偶联剂Si69改性秸秆纳米纤维素对炭黑补强天然橡胶性能的影响

采用偶联剂Si69对棒状秸秆纳米纤维素(SNC)进行改性,得到改性棒状秸秆纳米纤维素(MSNC),研究MSNC对炭黑(CB)补强天然橡胶(NR)性能的影响。结果表明:MSNC与橡胶基体的相容性较好;与CB/SNC/NR复合材料相比,CB/MSNC/NR复合材料的交联密度较大,能在保持较好抗湿滑性能的同时降低滚动阻力,具有更强的交联网络和更多的受限橡胶分子,热稳定性更好;用量比为35/10/100的CB/MSNC/NR复合材料物理性能最佳。     

天然橡胶/纤维素纳米丝增韧增强聚乳酸研究

通过溶液共混-共沉淀法制备了天然橡胶/纤维素纳米丝(NR/CNF)复合物,并将该复合物与聚乳酸(PLA)熔融共混,制备得到PLA/NR/CNF共混物。采用扫描电镜对PLA/NR/CNF共混物的断面形貌进行了表征,发现该共混物在脆断过程中,由于CNF与PLA的界面结合力较弱,会随着橡胶分散相一起脱落,从而形成较多的孔洞。拉伸测试结果表明,PLA/NR/CNF共混物的拉伸模量和拉伸强度均高于PLA/NR共混物,但是断裂伸长率有所下降,说明CNF对共混体系具有增强的效果。热失重测试结果表明,NR和CNF的引入会使PLA的初始分解温度降低。     

纳米纤维素/天然橡胶复合材料的制备及表征

采用共混法制备不同比率含量的纳米纤维素/天然橡胶(NCC/NR)复合材料,通过扫描电镜、力学性能、热稳定性以及动态力学性能的测定分析表明:纳米纤维素能较均匀分散在橡胶基质中,对天然橡胶起到较好的补强效果,复合材料的储能模量逐步增大,损耗因子逐步减小,纳米纤维素的加入对天然橡胶的热稳定性影响不大。     

纤维素补强天然橡胶的应用与研究进展

介绍了5种纤维素材料：微晶纤维素(MCC)、纤维素纳米晶(CNC)、纤维素纳米纤维(CNF)、纤维素纳米晶须(CNW)以及细菌纤维素(BC)补强天然橡胶的应用研究,总结了纤维素材料对天然橡胶性能的影响,并对其应用前景进行了展望。     

纳米纤维素三维网状增强聚乙烯醇复合材料的研究

通过一次性超细研磨方法得到纳米纤维素(CNF),其直径分布均匀,大小为15 nm,且长径比大于10 000,呈三维网状结构,成膜后呈高强度(210 MPa)、高模量(11.8 GPa)。将上述CNF与聚乙烯醇(PVA)在一定条件下混溶后制得CNF/PVA复合材料。通过场发射扫描电镜和静态热机械分析等手段研究了复合材料的形貌特征、热膨胀性及力学性能。扫描电镜测试结果表明,CNF与PVA混溶均匀,相互缠绕在一起形成互穿三维网状结构。与纯PVA比较,CNF/PVA复合材料的热膨胀系数(45×10-6K-1)降低了30%,拉伸强度(110 MPa)提高了45%,杨氏模量(6.6 GPa)提高了50%。     

硬脂酸改性纳米纤维素晶体/纳米ZnO复合材料的制备与表征

通过硫酸水解微晶纤维素法制备纳米纤维素晶体(CNC),将其与一定量的纳米氧化锌复合制得复合材料;然后使用一定量的硬脂酸对复合材料进行改性,并将所得改性后的溶胶在120℃下鼓风干燥2 h,即可得到硬脂酸改性的CNC/纳米ZnO复合疏水材料。并采用X-射线衍射仪、场发射扫描电镜、傅里叶红外光谱和接触角分析仪对复合材料的表面形貌和疏水性进行了表征及揭示。结果表明,CNC/纳米ZnO复合材料构成微/纳米双重粗糙结构,经硬脂酸表面改性后引入了憎水基团甲基,使其具备一定的疏水性能,在最优制备工艺条件下疏水角可高达到145.6°。     

