A Hybrid Dielectric Ink Consisting of up to 50 wt% of TiO2 Nanoparticles in Polyvinyl Alcohol （PVA）

PVA （Polyvinyl Alcohol） is a water soluble organic dielectric, easily solution processed to fabricate films by spin coating, dip coating or inkjet printing. It has been used as a dielectric layer in OTFTs （organic thin film transistors）, and its dielectric constant is around 3.5-10. For OTFTs operating at lower voltage, it is desirable to increase the dielectric constant. Here, we report a technique to incorporate upto 50 wt% of TiO2 nanoparticles （15-25 nm） in PVA to increase its dielectric constant. Rutile phase of TiO2 is used, because of its higher dielectric constant （e = 114） compared to anatase phase （E = 31）. We have made inks containing 10 and 50 wt% （of PVA） TiO2 nanoparticles, which is stable upto six months. PVA-TiO2 dispersions and PVA （without TiO2） were spin coated on indium tin oxide coated polyethylene terephthalate substrate. Film structure was studied using SEM （scanning electron microscopy）. Absorption study of the films confirms presence of TiO2 nanoparticles. M-I-M capacitors were fabricated by thermally evaporating aluminium on top of the dielectric films. We observed enhancement in dielectric constant by a factor of 2 for PVA containing 50 wt% TiO2 in comparison to PVA＇s dielectric constant. There is no concomitant increase in the leakage current.

A Polyvinyl Alcohol/Acrylamide Hydrogel with Enhanced Mechanical Properties Promotes Full-Thickness Skin Defect Healing by Regulating Immunomodulation and Angiogenesis Through Paracrine Secretion

Hydrogel-based tissue-engineered skin has attracted increased attention due to its potential to restore the structural integrity and functionality of skin.However,the mechanical properties of hydrogel scaffolds and natural skin are substantially different.Here,we developed a polyvinyl alcohol(PVA)/acrylamide based interpenetrating network(IPN)hydrogel that was surface modified with polydopamine(PDA)and termed Dopa-gel.The Dopa-gel exhibited mechanical properties similar to native skin tissue and a superior ability to modulate paracrine functions.Furthermore,a tough scaffold with tensile resistance was fabricated using this hydrogel by three-dimensional printing.The results showed that the interpenetration of PVA,alginate,and polyacrylamide networks notably enhanced the mechanical properties of the hydrogel.Surface modification with PDA endowed the hydrogels with increased secretion of immunomodulatory and proangiogenic factors.In an in vivo model,Dopa-gel treatment accelerated wound closure,increased vascularization,and promoted a shift in macrophages from a proinflammatory M1 phenotype to a prohealing and anti-inflammatory M2 phenotype within the wound area.Mechanistically,the focal adhesion kinase(FAK)/extracellular signal-related kinase(ERK)signaling pathway may mediate the promotion of skin defect healing by increasing paracrine secretion via the Dopa-gel.Additionally,proangiogenic factors can be induced through Rho-associated kinase-2(ROCK-2)/vascular endothelial growth factor(VEGF)-mediated paracrine secretion under tensile stress conditions.Taken together,these findings suggest that the multifunctional Dopa-gel,which has good mechanical properties similar to those of native skin tissue and enhanced immunomodulatory and angiogenic properties,is a promising scaffold for skin tissue regeneration.

Effect of Polyvinyl Alcohol in Inner Aqueous Phase on Stability of Millimeter-scale Capsules

The millimeter-scale capsules with controllable morphology,ultra-low permeability and excellent mechanical stability were fabricated by millifluidics.Viscosity of inner phase was adjusted to control the morphology and properties of the capsules.In detail,as the concentration of polyvinyl alcohol(PVA)increased from 0 to 8% in the inner phase of the capsules,the diameter of capsules decreased from 3.33 ± 0.01mm to 2.97 ± 0.01 mm,the shell thickness of capsules decreased from 0.183 ± 0.004 mm to 0.155 ± 0.003 mm.While the capsules had round shape and high sphericity.Notably,the capsules with 2% PVA in the inner phase had remarkably decreased water permeability and good morphological stability.Specifically,the end-time of water losing of the capsules was up to 49 days,while the dehydrated capsules maintained spherical appearance,and crushing force of the capsules was up to 13.73 ± 0.79 N,which ensured stability during processing and transportation.This research provides a new strategy for stable encapsulation of small molecules.

