纤维素纳米晶改性及其环氧树脂复合材料的制备与性能研究

采用酸水解法从微晶纤维素中提取纤维素纳米晶(CNC),再分别用硅烷偶联剂和2,2,6,6-四甲基哌啶氧化物(TEMPO)氧化剂对纤维素纳米晶进行改性，然后采用浇铸成膜法制备纯环氧树脂膜、含量为5%CNC、偶联改性CNC(K-CNC)及其TEMPO氧化改性CNC(T-CNC)/环氧树脂(EP)复合材料。利用扫描电子显微镜、透射电子显微镜、紫外-可见分光光度计、热重分析仪和万能材料试验机对试样表面薄膜形貌结构、透光性能、热学性能、机械性能进行测试。结果表明：加入T-CNC及其K-CNC的EP复合材料，断面比纯EP膜更加粗糙，裂纹增加。加入CNC及改性后的CNC,EP复合材料的透光率有所降低，T-CNC/EP复合膜的透光率为83.9%,降低幅度最小，K-CNC/EP膜的拉伸强力为38.37MPa,拉伸强力最大，K-CNC/EP膜弹性模量为513.89MPa,和纯EP膜相比，其弹性模量增加了36.8%,T-CNC/EP及K-CNC/EP复合膜的热分解温度分别增加了7℃和10℃,热稳定性得以改善。     

纤维素纳米晶的改性对其晶体结构及性能的影响

采用硫酸水解法制备纤维素纳米晶(CNC),并对CNC进行乙酰化改性(A-CNC)、TEMPO氧化(T-CNC)、阳离子疏水改性(C-CNC)、阳离子亲水改性(E-CNC)、烷基化改性(S-CNC)、聚丙烯酸接枝改性(P-CNC),之后采用红外光谱、固态碳谱、X射线衍射分析、透射电镜、原子力显微镜、热重分析、分散性分析等表征方法研究了不同改性方法对CNC晶体结构及性能的影响。结果表明,这些改性不会对CNC晶体结构产生严重影响,依然保持棒状结构和纳米尺寸;改性后的纤维素纳米晶结晶度有不同程度的下降,其中A-CNC下降最大,达21.2%;改性后的纤维素纳米晶基本在250～350℃发生降解,而未改性的在200℃就已开始降解;不同的改性可以改变CNC在不同溶剂中的分散性,阳离子亲水改性可以显著提高纤维素纳米晶的热稳定性。     

纤维素纳米晶增强生物可降解复合纤维研究进展

纤维素纳米晶(CNC)具有高强度、高模量、生物可降解和优良的机械性能，常被用作生物可降解纤维的增强材料。介绍了CNC的来源、制备方法以及表面改性方法，根据近年来国内外对CNC增强生物可降解复合纤维的研究，总结了CNC对生物可降解复合纤维热性能、力学性能、吸水性和抗菌性的影响。     

丙烯酸原位聚合改性纤维素纳米晶体/聚乙烯醇复合膜的制备及性能

利用丙烯酸原位聚合和纤维素纳米晶体与聚乙烯醇复合制备聚乙烯醇-聚丙烯酸-纤维素纳米晶体(PVA-(PAACNC))复合膜。通过傅里叶变换红外光谱、扫描电子显微镜分析、接触角测试、拉伸试验和透光率测试考察了CNC和PAA的共同添加对复合膜结构形态、耐水性、力学性能和透明性的影响。结果表明,与纯PVA膜相比,改性复合膜仍然保持较高的透光率,在可见光低波段最低只降低5.6%;表面疏水性得到改善,接触角提高了40°以上;只用CNC改性时,所得的PVA-CNC复合膜中CNC的团聚现象比较严重,且力学性能对环境湿度非常敏感;同时用PAA和CNC改性时,所得复合膜中CNC的团聚现象得到明显抑制,在100RH%湿态环境下仍保持较好的力学性能,且断裂伸长率大幅提高。     

