Effect of Fiber Loadings and Treatment on Dynamic Mechanical, Thermal and Flammability Properties of Pineapple Leaf Fiber and Kenaf Phenolic Composites

This study deals with the analysis of dynamic mechanical,thermal and flammability properties of treated and untreated pineapple leaf fiber(PALF)and kenaf fiber(KF)phenolic composites.Results indicated that storage modulus was decreased for all composites with increases in temperature and pattern of slopes for all composites,having almost the same values of E′at glass transition temperature(Tg).The peak of the loss modulus of pure phenolic composites was shown to be much less.After the addition of kenaf/PALF,peaks were higher and shifted towards a high temperature.The Tan delta peak height was low for pure phenolic composites and maximum for 60%PALF phenolic composites.Cole-Cole analysis was carried out to understand the phase behavior of the composite samples.Thermogravimetric analysis(TGA)results indicated that pure phenolic composites have better thermal stability than PALF and kenaf phenolic composites.Vertical and horizontal UL-94 tests were conducted and showed pure phenolic resin is highly fire resistant.The overall results showed that treated KF composites enhanced the dynamic mechanical and thermal properties among all PALF/KF composites.

Effect of Hybridization on the Mechanical Properties of Pineapple Leaf Fiber/Kenaf Phenolic Hybrid Composites

In this study,pineapple leaf fiber(PALF),kenaf fiber(KF)and PALF/KF/phenolic(PF)composites were fabricated and their mechanical properties were investigated.The mechanical properties(tensile,flexural and impact)of the PALF/KF/PF hybrid composites were investigated and compared with PALF/KF composites.The 3P7K exhibited enhanced tensile strength(46.96 MPa)and modulus(6.84 GPa),flexural strength(84.21 MPa)and modulus(5.81 GPa),and impact strength(5.39 kJ/m2)when compared with the PALF/PF and KF/PF composites.Scanning electron microscopy(SEM)was used to observe the fracture surfaces of the tensile testing samples.The microstructure of the 7P3K hybrid composite showed good interfacial bonding and the addition of KF improved the interfacial strength.It has been concluded that the 3P7K ratio allowed obtaining materials with better mechanical properties(tensile,flexural and impact strengths)than PALF/PF and KF/PF composites.The results obtained in this study will be used for further comparative study of untreated hybrid composites with treated hybrid composites.

Enhancement of the Mechanical Performance of SiCf/Phenolic Composites after High-temperature Pyrolysis Using ZrC/B_(4)C Particles

The composites were prepared by modifying silicon carbide fiber with particles of zirconium carbide(ZrC)and boron carbide(B_(4)C)and incorporating them into a phenolic resin matrix.The influence of ZrC and B_(4)C on the mechanical performance of SiCf/phenolic composites after high-temperature pyrolysis was studied through flexural performance test.The results show that the composite material has good thermal stability and high-temperature mechanical properties.After static ablation at 1400℃ for 15 minutes,the flexural strength of the composite material reaches 286 MPa,which is still 7.3%higher than at room temperature,indicating that the composite material still has good mechanical properties even after heat treatment at 1400℃.

Effect of KCI on Growth of Carbon Fibers During Carbonization of Phenolic Resin

Effects of the KCI additions （1%, 3%, 5% and 7% of the phenolic resin mass ） on phase composition and microstructure of the resin carbon and the growth mechanism of carbon fibers were investigated by using commercial liquid phenolic resin as carbon source and micron-scaled KCl us catalyzer, mixing, hexamethylene- tetramine solidification treating, carbon-embedded firing at 1 000 ℃ for 3 h in order to accelerate the graphitization of phenolic resin during carbonization. The results show that the graphitization degree of resin carbon is im- proved by catalysis of KCl, numerous carbon fibers with 30 - 200 nm in diameter and 10 - 20 μm in length and sheet-like carbon in situ grow in resin carbon. The opti- mal addition of KCl is 5% when lots of carbon fibers can be found in resin carbon, and doo2 diffraction peak of graphite appears obviously in the XRD pattern. The growth mechanism of carbon fiber is that the molten KCl at high temperatures absorbs carbonaceous gas from the decomposition of phenolic resin, accelerating the diffu- sion of solid C atoms in liquid KCl ; after the dissolution of C saturates, carbon atoms separate continuously in lo- cal parts to form carbon fibers or flakes ; meanwhile, the concentration gradient formed by local carbon atoms in the melt offers growth drive for the separation of carbon fibers or flakes on KCl surface.

