非离子纤维素醚改性水泥浆的孔结构

通过表现密度测试及宏观、微观孔结构观察,研究不同分子结构非离子纤维素醚对水泥浆孔结构的影响.结果表明,非离子纤维素醚会导致水泥浆孔隙率增加;非离子纤维素醚改性水泥浆黏度相近时,羟乙基纤维素醚(HEC)改性水泥浆的孔隙率比羟丙基甲基纤维素醚(HPMC)和甲基纤维素醚(MC)改性水泥浆小;基团含量相似的HPMC纤维素醚,黏度/相对分子质量越低,其改性水泥浆孔隙率越小.非离子纤维素醚掺入水泥浆后,降低了液相表面张力,使得水泥浆容易形成气泡;非离子纤维素醚分子定向吸附在气泡气-液界面,同时还增加了水泥浆液相黏度,使得水泥浆稳定气泡的能力增强.     

聚合物干粉对加气混凝土用抹灰砂浆性能的影响

针对加气混凝土普通抹灰砂浆存在的保水性差、粘结强度低、易开裂空鼓等缺陷,研究了聚合物干粉对加气混凝土用抹灰砂浆性能的影响,并对该影响机理进行了讨论.研究表明,在砂浆中同时掺入羟乙基甲基纤维素醚和聚乙烯-醋酸乙烯酯可再分散乳胶粉,大大改善了砂浆的保水性、提高了和易性和粘结强度,较好地解决了普通抹灰砂浆用于加气混凝土存在的开裂、空鼓甚至脱落等问题.     

纤维素基吸附剂对重金属离子吸附的研究进展

纤维素作为一种可再生、对环境友好的生物质资源,成为吸附领域的重点研究对象之一。本文着重介绍了氧化改性、酯化改性、醚化改性、接枝共聚、交联改性和复合改性的纤维素基吸附材料在重金属离子吸附领域的研究进展。这些改性方法均能改善纤维素对重金属离子的吸附性能,但存在着流程较长、吸附条件较为苛刻、金属适用范围各异的局限性。因此,应通过进一步系统研究,找到制备可选择性吸附重金属离子的纤维素基吸附材料经济有效的方法。     

增塑剂对纤维素膜表面结构和性能的影响

天然纤维素膜不经任何处理直接干燥,膜发脆、卷曲,作用不大.采用甘油做增塑剂来改变纤维素膜的柔顺性,研究了不同的增塑条件对纤维素膜表面结构和性能的影响及甘油的塑化机理.通过力学性能测试、表面形态的观察及红外光谱分析,研究表明,甘油在一定程度上改变了纤维素膜的柔顺性,但同时却使纤维素膜的力学性能变差,并且增塑的膜经水洗后,甘油易流失,增塑效果减弱.     

Cellulose/acrylic acid copolymer blends for films and coating applications

Enzymatically treated cellulose was dissolved in a NaOH/ZnO solvent system and mixed together with poly(ethylene‐co‐acrylic acid) (PE‐co‐AA) or poly(acrylamide‐co‐acrylic acid) (PAA‐co‐AA) polymers, in order to improve the properties of dissolved cellulose and to prepare homogeneous cellulose‐based blends for films and coatings. The solution stage properties of the blends were evaluated by rheological methods and the precipitated dry blends were characterized by dynamic mechanical analysis, differential scanning calorimetry, and scanning electron microscopy. Paperboard coating tests done at laboratory scale showed dissolved cellulose/acrylic acid copolymer‐based blends function well as coating materials. All of the tested blends showed a good resistance against grease in the coating trials, having grease resistance from 60 to 69 days despite a very thin (～2 µm) coating layer. In addition, cellulose/PE‐co‐AA coating showed improved water vapor and oxygen barrier properties when compared with neat dissolved cellulose‐coated paperboard. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40286.     

