低残余醛的聚乙烯醇缩丁烯醛水溶液

主要介绍了聚乙烯醇缩丁烯醛的制备及后处理过程,使它达到游离醛低含量的环保要求,另外初步探讨了以该水溶液为保护胶体合成白乳胶的研究,进而拓展了聚乙烯醇缩丁烯醛的应用领域。     

环保型聚乙烯醇缩丁烯醛胶的制备研究

探讨了聚乙烯醇(PVA)、盐酸、丁烯醛以及反应温度对聚乙烯醇缩丁烯醛水溶液粘度及强度的影响;并探讨了低残余醛水溶液制备的两类工艺方法,从而获得环保型聚乙烯醇缩丁烯醛胶。     

聚乙烯醇缩丁烯醛胶粘剂的研究进展

综述了聚乙烯醇缩丁烯醛胶的制备原理和制备方法,并主要讨论了聚乙烯醇缩丁烯醛在国内外的应用进展情况。     

聚乙烯醇缩丁烯醛胶的研究进展

综述了聚乙烯醇缩丁烯醛胶的制备原理和制备方法,并讨论了聚乙烯醇缩丁烯醛胶在国内外的应用进展情况.     

聚乙烯醇缩丁烯醛胶粘剂的改性研究

以聚乙烯醇(PVA)和丁烯醛为主要原料、盐酸(HCl)为催化剂和乙醛为改性剂,制备聚乙烯醇缩混合醛胶粘剂。采用单因素试验法探讨了各因素对胶粘剂的黏度、粘接强度和耐水性等影响。结果表明:当反应温度为(90±2)℃、反应时间为4 h、8%PVA溶液为200 mL、HCl为1 mL、丁烯醛为1.0～1.5 mL和乙醛为4 mL时,缩醛化产物的黏度适中、粘接强度相对最大(4.5 MPa)且耐水性相对较好;在其他条件保持不变的前提下,通过改变丁烯醛用量,可以进一步调节体系的最终黏度,使之满足木材用胶粘剂的使用要求。     

醇溶型聚乙烯醇缩混合醛（丁烯醛和乙醛）的制备

在温度不高于60℃下,以聚乙烯醇为主要原料,乙醛和丁烯醛为缩醛化试剂,当聚乙烯醇的缩醛度达到50．8％以上时,缩醛化产物就可以在乙醇溶剂中溶胀溶解形成均一溶液。该醇溶型聚乙烯醇缩混合醛胶达到最大粘接强度仅需6h,比水溶性胶粘剂的干燥时间缩短18h,并且其耐水性明显高于水溶性的聚乙烯醇缩丁烯醛胶。通过对薄膜的红外分析,可以看出过硫酸钾,可以打开缩醛化产物的碳碳不饱和双键,也使薄膜变脆。     

低醛耐寒改性聚乙烯醇缩甲醛胶粘剂的研制

通过对传统工艺聚乙烯醇缩甲醛胶的改进,制得游离醛含量低、耐寒抗冻、初粘力强的改性聚乙烯醇缩甲醛胶。     

微粒状聚乙烯醇缩丁醛制备新工艺

介绍用十二烷基磺酸钠作乳化剂，在常温下，以沉淀法制备微粒状ＰＶＢ。具有时间短，能耗低等特点，制得高缩醛度的粉末状ＰＶＢ。     

聚乙烯醇缩丁醛胶粘剂的制备

以聚乙烯醇(PVA)与正丁醛的质量比、反应体系的pH值、反应温度以及保温时间等作为制备聚乙烯醇缩丁醛(PVB)及其胶粘剂的主要因素,通过测定PVB的缩丁醛基含量、PVB胶粘剂的某些性能(如持粘力、黏度和固含量等)优选出制备PVB胶粘剂的最佳工艺条件。结果表明:当m(PVA)∶m(正丁醛)=100∶70、反应体系的pH值为2.0、反应温度为85℃、保温时间为3 h以及正丁醛的滴加速率为20~30滴/min时,PVB的缩醛度较高且形态较好,PVB胶粘剂的持粘力、黏度和固含量等指标均相对较高。     

