低聚合度、低醇解度聚乙烯醇的合成与性能研究——I.低聚合度聚醋酸乙烯酯的合成

以甲醇为溶剂,偶氮二异丁腈(AIBN)为引发剂,采用自由基聚合方法合成了低聚合度聚醋酸乙烯酯,并对其结构进行了表征。讨论了聚合时间、引发剂用量、物料配比、聚合温度等因素对聚合率的影响,获得了相对较佳的工艺参数。     

聚乙烯醇/蒙脱石纳米复合材料的结构与性能

通过溶液插层 流延成膜法,以聚乙烯醇和钠质蒙脱石为原料,制备出了不同蒙脱石含量的聚乙烯醇/蒙脱石纳米复合材料薄膜。用X射线衍射(XRD)、扫描电子显微镜(SEM)、热重分析(TGA)和力学性能测试对复合材料的结构和性能进行了表征。结果表明,聚乙烯醇分子成功进入蒙脱石的层间,实现了在纳米尺度上的复合;蒙脱石含量高于7 5wt%形成插层型的纳米复合材料,低于7 5wt%形成剥离型的纳米复合材料;在SEM图片上还观察到了纳米复合材料的微观结构。纳米复合材料的热稳定性、拉伸强度和直角撕裂强度均比纯聚乙烯醇有很大提高。     

宽分子量分布高聚合度PVC的合成和性能

针对高聚合度聚氯乙烯加工性能较差的缺点,采用２段聚合温度法合成了宽分子量分布的ＰＶＣ树脂,并对树脂的热稳定性、加工性能和力学性能进行了研究。     

低分子量聚N-乙烯基甲酰胺-co-乙烯胺的合成

以N-乙烯基甲酰胺为单体,N,N-二甲基甲酰胺和乙酸乙酯为混合溶剂,偶氮二异丁腈为引发剂,十二硫醇为链转移剂,通过沉淀聚合法制备了低分子量的聚N-乙烯基甲酰胺。详细研究了单体质量分数、混合溶剂配比、引发剂用量、链转移剂用量、反应温度及反应时间对聚合反应的影响。在最佳聚合条件下,聚合物收率可达93.1%、聚合物的数均分子量(Mn)为2 975.2,PDI=2.64,且聚合残液可循环利用。然后将所得聚合物在酸性条件下水解,制备了不同胺化度的聚N-乙烯基甲酰胺-co-乙烯胺,产品的数均分子量为1 000~1 400,PDI为1.34~1.40。     

高相对分子质量聚乙烯醇的研究进展

综述了高相对分子质量聚乙烯醇的发展及其用途。从聚合方法和引发方式两方面介绍了国内外合成高相对分子质量聚乙烯醇研究进展。简述了高强高模PVA的使用场合及其应用前景,并对今后我国高相对分子质量聚乙烯醇工业的发展提出了建议。     

有氧环境的氧化还原/乙烯基自缩合法制备超支化聚丙烯酰胺

采用了有氧条件下的乙烯基自缩合(SCVP)法制备了超支化的聚丙烯酰胺,并对SCVP反应机理及聚合物结构进行了讨论。结果表明:在有氧条件下合成超支化聚丙烯酰胺时,增加引发剂的用量能够提高聚丙烯酰胺的支化度;延长反应时间能够提高聚合物的分子量,提高支化度;增加单体用量,升高温度能够促使转化率及分子量提高,但会降低支化度;当氧化剂用量较大时,聚合物体现出超支化结构特征。     

聚合工艺对低不饱和度高相对分子质量聚醚性能的影响

采用双金属氰化络合物催化剂（DMC）合成了低不饱和度高相对分子质量聚醚（DL-4000D）,讨论了聚合温度、聚合压力、低聚物脱水时间等聚合工艺条件对DL-4000D及其制品性能的影响。结果表明,聚合温度在115~125℃、低聚物脱水时间在2 h左右,聚合压力小于100 kPa等工艺条件下,制备的聚醚不饱和度低,相对分子质量分布窄,由其制得的聚氨酯制品的综合性能好。     