CNC/甘油湿敏防伪包装膜

目的 将纤维素纳米晶体(Cellulosenanocrystals,CNC)悬浮液与甘油共混制备光学性质不同的手性向列型CNC/甘油复合膜,以期用于包装防伪.方法 通过硫酸水解法制备CNC,测定其粒径、薄膜的微观结构、偏光性能、最大反射波长和热质量损失性能;采用蒸发干燥自组装法将CNC悬浮液与甘油以不同比例共混制备CNC/甘油复合膜,测定复合膜的光学性能和湿敏特性.结果 纤维素纳米晶体的平均粒径为220 nm,Zeta电势值为?32 mV,结晶度为81.88％,CNC悬浮液干燥成膜后具有鲜艳的彩虹色,偏振光显微镜下具有双折射效应,薄膜截面具有胆甾相液晶的层状结构,螺距为178 nm.随着甘油量添加量从0.2 g增至1.2 g,复合膜的最大反射波长从200 nm向620 nm移动,出现明显的波长红移现象.CNC/甘油复合薄膜对水感应迅速,干燥的复合薄膜在遇水时颜色发生可逆変化.结论 甘油能够在一定范围内调控纤维素纳米晶薄膜的反射波长,且具有颜色可逆的湿敏快速响应能力.     

丙烯酸原位聚合改性纤维素纳米晶体/聚乙烯醇复合膜的制备及性能EI北大核心CSCD

利用丙烯酸原位聚合和纤维素纳米晶体与聚乙烯醇复合制备聚乙烯醇-聚丙烯酸-纤维素纳米晶体(PVA-(PAACNC))复合膜。通过傅里叶变换红外光谱、扫描电子显微镜分析、接触角测试、拉伸试验和透光率测试考察了CNC和PAA的共同添加对复合膜结构形态、耐水性、力学性能和透明性的影响。结果表明,与纯PVA膜相比,改性复合膜仍然保持较高的透光率,在可见光低波段最低只降低5.6%;表面疏水性得到改善,接触角提高了40°以上;只用CNC改性时,所得的PVA-CNC复合膜中CNC的团聚现象比较严重,且力学性能对环境湿度非常敏感;同时用PAA和CNC改性时,所得复合膜中CNC的团聚现象得到明显抑制,在100RH%湿态环境下仍保持较好的力学性能,且断裂伸长率大幅提高。     

纳米纤维素增强淀粉食品包装材料的研究进展

目的 为了解决纯淀粉材料力学性能低、脆性大等缺点,探索纳米纤维素对淀粉膜材料的影响,为食品包装材料领域和替代传统石油基的高分子材料方向提供新的思路。方法 通过跟进国内外纳米纤维增强淀粉相关研究和应用进展,概括3种纳米纤维素的性能,介绍淀粉食品包装材料未来将面临的挑战和机遇,重点分析纳米纤维素对淀粉膜性能的影响。结论 纤维素纳米纤维（CNF）、纤维素纳米晶（CNC）和微晶纤维素（MCC）对淀粉进行增强后,淀粉复合材料的力学性能、阻隔性能和热学性能均得到改善,纳米纤维素增强淀粉食品包装材料在未来食品包装领域将得到扩展。     

载银聚乙烯醇/纳米晶纤维素/氧化石墨烯复合膜的制备及性能研究

首先通过溶液共混浇铸成膜法制备了聚乙烯醇/纳米晶纤维素/氧化石墨烯(PVA/CNC/GO)复合膜,随后将其浸泡在AgNO3的乙醇/水混合溶液中,通过PVA还原Ag+制得了负载Ag的PVA/CNC/GO复合膜。使用扫描电子显微镜、紫外-可见分光光度计和万能材料试验机等手段对复合膜的结构与性能进行表征,结果表明:当CNC和GO质量比为1∶2时,Ag负载量达到最大值9.51%。所制备的载Ag复合膜对大肠杆菌和金黄色葡萄球菌均具有优异的抗菌活性,同时具有良好的机械强度和耐水性。     

