聚乙烯醇水溶液低温稳定性的影响因素

通过测定聚乙烯醇水溶液表观黏度随时间的变化,并结合结构分析,研究了低温(10℃)环境中聚乙烯醇聚合度、醇解度及质量分数对聚乙烯醇水溶液稳定性的影响。结果表明,当醇解度、质量分数一定时,聚合度越大,聚乙烯醇水溶液越容易发生凝胶;当聚合度、质量分数一定时,醇解度越大,聚乙烯醇水溶液的稳定性越差;当聚合度、醇解度一定时,质量分数越大,聚乙烯醇水溶液发生凝胶的时间越短。在此基础上,确定了醇解度99%的PVA水溶液发生凝胶的临界质量分数和凝胶化时间。     

Thymol在不同醇解度PVA/thymol膜中的释放动力学模拟

目的利用分子动力学定性定量地探讨PVA醇解度对thymol释放过程的影响,尝试从微观角度直观地展示thymol在PVA/thymol新型抗菌包装膜中的释放过程,揭示微观释放机理。方法利用Material Studio软件构建不同醇解度的PVA/thymol体系,模拟thymol分子动态释放过程,分别从高分子链运动性、自由体积分数以及扩散系数等角度对比分析thymol在不同醇解度PVA体系中的释放过程。结果 thymol分子在完全醇解的PVA体系中的扩散系数最小,醇解度为88%的体系中最大,醇解度为78%的次之;thymol分子在PVA体系中作缓慢蠕动而非跳跃运动。结论基质材料醇解度的差异对包装材料中抗菌剂的释放过程有较大影响。     

高聚合度高醇解度聚乙烯醇的制备工艺研究

本文用氧化还原引发体系和复合乳化荆进行了乙酸乙烯酯（VAC）的乳液聚合，再在碱性甲醇溶液中对聚乙酸乙烯酯进行醇解制得高聚合度高醇解度聚乙烯辞（PVA）。实验结果表明制备高聚合度高醇解度聚乙烯醇的最佳工艺条件为：乳液聚合中聚合温度70℃、引发剂用量0．1％、复合乳化剂的组成2：2时所得产品的聚合度较高；醇解过程中，水洛温度25％、碱溶液的溶度在8％左右时产品的醇解度较高。     

LDPE／PVA吸湿功能材料的熔融复合制备

选用聚合度为1700,醇解度为88％的聚乙烯醇（PVA）,并通过增塑剂、稳定剂的筛选得到适宜的配方,当PVA：增塑剂：稳定剂=100：30：2时可以较好地实现PVA的熔融加工。采用熔融复合技术成功制备了LDPE／PVA复合材料,添加PVA后,体系具有良好的吸湿性能,并且随着吸湿时间的增加,吸湿率逐渐增加,但材料韧性大幅下降。同时初步研究和探讨了增容剂马来酸酐接枝低密度聚乙稀（LDPE-g—MAH）对复合材料结构、力学性能和吸湿功能的影响。     

聚乙烯醇水溶性包装薄膜生物降解性研究

目的研究聚乙烯醇(PVA)水溶性包装薄膜的生物降解性。方法通过培养、筛选、分离、纯化等工序,获得其中降解效率最高的菌株,并对PVA的降解效果进行研究。同时通过控制变量法和正交实验,研究PVA水溶性包装薄膜组分中各种助剂对其降解性的影响。结果青霉菌对PVA水溶性包装薄膜的降解性效果最为明显;PVA水溶性包装薄膜组分中各种助剂含量在一定质量浓度下对PVA的降解效果有促进作用。结论丙三醇的质量分数为1.7%,十二烷基硫酸钠的质量分数为1.2%,吐温的质量分数为1.4%时,青霉菌对PVA降解效果最为明显。     

