用DSC测定聚氯乙烯的凝胶化度

介绍用差示扫描量热法（ＤＳＣ）测定聚氯乙烯（ＰＶＣ）复合物凝胶化度的原理和方法，比较了流变法和ＤＳＣ的测定结果，ＤＳＣ更适于测定填充ＰＶＣ的凝胶化度。     

聚乙烯醇（PVA）水凝胶的合成及性能研究

利川聚乙烯醇为原料.以硼酸为交联剂制备了高吸水性树脂,考察了交联剂的用量对水凝胶的吸水率的影响.同时对水凝胶的溶胀行为也进行了较详细的研究.     

净化废水用PVA水凝胶的开发

在固定微生物方面，对冷冻和融化法制备的ＰＶＡ水凝胶与聚合制备的聚乙二醇和内烯酰胺水凝胶的结构和性质进行了比较。通过扫找微镜观察和生物化学性能的测量，显示出冷冻的ＰＶＡ凝胶的含水量和氧渗透性优于其它类的凝胶。ＰＶＡ水凝胶具有高抗拉力和耐折强度、良好的手感和成型性能。也研究了ＰＶＡ凝胶抗磨损耐久性和耐化学笥。把活性污泥固定、凝固在ＰＶＡ凝胶粒子上进行培育，这种凝胶处理化工污水的能力大约是标准活性污泥法     

高聚合度聚氯乙烯凝胶特性的研究

采用差示扫描量热（DSC）法和毛细管流变法对高聚合度聚氯乙烯（HPVC）的凝胶特性进行了研究。结果表明,PVC2500具有与通用PVC类似的凝胶化机理,符合Benjamin的粉碎理论;HPVC加工温度高于175℃时有较高的凝胶度,加工温度在175～185℃,PVC2500的凝胶度可以达到60％～85％。相同的加工温度和加工时间下,PVC2500未熔融的主结晶体及等温结晶体更多,造成PVC2500的凝胶度比PVC1000小。     

室温交联PVA水凝胶的制备与性能研究

以环氧氯丙烷为交联剂,采用室温化学交联法制备了聚乙烯醇(PVA)水凝胶,研究了交联温度和交联时间对PVA溶胀性能和力学性能的影响,借助差示扫描量热法(DSC)和扫描电子显微镜(SEM)对PVA水凝胶进行分析表征。结果表明,当交联时间为3d且交联温度为50℃时PVA水凝胶的综合性能最佳。PVA的玻璃化转变温度为-54.50℃,PVA水凝胶中包含有自由水、束缚水和非冷冻水。     

PVC型材的凝胶化度分析

测试分析了2种聚氯乙烯(PVC)型材的凝胶化度,发现型材A的凝胶化度比型材B高10%,表明在其他工艺相同条件下,型材B的塑化程度低于型材A,这是型材B表面光泽度低的原因所在。单螺杆挤出机挤出实验也证明了这一点。     

PVA/明胶/淀粉水凝胶的制备及性能

采用反复冷冻一解冻法制备了不同配比的聚乙烯醇／明胶／淀粉水凝胶膜。测试了共混膜的力学性能、脱水率和溶胀度，用扫描电镜观察了共混膜的断面形貌。结果表明：除1：1配比的水凝胶膜成膜性差，其他配比的水凝胶成膜性较好，膜表面比较光滑。m（PVA）：m（明胶）为6：1时力学性能较好。脱水率和溶胀度均随PVA和明胶比例增大而减小。扫描电镜显示，水凝胶膜内部具有多孑L结构，可以用作组织工程支架材料。     

净化废水用PVA水凝胶的开发：II.用含微生物的PVA凝胶处理废水中的N,N—二甲

用含二甲基甲酰胺（ＤＭＦ）的废水充分培养活性污泥，并将其截留和固定在球形ＰＶＡ水凝胶粒子上。测试了合成ＰＶＡ凝胶中细菌的数目和分布特征。分离出含杆（状）菌仙影掌属Ｄ－１的ＤＭＦ－分解细菌。提示出细菌各自的形态和生理反应。对经冷冻－融化制备的含ＤＭＦ－分离细菌的球形ＰＶＡ凝胶进行了ＤＭＦ－废水处理试验。经基础研究和小型试验结果表明稳定运行和连续操作的处理能力为１ｋｇ／ｍ＾３／天。     

PVA水凝胶的制备及在生物医学工程中的应用

聚乙烯醇水凝胶在生物医学工程领域的用途非常广泛。本文就PVA水凝胶的制备、改性及其在生物医学工程中的应用进行综述,简述了PVA水凝胶的溶胀和收缩机理,同时对其发展方向进行了展望。     

