浸胶法测试PBO纤维的拉伸性能

采用浸胶法测试聚对苯撑苯并二噁唑(PBO)纤维的拉伸性能,并对其浸胶工艺及测试条件进行了研究。结果表明:采用E-51环氧树脂和三乙烯四胺浸胶体系,在卷绕速度为10.0 r/min,胶液质量分数为70.0%的浸胶条件下,制得含胶量为40%~65%的PBO浸胶丝,该浸胶丝在预加载荷为10 N,拉伸速度为20 mm/min的条件下进行拉伸性能测试,所得纤维的拉伸强度、模量、断裂伸长率结果稳定,其变异系数均小于5%,重复性好。该方法适用于PBO初生纤维和PBO高模量纤维的拉伸性能测定。     

热处理对PBO纤维结构和性能的影响

热处理是进一步提高聚苯撑苯并二噁唑(PBO)纤维性能的重要工艺。本文研究了固定张力下,热处理温度和时间对PBO纤维结构和性能的影响。结果表明:在固定张力下进行热处理可以促使PBO纤维进一步完成关环反应,提高大分子链的规整性;热处理会使PBO纤维表面粗糙化,并改善纤维的界面性能,600℃下处理40 s后其界面剪切强度提高了40%;提高热处理温度或延长热处理时间均能提高PBO纤维的强度和模量;氮气下550℃处理35 s后,PBO纤维的拉伸强度和模量分别比初生纤维提高了28%和45%。     

热处理温度对PBO纤维性能的影响

PBO纤维因其具有高强度、高模量、高耐热性以及高化学稳定性等性能而被公认为目前综合性能最好的有机纤维。对自制的初生PBO纤维分别在500℃、550℃、600℃、650℃和700℃进行高温热处理,并对处理后纤维的力学性能、耐热性能、表面形貌以及界面性能进行测试。结果表明,500℃下热处理后PBO纤维拉伸强度最大为4.72GPa,随着热处理温度升高,纤维的力学性能下降;600℃下热处理后PBO纤维的初始分解温度最高为641.3℃;随着热处理温度的提高,PBO纤维的表面粗糙度在增加,同时其界面剪切强度(IFSS)也随着温度的升高而增大。     

PBO纤维拉伸性能测试的影响因素探讨

参照Q/2019400—7.175—2009标准,测试聚对苯撑苯并二噁唑(PBO)初生纤维(AS-PBO)、高模量纤维(HM-PBO)的拉伸性能,探讨了加捻系数、试样标距、拉伸速率和预加张力等因素对测试结果的影响。结果表明:AS-PBO和HM-PBO干纱的拉伸性能测试的最佳条件是加捻系数为12,标距为(120±1)mm,拉伸速率为20 mm/min,预加张力为断裂载荷的1%;在此条件下测得的AS-PBO、HM-PBO干纱的拉伸强度分别为31.94,29.20 c N/dtex,模量分别为900.25,1 487.03 c N/dtex,断裂伸长率分别为4.1%,1.4%,所测结果与日本东洋纺报道的Zylon的拉伸性能接近。     

PBO纤维用于耐高温气体过滤材料的探讨

合成纤维过滤材料越来越多地被应用于高温烟气过滤器中。聚苯撑苯并二嗯唑（PBO）纤维具有强度大、模量高、耐热性能突出、密度小、耐化学性好等特点。对自制的初生PBO纤维进行了高温热处理并对其进行了耐热及耐酸性能的测试。热处理后,PBO纤维的拉伸强度由2．86GPa提高到了3．94GPa;长期使用温度达到600℃;纤维在60%浓度的浓硫酸和63％浓度的浓硝酸中浸泡60d以后,拉伸强度依然可以分别保持在2．71GPa和2．11GPa。同其它高温烟气过滤材料用纤维相比,PBO纤维具有明显的优势。     

