疏水缔合羟乙基纤维素的合成及性能表征

为改进羟乙基纤维素的溶液性能,通过羟乙基纤维素与长链溴代烷烃的大分子反应,制得疏水缔合羟乙基纤维素(BD-HAHEC);经由正交实验确定最优化工艺参数为:醚化剂∶羟乙基纤维素(质量比)=3∶10,活化剂浓度为4%,在80℃条件下反应5 h。用傅立叶红外光谱仪、粘度计和剪切流变仪对产品进行结构表征和性能测定,结果表明,与普通羟乙基纤维素相比,疏水改性羟乙基纤维素水溶液在增稠性、耐温耐盐性、抗剪切性等性能上均有明显提高;在相同反应条件下,由溴代十四烷改性的羟乙基纤维素具有比溴代十二烷改性更强的增稠性能。     

离子液体中疏水改性羟乙基纤维素的合成

采用大分子反应法,将疏水性单体l-溴代十二烷(BD)接枝到羟乙基纤维素(HEC)上,对羟乙基纤维素进行疏水改性,制备了疏水改性羟乙基纤维素(HMHEC)。研究了离子液体种类、反应温度、羟乙基纤维素浓度和BD用量对HMHEC性能的影响。最佳合成条件为:HEC浓度为3%(质量分数),溶解时间1 h,溶解温度100℃,反应时间2 h,反应温度80℃,BD用量为2 mL。在1-烯丙基-2-甲基-咪唑氯盐体系中合成的HMHEC性能好于在1-丁基-2-甲基咪唑氯盐中合成的HMHEC。     

阳离子羟乙基纤维素溶液黏度性能的研究

以羟乙基纤维素（HEC）为原料,2-氯-4,6-二（N,N-二甲基-N-苄基1,3-丙二胺）1,3,5-均三嗪为改性剂,制备出不同取代度阳离子羟乙基纤维素。同时探讨了取代度及其浓度、阳离子及其浓度、转子转速、温度、pH值对阳离子羟乙基纤维素（CHEC）的黏性行为的影响。结果表明,阳离子羟乙基纤维素溶液黏度随着CHEC浓度增大、温度的升高、pH值的增加而减小。同一CHEC质量浓度下,取代度越高,转子的转速降低,黏度增大。CHEC在K₂SO₄溶液中的黏度总低于MgSO₄溶液中黏度;随着阳离子浓度的增加,CHEC溶液的黏度降低。     

羟乙基纤维素精制的工业化实验

介绍了羟乙基纤维素的结构、性质及制备方法。通过实验选择以75%的丙酮溶液为洗液,采用旋转式压力洗涤过滤机洗涤,能有效去除羟乙基纤维素中的杂质,获得高纯度羟乙基纤维素产品,达到工业化提纯羟乙基纤维素的目的。     

改性纤维素和壳聚糖共混膜的制备及性能研究

将水溶性的纤维素衍生物——羟乙基纤维素与壳聚糖乙酸水溶液用溶液浇铸法制得羟乙基纤维素/壳聚糖(HEC/CS)共混膜。确定了该共混膜的最佳制备条件,并测试了其力学性能和生物降解性能。结果表明:HEC/CS共混膜具有好的抗菌性。     

羟乙基纤维素改性水性聚氨酯涂料的制备及性能研究

本文以甲苯二异氰酸酯(TDI)、聚醚二元醇(N210)、2,2-二羟甲基丙酸(DMPA)、一缩二乙二醇(DEG)和羟乙基纤维素(HEC)等为主要原料,制备纤维素改性水性聚氨酯涂料(WPU)。测试分析结果表明HEC成功接枝到聚氨酯分子链中,使乳液的粘度增加。而且,由于HEC与聚氨酯生成交联结构,胶膜的铅笔硬度、附着力等性能有所提高。当HEC含量为0.5%时性能最佳。     

阳离子纤维素醚的合成及流变性能研究

在自制碱催化剂存在下,工业羟乙基纤维素与N-(2,3-环氧丙基)三甲基氯化铵(GTA)阳离子化试剂反应,干法制备高取代度季铵盐型阳离子纤维素醚(CHEC)。用均匀实验方案考察了GTA与羟乙基纤维素(HEC)用量比、NaOH与HEC用量比、反应温度、反应时间对反应效率的影响,并通过蒙特卡洛蒙特卡罗模拟得到优化工艺条件,并通过实验验证得到阳离子醚化试剂的反应效率达到95%。同时探讨了其的流变性能。结果表明,CHEC的溶液呈现非牛顿流体特征,随着溶液质量浓度增大其表观粘度增大;在一定浓度的盐溶液中,CHEC表观粘度随着外加盐浓度的增大而减小。同一剪切速率下,CaCl2溶液体系中CHEC的表观粘度比NaCl溶液体系中CHEC的表观粘度大。     