Effect of electropolymer sizing of carbon fiber on mechanical properties of phenolic resin composites

Carbon fiber/phenolic resin composites were reinforced by the carbon fiber sized with the polymer films of phenol, m-phenylenediamine or acrylic acid, which was electropolymerized by cyclic voltammetry or chronopotentiometry. The contact angles of the sized carbon fibers with deionized water and diiodomethane were measured by the wicking method based on the modified Washburn equation, to show the effects of the different electropolymer film on the surface free energy of the carbon fiber after sizing by the electropolymerization. Compared with the unsized carbon fiber, which has 85.6°of contact angle of water, 52.2°of contact angle of diiodomethane, and 33.1 mJ/m2 of surface free energy with 29.3 mJ/m2 of dispersive components (γL) and 3.8 mJ/m2 of polar components (γsp), respectively. It is found that the electropolymer sized carbon fiber tends to reduce the surface energy due to the decrease of dispersiveγL with the increase of the polymer film on the surface of the carbon fiber that plays an important role in improving the mechanical properties of carbon/phenolic resin composites. Compared with the phenolic resin composites reinforced by the unsized carbon fiber, the impact, flexural and interlaminar shear strength of the phenolic resin composites were improved by 44 %, 68% and 87% when reinforced with the carbon fiber sized by the electropolymer of m-phenylenediamine, 66%, 100%, and 112% by the electropolymer of phenol, and 20%, 80 %, 100% by the electropolymer of acrylic acid. The results indicate the skills of electropolymerization may provide a feasible method for the sizing of carbon fiber in a composite system, so as to improve the interfacial performance between the reinforce materials and the matrix and to increase the mechanical properties of the composites.

Mechanical Properties of Phenolic-Resin Composites Reinforced with CF/BF Interlayer Hybrid Fibers

Phenolic-resin composites reinforced with carbon fiber（CF） and basalt fiber（BF） interlayer hybrid fibers plain fabric were fabricated.The tensile strength,compressive strength and interlaminar shear strength of the prepared composites were studied.The results indicated that hybrid fibers reinforced composites possessed the advantages of both CF and BF.When resin content was 35% by volume fraction,the comprehensive mechanical performance of BF/CF reinforced phenolic resin composites reached the optimal values with the warp and weft direction tensile strength,compressive strength and interlayer shear strength being 252 MPa and 487 MPa,105 MPa and 129 MPa,21 MPa and 20 MPa,respectively.The scanning electron microscope（SEM） observations showed that the BF/CF hybrid fibers reinforced composites had better interfacial adhesion.

Phenol Removal from Aqueous Solution Through Hollow Fiber Membrane Extraction

In this work, mass transfer mechanism was studied for 50%TBP (in kerosene)-phenol-water as the working system in different hydrophobic microporous hollow fiber modules. The effect of different operating conditions on the removal of phenol was analyzed. Solvent entrainment in this process was detected with MALVERN-2600 laser pellet diameter analytical equipment. Experimental results indicate the mass transfer coefficient is increased while the two phase flow rates are increased. With increases in the flow rate of the water phase, the removal ratio of phenol will be decreased. Highly effective removal of phenol could be reached by changing the experimental conditions and the module configuration. The solvent entrainment in the water phase in the membrane extraction process was found to be 5%—8% of that in conventional liquid-liquid extraction process. Thus, solvent pollution could be better controlled.

Extraction kinetics of phenol with N, N-di (1-methyl-heptyl)acetamide-kerosene using hollow fiber membrane extractor

Extraction kinetics of phenol with N,N-di(1-methyl-heptyl) acetamide-kerosene using hollow fiber membrane extractor has been studied. The rate regularities and kinetic types of forward and backward extraction were obtained respectively by determining the forward and backward extraction rate under various experimental conditions. The mass transfer mechanism was discussed. Both the forward and backward extraction of phenol might be controlled by diffusion processes, and the diffusion resistance for both forward and backward extraction mainly exists in aqueous phase. In addition, ways to optimize the extraction process of phenol were discussed as well.

