连续式蒸汽爆破对PBS/棉秆皮纤维复合材料拉伸性能的影响

采用连续式蒸汽爆破装置对含水量分别为20%、30%、40%及50%的棉秆皮纤维进行预处理,并制备预处理后棉秆皮纤维填充量分别为20%、30%、40%及50%的聚丁二酸丁二醇酯(PBS)/棉秆皮纤维复合材料标准拉伸样条。从外观形态、扫描电镜观察方面分析棉秆皮纤维含水量对其蒸汽爆破改性效果的影响;通过扫描电镜观察分析复合材料拉伸断面形貌,从拉伸强度、拉伸模量及断裂伸长率三方面研究了连续式蒸汽爆破对PBS/棉秆皮纤维复合材料拉伸性能的影响。结果表明,连续式蒸汽爆破预处理方法能有效改善棉秆皮纤维与PBS基体的界面黏结;爆破前纤维含水量及爆破后纤维填充量对PBS/棉秆皮纤维复合材料拉伸性能起决定性作用;综合考虑,当爆破前纤维含水量为40%、爆破后纤维填充量为40%时,PBS/棉秆皮纤维复合材料拉伸性能最佳。     

PE-HD/棉秆皮复合材料的制备及其性能研究

采用蒸汽爆破对含水率分别为30 %、40 %、50 %的棉秆皮进行预处理,并与高密度聚乙烯（PE-HD）复合制备PE-HD/棉秆皮复合材料,研究了蒸汽爆破、棉秆皮含量、棉秆皮含水率对PE-HD/棉秆皮复合材料力学性能和密度的影响。结果表明,与未经蒸汽爆破处理的PE-HD/棉秆皮复合材料相比,蒸汽爆破预处理后制备的PE-HD/棉秆皮复合材料的力学性能更好;当棉秆皮含量为30 %时,复合材料的综合力学性能最佳;复合材料的拉伸强度随棉秆皮含水率的增加而提高;复合材料的弯曲强度在棉秆皮含水率为40 %时达到最大值。     

PP/棉秆皮纤维复合材料非等温结晶行为的研究

采用差示扫描量热法(DSC)研究了纯聚丙烯(PP)及PP/棉秆皮纤维复合材料的非等温结晶行为;研究了不同棉秆皮纤维含量对PP/棉秆皮纤维复合材料结晶行为的影响;并分别采用Avrami模型、Ozawa模型和Mo模型描述了PP/棉秆皮纤维复合材料的非等温结晶动力学.结果表明:PP结晶速率随棉秆皮纤维含量的增加而提高;棉秆皮纤维的存在提高了PP的结晶度,纤维含量对结晶度的影响较小.Avrami和Mo模型能够较好描述PP/棉秆皮纤维复合材料的非等温结晶动力学过程,而Ozawa模型则不适合.     

分次闪爆对棉秆皮纤维结构和性能的影响

为了提升棉秆皮的分离效果,提出了一种简便、有效的分次闪爆的棉秆皮分离方式。研究了延长保压时间闪爆和分次闪爆的纤维表面形貌差异以及分次闪爆次数对棉秆皮纤维结构、性能和分离效果的影响。结果表明,分次闪爆法提高了高温高压水蒸气喷射对棉秆皮纤维分离的作用,减少了高温对纤维的损伤。分次闪爆最佳次数为3次,所得纤维得率为32.45%,长度47.7 mm,细度50.4 dtex,长径比726.9,纤维素含量68.5%,断裂强度2.2 cN/dtex;纤维分离效果好,可用于复合材料。     

锦葵纤维增强聚丙烯基复合材料力学性能研究

分别制备了锦葵纤维含量为10 %（质量分数,下同）、20 %、30 %、40 %和50 %的锦葵纤维增强增强聚丙烯基复合材料,研究了纤维含量对该复合材料拉伸性能和弯曲性能的影响,并与苎麻纤维增强聚丙烯基复合材料进行了对比。结果表明,随着锦葵纤维含量的增加,锦葵纤维增强聚丙烯基复合材料的拉伸强度和拉伸弹性模量逐渐增加,而弯曲强度和弯曲弹性模量呈现先增大后减小的趋势,当纤维含量为40 %时达最大值;纤维含量均为30 %时,除拉伸弹性模量外,锦葵纤维增强聚丙烯基复合材料的各项指标均低于苎麻纤维增强聚丙烯基复合材料。     

柔韧棉秆皮纤维/PLA复合材料的制备与性能

采用抄造与热压相结合的方法,制备了薄且柔韧的棉秆皮纤维/聚乳酸(PLA)复合材料。该复合材料是由聚乳酸包覆、填充的棉秆皮纤维网,具有较好的柔韧性。研究了棉秆皮纤维与聚乳酸质量比和热压时间对复合材料结构、拉伸性能和弯曲刚度的影响。结果表明,棉秆皮纤维与PLA质量比为1/1,热压15 min(温度190℃)为最佳条件。该条件制得的复合材料厚(0. 126±0. 006) mm,干、湿态下的拉伸强度分别为12. 15、4. 88 MPa,断裂伸长率分别为1. 55%、1. 5%,杨氏模量分别为1 126、508 MPa,弯曲刚度为0. 35 N·cm2/cm。该研究为纤维增强热塑性复合材料的制备方法提供了新的思路,也有利于提高废弃棉秆皮的利用率。     