PIPD纤维的制备及其结构与性能研究

以2,3,5,6-四氨基吡啶三盐酸盐一水合物(TAP·3HCl·H2O)和2,5-二羟基对苯二甲酸(DHTA)为单体,合成聚[2,5-二羟基-1,4-苯撑吡啶并二咪唑](PIPD),并采用干喷湿纺法制备了PIPD初生纤维,初生纤维在温度400℃,张力33 c N/dtex的条件下进行热处理得到PIPD纤维,研究了PIPD纤维的结构与性能。结果表明:PIPD初生纤维的线密度为959.6 tex,拉伸强度为2.15 GPa,拉伸模量为154.2 GPa;热处理后的PIPD纤维较初生纤维致密程度有所提高,线密度和拉伸强度有所下降,拉伸模量提高,热稳定性较好;纺丝原液脱泡良好、提高纺丝组件的温度均一性以及降低纤维中残酸量可进一步提高PIPD纤维的性能。     

国产PBO纤维的性能及形貌研究

采用扫描电子显微镜、元素分析仪、热分析仪以及复合材料单向环(NOL)法等对国产聚对苯撑苯并双噁唑(PBO)纤维和东洋纺Zylon纤维的形貌、元素组成、热性能和力学性能进行了比较分析。结果表明:Zylon纤维单丝直径约为12μm,国产PBO纤维直径稍大,约为20μm;Zylon纤维表面较为光滑和致密,国产PBO纤维表面存在微小的浅沟槽;国产PBO纤维的断裂强度最高达5.36 GPa,模量最大为239 GPa,分别比Zylon纤维低7.6%和14.6%,但其NOL环的层间剪切强度最高达26 MPa,比Zylon纤维制备的复合材料高14%;国产PBO纤维与Zylon纤维的组成基本一致,但其耐热性能优异,在氮气中的分解温度大于676℃,在空气中的分解温度大于634℃,分别比Zylon纤维高6℃和23℃。     

紫外光照射对PBO纤维结构与性能的影响

采用UVA,UVB,UVC 3种波段紫外光分别对聚对苯撑苯并双噁唑(PBO)纤维进行照射,研究了不同照射时间下PBO纤维的结构与性能。结果表明:PBO纤维经不同波段紫外光照射6 d时,UVA照射后纤维噁唑环稳定性降低,断裂强力下降率为5.42%,UVB照射后纤维噁唑环开始发生开环,断裂强力下降率为13.46%,UVC照射后纤维噁唑环已打开,断裂强力下降率为18.96%;经UVA,UVB,UVC照射13 d后,PBO纤维断裂强力下降率分别为19.36%,38.65%,53.13%,PBO纤维大分子均遭到破坏;UVC照射后PBO纤维起始分解温度下降至51℃,UVA,UVB照射后PBO纤维基本能保持自身良好的热学性能;PBO纤维最敏感的紫外光是UVC,其次是UVB,最后是UVA。     

干法纺聚酰亚胺纤维的结构与性能

以均苯四甲酸二酐、4,4'-二氨基二苯醚、3,3'-二氨基二苯醚为原料,以N,N-二甲基乙酰胺为溶剂,制得聚酰胺酸(PAA)纺丝液,采取干法纺丝制得PAA初生纤维,将PAA初生纤维经过300~380℃的热处理后,得到聚酰亚胺(PI)初生纤维,在400℃下对PI初生纤维进行热拉伸,最终得到PI纤维,研究了热处理温度、热拉伸倍数等对PI纤维的结构与性能的影响,比较了PI纤维与P84纤维和芳纶1313的性能。结果表明:在300~380℃的热处理温度下,随着温度升高,PI纤维的力学性能降低,最佳热处理温度为300℃时制得的PI初生纤维于400℃下进行热拉伸3.0倍,所得PI纤维的断裂强度为5.8 c N/dtex,初始模量为69.4c N/dtex,其力学性能优于P84纤维及芳纶1313;PI纤维在空气中失重5%和10%的温度分别为560,570℃,其起始分解温度高于P84纤维和芳纶1313,热性能更好;PI纤维经高温热拉伸,纤维内部分子链沿纤维轴向高度取向,表现出典型的取向诱导结晶效应。     