淀粉/聚乙烯醇泡沫塑料的制备及表面形貌分析

以淀粉和聚乙烯醇(PVA)为主要原料,在适当助剂作用下共混发泡制成泡沫塑料。研究了淀粉与PVA的比例、发泡剂用量、发泡温度、压力等条件对泡沫密度的影响。研究发现,当淀粉/PVA比例为6.3,发泡剂用量为共混物固含量的0.4%,发泡温度为190℃时,泡沫制品具有较低的密度。比较了由醇解度为88%和99%的PVA制备的淀粉泡沫塑料的吸水性,发现由PVA 1799制备的泡沫具有较好的耐水性。扫描电子显微镜照片显示淀粉与PVA具有很好的相容性。     

木质素降解菌对腐殖质形成的影响的研究

采用接种培养方法研究了不同木质素降解菌对木质素降解率、腐殖质总量、各组分含量及胡敏酸E4/E6的影响.结果表明,接种黄孢原毛平革菌和栗褐链霉菌对稻草的降解均有所提高,56天培养后,二者的木质素降解率分别达到40.86%和31.04%,而对照组(只含有土著微生物)只有10.56%.接种黄孢原毛平革菌和栗褐链霉菌显著提高了腐殖质产量,这两种不同木质素降解菌产生腐殖质的最大值分别是对照组的2.10和2.13倍,但二者降解木质素形成腐殖质的途径有所不同.培养结束后,各条件下土壤中胡敏酸E4/E6均有所增加,表明胡敏酸的芳构化程度有所减弱.     

聚乙烯醇改性及吹膜技术研究

研究了聚乙烯醇(PVA)改性及吹膜技术。经改性剂改性前后的IR分析结果表明，改性剂与PVA分子间发生了强烈的相互作用，并形成了较强的分子复合键。改性PVA塑化温度的研究表明，醇解度为88％的PVA，随相对分子质量的增加塑化温度升高。醇解度升高时，PVA塑化性能下降；改性剂用量增加，塑化温度下降。吹膜工艺研究表明，成膜助剂的加入能明显改善改性PFA的加工流动性，PVA膜对冷却效果要求较高，吹膜后的热定型处理能降低其吸湿性，延长水溶时间。     

PVA类高吸水性树脂的制备

以PVA为原料,用顺丁烯二酸酐作交联剂制得了PVA类高吸水性树脂.研究了交联剂用量、反应温度、PVA聚合度以及处理产物的溶液pH值对树脂吸水率的影响.得到的最佳制备条件为:ω(顺丁烯二酸酐/PVA)为30%,反应温度在98～105℃,所用PVA的聚合度为1700,处理产物的溶液pH值为10左右.     

温敏聚合物/聚乙烯醇复合溶液的性能

采用聚醋酸乙烯酯(PVAc)醇解的方法制备出了不同醇解度的聚乙烯醇(PVA)。以丙烯酰胺(AM)和温敏性功能单体Macromer为共聚单体,通过自由基水溶液聚合方法制备出了二元温敏水溶性共聚物P(AM-Macromer)。研究了PVA、P(AM-Macromer)及其复合溶液的性能。结果表明,P(AM-Macromer)溶液具有温敏性。PVA溶液黏度随温度的变化规律与其结构有关。PVA与P(AM-Macromer)复合效应明显,该复合溶液具有盐增稠和升温增粘的特性,溶液的弹性随温度的升高而增强;不具备升温增粘效应的高醇解度PVA与P(AM-Macromer)复合具有升温增粘的效应。醇解度较低的PVA与P(AM-Macromer)复合后,溶液出现升温增粘效应的温度明显降低。     

聚乙烯醇溶液的紫外光催化降解

以锐钛型二氧化钛作为催化剂在紫外光下催化降解聚乙烯醇（PVA）溶液。通过化学需氧量除去率和相对黏度测定,探讨了不同初始浓度PVA溶液紫外光催化降解的规律：随紫外光辐照时间延长,PVA溶液化学需氧量除去率增加;PVA溶液相对黏度呈先下降后上升再下降趋势;较低初始质量浓度（0.4 g/L）PVA溶液比较高初始质量浓度（1 ...     