毛竹纤维改性酚醛树脂运动装备专用胶黏剂制备研究

酚醛树脂具有良好的耐磨损性和热稳定性,常被用于粘接篮球鞋的碳纤维板、TPU板等。为降低酚醛树脂胶黏剂的制备成本并在一定程度上提升其综合性能,以毛竹纤维、苯酚、甲醛等为原材料制备了一种毛竹纤维改性酚醛树脂篮球鞋专用胶黏剂,对该胶黏剂的综合性能进行试验分析。结果表明:毛竹纤维、苯酚质量比为1.0:4.5,甲醛、氢氧化钠与苯酚摩尔比为1.8:0.4:1.0时,毛竹纤维改性酚醛树脂胶黏剂的综合性能最佳,可以更好地满足高端篮球鞋的需求。

粒径和含结合酚不溶性膳食纤维对白芸豆皮体外发酵特性的影响

为揭示不同粒径的白芸豆皮和含结合酚不溶性膳食纤维的体外发酵规律,本研究以白芸豆皮(WS)为原料,经过连续酶法提取得到含结合酚不溶性膳食纤维(IB),采用普通粉碎和超微粉碎方法对其进行改性,获得不同粒径分布的两组样品,利用扫描电子显微镜和激光共聚焦扫描显微镜对其微观形貌进行观察,并通过体外发酵实验和16S rRNA测序探究两组样品的酵解特性及其对肠道菌群组成丰度的影响。实验结果发现样品粒径越小,结合酚越均匀地分散于颗粒表面。WS和IB都具有慢发酵性,且其发酵速率和产酸量均随着粒径的减小而提高,菌群组成分析发现粒径越小的底物对Bacteroides丰度的促进效果也越显著,但是Lachnospira显示出了对较大粒度底物的偏好。结果表明IB可以促进Bacteroides、Bifidobacterium和Ruminococcaceae ruminococcus等有益菌的相对丰度,改善肠道微生物群的组成结构,其益生效应较相同粒径的WS更为显著。本研究可以为膳食纤维益生元效应的研究提供基础和方向,并可以指导膳食纤维的超微粉碎改性和白芸豆皮的综合利用。

连续法制备短切石英纤维/酚醛树脂预混料的固化反应动力学及其模压制品性能

采用连续浸胶法,使用自制的压辊式浸胶槽制备了短切石英纤维/酚醛树脂预混料,通过红外光谱法(FT-IR)、热重分析法(TG)和差示扫描量热法(DSC)对预混料进行了表征,并研究了其固化反应动力学。结果表明,溶剂乙醇影响石英纤维的浸胶过程,连续法制备的石英纤维/酚醛树脂预混料能够降低乙醇的影响;预混料的固化工艺参数为:凝胶温度108.40℃,固化温度183.04℃,后处理温度264.47℃;固化反应级数为0.95,固化反应动力学模型为:dα/dt=Aexp(-ΔE/RT)(1-α)n=4.3×10^(12)exp(-140.74/RT)(1-α)0.95。使用模压法对所制备的预混料进行压制,得到石英纤维/酚醛树脂复合材料的模压制品,该模压制品在800℃下的质量残留率为82.3%,拉伸强度为58 MPa,断裂伸长率为0.353%,剪切强度为105 MPa,线烧蚀率为0.088 mm/s,烧蚀表面形貌未见异常,结果表明采用连续法制备的石英纤维/酚醛树脂预混料的模压制品具有较好的耐热性、烧蚀性和力学性能。

膜传质强化催化臭氧氧化技术的研究与机理分析

为解决传统臭氧(O_(3))曝气技术O_(3)逸散及污染物处理效率不高等问题,以疏水性聚四氟乙烯(PTFE)中空纤维膜材料制成膜接触器,并进行膜接触O_(3)无气泡传质催化O_(3)氧化技术研究。以苯酚为污染物,通过对比实验、催化O_(3)氧化实验、动力学分析、自由基屏蔽实验、紫外-可见吸收光谱分析等对新技术的传质特性、氧化效果和氧化机理进行了研究。结果表明,相较于单独O_(3)氧化,催化氧化体系对苯酚的去除情况均存在不同程度的提升,其中α-Fe_(2)O_(3)表现出较高的O_(3)催化活性。屏蔽实验通过投加叔丁醇(TBA)和Na_(3)PO_(4)来屏蔽自由基和反应位点,COD去除率较正常实验时分别降低了21.05%和11.80%,说明催化剂表面的路易斯酸性位点是催生·OH的主要原因。膜接触O_(3)无气泡传质与α-Fe_(2)O_(3)催化O_(3)氧化具有良好的协同作用,高效去除苯酚的同时解决了O_(3)逸散问题。