Immobilization of activated sludge using improved polyvinyl alcohol (PVA) gel

The microbial immobilization method using polyvinyl alcohol （PVA） gel as an immobilizing material was improved and used for entrapment of activated sludge. The oxygen uptake rate （OUR） was used to characterize the biological activity of immobilized activated sludge. Three kinds of PVA-immobilized particles of activated sludge, that is, PVA-boric acid beads, PVA-sodium nitrate beads and PVA-orthophosphate beads were prepared, and their biological activity was compared by measuring the OUR value. The bioactivity of both autotrophic and heterotrophic microorganisms of activated sludge was determined using different synthetic wastewater media （containing 250 mg/L COD and 25 mg/L NH4^＋ -N）. The experimental results showed that the bioactivity and stability of the three kinds of immobilized activated sludge was greatly improved after activation. With respect of the bioactivity and the mechanical stability, the PVA-orthophosphate method may be a promising and economical technique for microbial immobilization.

高温后钢-PVA混杂纤维高性能混凝土与变形钢筋黏结性能试验

为研究高温后钢-聚乙烯醇(polyvinyl alcohols,PVA)混杂纤维高性能混凝土(hybrid fiber high performance concrete,HFHPC)与变形钢筋的黏结性能退化规律,以200、400、600、800℃为目标温度,选取钢纤维体积率、PVA纤维体积率、矿粉掺量为正交试验因素设计并制作25组HFHPC试件,完成了单调荷载下的中心拉拔试验。结果表明:高温后各组HFHPC试件黏结破坏形态均表现为钢筋拔出破坏;试验温度范围内,对HFHPC试件黏结强度的影响程度均为:钢纤维体积率最大、矿粉掺量次之、PVA纤维体积率最小;随着温度的升高,HFHPC试件黏结强度逐渐下降,且在相同温度条件下,HFHPC试件黏结强度和峰值滑移相比于未掺纤维的混凝土试件均有所提升,其中,200℃时HFHPC试件的黏结强度提升最为显著,分别提升了33.69%、35.76%、37.54%和46.03%;混杂纤维能显著提高高温后高性能混凝土与钢筋的峰值界面能,明显改善黏结延性和耗能能力;提出的考虑温度作用后的混杂纤维混凝土与钢筋黏结-滑移模型与试验实测结果吻合较好,可为火灾后混杂纤维高性能混凝土结构损伤评估及加固方案提供参考。

RTP-PVA混杂纤维的工程水泥基复合材料干缩性能试验研究

为研究回收轮胎聚合物(recycled tyre polymer,RTP)和聚乙烯醇(polyvinyl alcohol,PVA)混杂纤维对工程水泥基复合材料(engineered cementitious composites,ECC)干缩性能的影响,对RTP-PVA混杂纤维总体积分数为2.0%的ECC进行流动性、直接拉伸和干缩试验,并分析混杂纤维作用机理和干缩计算模型.结果表明:RTP纤维替代率为12.5%~50%对ECC流动性影响不大,比单掺PVA纤维的ECC流动性降低1.09%~3.69%.ECC的抗拉强度随RTP纤维替代率的增加而降低,不同比例的混杂纤维比单掺PVA纤维的ECC抗拉强度降低了23.6%~56.6%.不同比例混杂纤维ECC干缩率曲线趋势相近,7 d时干缩率为28 d时的80.92%~82.77%.ECC的干缩率随RTP纤维替代率的增加而降低,28 d时不同RTP纤维替代率的混杂纤维比单掺PVA纤维的ECC干缩率降低了0.80%~2.09%.RTP-PVA混杂纤维可在ECC中协同发挥作用抑制基体干缩,结合试验结果得到适合RTP-PVA混杂纤维ECC的指数型干缩预测模型.