Thermal and IR studies on copper doped polyvinyl alcohol

5 mol% PVA: x mol% Cu²⁺ polymer films were prepared by casting process. Thermal transitions and thermal degradation of samples with respect to copper concentration were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Increase in glass transition temperature as a function of copper concentration shows a strong branching and steric effects in copper doped PVA complexes. Thermal degradation of films to an extent of 4–5% was found with an increase in copper content. FTIR spectrum of PVA doped Cu²⁺ ions indicate the presence of O-H, C-H, C=C and C-O groups.     

聚乳酸/聚乙烯醇共混膜的制备

基于流延法和溶剂蒸发技术,以聚乳酸(PLA)和聚乙烯醇(PVA)为原料,制备可降解PLA/PVA共混膜。通过考察不同的共溶剂对共混膜成膜性能的影响,确定二甲基亚砜(DM SO)是制备PLA/PVA共混膜优良的共溶剂。研究PLA与PVA配比对PLA/PVA共混膜性能的影响,探索PLA与PVA分子链在共混膜中的结合状况。结果表明,当PLA的含量低于20%时,可以得到均质的PLA/PVA共混膜,且PLA与PVA分子链间以氢键结合。此外,在共混过程中,PLA与PVA的结晶均受到一定的破坏,结晶度比纯PLA与PVA下降。     

Poly(vinyl alcohol) reinforced with large-diameter carbon nanotubes via spray winding

For practical application of carbon nanotube (CNT)/polymer composites, it is critical to produce the composites at high speed and large scale. In this study, multi-walled carbon nanotubes (MWNTs) with large diameter (∼45 nm) and polyvinyl alcohol (PVA) were used to increase the processing speed of a recently developed spraying winding technique. The effect of the different winding speed and sprayed solution concentration to the performance of the composite films were investigated. The CNT/PVA composites exhibit tensile strength of up to 1 GPa, and modulus of up to 70 GPa, with a CNT weight fraction of 53%. In addition, an electrical conductivity of 747 S/cm was obtained for the CNT/PVA composites. The good mechanical and electrical properties are attributed to the uniform CNTs and PVA matrix integration and the high degree of tube alignment.     

Mechanical properties of nanohydroxyapatite reinforced poly(vinyl alcohol) gel composites as biomaterial

Nanohydroxyapatite reinforced poly(vinyl alcohol) gel (nano-HA/PVA gel) composites has been proposed as a promising biomaterial, especially used as an articular cartilage repair biomaterial. In this paper, nano-HA/PVA gel composites were prepared from mixing nano-HA particles modified by silicon coupling agent, with physiological saline solution (PSS) of PVA by freezing-thawing method. The effects of various factors on the mechanical properties of nano-HA/PVA gel composites were evaluated. It was shown that the mechanical behavior of nano-HA/PVA gel composites was similar to that of natural articular cartilage, which held special viscoelastic characteristics. The tensile strength and tensile modulus of the composites improved correspondingly with the increase of freezing-thawing times and concentration of PVA solution. The more concentration of PVA solution, the higher influence degree of concentration on the tensile strength of composites is. The tensile strength and tensile modulus of nano-HA/PVA hydrogel composites increased first and then decreased with the rising nano-HA content of the composites. The tensile modulus of the composites improved remarkably with the increase of elongation ratio.     

聚乙烯醇水凝胶/不锈钢摩擦性能研究

利用球-盘摩擦试验机研究润滑状态、载荷、滑动速度和不锈钢球直径对PVA水凝胶/不锈钢球摩擦副摩擦系数的影响.研究结果表明PVA凝胶内的自由水对摩擦副起着良好的润滑作用.在摩擦的起始阶段,干摩擦和润滑剂润滑状态下的摩擦系数相差甚微,随摩擦时间的延长,干摩擦状态下的摩擦系数在短时间内急剧上升,而润滑剂润滑状态下的摩擦系数基本保持不变;摩擦副的摩擦系数随滑动速度和不锈钢球直径的增加而下降,当滑动速度从45r/min升至225r/min时,摩擦副的摩擦系数下降54.24%;摩擦系数随载荷的增加而上升,但在低载荷区,摩擦副的摩擦系数的上升速率明显大于其在高载荷区的上升速率.随着载荷的增加,凝胶中自由水对摩擦副的润滑作用逐渐增强.     