聚乙烯醇聚合度对碱木质素/聚乙烯醇共混膜力学性能的影响

以3种不同聚合度的聚乙烯醇(PVA0588、PVA1788、PVA2488)为原料,添加相同质量分数的碱木质素采用流延法制备共混膜。采用电子万能试验机、扫描电子显微镜、热重分析仪等分析手段对共混膜进行分析表征,并测定了共混膜在不同极性溶剂中力学性能的变化。结果表明:在碱木质素添加量为15%时,碱木质素可较好地分散于PVA相中,3种共混膜的力学性能与各自对应的纯PVA膜相比都有了一定的提高,且当聚合度由PVA0588变化到PVA2488时,共混膜的拉伸强度从35.16MPa增加到48.30MPa,提高了37.37%,断裂伸长率从172.22%增加到247.08%,提高了43.47%;由于PVA聚合度的增大和碱木质素的添加,均使得共混膜的耐溶剂性能和热稳定性增加。     

超高相对分子质量聚氯乙烯高弹膜的研制

探讨了增塑剂、稳定剂、碳酸钙、润滑剂的用量对超高相对分子质量聚氯乙烯的加工性能及力学性能的影响,得到了合理的配方。     

Characterization of Poly(Vinyl Alcohol) and Poly(Vinyl Pyrrolidone) Co-polymer Blend Hydrogel Prepared by Application of Gamma Radiation

Hydrogel is prepared from a poly(vinyl pyrrolidone) (PVP) and poly(vinyl alcohol) (PVA) blend solution by gamma radiation with a ₆₀Co λ source at room temperature. Properties of the prepared hydrogel, such as gel fraction, gel strength swelling ratio, equilibrium water content, and water absorption in room temperature, were investigated. Blending hydrogel with PVP and PVA obviously increased the gel strength and decreased the swelling ratio of hydrogel. It was observed that the gel fraction increased while the swelling ratio and water content decreased with increased radiation dose, but gel strength increased up to a certain radiation dose and then decreased. The percentage of water absorption at room temperature increased with time but after a certain time it became steady and decreased with radiation dose.     

水性聚氨酯/聚乙烯醇复合纳米纤维的制备及结构研究

将水性聚氨酯(WPUR)与聚乙烯醇(PVAL)按照不同质量比制备质量分数为8%的纺丝溶液,通过静电纺丝制备WPUR/PVAL复合纳米纤维。运用扫描电子显微镜、傅立叶变换红外光谱仪和X射线衍射仪对WPUR与PVAL质量比不同的纺丝溶液制备的复合纳米纤维的微观形貌和结构进行分析。实验结果表明,PVAL的含量对复合纳米纤维的形成和形貌起着决定性的作用,随着溶液中PVAL含量的增加,纺丝过程中纺丝液逐渐从不连续复合纳米纤维转变为连续均匀的复合纳米纤维,纤维直径逐渐增大,当纺丝液中WPUR与PVAL的质量比为30∶70时,得到的复合纳米纤维形貌最佳,其平均直径为330.8 nm,具有最小标准差,为22 nm,同时随着纺丝溶液中PVAL含量的增加,所得复合纳米纤维的结晶性能增强。     

低温溶液缩聚法制备聚间苯二甲酰对苯二胺

采用低温溶液缩聚法制备了聚间苯二甲酰对苯二胺(PPIA),讨论了单体浓度、单体物质的量配比、反应温度等因素对聚合反应的影响,并用红外光谱(IR)、热重分析(TG)、X射线衍射(XRD)、扫描电镜(SEM)对实验产物进行了测定。红外检测出的特征峰符合PPIA的结构特征,热重测得热分解速率最大温度在520℃左右,X射线衍射表明聚合物有明显结晶现象,并且扫描电镜显示下的聚合物结构聚集状态良好。     