纳米纤维素晶/醋酸纤维素共混超滤膜材料的研究

采用浸没沉淀相转化法制备了纳米纤维素晶(CNC)/醋酸纤维素(CA)完全环境友好的共混膜材料,考察了在铸膜液中添加不同质量分数的CNC对共混膜各方面性能的影响。通过超滤装置测定了共混膜的水通量、截留率、含水率和孔隙率;通过万能试验机、环境扫描电子显微镜(SEM)、热重分析仪(TGA)对超滤膜进行了力学性能、形貌结构和热稳定分析。结果表明,随着CNC含量增加,共混膜的孔隙率呈增长趋势,由40.8%提高到66.4%,大孔由原来的规则圆形漏斗状变为狭长椭圆状且互相连通,水通量和拉伸强度呈先上升后减小的趋势。当CNC添加量为0.5%时,共混膜综合性能最优,相比纯CA膜,水通量提高64.7%,拉伸强度提高70%,热稳定性也得到增强。     

聚氨酯弹性体/纤维素纳米晶体复合材料的制备及性能研究

通过浓硫酸水解脱脂棉制备纤维素纳米晶体(CNC),并用3-氨基丙基三乙氧基硅烷(APTS)对其进行表面修饰。以4,4-二苯基甲烷二异氰酸酯(MDI)、聚四氢呋喃(PTMG)、CNC、1,4-丁二醇(BD)为原料制备聚氨酯弹性体/纤维素纳米晶体(PUE/CNC)复合材料,研究了CNC用量对PUE/CNC复合材料性能的影响。结果表明:当CNC用量达到1%(wt,质量分数,下同)时,复合材料的拉伸强度和断裂伸长率分别提高了178%和97.5%,热性能也有所提高;但CNC用量超过1.5%后,复合材料的力学性能下降,热性能仍保持提升。     

Introducing cellulose nanocrystals in sheet molding compounds (SMC)

The mechanical properties of short glass fiber/epoxy composites containing cellulose nanocrystals (CNC) made using sheet molding compound (SMC) manufacturing method as well as the rheological and thermomechanical properties of the CNC-epoxy composites were investigated as a function of the CNC content. CNC up to 1.4 wt% were dispersed in the epoxy to produce the resin for SMC production. The addition of CNC in the resin increased its viscosity and slightly reduced the heat of reaction during the polymerization without altering the curing time and temperature and the effective pot life of the resin. The incorporation of 0.9 wt% CNC in the SMC composite resulted in increases in elastic modulus and tensile strength by ∼25% and ∼30% and in flexural modulus and strength by ∼44% and ∼33% respectively. Concentrations of CNC up to 0.9 wt% in the SMC composite did not alter the impact energy.     

氧化石墨烯-SiO2杂化材料对环氧树脂拉伸性能的影响

为了提高环氧树脂的力学性能,采用一步合成法制备得到氧化石墨烯(GO)-SiO₂(GO-SiO₂)杂化材料,利用扫描电子显微镜(SEM)对杂化材料的形貌进行表征,成功制得了具有三维结构的GO-SiO₂杂化材料;将GO、SiO₂颗粒和GO-SiO₂以相同的含量(质量分数均为0.1%)添加到环氧树脂中制备复合材料,利用万能强力仪测试复合材料的拉伸性能,比较3种填料对树脂基复合材料拉伸性能的影响;再分别将质量分数为0.1%、0.3%和0.5%的GO-SiO₂添加到环氧树脂中制备GO-SiO₂/环氧树脂复合材料,比较不同质量分数的GO-SiO₂对树脂基复合材料拉伸性能的影响;利用SEM对拉伸样条的断截面进行扫描测试,分析了不同种类和不同比例的填料对树脂基复合材料的增强增韧效果,并分析其增强增韧机制。结果表明: GO-SiO₂的增强增韧效果明显优于GO和SiO₂颗粒,当GO-SiO₂的添加质量分数为0.3%时,其增强增韧效果最佳。     

Gradient of nanomechanical properties in the interphase of cellulose nanocrystal composites

