聚乙烯醇吹膜加工性能研究

研究了聚乙烯醇(PVA)吹膜加工性能。经两种不同的增塑剂复配增塑后，可明显改善其加工流动性，当复合增塑剂用量为25phr以上，PVA可以被较好地增塑，熔融塑化温度趋于定值。热性能研究表明，PVA为不完全结晶，其熔融曲线呈不规则分布。从PVA的流变性能可知，PVA熔体呈非牛顿性流体，剪切粘度随剪切速率增加而下降，并且醇解度较高的树脂，剪切粘度也较高。不同醇解度的PVA树脂，均能通过增塑改性后熔融挤出加工吹塑成膜。高醇解度PVA膜的水溶解温度高，而低醇解度PVA膜具有低温快速水解的性能。     

PVA醇解度对热致变导电PVA/AgNO3_薄膜结构和性能的影响

采用不同醇解度的聚乙烯醇(PVA)和硝酸银(AgNO_3)为原料,通过溶液成膜法制备了在固相具有热致变性能的导电PVA/AgNO_3复合薄膜。采用FTIR表征了各种醇解度的PVA与Ag+之间的络合作用。通过TG、SEM、X-射线衍射、X射线能谱(EDS)等方法研究了不同醇解度的PVA/AgNO_3复合薄膜的热性能和热处理后薄膜表面形貌和结构,结果表明:不同醇解度的PVA/AgNO_3复合薄膜在160~200℃均有一明显失重峰;随着醇解度增加,SEM显示热处理后纳米银粒子尺寸减小;实验发现在温度为170~200℃时,醇解度为80%、88%、92%的PVA/AgNO_3复合薄膜其表面电阻率能从300~500 kΩ突然降低到5~20Ω(降低4~5个数量级),而醇解度为97%的PVA/AgNO_3复合薄膜表面电阻率不能发生突变,反而升高。这种具有独特电阻率-温度特性的薄膜在热敏电阻或温度传感器等方面有潜在应用。     

聚乙烯醇醇解度影响因素及力学性能研究

研究了影响聚醋酸乙烯酯醇解度的因素,观察PVA的性能。用超声仪器超声醇解聚醋酸乙烯酯(PVAC),调节不同的温度和加入催化剂(NaOH)的量,制得PVA,通过测定PVA的挥发分、PVA中乙酸钠的含量和PVA中氢氧化钠的含量计算出PVA的醇解度,从实验中得出温度和催化剂对醇解度的影响,使用红外光谱仪得到红外光谱图,用它进行表征,用万能力学实验机,测定它的力学性能,深入了解PVA的性能。实验结果表明为含水量、不同的温度和不同的氢氧化钠浓度都影响着醇解度,在含有2.5%氢氧化钠和40℃的甲醇中,聚醋酸乙烯酯醇解的最完全,它的醇解度为97.54%。     

聚乙烯醇杂化膜的制备及性能

通过加入低分子量PVA205的方法提高高醇解度PVA117的流动性以降低加工过程中PVA的热氧降解。用HAAKE转矩流变仪、红外光谱(FTIR)、差示扫描量热仪(DSC)、力学性能以及热失重(TGA)等进行了表征。红外结果表明:PVA205的加入有效破坏了高醇解度PVA的规整性,PVA117和PVA205之间发生了新的氢键作用;DSC结果表明:随着PVA205含量的增加,熔融温度(Tm)和结晶度均降低;力学数据以及热稳定数据表明:共混后PVA塑化性能变好,薄膜韧性增加,热稳定性提高。     

改性聚乙烯醇的热性能

采用DSC、TGA等测试，研究了6种PVA改性体系中改性剂对PVA热性能的影响。初步表征了各体系的成膜性能。实验结果表明，改性剂与PVA分子间发生强烈的相互作用，从而降低了PVA的熔点，提高了其热分解温度，在不同程度上改善了PVA的熔融性，通过热压成型可以将改性PVA制成透明性很好的薄膜。     

