聚乙烯醇缩乙醛酸树脂的研制

聚乙烯醇缩醛型胶粘剂可通过聚乙烯醇(PVA)与醛类缩合而得,其性质取决于原料PVA的结构、水解程度、醛类的化学结构和缩醛化程度等。将PVA与乙醛酸(无毒、无味和不挥发)进行缩醛化反应,可制备出一种安全环保型聚乙烯醇缩乙醛酸树脂(PVGa)胶粘剂。以n(乙醛酸)∶n(PVA中-OH基)比例、反应时间、反应温度和PVA水溶液浓度为试验因素,缩醛度为衡量指标,采用正交试验法优选出制备PVGa的最适宜工艺条件。结果表明:当反应温度为80℃、PVA水溶液浓度为15%、n(乙醛酸)∶n(PVA中-OH基)=1∶5和反应时间为40min时,PVGa的缩醛度为39.85%;PVGa的吸湿性能比PVA高4～6倍,PVGa的力学性能优于PVA,两者的热失重情况基本相似。     

后处理对胶原蛋白/PVA复合纤维结构与性能的影响

研究了环氧氯丙烷(ECH)处理和缩醛化反应对胶原蛋白/聚乙烯醇(PVA)初生复合纤维中蛋白质存留率、水中软化点的影响。结果表明:当ECH浴处理温度50℃,处理时间2 h,pH值11;缩醛化浴温度50℃,处理时间40 min,缩醛化浴中硫酸质量浓度180 g/L,甲醛质量浓度45 g/L时,复合纤维水中软化点为101℃,胶原蛋白存留率为90.33%。     

聚乙烯醇在乙醇水溶液中缩醛化的研究

聚乙烯醇（ＰＶＡ）在乙醇水溶液中在酸性条件下与醛类缩醛化制成ＰＶＡ缩醛的乙醇水溶液。缩醛化度可由乙醇的浓度来控制。ＰＶＡ缩醛的乙醇水溶液经氧化降解后可直接用作配制胶粘剂和涂料的胶料。     

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。     

聚乙烯醇胶粘剂的缩醛化研究

首先研究了聚乙烯醇与甲醛的缩醛化反应条件,然后用乙醛代替部分甲醛进行改性研究,发现用乙醛代替部分甲醛后,在胶粘剂的各项性能上都有很大改善。     

聚乙烯醇生产工艺的专利申请分析

聚乙烯醇(PVA)有较好的化学稳定性、良好的绝缘性、成膜性、及气体阻隔性等,能进行酯化、醚化及缩醛化等反应,因此得到广泛应用。本文在检索分析了大量国内外专利文献的基础上,对聚乙烯醇的生产工艺现状相关专利技术进行收集和分析。     

火柴盒黏合剂的研制

研究了以聚乙烯醇为原料，经过缩醛化改性后制得用于火柴盒糊盒的黏合剂，着重探讨了影响缩醛化反应的几个重要因素；甲醛用量，反应液酸度，反应温度，确定了最佳工艺条件。     

影响合成聚乙烯醇缩甲醛树脂泡沫塑料性能的条件研究

本文对聚乙烯醇的质量分数,酸的用量,缩醛化时间对聚乙烯醇缩甲醛泡沫塑料性能的影响的研究,找出其中的规律,并选出合成聚乙烯醇缩甲醛泡沫塑料的最佳方案。     

聚乙烯醇缩丁醛树脂分子量和热性能的测定

用凝胶渗透色谱(GPC)测定了高粘度PVB树脂(BH)和低粘度PVB树脂(BL)两种样品的平均分子量和分子量分布，并对所测结果进行了验证和讨论。对平均聚合度的验算表明，BH的平均聚合度与原料聚乙烯醇的平均聚合度相等，说明BH在缩醛化反应中大分子主链长度没有变化；而BL的平均聚合度却比原料聚乙烯醇的平均聚合度减小了62％，这是由于在制备BL时，在缩醛化之前对原料PVA用降解剂使其主链发生降解之故。用示差扫描量热法(DSC)对上述两种样品进行了热性能分析，分析结果表明，PVB中乙烯醇链节(VOH)的含量增加5．1l％(质量分数)，可使PVB的熔点增高9℃，PVB的结晶度增大1．4倍；结晶度增大使PVB的宏观物理性能(如溶解度等)发生显著的变化。     

胶原蛋白/聚乙烯醇复合纤维的初步探索

将胶原蛋白和聚乙烯醇(PVA)分别溶解后复合纺丝,制得胶原蛋白/PVA复合纤维,对复合纤维的可纺性、力学性能和结构进行了初步探索。结果表明,胶原蛋白和PVA复合纺丝,具有较好的可纺性,复合纤维经过热拉伸、热定型和缩醛化处理后,纤维强度、模量和伸长率分别达到了2.3cN/dtex,30.69cN/dtex,20.12%;结晶度较高为70.57%;水中软化点由缩醛化前的89℃提高到110℃。通过扫描电镜照片观察复合纤维,未发现两相结构,胶原蛋白和PVA结合较好。     

Surface modification of polyethylene by plasma pretreatment and UV‐induced graft polymerization for improvement of antithrombogenicity