Bio‐composites for structural applications: Poly‐l‐lactide reinforced with long sisal fiber bundles

Fully bio‐based and biodegradable composites were compression molded from unidirectionally aligned sisal fiber bundles and a polylactide polymer matrix (PLLA). Caustic soda treatment was employed to modify the strength of sisal fibers and to improve fiber to matrix adhesion. Mechanical properties of PLLA/sisal fiber composites improved with caustic soda treatment: the mean flexural strength and modulus increased from 279 MPa and 19.4 GPa respectively to 286 MPa and 22 GPa at a fiber volume fraction of V_f = 0.6. The glass transition temperature decreased with increasing fiber content in composites reinforced with untreated sisal fibers due to interfacial friction. The damping at the caustic soda‐treated fibers‐PLLA interface was reduced due to the presence of transcrystalline morphology at the fiber to matrix interface. It was demonstrated that high strength, high modulus sisal‐PLLA composites can be produced with effective stress transfer at well‐bonded fiber to matrix interfaces. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40999.     

High performance films of cellulose butyral derivative having a necklace-like annular structure in the side chains

We fabricated high performance films using cellulose butyral (CB) synthesized from native cellulose. Two-step reactions were adopted to produce the derivative CB, including etherification of cellulose with glycidol in NaOH/urea aqueous solution to yield O-(2,3-dihydroxypropyl) cellulose (DHPC), and butyralization of DHPC. Both DHPC and CB products were easily processed into a thin film by hot-press molding. The butyral modifier significantly improved the tenacity of highly ductile DHPC, by virtue of the possible chain-entangling action of the ring structures in the stretching process. Thereby the film toughness was markedly enhanced. The CB films exhibited excellent optical transparency and a good adhesive property to glass plates. Thus the films may be comparable to commercial poly(vinyl butyral) (PVB) films in optical and mechanical performances and therefore possess a potential applicability as interlayer for laminated glasses.     

Regenerated cellulose nanocomposites reinforced with exfoliated graphite nanosheets using BMIMCL ionic liquid

Green nanocomposites of regenerated cellulose/exfoliated graphite nanosheets films with low nanofiller loadings were prepared using environmentally benign 1-butyl-3-methylimidazolium chloride (BMIMCl) ionic liquid. X-ray diffraction revealed well developed intercalated nanocomposites. The tensile strength and Young's modulus of the prepared nanocomposites were increased by 97.5% and 172% respectively when 0.75 wt.% and 1 wt.% exfoliated graphite nanosheets were added. The results were validated using the Halpin–Tsai model. The exfoliated graphite nanosheets were unidirectionally aligned in the regenerated cellulose parallel to the surface of the nanocomposites as revealed by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). Also, the TEM and FESEM revealed uniform dispersion of the exfoliated graphite nanosheets and good interaction between the nanofillers and the matrix. The addition of the exfoliated graphite nanosheets enhanced the thermal stability and reduced the water absorption and diffusivity of the nanocomposites.     

Atom transfer radical polymerization (ATRP): A versatile and forceful tool for functional membranes

The progress in atom transfer radical polymerization (ATRP) provides an effective means for the design and preparation of functional membranes. Polymeric membranes with different macromolecular architectures applied in fuel cells, including block and graft copolymers are conveniently prepared via ATRP. Moreover, ATRP has also been widely used to introduce functionality onto the membrane surface to enhance its use in specific applications, such as antifouling, stimuli-responsive, adsorption function and pervaporation. In this review, the recent design and synthesis of advanced functional membranes via the ATRP technique are discussed in detail and their especial advantages are highlighted by selected examples extract the principles for preparation or modification of membranes using the ATRP methodology.     

Improvement in impact strength of modified cardanol‐bonded cellulose thermoplastic resin by adding modified silicones

The impact strength of cellulose diacetate (CDA) bonded with a modified cardanol (3‐pentadecylphenoxy acetic acid: PAA) was greatly improved up to 9 kJ/m² by adding a relatively small amount of modified silicones while suppressing a decrease in bending strength. In our recent research, this thermoplastic resin (PAA‐bonded CDA) exhibited high rigidity, glass transition temperature, and water resistance. However, its impact strength was insufficient for use in durable products. Therefore, silicones modified with polyether, amino, and epoxy groups were investigated as possible ways to improve the impact strength. The results show that adding polyether‐modified silicone (polyether silicone) with moderate polarity relative to PAA‐bonded CDA resulted in shearing deformation greatly enhances its impact strength while maintaining other properties, including glass transition temperature (T_g), water resistance, and thermoplasticity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40366.