Preparation and characterization of a bioadhesive with poly (vinyl alcohol) crosslinking agent

Synthetic adhesives containing 3,4‐dihydroxy‐L‐phenylalanine and its derivatives have strong adhesion strength and good biocompatibility, which make them prime candidates for adhesives or bioadhesives applications. In this study, a new photocurable poly (vinyl alcohol) (UV‐PVA) derivative was prepared and used as crosslinking agent to further improve adhesion strength of dopamine methacrylamide (DMA) system. The structure of UV‐PVA was confirmed, and the degree of acryloyl group substitution (DS) was easily varied from 10 to 40% by varying the molar ratio of acryloyl chloride to ? OH of PVA. The effects of ultraviolet light intensity, content of DMA and DS values of PVA on the photopolymerization kinetics were studied, and the effects of DS value on the adhesive strength, swelling performance and cell attachment were also investigated. It was found that adhesive containing UV‐PVA with 40% DS value yielded the highest adhesive strength, a relatively low swelling ratio and good biocompatibility. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Properties of branched and network poly(vinyl alcohols) prepared with poly(vinyl alcohol) having aldehyde groups at the chain ends

Branched and network poly(vinyl alcohols) (PVAs) were prepared with inter-acetalization of the PVA with aldehyde groups at the chain ends which was prepared by the cleavage of 1,2 glycol bonds in commercial PVA. The numbers of branches estimated from molecular weights were compared with those estimated by theory. Huggins' constant and crystallinity decreased with increasing branch number. Dissolution of branched PVAs into dimethylsulphoxide was not so easy compared with commercial PVA. The colour of branched PVA–iodine complex decreased rapidly with standing while that of commercial PVA decreased gradually. Network PVAs with Young's modulus of 1–8 MPa were prepared.     

Preparation and application of triglyceride plasticizers for poly(vinyl chloride)

A series of triglyceride plasticizers were prepared from glycerol, acetic acid, and benzoic acid through a two‐step reaction to develop potential uses of glycerol. The optimum reaction conditions were determined by the esterification of glycerol and acetic acid to produce glyceryl triacetate. When the molar ratio of glycerol to benzoic acid to acetic acid was 1:1:3.5, a novel plasticizer triglyceride mixture (GTM) was successfully synthesized; it had a good plasticizing effect on poly(vinyl chloride) (PVC). The elongation at break of PVC composites containing 80 phr GTM increased around 350%; the corresponding hardness (Shore D) and tensile strength decreased to around 35 D and 20 MPa, respectively. Moreover, the glass‐transition temperature (T_g) of PVC composites containing 40 phr GTM decreased to around 50°C. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Physical properties of acrylic copolymer emulsions using poly(vinyl alcohol) as a protective colloid in comparison with those using surfactants

Properties of copolymer emulsions of methyl methacrylate and butyl acrylate prepared using poly(vinyl alcohol) (PVA) as a protective colloid have been studied and compared with those prepared using anionic and anionic/non‐ionic surfactants. The emulsions with PVA revealed a Newtonian flow, while those with surfactants had a thixotropic flow. Cast films of the emulsions with PVA afforded much larger tensile strengths, higher Young's moduli, and poorer resistance to water compared with those with surfactants. Adhesive layer composed of the copolymers with PVA revealed markedly higher creep resistance to shearing stress, while that with surfactants had poor resistance; these phenomena appear to arise from the canal‐like morphology of PVA in the former cast films, while the surfactants in the latter existed in island morphology. © 2000 Society of Chemical Industry     

Thermal characteristics of poly(vinyl alcohol) and poly(vinylpyrrolidone) IPNs

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) (PVA) and 1‐vinyl‐2‐pyrrolidone (VP) were prepared by radical polymerization using 2,2‐dimethyl‐2‐phenylacetophenone (DMPAP) and methylene bisacrylicamide (MBAAm) as initiator and crosslinker, respectively. The thermal characterization of the IPNs was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). Depressions of the melting temperatures of PVA segments in IPNs were observed with increasing VP content via the DSC. The DEA was employed to ascertain the glass transition temperature (T_g) of IPNs. From the result of DEA, IPNs exhibited two T_gs indicating the presence of phase separation in the IPN. The thermal decomposition of IPNs was investigated using TGA and appeared at near 270°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1844–1847, 2002     