聚乙烯吡咯烷酮/壳聚糖共混水凝胶的制备与水的状态

以戊二醛作为交联剂,制备了聚乙烯吡咯烷酮（PVP）/壳聚糖（CHI）共混水凝胶,共混物的玻璃化转变温度T_g随CHI含量的升高而升高,SEM图谱观察到PVP/CHI凝胶表面呈现随CHI∶PVP比而变化的微相分离.凝胶溶胀率随着PVP含量升高、PVP分子量降低、CHI脱乙酰度增大而升高.DSC分析表明,非冷冻状态下,CHI∶PVP为1∶2时,游离水、可冻结结合水、非冻结结合水含量分别为42.7%、43.3 %、14.0 %;CHI∶PVP为1∶8时,凝胶中含非冻结结合水少,DSC曲线上只有一个明显的失水吸热峰,由游离水与可冻结结合水叠加而成.-123℃冷冻条件下凝胶的DSC升温曲线在0、38、53℃观察到一组明显的焓化峰,这是由于低温时冻结为结晶相的游离水、可冻结结合水,随温度升高吸热又转化为游离水、可冻结结合水所致.     

Crosslinked poly(vinyl alcohol) and starch composite films: Study of their physicomechanical,thermal, and swelling properties

Crosslinked poly(vinyl alcohol) was blended with 10, 20, 40, and 50 wt % starch by a solution‐casting process. The solution‐cast films were dried, and then their physicomechanical properties including tensile strength, tensile elongation, tensile modulus, tear strength and density, and burst strength and density were tested. Thermal analysis was performed by differential scanning calorimetry. A moisture analysis of the PVA/starch films was performed and their moisture content determined. Also investigated were the films'resistance to solubility in water, 5% acetic acid, 50% ethanol, and sunflower oil and their swelling characteristics in 50% ethanol and sunflower oil. The prepared PVA/starch blends showed significant improvement in tensile modulus and in resistance to solubility in water, 5% acetic acid, and 50% ethanol. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1127–1132, 2007     

Rigid poly(vinyl chloride) gelation in a Brabender measuring mixer. III. Transformation in the torque maximum

The processing and structural effects occurring in a poly(vinyl chloride) (PVC) compound processed in a plastograph, at the time at which the maximum value of the torque (point X on the torque curve) was reached, were studied. The unplasticized PVC compound was processed at various temperatures (150–200°C) with a kneader operating at rotors speeds of 5–40 min^?1. The changes in the temperature of the compound due to kneading and its influence on the progress of PVC gelation were analyzed. The gelation progress was studied with differential scanning calorimetry, rheological measurements, and scanning electron microscopy. The maximum value of the torque occurred within the temperature range (170–180°C) of the PVC compound, and it was independent of the adjusted temperature of the mixing chamber. The processing of the PVC compound in the kneader, with high mechanical charges and a comparatively low adjusted temperature (150–170°C), spontaneously generated an effect of self‐heating, resulting in an increasing temperature of the compound. Despite the surprisingly high degree of gelation (80–98%) of the PVC compound processed under these conditions (as determined by differential scanning calorimetry), the scanning electron microscopy observations indicated significant nonhomogeneity of the fracture surface. Consequently, the kneaded PVC compound at point X of the torque curve could be treated as a two‐phase system composed of a liquid, amorphous phase and elements of a grain structure. The transformation of both phases (particularly the quantitative and qualitative changes), which was significantly dependent on the PVC temperature and the shear rate applied by the rotors, determined the state of the melted compound at this point of the torque curve. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

D.s.c. investigation of the states of water in poly(vinyl alcohol) membranes

D.s.c. analysis shows that heat absorbed in the heating process of water in poly(vinyl alcohol) membranes is higher than that evolved in the cooling process. A remarkable discrepancy is found between these heats when the water retention, H, of the membrane is lower than 0.5 g H₂O/g swollen membrane. The amounts of freezable water in the membranes were estimated by use of the relation observed between the temperature and the enthalpy of the crystallization of super-cooled water. The amounts estimated from the heats absorbed or evolved agree within 2% when H was above 0.6. When H is below 0.5, however, the ratio of these two amounts was greater than 2. This difference is explained by the heat capacity of the water below 250 K increasing anomalously compared with that of bulk water.     

Soft PVC foams: Study of the gelation,fusion, and foaming processes. II. Adipate,citrate and other types of plasticizers