酰胺化纳米晶纤维素提高乙烯-醋酸乙烯酯共聚物薄膜阻透性的研究

合成了三种酰胺化纳米晶纤维素,并采用溶液共混成膜法制备了酰胺化纳米晶纤维素（CNC）/乙烯醋酸乙烯醋共聚物(EVA)复合膜材料。通过紫外-可见分光光度计、电子万能试验机和透湿仪研究了酰胺化CNC/ EVA复合膜的光学性能、力学性能以及水蒸气阻隔性,并通过原子力显微镜研究热压处理的EVA复合膜的表面形貌。结果表明,添加三种不同碳链的酰胺化CNC都使 EVA膜的透光率有所降低,当添加量为5 %时,EVA膜透光率仍高达90%。一定程度的热压能够让酰胺化纳米晶纤维素在EVA基体中分散更均匀,使EVA复合膜的透光率提高了2%～3%;随着纳米晶纤维素含量的逐渐增加,三种酰胺化CNC/EVA膜的拉伸强度均逐渐增强,透湿率（WVTR值）均减小;酰胺化CNC含量相同时, 十六胺改性的纳米晶纤维素(CNC-N16)/EVA复合膜的力学性能和水蒸气阻隔效果优于相应的十二胺和正辛胺。     

母粒法制备聚丙烯/炭化纤维素纳米晶复合材料

将冷冻干燥的纤维素纳米晶(CNC)进行高温处理,制成炭化纤维素纳米晶(CCNC),采用超声母料法将CCNC以母料的形式与聚丙烯(PP)制成PP/CCNC复合材料。使用SEM观察了CNC炭化前后的形貌变化情况以及CCNC在复合材料的分散情况;通过拉伸性能测试考察了CCNC对复合材料力学性能的影响;采用DMA测试了CCNC对复合材料黏弹性的影响。SEM结果表明:CNC经过冷冻干燥、高温炭化后,由纳米棒状结构变成有序带状结构;复合材料的断面表明CCNC可以以纳米片的形式分散在PP基体中。拉伸测试结果表明:CCNC的加入使复合材料的拉伸强度和断裂伸长率下降,模量上升。强度下降表明CCNC与基体的界面相容性有待进一步提高。DMA测试结果发现:CCNC可明显增加复合材料的储能模量,30%的CCNC即可使模量提高135.7%;复合材料的损耗模量随着CCNC的加入呈现上升趋势。     

MC尼龙6/纤维素纳米晶复合材料原位制备及性能

首先对纤维素纳米晶(CNC)分别进行80℃烘箱干燥24 h和120℃抽真空除水48 h两种预处理,然后将CNC分散到己内酰胺(CL)中并选用低碱性的乙基溴化镁作为引发剂,利用CL阴离子开环聚合制备得到单体浇铸尼龙6/CNC(MCPA6/CNC)复合材料.研究CNC不同预处理方式和添加量对复合材料性能的影响.比较复合材料...     

精氨酸辅助制备白炭黑补强天然橡胶的研究

采用精氨酸辅助制备白炭黑(简称自制白炭黑),通过白炭黑分散液与天然胶乳混合和凝聚共沉,制备白炭黑/天然橡胶(NR)纳米复合材料,研究白炭黑对NR的补强效果。结果表明,与普通白炭黑相比,自制白炭黑具有较好的单分散性,在NR中分布更加均匀,分散程度更高;与普通白炭黑/NR纳米复合材料相比,自制白炭黑/NR纳米复合材料的硫化速率加快,强度性能明显提高,拉伸强度增大13. 6%,撕裂强度增大8. 8%。     

Surface modification of nanocrystalline cellulose and its application in natural rubber composites

As a biopolymer with high mechanical strength, nanocellulose was generally considered as a green filler for reinforcing polymer. In this study, nanocrystalline cellulose (NCC) isolated from softwood pulp was successfully modified by cetyltrimethyl ammonium bromide (CTMAB), a cationic surfactant, and the modified nanocrystalline cellulose (m-NCC) was used to reinforce natural rubber (NR). In this composite architecture, it was found that when the filler content was 5 or 10 phr, the surface modification of NCC improved the dispersion state of NCC in NR matrix and the interfacial interaction between NR and NCC. Therefore, the NR/m-NCC composites exhibited outstanding mechanical properties, and its tensile strength, elongation at break and tear strength was increased by 132.8, 20, and 66.1%, respectively, compared to pristine NR composites. Besides, the modified NCC could accelerate the vulcanization and improve wet-skid resistance and aging resistance of NR composites. It is envisioned that the modified NCC has the potential to be generalized to manufacturing other polymer matrix composites strengthened with nanocellulose.     

Flexible polyurethane foams reinforced with organic and inorganic nanofillers

The effect of three different types of cellulose nanofillers on the morphology, mechanical, and thermal properties of flexible polyurethane foam was studied. Cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), and cellulose filaments (CelFil) were used as fillers at 0.1–0.8 wt% loading levels. The comparison of the results showed that smaller loading levels resulted in foams with better performance in almost all cases. In the next step, the properties of foams containing CNC, CNF, or CelFil at 0.025%–0.1% loading levels were compared with those made with inorganic nanofillers including nanosilica (nSi), reduced graphene oxide, and halloysite nanotubes (HNT). Among all the properties evaluated, the tensile modulus of the foams was improved up to 40% by adding HNT at 0.05 wt% loading level whereas the addition of CNF resulted in a 44% increase in the compressive modulus of the foams at 0.1 wt% loading level.     