水溶性KGM/PVA涂膜的制备及性能研究

水溶性保鲜涂膜可以有效延缓果蔬的腐烂,同时可以解决传统涂膜影响果蔬品质、味道和色泽等问题。以魔芋葡甘聚糖(KGM)和聚乙烯醇(PVA)为基料,甘油和山梨醇作为复配增塑剂,研究了原料配比对KGM/PVA涂膜水溶性以及光学和力学性能的影响。结果表明:原料配比一定时,KGM/PVA涂膜5min内溶解率随水温的升高而升高;在水温确定的条件下,KGM/PVA涂膜5min内溶解率随着PVA用量的增加而降低。影响涂膜水溶性的主次因素排序为PVA>KGM>山梨醇>甘油。每100mL纯水中,PVA、KGM、甘油、山梨醇用量分别为3g,0.4g,0.3mL,0.1g时涂膜综合性能最佳,在20℃左右冷水中基本不溶,而在30℃及以上温水中可溶,涂膜透光率达到93.68%,拉伸强度为16.66MPa,断裂伸长率为125.87%。

PVDF/PVA共混膜的制备及其在去除污水COD中的应用

以聚乙烯醇(PVA)、聚偏氟乙烯(PVDF)为原料,聚乙烯吡咯烷酮为溶剂,制备了PVDF/PVA共混膜。将该膜应用于膜生物反应器处理污水,测试化学需氧量(COD)去除率和膜的使用性能。结果表明:膜的水通量随PVA加入量的增加而逐渐增加,在牵伸比为1.7时,膜的水通量达到最大值;平板膜用清水清洗后,膜的水通量恢复率较高,膜的运行周期经第一次清洗后下降了18 h,经第二次和第三次清洗后,膜的运行周期基本稳定在6~8 h,COD去除率高于90%,表明该膜具有良好的使用性能。

PVA-甜玉米芯多糖纳米银复合薄膜的制备及草莓保鲜应用

以聚乙烯醇(PVA)和可溶性淀粉为成膜基质、甘油为增塑剂、甜玉米芯多糖(SCP)为原料制备的纳米银(AgNPs)为填料,通过流延成膜法制备了复合薄膜PVA-AgNPs。以抗拉伸强度为指标,通过单因素实验和响应面实验探究了PVA-AgNPs的最佳制备工艺,采用FTIR、SEM对PVA-AgNPs进行了表征,对其性能进行了测试,评价了PVA-AgNPs在草莓保鲜中的应用。结果表明,PVA、可溶性淀粉、甘油和AgNPs用量分别为2.3 g、2.0 g、4.0 mL和4.0 mg时制备的PVA-AgNPs具有最高抗拉伸强度〔(14.08±0.58)MPa〕和断裂伸长率(223.10%±5.29%),其水接触角(50.04°±0.03°)高于PVA薄膜(25.72°±0.69°),其在水中的溶解率(61.87%±0.17%)低于PVA薄膜(69.44%±0.16%),PVA-AgNPs的水蒸气透过率(2.0%~2.5%)比PVA薄膜(0.8%~2.3%)更稳定,其在室温土壤中30 d的降解率为44.67%±2.51%。用PVA-AgNPs包覆草莓,降低了草莓的失重率、腐败率,减少了草莓硬度、可溶性固形物含量与VC含量的损失,稳定了草莓的pH。PVA-AgNPs表面粗糙,有轻微的褶皱,内部存在部分孔隙和裂纹;AgNPs通过覆盖PVA表面亲水性基团增强了复合薄膜疏水性,通过改变水蒸气透过的通路,降低了PVA-AgNPs在水中的溶解率,通过对可见光的吸收,加深了复合薄膜的颜色,降低了其透光率;AgNPs的添加改善了PVA-AgNPs对可见光、水与氧气的阻隔性,实现了对草莓的保鲜。