温度和封端剂马来酸酐对聚碳酸亚丙酯相对分子质量的影响

考察了加工温度和封端剂马来酸酐（MAH）含量对聚碳酸亚丙酯(PPC)黏均相对分子质量的影响。结果表明,PPC对温度非常敏感,加工温度在120 ℃以上时,其黏均相对分子质量就有很大的下降,温度越高,下降得越多;少量的MAH对PPC的封端作用就很明显,加工温度相同时,MAH的添加量越多,对PPC的封端作用越强,但MAH的添加量不宜超过1 %。     

Preparation of high molecular weight poly(vinyl alcohol) with high yield using low‐temperature solution polymerization of vinyl acetate

Vinyl acetate (VAc) was solution‐polymerized in tertiary butyl alcohol (TBA) and in dimethyl sulfoxide (DMSO) having low chain transfer constant at 30, 40, and 50°C, using a low temperature initiator, 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN). The effects of polymerization temperature and initiator concentration were investigated in terms of polymerization behavior and molecular structures of poly(vinyl acetate) (PVAc) and corresponding poly(vinyl alcohol) (PVA) obtained by saponification with sodium hydroxide. The polymerization rates of VAc in TBA and in DMSO were proportional to the 0.49 and 0.72 powers of ADMVN concentration, respectively. For the same polymerization conditions, TBA was absolutely superior to DMSO in increasing the molecular weight of PVA. In contrast, TBA was inferior to DMSO in causing conversion to polymer, indicating that the initiation rate of VAc in TBA was lower than that in DMSO. These effects could be explained by a kinetic order of ADMVN concentration calculated using initial rate method and by an activation energy difference of polymerization obtained from the Arrhenius plot. Low‐temperature solution polymerization of VAc in TBA or DMSO by adopting ADMVN proved successful in obtaining PVA of high molecular weight (number–average degree of polymerization (P_n): 4100–6100) and of high yield (ultimate conversion of VAc into PVAc: 55–80%) with diminishing heat generated during polymerization. In the case of bulk polymerization of VAc at the same conditions, maximum P_n and conversion of 5200–6200 and 20–30% was obtained, respectively. The P_n and lightness were higher, and the degree of branching was lower with PVA prepared from PVAc polymerized at lower temperatures in TBA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1003–1012, 2001     

Molecular Orientation and Mechanical Properties of Poly(Vinyl Alcohol) Fibers

Abstract

A number of poly(vinyl alcohol) fibers with different draw ratios was characterized by measuring the birefringence, crystalline orientational order, crystallinity, tensile strength, and modulus. The birefringence, tensile strength and modulus increased with increasing draw ratio whereas the crystallinity and crystalline order parameters remained constant within narrow limits. The increase in birefringence has to be attributed solely to an increase in chain orientation in the amorphous phase of the semicrystalline fiber. The tensile strength and modulus are therefore directly related to the chain orientation in the amorphous phase. With the aid of a simple two-phase model it was found that the modulus of the amorphous phase in its disordered conformation was 4.8 GPa. The intrinsic birefringence of the amorphous phase was found to be 79 × 10^?3, i.e. much higher than the value obtained for the crystalline phase (52 × 10^?3). When this value was used in calculations, it was found that the order parameter of the amorphous phase increased from around 0.1 for a draw ratio of 1 to approximately 0.6 for a draw ratio of 5, whereas the order parameter of the crystalline phase was close to 1 for all draw ratios.     

过氧甲酸法低相对分子质量聚丁二烯环氧化的动力学研究

红外光谱表明过氧甲酸法可以实现对低相对分子质量聚(1,2-丁二烯)(LPB)的改性,得到环氧化低相对分子质量聚丁二烯(LOPB)。反应温度大于50℃会造成开环化反应或过度交联。在反应温度45℃,通过间隔取样法,由实验测定的环氧值-时间关系曲线与理论推导速率方程的拟合结果表明,LPB的环氧化反应为一级反应,反应速率方程简化为r=kC(C为环氧值),反应速率常数k=0.074 5 kg.L-1.h-1;得到环氧值随时间呈指数变化C=0.4 e0.42t。     