Preparation of treelike and rodlike carboxymethylated nanocellulose and their effect on carboxymethyl cellulose films

In this work, carboxymethyl cellulose (CMC) with low substitution degree, followed by different posttreatments, was applied to prepare treelike CMC nanofibrils (CMCNFs) and rodlike CMC nanocrystals (CMCNCs), and their performance in CMC composite film was evaluated simultaneously. From transmission electron microscopy results, it was found that the treelike CMCNCFs exhibited a lager aspect ratio compared to the rodlike CMCNCs. As for reinforcing CMC film, 4 wt% was the best adding amount, at this time, the tensile strength of CMC/CMCNFs and CMC/CMCNCs composite films was increased by 72.1% and 47.3%, respectively. Moreover, adding these nanofillers to CMC also could enhance the thermal stability of composite films slightly, while the transmittance of composite films was reduced at the same time. In addition, CMC/CMCNFs film was designed as a packaging box to determine its performance. Therefore, this study could reveal the differences of properties for composites with different types of nanocellulose and provide a foundation for further application of nanocellulose.     

Novel CNC/silica hybrid as potential reinforcing filler for natural rubber compounds

This work describes the development of a low-density, renewable, and high reinforcing filler for natural rubber (NR) compounds. The cellulose nanocrystal (CNC)-based hybrid filler was synthesized by decorating the surface of CNCs with silica using a simple and efficient coprecipitation method. The properties of the prepared hybrid were investigated by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, nitrogen physisorption measurements, and Thermogravimetric analysis. Then, the prepared hybrid was incorporated in NR using two different approaches, namely, dry mixing and coprecipitation. The dynamic and tensile mechanical properties of the hybrid/NR compounds were evaluated indicating that: the coprecipitation method was found much more effective for homogeneous dispersion and the CNC/silica hybrid provided quite higher reinforcement to NR than reference silica; however, much lower density of the final compounds was obtained. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48332.     

Melt compounded nanocomposites with semi‐interpenetrated network structure based on natural rubber,polyethylene, and carrot nanofibers

The present study deals with the processing and characterization of cellulose nanocomposites natural rubber (NR), low‐density polyethylene (LDPE) reinforced with carrot nanofibers (CNF) with the semi‐interpenetrated network (S‐IPN) structure. The nanocomposites were compounded using a co‐rotating twin‐screw extruder where a master‐batch of NR and CNF was fed to the LDPE melt, and the NR phase was crosslinked with dicumyl peroxide. The prepared S‐IPN nanocomposites exhibited a significant improvement in tensile modulus and yield strength with 5 wt % CNF content. These improvements are due to a better phase dispersion in the S‐IPN nanocomposites compared with the normal blend materials, as demonstrated by optical microscopy, electron microscopy and ultraviolet–visible spectroscopy. The S‐IPN nanocomposite also displayed an improved crystallinity and higher thermal resistance compared with NR, CNF, and the normal blend materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45961.     

Cellulose nanopapers as tight aqueous ultra-filtration membranes

Recently, we have demonstrated the use of wood-derived nanocellulose papers, herein termed nanopapers, for organic solvent nanofiltration applications. In this study, we extend the use of these nanopapers to tight ultrafiltration (UF) membranes. The feasibility of such nanopaper-based UF membranes intended for use in water purification is shown. Four types of nanocelluloses, namely bacterial cellulose, wood-derived nanocellulose, TEMPO-oxidized cellulose nanofibrils and cellulose nanocrystals, were used as raw materials for the production of these nanopaper-based membranes. The resulting nanopapers exhibit a transmembrane permeance in the range of commercially available tight UF membranes with molecular weight cut-offs ranging from 6 to 25 kDa, which depends on the type of nanocellulose used. These molecular weight cut-offs correspond to average pore sizes of a few nanometres. The rejection performance of the nanopapers is on the border of nanofiltration and UF. We demonstrate that the pore size of the nanopapers can be controlled by using different types of nanocellulose fibrils.     