玉米秸秆-PVA复合气凝胶的制备及其吸附性能研究

以玉米秸秆为原料,用溴化锂和聚乙烯醇(PVA)溶液将其溶解,制备玉米秸秆-PVA复合气凝胶。采用正交试验法对制备工艺进行优化,并通过FT-IR、吸附率等手段对气凝胶的相关性能进行表征。结果表明:复合气凝胶的优化制备工艺条件为:固液质量比(秸秆∶混合溶液)为1∶100,PVA添加量与秸秆的质量比为100∶15,PVA浓度为5%,溴化锂浓度为66%,溴化锂溶液和PVA的质量比为13.85∶1。该工艺下所制得的复合气凝胶密度低至0.0268 g/cm^(3),比表面积为175.00 m^(2)/g,对废弃机油的最大吸附倍率为35.01 g/g。制备过程中,纤维素的氢键被破坏,PVA与纤维素之间通过氢键连接。复合气凝胶的密度越小,其吸油率越大。复合气凝胶具有全范围内的孔径,且大部分孔径处于介孔范围内,因此有利于对大分子污染物的吸附。

Fabrication of High-Efficiency Polyvinyl Alcohol Nanofiber Membranes for Air Filtration Based on Principle of Stable Electrospinning

A mass flow matching model(MFMM)was established for studying the stable status of solution electrospinning.The study of the solution droplet status at the needle tip focused on various combinations of applied voltages and injection rates to figure out their influence on steadily fabricating polyvinyl alcohol(PVA)nanofibers prepared from PVA spinning solutions with two different mass fractions(10%and 16%).The results revealed that during the stable electrospinning,the influence resulted from the change of the injection rate approximately canceled out the impact brought by adjusting the applied voltage,leading to almost the same morphology as that of the PVA nanofibers.And the mass fraction of PVA in the spinning solution dominated the structure and the diameter distribution of the electrospun nanofibers.Under stable electrospinning conditions,the composite membrane was produced by depositing PVA nanofibers on the polyethylene terephthalate(PET)nonwoven substrate for an air filtration test.Furthermore,the prepared composite membrane exhibited a high air filtration efficiency(99.97%)and a low pressure drop(120 Pa)for 300-500 nm neutralized polystyrene latex(PSL)aerosol particles,demonstrating its potential as an alternative for a variety of commercial applications in air filtration.

PVA基复合材料导热性能的研究进展

聚乙烯醇(PVA)基复合材料是一种具有广阔应用前景的高分子材料,导热性能是影响其在热管理、电子器件散热等领域实际应用的重要因素之一。近年来,许多学者对PVA基复合材料的导热性能进行了深入研究,涉及不同的导热填料和制备方法。本文介绍了导热填料的类型、添加量、尺寸与形态对PVA导热性能的影响,以及复合材料的结构设计和界面工程对导热性能的调控,并总结了PVA基复合材料的导热机理及导热性能,为其在各种领域的应用提供了更多的参考。

硼砂交联PVA降失水剂的合成及滤失性能研究

以聚乙烯醇(PVA1788)为水泥浆降失水剂基础原料,考察了交联剂种类和用量、反应温度、溶液pH值等对PVA胶液粘度和水泥浆滤失性能的影响规律,发现硼砂水解后对PVA的交联效果最显著,而且随着硼砂与PVA配比、反应温度和pH值升高,PVA胶液粘度及水泥浆滤失性能呈现显著增高趋势,所形成的滤饼更加致密,保水能力更好。但一旦超过最佳配比时,水泥颗粒表面降滤失剂膜层变厚,滤饼致密性变差,反而不利于水泥浆保水,滤失性能下降。