The purpose of this study was to enhance blood compatibility of polyethylene (PE) films. Glycidyl methacrylate (GMA) was grafted onto the surface of PE by Ar plasma pretreatment and UV‐induced graft polymerization without photo‐initiator, then heparin was immobilized onto the poly (glycidyl methacrylate) segments. The surface compositions and microstructure of GMA graft polymerized PE films were studied by X‐ray photoelectron spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transfer Infrared (ATR‐FTIR) spectroscopy. It was confirmed that heparin was successfully immobilized onto the surface of PE films by XPS analysis. The antithrombogenicity of the samples was determined by the activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), and plasma recalcification time (PRT) tests and platelet adhesion experiment. Results indicated that the antithrombogenicity of modified PE was improved remarkably. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2014–2018, 2004     

Polyurethane films modified by antithrombin–heparin complex to enhance endothelialization: An original impedimetric analysis

In this paper, polyurethane (PU) was deposited as a thin layer onto the surface of ITO (indium tin oxide) and was then modified with an antithrombin–heparin complex (ATH). The resulting films were characterized by ATR spectroscopy, contact angle measurements and electrochemical impedance spectroscopy (EIS). Physicochemical characterization confirmed the surface modifications.The obtained films were used as substrates for endothelial cell attachment and growth. These processes were characterized using electrochemical impedance spectroscopy (EIS). We observed that the addition of a small amount of heparin and AT additives onto the polymer surface resulted in a considerable change in the surface characteristics, and we found that PU films that were modified by the ATH complex were able to greatly enhance adhesion and proliferation of endothelial cells (ECs).     

Surface modification of polypropylene film by radiation‐induced grafting and its blood compatibility

To endow blood‐compatible properties onto polypropylene (PP) film, we grafted 2,3‐epoxypropyl methacrylate (EPMA) to PP film with a preirradiation grafting technique and then introduced various functional groups onto the grafted PP film. The EPMA grafting extent was dependent on the absorbed dose, reaction time, and temperature. The reactions of hydroxylation, iminodiacetation, sulfonation, phosphonation, and amination were performed under various conditions to introduce functional groups into the epoxy group of EPMA‐grafted PP films, respectively. We also immobilized heparin on aminated PP film to compare blood compatibility with various functionalized samples. The grafting, functionalization, and heparinization reaction were confirmed by Fourier transform infrared spectroscopy in the attenuated total reflectance mode and electron spectroscopy for chemical analysis. The blood compatibility of various functional groups and heparin‐introduced samples as well as control samples was examined by the determination of platelet adsorption and thrombus formation. For the examination of the blood compatibility of functionalized PP samples, acid citrate dextrose human whole blood and platelet‐rich plasma were used. The amount of the formed thrombus and the adherent platelets on functionalized PP sample surfaces were evaluated by an in vitro method following Imai and Nose's technique and by scanning electron microscopy, respectively. The blood compatibility of various functional‐group‐introduced PP films after grafting was better than that of the PP control. Phosphoric‐acid‐group‐ and heparin‐introduced PP films had especially good blood compatibility. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1726–1736, 2003     

Thermal,Mechanical and Chemical Properties of Hydrophilic Poly(vinyl alcohol) Film Improved by Hydrophobic Poly(propylene glycol)

A series of poly(vinyl alcohol)/poly(propylene glycol) (PVA/PPG) blend films with different PPG contents were prepared by casting the polymer blend solutions. Structure and morphologies of the PVA/PPG blend films were studied by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PVA/PPG blend films were investigated by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), tensile strength tests, and other physical methods. It was revealed that the introduction of PPG could exert marked effects on the morphology and the properties of PVA film.     

Thermal and surface characterization of plasticized starch polyvinyl alcohol blends crosslinked with epichlorohydrin

Starch‐polyvinyl alcohol (PVA) blends in 2:8 wt % were prepared with various plasticizers such as polyethylene glycol (PEG‐200, PEG‐400) and glycerol. The crosslinking of starch‐PVA blends by epichlorohydrin was carried out in the presence of a plasticizer in situ. The obtained films were analyzed by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), dynamic mechanical and thermal analysis (DMTA), and X‐ray photoelectron spectroscopy (XPS), and remarkable changes in thermal stability and glass‐transition temperature have been observed on plasticizing and crosslinking in different concentrations. Different kinetic models such as Coats–Redfern, Broido, Friedman, and Chang were used to calculate the kinetic parameters of thermal decomposition. The results suggest that the thermal stability and activation energy of thermal decomposition passes through maxima at a critical concentration of plasticizer and increases with increasing crosslinker concentration. High‐resolution C 1s XPS analysis was used to provide a method of differentiating the presence of various carbons associated with different environment in the films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 25–34, 2006     

Mechanical and Dynamic Analysis of Poly (Vinyl Alcohol)-Modified Wood Dust Nanocomposite

Wood dust was modified by maleic anhydride and to know the effect of various filler loading on the properties of PVA-modified wood dust composite prepared by a conventional solvent casting technique. The as-synthesized composite films were typically characterized by FTIR spectroscopy and X-ray diffraction. To study the temperature dependencies of the dynamic modulii, stress relaxation, mechanical loss, and damping phenomena of the composite material, dynamic mechanical analysis (DMA) was done. The tensile behavior of the composite films was analyzed. The biodegradability study of the composite materials was done by soil burial test and their morphological modification study was done using SEM.     