酚醛纤维对芳氧基聚磷腈绝热层的性能影响研究

由于酚醛纤维具有优异的阻燃、耐烧蚀、隔热性能,研究酰胺改性剂处理后的酚醛纤维的性能,以及三种规格酚醛纤维(Pf-10、Pf-15和Pf-20)增强的芳氧基聚磷腈(PDPP)和三元乙丙(EPDM)绝热材料。结果表明,酰胺结构含量对酚醛纤维力学性能具有显著影响,Pf-15力学强度最优,为290.2MPa,伸长率为5.8%。不同结构的酚醛纤维增强PDPP的力学性能影响接近,PDPP/Pf-15材料的力学强度达8.6MPa,伸长率204%;同时,EPDM对纤维结构的选择性差异较大,Pf-15纤维补强的效果最优,拉伸强度可达16.1MPa。而随着酰胺含量的提高,酚醛纤维复合的芳氧基聚磷腈和三元乙丙绝热材料的线性烧蚀率均逐渐下降,PDPP/Pf-20和EPDM/Pf-20的线烧蚀率最低分别为0.0284mm/s和0.0156mm/s。对比烧蚀层形貌发现,PDPP/Pf比EPDM/Pf形成的绝热层炭层更坚固、结构更完整。

硝酸改性活性炭纤维对苯酚吸附性能研究

以粘胶基活性炭纤维(ACF)为吸附材料,通过硝酸改性得到ACF-1,对改性前后活性炭纤维吸附苯酚性能进行分析表征。结果表明:在酸性、中性和低温条件下利于活性炭纤维吸附苯酚,酸处理使活性炭纤维孔结构改变,表面含氧官能团增加。经过碱脱除再生3次后,ACF-1的吸附能力为初始吸附率的64.97%。吸附等温模型和动力学模型计算结果表明:准二级动力学模型和Langmuir吸附等温模型能够更好地描述活性炭纤维吸附苯酚过程。

碳纤维/酚醛树脂复合材料热解特性研究

使用热重-差热同步分析仪研究了某飞机框架部位用碳纤维/酚醛树脂复合材料在不同气氛和不同升温速率条件下的热分解特性。结果表明:在空气气氛下碳纤维/酚醛树脂复合材料热解反应分为3个阶段,在氮气气氛下热解反应分为2个阶段;随着升温速率的提高,氮气气氛下复合材料热解的初始分解温度、第2阶段起始温度都随着升温速率的提高而增加,2个阶段的热解温度范围都逐渐变宽且每一阶段的温度范围都要高于前一个热解阶段,最大失重速率温度也向高温方向移动,相同温度下失重明显变大。采用Kissnger法、FWO法、Starink法对碳纤维/酚醛树脂复合材料的热解动力学进行计算,得到其表观活化能。

石墨烯/酚醛复合纤维的制备及性能

石墨烯纤维是新一代柔性器件的潜力电极材料,制备同时具有良好力学性能和电化学性能的石墨烯基复合纤维是研究的重点。以改良的Hummers法制备的氧化石墨烯为基体,酚醛树脂为增强体,冰乙酸为凝固浴,通过非液晶湿法纺丝的方法制备了石墨烯/酚醛复合纤维,并对得到的石墨烯/酚醛复合纤维的表面形貌、力学性能和电化学性能进行了研究。结果表明,酚醛树脂通过氢键与石墨烯片层相结合,从而减少石墨烯片层间的堆叠,使复合纤维的表面褶皱丰富且均匀。通过调控酚醛树脂的含量,可以得到具有不同表面褶皱程度的复合纤维。随着酚醛树脂用量的增加,纺丝液浓度增大,挤出胀大现象明显,复合纤维片层间隙增大,表面沟壑加深,缺陷增加。石墨烯/酚醛复合纤维的拉伸强度随着酚醛树脂用量的增加呈现先增大后减小的趋势,酚醛树脂用量为10%时纤维的拉伸强度和拉伸弹性模量分别为65.53 MPa和672.91 MPa。得益于表面丰富均匀的褶皱,在电流密度为0.2 A/cm^(3)时,氧化石墨烯∶酚醛为100∶10时体积比电容为583.4 F/cm^(3),远高于纯石墨烯纤维。

