanning electron microscopy (SEM). structure analysis indicated good miscibility existed between alginate and water‐soluble chitin, due to the strong interaction from the intermolecular hydrogen bonds and electrostatic interactions. Best values for the dry tensile strength and breaking elongation were obtained when the water‐soluble chitin content was 30 wt%. The wet tensile strength and breaking elongation decreased with the increase of water‐soluble chitin content. The introduction of water‐soluble chitin in the blend fiber can improve the water‐retention properties of the blend fiber compared to pure alginate fiber. The fibers treated with aqueous solution of silver nitrate have good antibacterial activity to Staphylococcus aureus.