PVA纤维、减缩剂和轻烧氧化镁对水工衬砌混凝土性能影响对比研究

依托于滇中引水工程,研究了掺入聚乙烯醇纤维(PVA纤维)、减缩剂和轻烧氧化镁对衬砌混凝土性能的影响。结果表明:掺入0.9 kg/m^(3)PVA纤维和1.5%减缩剂对混凝土坍落度影响不显著,掺入5%轻烧氧化镁后,混凝土拌和物坍落度下降了36.8%;掺入0.9 kg/m^(3)PVA纤维、1.5%减缩剂和5%轻烧氧化镁后,混凝土7 d、28 d龄期的抗压强度和劈拉强度差异不明显;掺入1.5%减缩剂和5%轻烧氧化镁对混凝土7 d、28 d龄期的极限拉伸值影响不显著,但掺入0.9 kg/m^(3)的PVA纤维后,混凝土28 d龄期的极限拉伸值提高了18×10-6;掺入0.9 kg/m^(3)的PVA纤维对混凝土120 d龄期内的干缩率影响不显著,掺入减缩剂和轻烧氧化镁后,混凝土120 d龄期的干缩率分别降低了100×10-6和33×10-6;掺入PVA纤维、减缩剂和轻烧氧化镁后,混凝土裂缝降低率分别为44.1%、31.9%和25.0%,可以有效减少裂缝的产生。

Preparation of Film Based on Polyvinyl Alcohol Modified by Alkaline Starch and Lignin Fiber

This study presents an easily prepared film based on alkaline starch-polyvinyl alcohol hybrid and lignin fiber as an additive(SPL film).The SPL film was prepared under acidic conditions through a polycondensation reaction of PVA and a mixture incorporating alkaline starch and lignin fiber from agriculture or forest source.The examination using scanning electron microscopy(SEM)showed that the surface of SPL film was smooth and the lignin fiber had good compatibility within the film hybrid.Electrospray ionization mass spectroscopy(ESI-MS)and fourier transform infrared(FTIR)investigations indicated that alkaline starch and lignin fiber reacted with PVA under acidic conditions and that–CH_(2)–O–groups were involved in the cross-linking of the SPL system.In addition,the SPL film exhibited only 4%light transmittance,which effectively reduces the ultraviolet and visible light(UV-Vis)penetration,along with good performance when exposed to thermal degradation,in which the mass loss reached around 60%at 400℃.More-over,the SPL film acquired excellent tensile strength,which is much higher than that of PVA-lignin(PL)composite film.

Experimental study on mechanical and frost heave behaviors of silty clay improved by polyvinyl alcohol and polypropylene fiber

Silty clay is widely used as subgrade filler in cold regions,which suffer from frost heave in winter and mud pumping in spring.In this study,polyvinyl alcohol(PVA)and polypropylene(PP)fiber were used to improve the mechanical and frost heave behavior of silty clay in cold regions,and the direct shear test and one-dimensional frost heave test were employed in studying improvement effects.Moreover,improvement mechanisms of PVA and PP fiber were analyzed based on test results.The main findings are as follows.(1)Both PP and PVA can heighten the strength of silty clay and suppress frost heave,but the PVA solution has a more decisive influence on improving mechanical properties than PP fiber.(2)The improvement mechanism of the PVA solution is cementing.The improvement effect of 2%PVA solution is the best,which can increase the shear strength by approximately 40%–60%at different stress levels and decrease the frost heave ratio from 0.89%to 0.16%at optimal water content.(3)For 2%PVA improved samples,0.25%PP fiber can further increase soil cohesion by approximately 20–30 kPa at different stress levels and further decrease the frost heave ratio from 0.16%to 0.07%at optimal water content.The improvement effect is neglectable when the PP fiber content exceeds 0.25%.Overall,2%PVA with 0.25%PP fiber is the optimum combination to improve silty clay in cold regions.