The nanoscale transitional zone between a nanofiber and surrounding matrix (interphase) defines the ultimate mechanical characteristics in nanocomposite systems. In spite of this importance, one can hardly find quantitative data on the mechanical properties of this transitional zone in the cellulose–nanofiber composites. In addition, most of the theoretical models to predict the mechanical properties of interphase are developed with the assumption that this transitional zone is independent of the nanofiber size. In the current study, we show that the mechanical properties of interphase in cellulose nanocrystal (CNC) composites can be quantitatively characterized and the correlation with the size of CNCs can be mapped. The peak force tapping mode in atomic force microscope (AFM) was used to characterize deformation, adhesion, and modulus gradient of the interphase region in poly(vinyl alcohol) (PVA)–poly(acrylic acid) (PAA)–cellulose nanocrystal (CNC) composites. In comparison to the polymer matrix, the adhesion force of CNC was lower. The average elastic modulus in the interphase varied from 12.8 GPa at the interface of CNC to 9.9 GPa in PVA–PAA matrix. It was observed that the existence of PAA increased the gradient of mechanical and adhesion properties of the interphase zone. This occurs due to the variation in the ester linkage density from the CNC interface to the polymer matrix. Finally, it is shown that interphase thickness is higher for CNCs with larger diameter.     

不同秸秆增强环氧树脂复合材料的力学性能研究

秸秆具有生物降解、绿色环保等特性,且来源丰富,在绿色纺织复合材料领域受到广泛关注。本文采用真空辅助法制备了长芦苇秆、麦秆、高粱秆、稻草秆增强环氧树脂复合材料,研究了芦苇秸秆在整体和劈裂状态下复合材料的力学性能,并比较了在劈裂状态下芦苇秸秆和其他3种秸秆增强复合材料的力学性能及形态特征,分析了4种秸秆的红外光谱、表面润湿性、表面元素及微观结构。结果表明:4种秸秆均有相似的振动吸收峰位置,且它们表面微观结构差异较大,但其相同之处是表面均有硅元素、氧元素以及碳元素。同时4种秸秆都具有疏水性,芦苇秆、高粱秆、麦秆和稻草秆与水的接触角依次降低。在力学性能上,由于纤维素纤维在秸秆内合理有效分布使其出现结构物效应,秸秆增强复合材料的弯曲性能较拉伸性能具有明显的优势,同时芦苇秆劈材增强环氧树脂复合材料的拉伸强度和弯曲强度比芦苇秆复合材料高165.07%、55.72%。在4种秸秆劈材复合材料中,芦苇秆劈材复合材料的拉伸、弯曲性能最好,其次是稻草杆、高粱杆、麦秆复合材料。秸秆增强复合材料的开发有利于提高秸秆资源利用率,为复合材料的开发利用提供了新路径。     

表面官能团化多壁碳纳米管/环氧树脂复合材料的制备及性能

本文首先将多壁碳纳米管(MWNT)进行表面化学修饰,接入羧基、胺基等官能团,采用红外光谱进行了表征.以纯化后的MWNT和表面化学修饰的MWNT作为填料,制备了MWNT /环氧树脂复合材料,研究了MWNT的加入对环氧树脂的力学性能、电学性能、热稳定性和玻璃化转变温度等的影响,并利用场发射电镜观察了胺基化MWNT在环氧树脂基体中的分散情况.     

The impact of fluorinated MWCNT additives on the enhanced dynamic mechanical properties of e-beam-cured epoxy

Multi-walled carbon nanotubes were embedded into e-beam-cured epoxy resin to improve the mechanical properties of epoxy resin. The surfaces of these carbon nanotubes were modified using a fluorination treatment to improve their dispersion and adhesion in epoxy resin. The dynamic mechanical properties of epoxy/carbon nanotube composites were investigated at various heating rates and frequencies. As an effect of fluorination treatment, the semi-ionic bond of C–F on the surface of multi-walled carbon nanotubes played an important role in the improved dispersion and adhesion of carbon nanotubes into the epoxy resin. The storage modulus and loss modulus of the composites increased with higher applied frequency. The activation energy of the composites was increased by the effects of a higher heating rate due to the slow heat transfer in the epoxy/carbon nanotube composites. Eventually, the dynamic mechanical properties of the investigated epoxy were significantly improved by the carbon nanotubes dispersed therein via the fluorination treatment.     