锦葵茎皮纤维/聚丙烯复合材料的力学与隔声性研究

采用高锰酸钾、KH-570偶联剂对锦葵茎皮纤维进行了表面处理,并以处理前后的锦葵茎皮纤维作为增强体、聚丙烯纤维为基体制备锦葵茎皮纤维含量为30%的增强复合材料,探讨了表面处理对锦葵茎皮纤维微观结构、物理机械性能的变化,讨论了表面处理前后锦葵茎皮纤维增强聚丙烯复合材料力学与隔声性能的变化。研究结果表明,锦葵茎皮纤维表面处理前后,表面的微观结构发生一定程度的变化,锦葵茎皮纤维/聚丙烯复合材料的力学性能与隔声性有一定幅度的提升,偶联剂处理后的复合材料的力学性能和隔声性能优于高锰酸钾处理后的复合材料。     

X射线衍射法分析棉秆皮纤维结晶结构

棉秆皮纤维是从棉秆皮中提取的新型纤维素纤维。利用X射线衍射分析仪测试棉秆皮纤维,根据X射线衍射图的分峰结果计算棉秆皮纤维的结晶度、结晶指数和晶粒尺寸等结晶结构参数。     

聚丙烯/剑麻纤维木塑复合材料的耐水性能研究

采用熔融共混、热压成型工艺制备聚丙烯（PP）/剑麻纤维（SF）木塑复合材料装饰板,研究了木塑复合材料浸水后力学性能、热性能和微观结构的变化趋势及原因。结果表明,当SF含量为50 %（质量分数,下同）、浸水时间为8 d时,木塑复合材料的冲击强度和弯曲强度下降幅度最大,分别达9.88 kJ/m2和21.02 MPa,与未浸水相比,分别下降了33.74 %和51.42 %;同时,木塑复合材料的热稳定性、PP相的结晶速率及结晶度也有所降低。     

棉秆皮脱胶工艺比较研究

以纤维的可挠度、残胶率、木质素为指标,对棉秆皮的三种脱胶工艺进行比较。实验结果表明,碱煮时间、碱的浓度等因素对棉秆皮纤维的残胶率影响较大;在一煮中加入亚硫酸钠和硫化钠,可以减少棉秆皮纤维中的木质素含量;棉秆皮纤维中木质素含量较小,纤维的可挠度较大。     

Chemical modification of cotton fiber by alkali-swelling and substitution reactions—acetylation,cyanoethylation, benzoylation,and oleoylation

By impregnating cotton fiber with alkaline swelling agents and reacting with some chemical agents which can be substituted for the hydroxyl groups on cellulose molecules in the presence of alkali, highly accessible or decrystallized cotton fibers can be obtained. As the effective substitution reactions, acetylation by acetic anhydride and cyanoethylation by acrylonitrile were applied. The cotton fibers modified by these chemical treatments showed no decrease of tensile strength, and had moisture regain higher than the untreated cotton though the degrees of substitution were as high as 20–30 mol %. The resistance to heat or acid and the soil removal were improved. Dyeability for direct dye was increased, and dyeability for disperse or cationic dye was also given. Benzoylation and oleoylation were also investigated. Crease recovery of the cotton fabrics was somewhat improved and dyeability for disperse dye was given. The cotton fabrics oleoylated after decrystallizing by alkali–acrylonitrile treatment had moisture regain almost the same as the untreated cotton, while high water repellency was given.     

Y—β复合分子筛负载磷钨酸催化合成乙酸仲丁酯

以乙酸酐与仲丁醇为原料,Y-β复合分子筛负载磷钨酸(H3PW12O40/Y-β)为催化剂,使其发生酰化反应合成乙酸仲丁酯,考察了催化剂用量、反应时间、酐醇摩尔比对乙酸仲丁酯产率的影响.结果表明,Y-β复合分子筛负载磷钨酸催化活性良好,当乙酸酐的加入量为0.1 mol,醇酐摩尔比为1.2时,使用0.75 g催化剂,反应30 min后,乙酸仲丁酯收率可达到94.5％,且催化剂重复使用5次仍保持活性良好.产品经折光率和红外光谱进行了表征.     