Plasticized poly(vinyl chloride) (PVC) is one of the most useful polymeric materials on an industrial scale because of its processability, wide range of obtainable properties, and low cost. PVC plastisols are used in the production of flexible PVC foams. Phthalates are the most used plasticizers for PVC, and in a previous article (part I of this series), we discussed the influence of phthalate ester type plasticizers on the foaming process and on the quality of the foams obtained from the corresponding plastisols. Because the use of phthalate plasticizers has been questioned because of possible health implications, the objective of this work was to undertake a similar study with 11 commercial alternative plasticizers to phthalates. The evolution of the dynamic and extensional viscosity and the interactions and thermal transitions undergone by the plastisols during the heating process were studied. Foams were obtained by rotational molding and were characterized by the determination of their thermomechanical properties, density, and cell size distribution. Correlations were obtained between the molecular weight and structure of the plasticizer and the behavior of the corresponding plastisols. After the characterization of the final foamed product, we concluded that foams of relatively good quality could be prepared with alternative plasticizers for replacing phthalates. Several plasticizers {Mesamoll (alkylsulfonic phenyl ester), Eastman 168 [bis(2‐ethylhexyl)‐1,4‐benzenedicarboxylate], Hexamoll [di(isononyl) cyclohexane‐1,2‐dicarboxylate], Citroflex A4 acetyl tributyl citrate (ATBC), and Plastomoll (dihexyl adipate)} were found to be interesting alternatives in the production of soft PVC foams because they provided very good quality foams with properties similar to, or even better than, those obtained with phthalate plasticizers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Hydrogels from glycidyl derivatives of poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) was modified with phthalic anhydride to obtain half esters with carboxylic acid groups, which made the reaction with epichlorohydrin easier. The oxirane ring underwent a further crosslinking that led to crosslinked polymers with polar groups capable of interacting strongly with water and therefore with properties of hydrogels. The curing kinetics of the crosslinking were studied by differential scanning calorimetry, and the dependence of the activation energy on conversion degree was studied by isoconversional kinetic analysis. Water absorption was determined gravimetrically as a function of time at room temperature. The swelling behavior of these hydrogels was related to the degree of crosslinking. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 693–698, 2003     

Thermal aging and accelerated weathering of PVC/MMT nanocomposites: Structural and morphological studies

This work focuses on the influence of weathering factors—UV radiation, humidity, and temperature on the structure and morphology of poly(vinyl chloride)/montmorillonite (PVC/MMT) nanocomposites obtained by melt blending. It has been observed that organically modified MMT (OMMT) deteriorates the weathering resistance, the thermal behavior, as well as the long‐term stability of PVC. Decomposition of the organic modifier of MMT causes substantial color changes in the PVC nanocomposites as it facilitates the dehydrochlorination process of the polymer. However, the nonmodified MMT provides some stabilization during PVC weathering. The nanocomposites after annealing are characterized by higher glass transition temperature. The increase in heat capacity step (Δc_p) during glass transition suggests that in the PVC composites with nonmodified MMT stronger molecular interactions between the polymer and clay platelets occur than in PVC/OMMT nanocomposites. The scanning electron microscopy images on the surface and the cross section show that thermal aging and weathering proceed by different mechanisms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42090.     

PVA与淀粉薄膜的研究进展与应用

介绍了聚乙烯醇(PVA)和淀粉多羟基、多氢键、高结晶等结构特点,以及根据此开发的可塑化方法和水溶性薄膜生产方法,包括最新的PVA薄膜一步熔融挤出法。PVA和淀粉水溶性薄膜熔融挤出法的难点在于均要破坏结晶结构,达到可塑化,前者主要是要获得增塑凝胶化可自由流动粒子,后者在于糊化处理。     

Acid-treated Bentonite as filler in the development of novel composite PVA hydrogels

In this study, novel eco-friendly hydrogel adsorbents were synthesized based on poly(vinyl alcohol) (PVA) and different contents of an acid-treated bentonite (1–5 wt %). The hydrogels were prepared by freezing–thawing, which is a simple and nontoxic method. The materials were morphologically and thermally characterized by means of swelling assays, X-ray diffraction, scanning electron microscopy, dynamic scanning calorimetry, and thermogravimetric analysis in order to evaluate the effect of acid-treated bentonite loading. The composite hydrogels showed very distinct porous structure and thermal features in comparison to neat PVA as a consequence of the addition of the clay. Moreover, the performance of the obtained composite hydrogels was tested toward the adsorption of cationic (methylene blue) and anionic dyes (methyl red and methyl orange) from aqueous media. The presence of acid bentonite seems to be beneficial for improving the removal capacity of PVA-based hydrogels. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47663.     

State of the water in crosslinked sulfonated poly(ether ether ketone)

We investigated the material properties of different crosslinked sulfonated poly(aryl ether ketone) membranes, focusing on the effect of the degree of sulfonation and crosslinking density on the water uptake, the physical state of the water, and the pore size distribution within the membranes. We observed that the degree of sulfonation and, in particular, the ion‐exchange capacity (IEC) had less effect on the control of the extent of water absorbed than the crosslinking density of the membranes. Crosslinking also enabled the membranes to reach a higher water contents without losing mechanical integrity. Moreover, increasing the crosslinking density resulted in the presence of more bound water, without dissolution of the membrane. The crosslinked membranes had lower methanol permeability and electroosmotic drag values. Only at low IEC values and low water uptake in partially crystalline sulphonated poly(ether ether ketone), SPEEK could the presence of nanometer pores in the water‐equilibrated crosslinked membranes be confirmed by thermoporometry and the pore size distributions were then comparable to those reported for Nafion membranes. At higher IEC values, the water uptake was extremely high, up to 300%, and then the structure of the swollen membranes was more analogous to that of a dilute aqueous solution of the sulfonated polymer, and no nanopores were present. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013