粹文详摘

CW189 聚乙烯醇的吹膜工艺聚乙烯醇(PVA)具有水溶性和生物降解性,用作包装薄膜较一般的包装材料在透明度、光泽、抗静电、透湿、耐油耐有机溶剂、热熔性、强韧性及印刷性能等方面都优于聚烯烃膜。PVA膜的生产方法有水溶液涂布法和熔融吹塑法,作为包装膜最常用的是熔融吹塑法。但是由于PVA分子内存在很多氢链结晶度又高,使它的熔融温度高于分解温度而难以热塑成型。故在PVA的热加工时须选用合适的增塑剂和润滑剂以降低它的熔体粘度和熔融温度,提高加工温度下的热稳定性。本文主要研究了不同醇解度和聚合度的PVA的成膜加工条件、流变性…     

聚乙烯醇水凝胶的制备及其溶胀性能

采用化学交联方法制备了PVA水凝胶，研究了PVA聚合度、醇解度等分子结构参数，反应温度、反应时间等合成工艺参数，交联剂用量、疏水单体用量、阴离子单体用量等化学组成对PVA水凝胶溶胀性能的影响。结果表明，采用聚合度为1700、醇解度为95％的PVA1795为基体，当交联剂用量为1mL，反应温度为80℃，反应时间为8h，所制得的PVA水凝胶具有较高的溶胀率。     

高浓度聚乙烯醇水凝胶性能研究

利用冷冻-解冻法制备了不同类型高浓度(30wt.%)聚乙烯醇(PVA)水凝胶,研究了PVA水凝胶的溶胀率、拉伸强度和流变特性。结果表明,高浓度PVA水凝胶的溶胀率受PVA的分子量和醇解度影响较大,PVA分子量越大,水凝胶的溶胀率越高;醇解度越高,溶胀率越低。随着冻融循环次数的增加,PVA水凝胶的强度增强;分子量越大,PVA水凝胶的强度反而越弱。在一定的频率范围内,PVA水凝胶的模量随着频率的增加而增加;随着冻融循环次数的增加,PVA水凝胶的储能模量增大。     

冻胶法聚乙烯醇水溶纤维的结构研究

由冻胶纺丝制备聚乙烯醇(PVA)水溶纤维，用X-衍射、双折射、扫描电镜、电子强伸仪等测试了纤维的结晶度、取向度、横截面形态、应力应变曲线和纤维的水溶温度。实验证明：纤维的结晶度和取向度随拉伸倍数和热处理温度的增加而增加；在同一条件下醇解度较高的PVA纤维的结晶度和取向度高于醇解度较低的PVA纤维；纤维横截面为圆形、无皮芯层，结构均匀；具有良好的力学性能；水溶温度范围宽。     

改性剂对聚乙烯醇薄膜力学性能的影响

聚乙烯醇(PVA)是一种性能优异的可降解包装材料,但是,其熔点与分解温度接近,在受热熔融时发生分解。改性剂能降低聚乙烯醇的熔点,延缓分解,改善PVA的热塑加工性能,但是,影响了PVA薄膜的力学性能。实验研究了增塑剂、交联剂、稳定剂等改性助剂对PVA薄膜力学性能的影响。结果表明,随着丙三醇的添加,PVA薄膜拉伸强度降低,断裂伸长率提高,当丙三醇含量增加至40%时,断裂伸长率为293.84%;当醇解度为92时,薄膜的拉伸强度为30.54 MPa;添加硼砂能提升薄膜的拉伸强度,降低薄膜的断裂伸长率;当添加1份的氯化钙热稳定剂时,减少了PVA薄膜在加工过程中的热分解,对薄膜力学性能提升幅度较大,拉伸强度和断裂伸长率分别达到27.89 MPa、250.36%。     