剑麻纤维的溶胶–凝胶技术改性

通过溶胶–凝胶技术以正硅酸乙酯作为溶胶前驱体对剑麻纤维进行改性,采用傅里叶变换红外光谱(FTIR)、热重(TG)分析、X射线光电子能谱(XPS)分析以及单根纤维拉伸性能测试对改性剑麻纤维进行表征。FTIR和XPS测试结果表明,SiO_2凝胶成功引入剑麻纤维中;TG分析结果表明,经过溶胶–凝胶技术改性后,剑麻纤维的起始热分解温度变化很小,仅提高约0.5℃,但失重率明显降低;拉伸性能测试结果表明,溶胶–凝胶技术改性剑麻纤维的拉伸强度高于未改性的纤维,且剑麻纤维的吸湿率越高,单根纤维的拉伸强度越高,当纤维吸湿率为22.7%时,其拉伸强度较未改性纤维提高了29.21%,较KH550改性纤维提高了7.84%。     

高温碳化工艺与聚丙烯腈基碳纤维力学性能的关联性

考察了2种由不同规格聚丙烯腈原丝制成的碳纤维在高温碳化过程中力学性能与高温碳化工艺的相关性。试验结果表明:碳纤维的拉伸强度随着高温碳化最高温度的提高而增加,两种不同规格碳纤维在高温碳化最高温度分别超过1 500℃和1 550℃后拉伸强度开始呈下降趋势;碳纤维的弹性模量随着高温碳化温度的提高而增加;在高温碳化时间40 s前,碳纤维的力学性能随停留时间延长而提高,这说明40 s之前时间驱动效应明显;在-2.5%~-5.0%牵伸条件下,弹性模量随牵伸率增加而增加,抗拉强度在牵伸率为-3.5%时出现峰值。     

PBO纤维热处理技术及其应用研究进展

对国内外聚对苯撑苯并双恶唑(PBO)纤维热处理工艺技术、PBO纤维热处理工艺机理研究进展、高模量PBO纤维的性能及应用进行了综述,对比了国内外成果及研究差距。阐明了国内PBO纤维关于热处理工艺研究尚处于试验阶段,虽能够小批量制备PBO高模量纤维,但与Toyobo公司产Zylon-HM纤维相比,在强度保持率、模量增长率、性能稳定性、产量及类型等方面还有差距。PBO纤维具有高强度、高模量、耐高热等性能,在航空航天、国防军工等领域的增强材料、耐高温、耐烧蚀材料之中,具有良好的应用前景和较高的市场价值。     

Rigid‐rod polymeric fibers

This paper traces the historical development of high temperature resistant rigid‐rod polymers. Synthesis, fiber processing, structure, properties, and applications of poly(p‐phenylene benzobisoxazole) (PBO) fibers have been discussed. After nearly 20 years of development in the United States and Japan, PBO fiber was commercialized with the trade name Zylon® in 1998. Properties of this fiber have been compared with the properties of poly(ethylene terephthalate) (PET), thermotropic polyester (Vectran®), extended chain polyethylene (Spectra®), p‐aramid (Kevlar®), m‐aramid (Nomex®), aramid copolymer (Technora®), polyimide (PBI), steel, and the experimental high compressive strength rigid‐rod polymeric fiber (PIPD, M5). PBO is currently the highest tensile modulus, highest tensile strength, and most thermally stable commercial polymeric fiber. However, PBO has low axial compressive strength and poor resistance to ultraviolet and visible radiation. The fiber also looses tensile strength in hot and humid environment. In the coming decades, further improvements in tensile strength (10–20 GPa range), compressive strength, and radiation resistance are expected in polymeric fibers. Incorporation of carbon nanotubes is expected to result in the development of next generation high performance polymeric fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 100: 791–802, 2006     

Effects of Basic Chemical Surface Treatment on PBO and PBO Fiber Reinforced Epoxy Composites

The effects of chemical surface treatment on PBO fiber and its composite materials were investigated using a basic sodium hydroxide solution. We evaluated several important treatment parameters quantitatively, including treatment concentration, treatment temperature and treatment time. Both as-spun (AS) and high-modulus (HM) PBO fibers were studied. The results showed that PBO fibers exhibited minimum or negligible reduction in their tensile strengths after the proposed treatment processes. The fibers’ contact angles with several liquid media were greatly reduced and the surface free energy could be increased to 58 mJ/m² or by 17%. The interfacial shear strength between PBO fiber and the epoxy matrix was improved to 38 MPa or by 11% with the same treatment process. The composite’s failure mode also shifted from fiber/matrix interface adhesive failure to partly cohesive failure.     