聚乙烯基吡咯烷酮水溶胶网络结构的表征

本文采用60Co辐照乙烯基吡咯烷酮(NVP)水溶液和5wt.%磷酸二氢钠(NaH2PO4)溶液引发NVP聚合交联的方法,制备由超高分子量聚乙烯基吡咯烷酮(UPVP)和部分交联的PVP((CPVP)组成的水溶胶,测定PVP水溶胶中未交联的PVP分子量、交联部分的交联度、数均网络分子量和溶胀比,结果表明,PVP的分子量约为通用PVPK90的10倍;随着反应体系中NVP浓度和辐照剂量的增加,交联度变大,数均网络分子量变小;溶胀比与单体浓度成正比,与辐照剂量成反比。     

Comparison Properties of Natural Rubber (SMR L)/Ethylene Vinyl Acetate (EVA) Copolymer Blends and Epoxidized Natural Rubber (ENR-50)/Ethylene Vinyl Acetate (EVA) Copolymer Blends

Mixing torque, morphology, tensile properties and swelling studies of natural rubber/ethylene vinyl acetate copolymer blends were studied. Two series of unvulcanized blends, natural rubber/ethylene vinyl acetate (SMRL/EVA) copolymer blend and epoxidized natural rubber (50% epoxidation)/ethylene vinyl acetate (ENR-50/EVA) copolymer blend were prepared. Blends were prepared using a laboratory internal mixer, Haake Rheomix polydrive with rotor speed of 50 rpm at 120°C. Results indicated that mixing torque value and stabilization torque value in ENR-50 blends are lower than SMRL blends. The process efficiency of ENR-50/EVA blends is better due to less viscous nature of the blend compared to SMRL/EVA blends as indicated in stabilization torque graph. Tensile properties like tensile strength, M100 (modulus at 100% elongation) and E _b (elongation at break) increase with increasing EVA fraction in the blend. At the similar blend composition, ENR-50 blend shows better tensile properties than SMRL blends. In oil resistance test, swelling percentage increased with immersion time and rubber composition. At a similar immersion time, ENR-50 blends exhibit better oil resistance compared to SMRL blends. Scanning electron microscopy (SEM) of tensile fractured surface indicated that EVA/ENR-50 blends need higher energy to cause catastrophic failure compared to EVA/SMRL blends. In etched cryogenically fractured surface, size and distribution of holes due to extraction of rubber phase by methyl ethyl ketone (MEK) were studied and holes became bigger as rubber composition increased due to coalescence of rubber particle.     

部分水解聚醋酸乙烯酯的制备及其分离苯/环己烷混合物的渗透汽化特性

聚醋酸乙烯酯（PVAc）经醇解反应制备了不同水解度的聚醋酸乙烯酯（PHPVAc）,并探索了PHPVAc水解度、成膜技术、测试条件对膜渗透汽化性能影响的规律.实验发现,改变膜材料的水解度、铸膜溶剂组成、操作温度以及料液组成可以调节膜的分离性能,获得较佳的分离效果.     

缩醛化乙烯醇-丙烯酸钠共聚物的合成及温敏性质

首先合成了室温下可溶于水的聚乙烯醇-丙烯酸钠共聚物(PVA-co-AANa),然后部分缩醛后得到一系列不同缩醛度(DA)、不同相对分子质量和单体组成的高分子材料(APVA-co-AANa),该材料具有温敏性。用FTIR和1HNMR表征了其结构。通过APVA-co-AANa水溶液在不同温度的浊度测定,考察了母体PVA-co-AANa相对分子质量、DA和单体组成对APVA-co-AANa的低临界溶解温度(LCST)的影响,发现APVA-co-AANa的DA越高、分子链越长、AA组分用量越小,相对LCST越低。而且,APVA-co-AANa水溶液还表现出盐敏性,LCST随NaCl用量增加而降低。APVA-co-AANa膜的AFM表面形貌的变化也证实了APVA-co-AANa的温敏性。