水性多彩涂料彩粒渗色性能研究

利用人工合成锂皂石层状结构中的可交换阳离子与含大量羟基的羟乙基纤维素(HEC)之间的凝胶化反应制备水性多彩涂料。考察了乳液类型和掺量、羟乙基纤维素(HEC)用量、高浓度保护胶用量、助剂和水性色浆种类等对彩粒渗色性能的影响,优化了水性多彩涂料的制备工艺,制备出的水性多彩涂料抗渗色性能优异、彩粒强度高、体系稳定性好。     

羟乙基纤维素改性材料的研究现状

从长碳链烷基醚化或酯化、乙烯基单体和脂肪族聚酯引发转移自由基聚合改性、非共价聚合法、高分子共混法等方面介绍了羟乙基纤维素(HEC)改性处理后功能材料的最新研究进展。HEC主链和聚合物支链化学结构和性能的不同,赋予HEC接枝共聚物双亲性、环境刺激响应性等特性,且共聚物能够发生丰富的自组装行为,在生物医学领域有着重要的应用,尤其在可控药物释放方面。     

羟乙基纤维素接枝聚合及衍生基团取代值的测定

利用三甲基硅(TMS)基团改性保护技术,成功制备了羟乙基纤维素接枝聚己内酯(HEC-g-PCL)聚合物;利用红外光谱及核磁共振波谱对合成产物进行了结构验证;利用化学滴定法测定了原料HEC的醚化取代度,通过1H-NMR确定了中间产物的取代度及聚己内酯接枝侧链的重复单元数,并测定了终产物接枝聚己内酯侧链的接枝率和ε-己内酯接枝效率。研究结果有助于对反应历程的探讨。     

Synthesis of biodegradable hydroxyethylcellulose cryogels by UV irradiation

Biodegradable macroporous hydroxyethylcellulose (HEC) cryogels of good quality and high gel fraction yield (95%) were synthesized via a facile method. The latter involved a relatively fast preparation of homogeneous semidilute solution of polymer and photoinitiator, (4-benzoylbenzyl)trimethylammonium chloride, followed by freezing at a defined negative temperature, an extremely short UV irradiation and subsequent thawing. HEC cryogels were successfully prepared also by using H₂O₂ as a photoinitiator. The effects of the temperature of freezing, the HEC molecular weight and the concentration of HEC solution on the cross-linking efficiency, the swelling ratio and the enzymatic degradation of HEC cryogels were investigated. Due to the cryoconcentration phenomenon, cryogels are formed at substantially low initial concentrations of the studied polymers. The highest values of gel fraction yield are achieved in the 1-2 wt.% concentration range at −20 °C. As a rule, the higher the molecular weight, the greater the gel fraction yield of the resulting cryogels. Scanning electron microscopy (SEM) analysis reveals that the interior structure of HEC cryogels is completely different from the conventional HEC hydrogels. HEC cryogels undergo decomposition by the action of cellulase enzyme, however, due to their specific morphology, the rate of degradation is slower compared to the conventional HEC hydrogel of similar gel fraction yield.     

Morphology of electrically conductive grades of carbon black

In recent years, several new types of highly electrically conductive (HEC) carbon blacks have been commercially introduced for use in plastic. Morphological features of these HEC carbon blacks are directly related to polymer melt rheology, proper loading concentration, resistivity and overall performance of the plastic composite. It was found that the unique mesoporous structure of these new HEC carbon blacks are primarily responsible for their success in Polyvinylchloride formulations.     

AKD改性羟乙基纤维素的合成及使用性能

采用异丙醇为溶剂,利用淤浆法在羟乙基纤维素(HEC)的制备过程引入一种改性试剂烷基或链烯基乙烯酮二聚体(AKD)以对其进行改性,比较改性HEC与未改性HEC的耐温性、耐盐性及耐酶性等使用性能,测试结果表明,AKD的引入使得改性HEC的使用性能得到一定的提高。     

快速吸水响应性PVA/HEC多孔复合材料的制备及性能

将酵母菌作为微生物发泡剂引入到聚乙烯醇(PVA)/羟乙基纤维素(HEC)复合材料中,结合循环冷冻-解冻法制备PVA/HEC多孔复合材料。测试不同实验条件PVA/HEC多孔复合材料的孔隙率、吸水性、保水性。通过FTIR和SEM表征样品的微观结构;采用热重分析仪(TG)、X射线衍射(XRD)仪、万能拉力试验机分析样品热稳定性、结晶性、力学性能。结果表明：酵母菌发泡PVA/HEC多孔复合材料孔呈大孔套小孔的椭圆状开孔结构,吸水响应速率快。保水性良好,24h后保水率降至最低。与未经酵母菌发泡的PVA/HEC复合材料相比,酵母菌发泡PVA/HEC多孔复合材料热稳定性和力学性能均有所提高,压缩强度和极限抗压应力分别是13.2、6.4MPa。     

The role of Cr addition on the processing and mechanical properties of high entropy carbides