改性剂对聚乙烯醇薄膜性能的影响

研究了聚乙烯醇(PVA)在熔融吹塑薄膜加工过程中，各种改性剂对薄膜性能的影响。复配增塑剂可与各种型号的PVA发生键合作用，很好地增塑PVA，使其加工性能提高，成型容易，力学性能也有很大改善；稳定剂的添加，可明显改善PVA的熔融加工稳定性，使其交联老化程度降低，薄膜的溶解性能显著提高；速溶剂的添加可以降低PVA在吹塑加工过程中的结晶度，提高薄膜常温下快速溶解的性能；开口剂的加入可以很好地改善薄膜的滑爽性。     

聚乙烯醇吹塑管坯汽油阻隔性能的研究

采用分子复合和增塑方法改性聚乙烯醇(PVA)1799,在单螺杆挤出机和自行设计的吹塑装置上实现了PVA的挤出吹塑成型,获得了均匀透明的PVA吹塑管坯。研究了改性PVA的热性能及改性剂含量对PVA吹塑管坯汽油阻隔性能的影响,并比较了PVA与HDPE吹塑管坯的汽油阻隔性。结果表明:改性剂的加入,削弱了PVA自身强氢键,抑制了其结晶,降低了其熔点,有利于其熔融加工,但降低了PVA吹塑管坯的汽油阻隔性;经后处理除去部分改性剂后,PVA吹塑管坯汽油阻隔性提高,明显优于HDPE,具有广阔应用前景。     

Biodegradable PPC/(PVA-TPU) ternary blend blown films with enhanced mechanical properties

Biodegradable films of poly(propylene carbonate)/poly(vinyl alcohol)-thermoplastic polyurethane [PPC/(PVA-TPU)] ternary blends were successfully prepared by melting blending method. The mechanical properties of poly(propylene carbonate) blown film were greatly improved by blending PPC with PVA-TPU. In order to afford the melt processing of PVA, the PVA-TPU binary blend was firstly prepared using thermoplastic polyurethane as a polymeric plasticizer. The rheological behavior, mechanical properties and morphology of these blends were studied. Considering its melt viscosity and thermally processing temperature, the PVA-50%TPU, as a modifier, was blended with PPC to prepare PPC/(PVA-TPU) ternary blend. SEM observation revealed a basic one-phase morphological structure with very good interfacial adhesion between the extremely blurred PPC and PVA-TPU two components. Meanwhile, the miscibility of the ternary components was verified by only one glass-transition temperature obtained from DMA tests. The tensile strength and tear strength of PPC/(PVA-TPU) blown films were determined at different temperatures. The results demonstrate that the mechanical properties of PPC/(PVA-TPU) films were enhanced dramatically at low temperature when compared with neat PPC. At room temperature, PPC/30 %(PVA-50%TPU) blown film exhibited a tensile strength of 26 MPa, and an elongation at break of 484.0 %. Its tear strength in the take-up direction is 124.1 kN/m, and the one in machine direction is 141.9 kN/m. At a low temperature of 0 °C, PPC/30 %(PVA-50%TPU) exhibited a tensile strength of 40.7 MPa and tear strength of 107 kN/m, which are 153 % and 142 % of those of neat PPC respectively. The blending of PPC with the PVA plasticized with TPU provides a practical way to extend the application of the new biodegradable polymer of PPC in the area of blown films.     

Water states and thermal processability of boric acid modified poly(vinyl alcohol)

To further improve the processability of water plasticized poly(vinyl alcohol) (PVA), boric acid (BA), which can rapidly form reversible crosslinked structure with the hydroxyl groups of PVA, was adopted as a modifier, and the water states, thermal performance, and rheological properties of modified PVA were investigated. The results showed that ascribing to the formation of the crosslinked structure between PVA and BA, the content of nonfreezing water in system increased, indicating that the bondage of PVA matrix on water enhanced, thus retarding the tempestuous evaporation of water in system during melt process and making more water remained in system to play the role of plasticizer. Meanwhile, this crosslinked structure shielded part hydroxyl groups in PVA chains, leading to the further weakening of the self‐hydrogen bonding of PVA, and guaranteeing a lower melting point and higher decomposition temperature, thus obtaining a quite wide thermal processing window, i.e., ≥179°C. The melt viscosity of BA modified PVA slightly increased, but still satisfied the requirements for thermal processing, thus reinforcing the flow stability of the melt at high shearing rate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43246.     