PVAL/β-CD-CIN薄膜的制备及性能

以β-环糊精(β-CD)为壁材,肉桂醛(CIN)为芯材,采用饱和水溶液法制备β-环糊精-肉桂醛(β-CD-CIN)包合物。然后采用流延法,以聚乙烯醇(PVAL)为成膜基材,加入β-CD-CIN包合物,制备PVAL/β-CD-CIN薄膜,通过改变β-CD-CIN包合物的添加量来研究包合物对PVAL薄膜的热性能、力学性能、阻隔性能等的影响。傅里叶变换红外光谱分析证明CIN被成功地包埋于β-CD空腔,相比于未添加包合物的PVAL薄膜,PVAL/β-CD-CIN薄膜的熔融温度降低了26.90℃,结晶度降低了6.15%。当包合物质量分数为15%时,PVAL/β-CD-CIN薄膜的拉伸强度和断裂伸长率达到最大值,分别为22.79 MPa和430.60%,此时力学性能最佳。当包合物添加质量分数为30%时,PVAL/β-CD-CIN薄膜的水蒸气透过系数达到最小值为0.41(g·mm)/(kPa·m^(2)·h),吸水率达到最低为11.97%。加入β-CD-CIN包合物,可以有效提升薄膜的力学性能、水蒸气透过率、耐水性等,为薄膜在食品包装领域的应用奠定基础。

2,4-Dinitrophenyl Ether of Polyvinyl Alcohol and Polymer Bound Anionic SIGMA Complexes

A new electrophilic polymer, 2,4-dinitrophenyl ether of polyvinyl alcohol (PVA-DNP), having a degree of substitution of 0.5 was prepared from polyvinyl alcohol (PVA) and 1-fluro-2,4-dinitrobenzene (DNFB). The PVA-DNP polymer was characterized by NMR, IR, and UV-visible spectroscopy. The reaction of PVA-DNP with sodium methoxide was followed by NMR and UV-visible spectroscopy. Evidence of polymer bound spirocyclic SIGMA complex, C-1 and C-3 polymer bound DNP-methoxy SIGMA complexes and the formation and C-1 methoxy complex of 2,4-dinitroanisole was observed.

基于同轴微流控纺丝技术的CS/SA掺杂PVA复合载药纤维的制备及其释药性能

为延长药物的可控释放时间,提高累计释放率,将生物相容性良好的天然高分子材料壳聚糖(CS)和海藻酸钠(SA)分别与聚乙烯醇(PVA)溶液混合作为纺丝液,通过同轴微流控纺丝技术制备具有药物缓释性能的复合载药纤维。以氨苄西林钠(AS)为药物模型,比较研究了PVA/CS/AS(PCA)和PVA/SA/AS(PSA)两种复合载药纤维的药物缓释效果,并分析了两种天然高分子材料及其含量对载药纤维形貌结构、力学性能以及释药性能的影响。结果表明:PCA和PSA载药纤维均具有稳定的成型性和良好的形貌结构。PCA的断裂强度高于PSA复合纤维,而PSA的断裂伸长率远大于PCA复合纤维。此外,这两种纤维对药物均具有良好的缓释效果。其中,PCA复合纤维在短期内释药量大,当PVA与CS质量比为5∶1时,PCA复合纤维在180 min内药物的累计释放率最高为60%;而PSA复合纤维可以实现58 h的长时间药物释放,当PVA与SA质量比为64∶1时,PSA复合纤维药物累计释放率最高为94.1%,适合治疗慢性疾病,达到长期有效释药的目的。利用这两种载药复合纤维可设计适用于不同给药患者的药物缓释系统,展现出其在药物缓控释中的广阔应用前景。

CMC-PVA-β-CD三元复合水凝胶的制备

以羧甲基纤维素(CMC)、聚乙烯醇(PVA)、β-环糊精(β-CD)为原料,在碱性条件下与环氧氯丙烷(ECH)发生交联反应,制备具有高溶胀性能的CMC-PVA-β-CD三元复合水凝胶,并研究了CMC,PVA,ECH,β-CD添加量对水凝胶溶胀性能、力学性能的影响。结果表明:加入20.0 mL水,0.52 g CMC,0.20 g PVA,1.2 mL ECH,0.24 gβ-CD时,水凝胶溶胀率最高,为2 040.62 g/g,压缩应力为7.90 kPa。与PVA-CMC二元水凝胶相比,CMC-PVA-β-CD三元水凝胶的压缩应力和结晶度均有提高。该三元复合水凝胶具有较高的溶胀率和良好的力学性能,在生物医药、消毒杀菌领域具有很高的应用价值。