谷物膳食纤维和酚类物质结合对肠道健康影响的研究进展

谷物是膳食纤维和酚类物质的良好来源,二者多以结合态形式存在,发挥调节肠道菌群及增强健康体质的作用。介绍了谷物膳食纤维和酚类物质的组分、结构及相互结合作用机制,阐述了膳食纤维与酚类物质在体内的吸收代谢途径,以及二者对肠道菌群、短链脂肪酸和酚酸的协同调节作用,为肠道健康领域功能性产品的开发和应用提供科学依据。

防热复合材料湿热老化行为与贮存寿命研究

目的研究装备用防热复合材料在贮存条件下的性能变化规律和寿命评估。方法在90℃/90%RH、80℃/90%RH、70℃/90%RH和80℃/80%RH共4个试验条件下,对玻璃纤维增强酚醛树脂防热复合材料开展加速湿热老化试验,借助红外光谱分析、扫描电镜、导热系数和力学性能测试研究老化过程中材料的质量、导热系数、力学性能、化学组分、微观形貌的变化规律,使用Peck模型对材料的贮存寿命进行计算。结果材料在老化初期吸湿后,质量快速增加,吸湿趋于饱和后,质量达到最大值。随着老化时间的延长,材料的质量呈缓慢下降趋势。不同湿热条件下,材料的导热系数未出现性能退化现象,材料的拉伸强度均出现退化现象,老化温度越高,性能下降越明显。在90℃/90%RH条件下,老化时间为80d时,材料强度大约下降到初始性能的53.4%。湿热老化过程中,红外光谱中960cm^(‒1)处特征峰逐渐减弱,直至完全消失,1098cm^(‒1)处特征峰相对强度逐渐变强。湿热老化后,材料部分玻璃纤维与基体间界面有微裂纹产生,拉伸断裂后,大部分纤维从树脂基体中拔出,表面平整光滑,黏连树脂较少。结论防热复合材料的老化是由氧化反应的化学老化与湿热条件导致界面脱黏、基体开裂、微裂纹等物理老化综合作用的结果。防热复合材料在20℃/60%RH条件的贮存寿命为36.3a,满足实际构件的设计寿命。

高性能内燃机用滤纸的制备及其对性能的影响

采用高强高模聚乙烯(UHMWPE)纤维与针叶木浆混抄,制备具有力学性能高、疏水性好和透气性适当的内燃机用滤纸。通过探讨原纸制备工艺、树脂浸渍和热压工艺对滤纸性能的影响,确定试验条件下的最佳参数,并采用相关手段表征了滤纸的力学性能、热稳定性能、孔径大小以及疏水性能。结果表明:在试验条件下,当UHMWPE纤维与针叶木浆的质量比为8∶2、针叶木浆打浆度为22°SR、分散剂PEO和增强剂CPAM相对于绝干浆的质量分数分别为0.5%和0.1%、热压时间为15 min、热压压力为10 MPa、热压温度为140℃时,制备的内燃机用UHMWPE滤纸性能最佳,其中,滤纸抗张指数为50.28 N·m/g,耐破度为503.55 kPa,接触角为123.52°且1 min内不渗透,熔点提高至155℃。

预制体制备条件下几种纤维增强酚醛树脂基复合材料性能比较研究

针对纤维增强酚醛树脂基复合材料,比较研究了四种不同结构预制体结构对这类复合材料性能的影响。对复合材料的密度、热稳定性、老化前后的力学性能以及比表面积及孔隙进行测试和分析,结果表明采用碳纤维网胎预制体制备的树脂基复合材料的F在各项性能测试中均表现优异。试件F重量轻,红外光谱分析揭示,采用碳纤维网胎的F试件在固化程度上超越了其他试件。比表面积及孔隙测试显示,F试件拥有更小且更加均匀分布的孔隙,其在力学性能和热稳定性方面优势明显。在力学性能方面,F试件的表现依旧优异,拉伸强度达到535.8 MPa,并且在200℃下热氧老化72 h后性能仍然稳定。SEM观察到碳纤维表面被树脂紧密黏附,纤维与树脂的界面相容性良好,宏观表现为拉伸强度和层间剪切强度高,可应用于对树脂基复合材料性能需求为轻量化、高强度和耐高温的场合。