石墨烯微片表面接枝PMMA及其环氧树脂复合材料性能

利用石墨烯微片（GNPs）表面羟基与硅烷偶联剂反应,并通过原子转移自由基聚合（ATRP）方法在GNPs表面接枝了聚甲基丙烯酸甲酯（PMMA）。应用扫描电子显微镜、透射电子显微镜、红外光谱和X射线衍射方法分析了化学接枝前后GNPs的微观结构变化。将接枝PMMA的GNPs加入环氧树脂中,研究其对环氧树脂力学性能与尺寸稳定性的影响。研究结果表明,与原始GNPs相比,表面接枝PMMA的GNPs对环氧树脂力学性能的增强作用更明显。添加质量分数为0.5%的GNPs-PMMA可以使环氧树脂拉伸强度和模量分别提高17.4%和75%,弯曲强度和模量也分别增加了6%和12%,同时可以使环氧树脂在低于玻璃化转变温度的线性热膨胀系数（CTE）降低25%。     

Effect of surface modification of bamboo cellulose fibers on mechanical properties of cellulose/epoxy composites

Bamboo cellulose fibers were treated with NaOH aqueous solution and silane coupling agent, respectively, before they were applied into epoxy composites. The effect of surface modification on mechanical properties was evaluated by tensile and impact tests under controlled conditions. Compared with the untreated cellulose filled epoxy composites, the NaOH solution treatment increased the tensile strength by 34% and elongation at break by 31%. While silane coupling agent treatment produced 71% enhancement in tensile strength and 53% increase in elongation at break. The scanning electron microscopy (SEM) was used to observe the surface feature of the cellulose fibers and the tensile fractures as well as cryo-fractures of the composites. The Fourier transform infrared (FTIR) was employed to analyze the chemical structure of the cellulose fibers before and after modifications. The results indicated different mechanisms for the two modifications of cellulose. The NaOH solution partly dissolved the lignin and amorphous cellulose, which resulting in splitting the fibers into smaller size. This led to easier permeating into the gaps of the fibers for epoxy resin (EP) oligmer and forming effective interfacial adhesion. Based on the emergence of Si–O–C and Si–O–Si on the cellulose surface, it was concluded that the enhancement of mechanical properties after coupling agent modification could be ascribed to the formation of chemical bonds between the cellulose and the epoxy coupled with the coupling agent.     

聚乳酸/酯化纤维素纳米晶体共混膜性能研究

以聚乳酸（PLA）为基体,酯化纤维素纳米晶体（ECNC）为添加剂,制备了PLA/ ECNC共混膜。探讨了原始纤维素纳米晶体（CNC）与ECNC对PLA膜的透光率、表面形貌、热稳定性、亲疏水性及力学性能的影响。结果表明,与CNC相比,ECNC与PLA的相容性提高,透光率、热稳定性及力学性能也显著增强;经酯化的纤维素纳米晶体能降低CNC的亲水性,从而增强与PLA的界面黏合力,使CNC在PLA共混膜中的质量分数由小于1%提高到5%。该PLA/ECNC共混膜在包装塑料领域具有潜力,为制备出性能更加优良的可降解包装用塑料提供了一种简单可行的方法。     

Improvements in mechanical properties of carbon fiber-reinforced epoxy composites: A microwave-assisted approach in functionalization of carbon fiber via diamines

A microwave-assisted approach was introduced for functionalization of carbon fibers (CFs) via aliphatic and aromatic diamines in order to enhance the interactions between CF filaments and epoxy resin. CFs was successfully functionalized via one monoamine and three diamine functions. Qualitative (FT-IR) and quantitative (TGA) characterizations have been performed to study the effect of operational parameters, such as retention time and microwave output power, on functionalization degree of CFs. Single fiber tensile testing was employed to investigate possible disruption of CF structure during the functionalization. Moreover, wettability of functionalized CFs was characterized in order to assay the compatibility of functionalized CF with epoxy resin. Mechanical properties of CF-reinforced composites also evaluated for all functionalized CFs. Results revealed that the proposed functionalization procedure is able to highly functionalize the CFs without any discernable structural disruption. Moreover, functionalized CFs demonstrates better compatibility with epoxy resin which led to considerable improvements in mechanical properties of composites (60%). The reinforcing mechanism of different aliphatic and aromatic diamines was also compared in detail.