低温等离子体对ＰＢＯ纤维表面改性的研究

 为提高ＰＢＯ纤维／环氧树脂复合材料的剪切强度,采用低温等离子体结合涂层技术对聚对苯撑苯并双唑（ＰＢＯ）纤维进行表面改性,分别用ＳＥＭ、ＩＲ对等离子体处理前后纤维表面形态、化学结构进行了表征,通过复合材料层间剪切强度测试,研究不同处理方式对复合材料层间剪切强度的影响。结果表明,等离子体处理后纤维表面粗糙度增加,极性增强。经低温等离子体结合涂层技术处理后,ＰＢＯ纤维／环氧树脂复合材料的层间剪切强度得到显著提高,较未处理样品提高了３９％。     

Increasing the strength and toughness of a carbon fiber/silicon carbide composite by heat treatment

The effect of heat treatment on the strengthening and toughening of a carbon fiber/silicon carbide composite (C/SiC) with a thin pyrolytic carbon (PyC) interphase was investigated. Tensile strength and modulus were measured using tensile tests, and toughness was obtained by calculating the area under the stress–strain curves. Results show that with increasing heat treatment temperature both the strength and toughness of the C/SiC composite increased, but the modulus decreased. After heat treatment at 1900 °C the tensile strength and toughness increased by a maximum of 42% and 252%, respectively, and the modulus decreased by 48%. X-ray diffraction analysis and microstructural observation confirmed that the heat treatment mainly increased the graphitization of the amorphous PyC interphase, and this was responsible for the property changes observed because it decreased the interfacial sliding resistance associated with long fiber pull-out, relieved the thermal residual stress and lower stress concentrations on the fibers to uniformly share the load for improving the strength and toughness.     

Structural evolution and mechanical properties of Cansas-III SiC fibers after thermal treatment up to 1700 °C

The effects of thermal treatment on the Cansas-Ⅲ SiC fibers were investigated via heating at temperatures from 900 to 1700 ℃ for 1–5 h in argon atmosphere. The composition and morphology of the SiC fibers were characterized and the tensile strength of the SiC fiber bundles was analyzed via two-parameter Weibull distribution analysis. The results showed that the thermal treatment has negligible influence on the microstructure of the SiC fibers at temperatures ≤ 1100 ℃. At temperatures ≥ 1300 ℃, the surface of the fibers became rough with some visible particles. Particularly, at 1700 °C, numbers of holes appeared. With the increasing of heating temperature and holding time, the average tensile strength of the SiC fibers decreased gradually from 1.81 to 1.01 GPa. The decreasing of tensile strength can be attributed to the increase of critical defect sizes, grain growth and phase transformation (β→α) of SiC.     

Heat resistance properties of poly(p-phenylene-2,6-benzobisoxazole) fiber

The high temperature properties of Poly(p-phenylene-2,6-benzobisoxazole) (PBO) fiber are examined and compared with those of the p-Aramid fiber. In particular, the temperature dependence of tensile strength of the PBO fiber is reported for the first time. The PBO fiber has 100°C higher decomposition temperature than the p-Aramid fiber, and the amount of toxic gases in combustion is much smaller than the p-Aramid fiber. Although the relative strength decreased proportionally in the range of room temperature to 500°C, the PBO fiber has 40% of the strength at room temperature even at a temperature of 500°C. After thermal treatment at 500°C for 60 s, the PBO fiber retained 90% of its original strength. The PBO fiber is expected to substitute for asbestos, which is still used as a heat resistant cushion material. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1031–1036, 1997