硼酸改性聚乙烯醇薄膜的制备及性能研究

将溶液浇铸法制得的聚乙烯醇(PVA)薄膜用不同温度的硼酸饱和溶液进行不同时间的改性处理,对改性后薄膜的耐热性和耐水性进行了研究。结果表明:经过硼酸溶液改性处理后,PVA薄膜的热变形温度Tg小幅度上升,Tm呈下降趋势;从吸湿率的变化来看,改性处理后,薄膜的耐水性得到明显提高。     

丙烯酰胺改性玉米淀粉/PVA复合膜的制备与表征

为了改善聚乙烯醇（PVA）膜的机械性能,选用玉米淀粉为原材料,50℃条件下以过硫酸铵和尿素为引发剂,同时加入丙烯酰胺对淀粉进行接枝改性,制备得到丙烯酰胺改性的玉米淀粉/PVA复合膜。其中,优化改性淀粉的接枝率确定最佳合成条件为淀粉/丙烯酰胺的质量比为3∶7、引发剂过硫酸铵占单体总质量的0.5%、尿素占单体总质量的0.5%。进一步利用优化的改性淀粉为改性剂,制备了系列改性玉米淀粉/PVA复合膜。采用傅里叶红外光谱、扫描电子显微镜（SEM）对复合膜的组成与结构进行表征,同时测定复合膜的机械性能、耐水性、耐热性等物化特性,结果表明30%ST-0.50%APSU改性淀粉的单体转化率为95.0%,接枝率为85.2%。 30%ST-0.50%APSU/PVA复合膜的耐热性能轻微下降,但断裂伸长率提高了256%,耐水性能提高了43.1%。     

淀粉基聚乙烯醇完全生物降解塑料薄膜的结构与性能

通过优化工艺条件，制备了高淀粉填充量的淀粉／聚乙烯醇完全生物降解塑料薄膜，研究了提高淀粉用量对淀粉／聚乙烯醇（PVA）完全生物降解塑料薄膜的力学性能和耐水性影响；并分析了耐水改性助剂尿素用量对薄膜的吸水率和生物降解性能的影响。结果表明，通过先糊化、后共混、再交联的薄膜制备工艺过程，能够获得高淀粉填充量的淀粉／聚乙烯醇完全生物降解塑料薄膜；先糊化打破了淀粉颗粒的原有形态结构，促进了淀粉与聚乙烯醇的共混相容性，从而获得了优良的力学性能；耐水改性助剂尿素的使用，能够大幅度地降低材料的吸水率，同时提高材料的生物降解性和环境友好程度。     

Dopamine‐functionalized poly(vinyl alcohol) elastomer with melt processability and self‐healing properties

A dopamine‐functionalized poly(vinyl alcohol) (PVA) elastomer with melt processability and self‐healing properties was prepared by a new chemical route of graft modification, that is, PVA carboxylation and a carbodiimide reaction. The conventional modifier for PVA sacrificed the intrinsic hydrogen‐bonding interactions and dramatically decreased the mechanical strength. The modifier dopamine, as a catechol derivative, has two hydroxyl groups, which formed hydrogen bonds with the hydroxyl groups of PVA; it also has one benzene ring, which increased the thermal stability. We found that the introduction of dopamine into the PVA molecular structure lowered the melting point, improved the thermal stability, broke the crystalline structure, and enabled thermal processing. Moreover, the modified PVA possessed good mechanical properties, could be self‐healed, and is believed to have potential applications in many fields. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45072.