Group VI transition metals do not form room temperature stable carbides with a rock salt structure, however, they can be incorporated into a rock salt high entropy carbide lattice. Novel 5-metal high entropy carbides (Cr, Zr, Nb, Hf, Ta)C (HEC5-Cr) were produced using spark plasma sintering and compared with 4-metal carbide (Zr_0.25Nb_0.25Hf_0.25Ta_0.25)C (HEC4) and 8-metal carbide containing Cr (HEC8-Cr). The HEC5-Cr ceramics had higher density and smaller grain size (~14 µm) compared with HEC4 (~28 µm). The solubility limit of Cr on the metal site increased from ~2.5 at% for HEC5-Cr to ~6.0 at% for HEC8-Cr, implying that the high entropy effect increased the solubility of Cr. A significant Cr enrichment was observed at the grain boundaries of HEC5-Cr, and it showed a ~14% increase in nanohardness and a similar indentation modulus compared with HEC4. The nanohardness of HEC5-Cr was up to 41.2 GPa due to increased solid solution strengthening.     

快速吸水响应性PVA/HEC多孔复合材料的制备及性能

将酵母菌作为微生物发泡剂引入到聚乙烯醇(PVA)/羟乙基纤维素(HEC)复合材料中,结合循环冷冻-解冻法制备PVA/HEC多孔复合材料。测试了不同实验条件下PVA/HEC多孔复合材料的孔隙率、吸水性、保水性。通过FTIR和SEM表征样品的微观结构;采用热重分析仪(TG)、X射线衍射仪(XRD)、万能拉力试验机分析样品热稳定性、结晶性、力学性能。结果表明:酵母菌发泡PVA/HEC多孔复合材料孔呈大孔套小孔的椭圆状开孔结构,具有快速吸水响应性;保水性良好,24 h后保水率降至最低;与PVA/HEC复合材料相比,PVA/HEC多孔复合材料热稳定性和力学性能均有所提高,压缩强度和极限抗压应力分别是13.2、6.4 MPa。     

HEC/CMC混合物水溶液流变性质的研究

采用旋转粘度计研究了HEC/CMC混合物水溶液的流变性质。结果表明 ,混合物体系中羧甲基纤维素 (CMC)含量高时 ,流动曲线符合幂律模型 ;羟乙基纤维素 (HEC)含量高时 ,则偏离幂律模型。同时还探讨了混合体系中溶液粘度的加和性以及温度依赖性     

羟乙基纤维素水凝胶的制备及吸附性能

以羟乙基纤维素(HEC)(作为水凝胶的骨架增强水凝胶的强度)和丙烯酸(AA)为原料,过氧化氢/维生素C混合溶液作为氧化还原引发剂,通过自由基聚合的方法制备HEC-AA水凝胶.通过傅里叶变换红外光谱对HEC-AA水凝胶的结构进行了表征,分析表明水凝胶内部存在氢键.通过扫描电子显微镜对HEC-AA水凝胶的微观结构进行研究,...     

Diffusion bonding of (Hf0.2Zr0.2Ti0.2Ta0.2Nb0.2)C high-entropy ceramic with metallic Ni foil

To prepare large-sized and complex-shaped components, the feasibility of direct diffusion bonding of (Hf_0.2Zr_0.2Ti_0.2Ta_0.2Nb_0.2)C high-entropy ceramic (HEC) and its diffusion bonding with a metallic Ni foil was investigated, and the interfacial microstructure and mechanical properties of HEC/HEC and HEC/Ni/HEC joints were analyzed. For the direct diffusion bonding, reliable joints with a shear strength of 146 MPa could be achieved when the bonding temperature reached 1500 °C under a pressure of 30 MPa. By introducing a metallic Ni foil as the interlayer, the HEC was successfully bonded at the diffusion temperatures from 1150 °C to 1250 °C under 10 MPa through the formation of Ti₂Ni compound phase. Meanwhile, the HEC(Ni) phase formed by the diffusion of Ni into HEC and Ni(s, s) bulks precipitated in the bonding transition zone. The maximum joint shear strength of 151 MPa was obtained by optimizing the Ni-foil thickness, bonding temperature, and holding time.     

High entropy carbide ceramics from different starting materials

Three typical ceramic processing were respectively used to synthesize (Ti_0.2Zr_0.2Nb_0.2Ta_0.2W_0.2)C high-entropy carbide (HEC) ceramics by spark plasma sintering. Although single-phase composition characterized by X-ray diffraction were obtained by the three processes, the microstructures and elemental distributions are different. The reasons for the formation of these features are preliminarily discussed. The results demonstrate that the particle sizes of the starting metallic powders was a key factor for obtaining a homogeneous distribution of each elements in the HEC. Carbide process with relatively finer starting carbide powders compared to the above metallic starting powders resulted in an HEC with homogeneous distribution of elements, but the obtained ceramics showed the lowest relative density. For oxide process, it is considered that the obviously higher reaction temperature between ZrO₂ and graphite resulted in a two-phase structure of an HEC and a zirconium-rich phase, but the obtained HEC showed the highest relative density.