Effect of processing techniques and residual solvent on the thermal/mechanical properties of epoxy-cellulose nanocrystal nanocomposites

Epoxy nanocomposites reinforced with 0–5 wt% cellulose nanocrystal (CNC) were fabricated by solution casting method. The CNCs were first dispersed in the hardener together with a co-solvent and subsequently mixed with epoxy monomer using two different protocols: bulk mixing and dropwise mixing. The dropwise mixing resulted in more homogeneously-dispersed CNCs and provided better mechanical properties, particularly higher tensile strength, tensile modulus, and work of fracture with increasing CNC content. Investigation of various CNC/hardener mixtures with different solvent content showed that the residual solvent in the composite mixture had an impact on the curing behavior of the nanocomposite epoxy and may have lowered its crosslinking density, leading to T_g depression. However, the presence of the solvent was shown to be essential for the preparation of a well-dispersed CNC phase in the hardener solution, and to form homogenous composite mixtures. Our results show that the reinforcement effect due to higher CNC concentration is more significant than the solvent effect in the hardener system and shows greater improvement in mechanical properties. The CNC component reversed the solvent plasticizing effect through its superior mechanical reinforcing effects, and the dropwise mixing process led to better dispersion compared with the bulk mixing process.     

Development and molecular dynamics simulation of green natural rubber composites with modified sisal microcrystalline cellulose

In this study, green composites were prepared using natural rubber (NR) as the matrix and the sisal microcrystalline cellulose (MCC) as the filler. Three modifying agents oleic acid (OA), γ-aminopropyltriethoxylsilane (KH550), and bis-γ-(triethoxysilylpropyl)-tetrasulfide (Si69) were individually tested to modify the MCC to improve the interfacial compatibility of the NR and MCC. Combined with modern instrumental analysis technology and molecular dynamics simulation, the reinforcing effect and microscopic mechanism of modified MCC on NR were analyzed. The structure–activity relationship of NR and MCC composites was further revealed, and the interaction between the two components was clarified. At the same time, the reinforcing and compatibilizing effect of three kinds of modified MCC in NR matrix were also revealed. The results showed that the properties of NR/Mod-MCC composites were better than those of NR/MCC composites, where NR/OA-MCC presented the highest tensile strength, followed by NR/Si69-MCC. In addition, NR/Si69-MCC exhibited higher elongation at break and NR/KH550-MCC exhibited higher vulcanization characteristics. Molecular model systems were constructed through molecular dynamics simulation to investigate the interactions between the three modified cellulose molecules and the NR molecules. OA-cellulose has a better interaction with NR than KH550-cellulose and Si69-cellulose, The simulation results were consistent with the experimental results.     

Facile Synthesis and Characterization of Palm CNF-ZnO Nanocomposites with Antibacterial and Reinforcing Properties

Cellulose nanofibers (CNF) isolated from plant biomass have attracted considerable interests in polymer engineering. The limitations associated with CNF-based nanocomposites are often linked to the time-consuming preparation methods and lack of desired surface functionalities. Herein, we demonstrate the feasibility of preparing a multifunctional CNF-zinc oxide (CNF-ZnO) nanocomposite with dual antibacterial and reinforcing properties via a facile and efficient ultrasound route. We characterized and examined the antibacterial and mechanical reinforcement performances of our ultrasonically induced nanocomposite. Based on our electron microscopy analyses, the ZnO deposited onto the nanofibrous network had a flake-like morphology with particle sizes ranging between 21 to 34 nm. pH levels between 8–10 led to the formation of ultrafine ZnO particles with a uniform size distribution. The resultant CNF-ZnO composite showed improved thermal stability compared to pure CNF. The composite showed potent inhibitory activities against Gram-positive (methicillin-resistant Staphylococcus aureus (MRSA)) and Gram-negative Salmonella typhi (S. typhi) bacteria. A CNF-ZnO-reinforced natural rubber (NR/CNF-ZnO) composite film, which was produced via latex mixing and casting methods, exhibited up to 42% improvement in tensile strength compared with the neat NR. The findings of this study suggest that ultrasonically-synthesized palm CNF-ZnO nanocomposites could find potential applications in the biomedical field and in the development of high strength rubber composites.     

Chemically modified cellulose nanofibril as an additive for two‐component polyurethane coatings

The increasing demand for the use of sustainable materials in industrial applications has created an urge to develop technologies that enable the use of biopolymers such as cellulose for the improvement of properties of commercial products. In this study, the potential of the silyl functionalized cellulose nanofibrils (CNF) as a reinforcing additive for the water‐ and solvent‐based two‐component polyurethane (PU) lacquer coatings was evaluated. The addition of the silylated CNF improved the abrasion resistance, strength, and elasticity of the PU coatings. When using the silylated CNF as an additive, the adhesion of the PU coatings was retained. The oxygen permeation rate of the silylated CNF films was strongly influenced by the nature of the solvent. The silylated CNF showed potential as a reinforcing additive even at low loadings in the two‐component PU lacquers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44801.