聚乙烯醇/聚丙烯酸水凝胶的电刺激响应性研究

通过冰冻－解冻循环方法制备了机理交联水凝胶聚乙烯醇（PVA）／聚丙烯酸（PAA），研究了该水凝胶在直流电场作用下的弯曲响应性质，考察不同浓度和组成的凝胶在0．01mol/L Na2Co3电解质水溶液中，。作用电场的电场强度对凝胶弯曲速率的影响，以及电解质溶液的浓度对凝胶弯曲速率的影响，初步探索了凝胶在电场作用下的弯曲机理。     

Biodegradable progesterone microsphere delivery system for osteoporosis therapy

The purpose of this study was to formulate and characterize a controlled-release biodegradable delivery system of progesterone for the treatment or prevention of osteoporosis. Microspheres of progesterone were formulated using copolymers of poly(glycolic acid-co-dl-lactic acid)(PGLA 50/50 and PGLA 15/85) and poly(L-lactic acid)(L-PLA) of similar molecular weight by the emulsion solvent evaporation technique. The effects of process variables, such as volume fraction, polyvinyl alcohol (PVA) concentration, polymer composition, and stir speed during preparation, on the yield, encapsulation efficiency (EEF), particle size distribution, in vitro release profiles of progesterone, and surface morphology of progesterone microspheres were investigated. Increasing the volume fraction from 9% to 22% increased the EEF without significantly increasing the yield; however, the rate of progesterone release from the microspheres decreased. Increasing the PVA concentration from 1% to 5% had no significant influence on the EEF, but the rate of progesterone release from microspheres increased. Polymer composition had no significant effect on the EEF, but had a significant effect on the particle size distribution, surface morphology, and release rate of progesterone from the microspheres. Stir speed did not have a significant influence on the EEF; however, stir speed influenced particle size distribution and the rate of progesterone release from microspheres of the same sieve-size range. The results suggest that controlled release of progesterone is possible by varying the different process variables, and that PGLA 50/50 provided the slowest release of progesterone. This should provide a means of delivering progesterone for months for the treatment or prevention of osteoporosis in postmenopausal women.     

Biodegradable Progesterone Microsphere Delivery System for Osteoporosis Therapy

The purpose of this study was to formulate and characterize a controlled-release biodegradable delivery system of progesterone for the treatment or prevention of osteoporosis. Microspheres of progesterone were formulated using copolymers of poly(glycolic acid-co-dl-lactic acid)(PGLA 50/50 and PGLA 15/85) and poly(L-lactic acid)(L-PLA) of similar molecular weight by the emulsion solvent evaporation technique. The effects of process variables, such as volume fraction, polyvinyl alcohol (PVA) concentration, polymer composition, and stir speed during preparation, on the yield, encapsulation efficiency (EEF), particle size distribution, in vitro release profiles of progesterone, and surface morphology of progesterone microspheres were investigated. Increasing the volume fraction from 9% to 22% increased the EEF without significantly increasing the yield; however, the rate of progesterone release from the microspheres decreased. Increasing the PVA concentration from 1% to 5% had no significant influence on the EEF, but the rate of progesterone release from microspheres increased. Polymer composition had no significant effect on the EEF, but had a significant effect on the particle size distribution, surface morphology, and release rate of progesterone from the microspheres. Stir speed did not have a significant influence on the EEF; however, stir speed influenced particle size distribution and the rate of progesterone release from microspheres of the same sieve-size range. The results suggest that controlled release of progesterone is possible by varying the different process variables, and that PGLA 50/50 provided the slowest release of progesterone. This should provide a means of delivering progesterone for months for the treatment or prevention of osteoporosis in postmenopausal women.