Clotting times and tensile properties of insoluble silk fibroin films containing heparin

Although many novel approaches for producing small‐caliber arterial grafts have been developed, problems with mechanical properties and blood compatibility have up to now prevented clinical implementation. Blending anticoagulant agents with natural biomaterials having excellent cell attachment and growth properties, and making the release time of anticoagulant agents exceed the time required by endothelial tissue regeneration, might be a novel method to prepare appropriate biomaterials used in small‐diameter arterial grafts. In this article, an insoluble fibroin film, having excellent blood compatibility and mechanical properties, was obtained by blending with heparin. The structural properties of the films were examined through Fourier‐transform infrared attenuated total reflectance (FTIR‐ATR) and X‐ray diffraction (XRD). The results indicated that plentiful β‐sheet crystals existed in fibroin films containing heparin. The tensile strength and elongation at break of film containing heparin were, respectively, 10.3 MPa and 54 % in the wet state, which can satisfy the mechanical requirements of blood‐contacting materials such as small‐diameter tubing. The clot times [activated partial thromboplastin time (APTT), thrombin time (TT) and prothrombin time (PT)] all exceeded the measurement limit of the clot detection instrument. Even the APTT and TT of film immersed in water for 28 days exceeded the measurement limit of the clot detection instrument. The in vitro culture of endothelial cells on the film was also investigated, and the result indicated that cells can grow to cover all of the available surface area of the film within 8 days. Fibroin films containing heparin could retain blood compatibility for 28 days, which means that this is a promising material for small‐diameter artery applications. Copyright © 2005 Society of Chemical Industry     

Influence of K2CrO4 Doping on the Structural,Optical and Dielectric Properties of Polyvinyl Alcohol/K2CrO4 Composite Films

Polyvinyl alcohol/potassium chromate (K₂CrO₄) composite films were prepared by solution casting technique using distilled water as a solvent, and were further investigated using Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray diffraction, thermogravimetric analysis, optical microscopy, scanning electron microscopy, and dielectric measurements. Microscopic studies reveal that K₂CrO₄ was homogenously mixed with polyvinyl alcohol matrix due to interfacial interaction between polyvinyl alcohol and K₂CrO₄. The composite films showed very high dielectric constant and relatively low dielectric loss. Hence, such composite materials with improved dielectric properties could be useful for fabrication of electrical charge storage device.     

Polycarbonate urethane films modified by heparin to enhance hemocompatibility and endothelialization

Polyurethane with pendant carboxyl groups was synthesized by a two‐step reaction using methylene diphenyl diisocyanate as hard segments, polycarbonate diols as soft segments and 2,2‐bis(hydroxymethyl) propionic acid as chain extenders. The surfaces of the casting polymer films were further covalently conjugated with heparin as confirmed by Fourier transform infrared spectroscopy. The associated surface‐exposed heparin content was measured to be 1.92 µg cm^?2 and was shown to be active. Meanwhile, surface hydrophobicity decreased after heparin modification. Heparin immobilization greatly improved the hemocompatibility of polyurethane films both in vitro and in vivo. The in vitro cell responses revealed that the expression of proinflammatory markers CD106 and CD62E of human vein endothelial cells was significantly suppressed on the surfaces of the heparinized polyurethane films, while the affinity and proliferation of the cells were improved. The in vivo performance of this material before and after heparin modification was evaluated as a stent coating material in a porcine coronary artery injury model. Histological analysis indicated that heparinized polyurethane induced mild foreign body reactions and inflammation, which were much lower than those induced by unmodified polyurethane. Heparin immobilization also accelerated the endothelialization process on the surface of the polymer‐coated stents when implanted in porcine coronary arteries. More detailed long‐term studies are needed to confirm the biostability of the heparin and the endothelialized surfaces. Copyright © 2012 Society of Chemical Industry     

Preparation and Evaluation of a Self-Nanoemulsifying Drug Delivery System Loaded with Heparin Phospholipid Complex

A self-nanoemulsifying drug delivery system (SNEDDS) was developed to enhance the absorption of heparin after oral administration, in which heparin was compounded with phospholipids to achieve better fat solubility in the form of heparin-phospholipid (HEP-Pc) complex. HEP-Pc complex was prepared using the solvent evaporation method, which increased the solubility of heparin in n-octanol. The successful preparation of HEP-Pc complex was confirmed by differential scanning calorimetry (DSC), Fourier-transform infrared (FT-IR) spectroscopy, NMR, and SEM. A heparin lipid microemulsion (HEP-LM) was prepared by high-pressure homogenization and characterized. HEP-LM can enhance the absorption of heparin after oral administration, significantly prolong activated partial thromboplastin time (APTT) and thrombin time (TT) in mice, and reduce fibrinogen (FIB) content. All these outcomes indicate that HEP-LM has great potential as an oral heparin formulation.