Dry-jet wet spinning of aromatic polyamic acid fiber using chemical imidization

A solution of about 15% polyamic acid (PAA) prepared from 4,4′-oxydianiline and pyromellitic dianhyride in N,N-dimethyl acetamide (DMAc) was used for fiber spinning. To obtain a high draw ratio of the PAA fiber during spinning, acetic anhydride or acetic anhydride and pyridine were added to the PAA solution to make it slightly gelled; such gelling contributed to high drawing of the PAA fibers during spinning. Before spinning the properties of the solution after acetic anhydride or acetic anhydride and pyridine were added, and the diffusion property of DMAc into various coagulants were examined. Even though acetic anhydride was only added to the spinning solution, the diffusion rate became slower and the solution viscosity increased, because PAA was converted to the corresponding polyimide (PI). Pyridine affected the rate dramatically. The mechanical properties of the PAA fibers obtained in this system were examined. Solid PI fibers were also obtained by annealing of the PAA fibers. The ultimate stress and initial modulus of the PAA fiber were around 268 MPa and 4.1 GPa, respectively. After the fiber was annealed at 350°C without tension for 30 min under nitrogen, these values increased to around 399 MPa and 5.2 GPa, respectively.     

棉皮纤维增强聚丁二酸丁二醇酯复合材料的热性能及力学性能研究

采用连续式蒸汽爆破法对棉皮纤维进行预处理,将其与聚丁二酸丁二醇酯(PBS)进行共混,制备了PBS/棉皮纤维复合材料。利用扫描电镜对棉皮纤维及PBS/棉皮纤维复合材料的微观形貌进行了分析,并研究了棉皮纤维含量对PBS/棉皮纤维复合材料熔融及结晶行为、热降解性能、热变形温度以及力学性能的影响。结果表明:经蒸汽爆破处理后,棉皮纤维直径变小,比表面积变大,在PBS基体中分散均匀;棉皮纤维的存在改变了PBS的熔融峰值温度,提高了其结晶度;与纯PBS相比,PBS/棉皮纤维复合材料在高温条件下的热稳定性得到改善维,卡软化温度和弯曲强度提高。     

环氧树脂/PBO纤维复合材料性能研究

对环氧树脂(EP)/聚对苯撑苯并二恶唑(PBO)纤维复合材料的性能进行初步研究。结果表明,用浓度70%的甲基磺酸(MSA)溶液对PBO纤维表面进行处理,可改善PBO纤维与EP基体的粘结强度,但同时使PBO纤维的拉伸性能降低;对PBO纤维处理2h后,以胺类固化剂固化的EP/PBO纤维复合材料的层间剪切强度比处理前提高41%,以酸酐固化剂固化的EP/PBO纤维复合材料的层间剪切强度比处理前提高48%;前者的层间剪切强度大于后者。     

Kenaf‐bast‐fiber‐filled biodegradable poly(butylene succinate) composites: Effects of fiber loading,fiber length,and maleated poly(butylene succinate) on the flexural and impact properties

Poly(butylene succinate) (PBS) filled kenaf bast fiber (KBF) composites were fabricated via compression molding. The effects of KBF loading on the flexural and impact properties of the composites were investigated for fiber loadings of 10–40 wt %. The optimum flexural strength of the composites was achieved at 30 wt % fiber loading. However, the flexural modulus of the composites kept increasing with increasing fiber loading. Increasing the fiber loading led to a drop in the impact strength of about 57.5–73.6%; this was due to the stiff nature of the KBF. The effect of the fiber length (5, 10, 15, and 20 mm) on the flexural and impact properties was investigated for the 30 wt % KBF loaded composites. The composites with 10‐mm KBF showed the highest flexural and impact properties in comparison to the others. The inferior flexural and impact strength of the composites with 15‐ and 20‐mm KBF could be attributed to the relatively longer fibers that underwent fiber attrition during compounding, which consequently led to the deterioration of the fiber. This was proven by analyses of the fiber length, diameter, and aspect ratio. The addition of maleated PBS as a compatibilizer resulted in the enhancement of the composite's flexural and impact properties due to the formation of better fiber–matrix interfacial adhesion. This was proven by scanning electron microscopy observations of the composites' fracture surfaces. The removal of unreacted maleic anhydride and dicumyl peroxide residuals from the compatibilizers led to better fiber–matrix interfacial adhesion and a slightly enhanced composite strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical performance and moisture absorption of various natural fiber reinforced thermoplastic composites

Natural fibers are seeing increased use in composite applications due to their reduced cost, low density, and environmental benefits (more sustainable and lower carbon footprint). Although many natural fiber systems have been examined over the last decade, there have been relatively few studies which have compared a variety of fiber types and processing methods directly in the same experimental set. In this study, natural fiber composites made from low density polyethylene (LDPE) and a variety of Canadian based fiber feedstocks were examined including hemp bast, flax bast, chemically pulped wood, wood chips, wheat straw, and mechanically pulped triticale. The effect of fiber type, fiber fraction and maleic anhydride polyethylene (MAPE) coupling agent on the mechanical properties and long‐term moisture absorption behavior was quantified. In general, addition of natural fiber to LDPE results in an increase in modulus (stiffness) with a corresponding loss of material elongation and impact toughness. Of the fiber types tested, composites made from chemically pulped wood had the best mechanical properties and the least moisture absorption. However, the use of MAPE coupling agent was found to significantly increase the mechanical performance and reduce moisture absorption for all other natural fiber types. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 969‐980, 2013