聚乳酸/聚乙烯醇纳米纤维的制备及结构

以二甲基亚砜为溶剂,制备不同配比的聚乳酸(PLLA)和聚乙烯醇(PVA)的混合溶液,静电纺丝制得PLLA/PVA纳米纤维。采用红外光谱仪、原子力显微镜等对PLLA/PVA纳米纤维结构与性能进行了表征。结果表明:PLLA/PVA纳米纤维中PVA上的羟基与PLLA上的羰基形成了氢键,PLLA与PVA之间存在一定的相互作用,但PLLA/PVA纳米纤维存在相分离现象;混合溶液的PLLA质量分数为11%,PVA质量分数为8%时可以得到较好的PLLA/PVA纳米纤维,但PVA质量分数为6%时出现液滴及珠丝,PVA质量分数为4%时,不能制得纳米纤维。     

Preparation and characterization of poly(vinyl alcohol)‐poly(vinyl pyrrolidone) blend: A biomaterial with latent medical applications

Aqueous solutions of poly(vinyl alcohol) and poly(vinyl pyrrolidone) are blended and films are produced by casting method with the further intention of being used as bio‐materials with latent medical application. Glutaraldehyde, 4,4′‐diazido‐2,2′‐stilbenedisulfonic acid disodium salt tetra‐hydrate are used as crosslinker agents, whereas lactic acid is the plasticizer in the blend. The obtained films are characterized by differential scanning calorimetry (DSC), mechanical properties, swelling and solubility behavior. DSC measurements show that the blends exhibit a single glass transition temperature indicating that they are miscible, even in the presence of the plasticizer and crosslinker agents. By the combination of all mentioned additives, a relevant enhancement of the swelling is observed, accompanied by a stabilization of the solubility during the tested time. Finally, mechanical properties show an appropriate performance in the studied parameters. As a consequence, the obtained films could be suitable for use as medium or long‐term implants. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The influence of poly(vinyl alcohol) suspending agents on suspension poly(vinyl chloride) morphology

The requirements for PVC suspension resin have changed considerably in the last few years, so much so that few companies have products on their ranges that are more than 4 or 5 years old. The suspending agent has a crucial influence on the morphology of the resin, so the changes in resin characteristics have largely been achieved by changes in the suspending agent systems. After a brief review of the mechanism of PVC suspension polymerisation, the properties of polymers made using PVOH suspending agents are related to changes in the latter. The effect of variations in PVAc degree of hydrolysis and viscosity are related to changes in surface tension. Methods of achieving higher porosity by using low hydrolysis co-suspending agents are described. It is shown that higher bulk densities can be achieved by delayed addition of the PVOH. Levels of conjugated unsaturation and copolymer distributions are also shown to have important influences.     

Preparation of poly(vinyl butyral) with high acetalization rate

Poly(vinyl alcohol) (PVA) can be dissolved in a nonaqueous medium in the presence of catalytic concentration of ethyl nitrate dimethyl sulfoxide, C₂H₅ONO₂ · DMSO (EN · DMSO). From the PVA solution, poly(vinyl butyral) (PVBu) was prepared by acid‐catalyzed homogeneous acetalization of PVA with butyraldehyde. The formation of PVBu was confirmed by IR and ¹H‐NMR spectra. The degree of acetalization of PVBu was found to be 95 mol %, which was verified by ¹H‐NMR data and acetylation method. The molecular mass of the polymer was determined by GPC method. The glass transition temperature, T_g, was measured from differential scanning calorimetric (DSC) thermograms. Thermal stabilities were checked by thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). The acetal decomposed in three stages. The corresponding initial decomposition temperatures were found to be 285, 390, and above 500°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1182–1186, 2001