拉伸条件对高强PVA纤维结构和性能的影响

将聚乙烯醇(PVA)加入到二甲基亚砜(DMSO)和水(质量比94:6)的混合溶剂中,以甲醇为凝固剂,采用干湿法凝胶纺丝,经热拉伸和热定型后,制得高强度PVA纤维。探讨了拉伸工艺对高强PVA纤维结构和性能的影响。结果表明:对于负拉伸为40%,初拉伸2倍,220℃热拉伸9.9倍,热定型2 min的PVA纤维,纤维的结晶结构比较完善,断裂强度为17.8 cN/dtex,初始模量为310.7 cN/dtex;PVA纤维在光学显微镜下观察到的横纹反映出结晶聚集体的光学现象,横纹较多时,纤维的断裂强度和初始模量较高。     

聚醚醚酮纤维的拉伸定形后处理研究

通过熔融纺丝制得聚醚醚酮(PEEK)纤维,并采用差示扫描量热仪(DSC)、声速取向测量仪、热重分析仪、单纱电子强力仪分别研究了干热拉伸及热定形处理对PEEK纤维结晶和取向、热稳定性及力学性能的影响。结果表明:随着热拉伸倍数增大,PEEK纤维取向度、结晶度增加,纤维的断裂强度增加,断裂伸长减小;PEEK纤维的热拉伸温度应选在200～240℃,热定形温度应为220～260℃;PEEK纤维的重结晶主要是在热拉伸过程中完成,热定形则进一步完善纤维的结晶结构;经过后处理,PEEK纤维的断裂强度可达到6.12cN/dtex;且具有优异的热稳定性能,热分解温度高达505℃,后处理几乎不影响PEEK纤维的热稳定性。     

热拉伸条件对聚酰亚胺纤维结构和性能的影响

研究了热拉伸温度以及拉伸倍率对3,3',4,4'-联苯四甲酸酐(BPDA)、对苯二胺(PDA)以及2-(4-氨基苯基)-5-氨基苯并咪唑(BIA)三元共聚聚酰亚胺纤维聚集态结构和性能的影响。结果表明:提高热拉伸温度,可促进聚合物分子链运动,形成更规整的聚集态结构;合适的拉伸倍率使纤维获得充分拉伸;在460℃、热拉伸倍率为2.5时,所制备的共聚聚酰亚胺纤维的拉伸强度和弹性模量分别为3.31 GPa和137 GPa,表现出最优的力学性能。     

喷丝头拉伸对聚甲醛纤维结构与性能的影响

采用自主开发的聚甲醛(POM)熔融纺丝设备,在其他纺丝工艺不变的条件下,改变喷丝头拉伸倍数,制备POM纤维;研究了喷丝头拉伸倍数对POM初生纤维的取向度、后拉伸性能以及POM纤维力学性能的影响。结果表明:随着喷丝头拉伸倍数的增大,POM初生纤维的取向度呈现先上升后下降的趋势,而初生纤维的直径呈逐渐减小的趋势;喷丝头拉伸倍数为90时,整体工艺状况最佳,POM初生纤维的最大拉伸倍数达7.1,制备的POM纤维断裂强度为6.35 cN/dtex,断裂伸长率为13.5%。     

热拉伸工艺对聚醚酰亚胺纤维结构与性能的影响

采用牌号为Ultem 1010的聚醚酰亚胺(PEI)切片进行熔融纺丝,制备PEI纤维,探讨了PEI熔融纺丝的可纺性,重点研究了热拉伸工艺中拉伸倍数和拉伸温度对PEI纤维结构和性能的影响。结果表明:PEI具有良好的耐热性和较宽的加工温度范围,适合熔融纺丝;控制PEI的纺丝温度在340～350℃,卷绕速度在250～300 m/min,所得纤维的均匀性和稳定性较好;热拉伸不能促进PEI纤维结晶,无论拉伸与否,PEI纤维的结构都是无定形的;随着拉伸倍数的增大和拉伸温度的提高,PEI纤维的断裂强度和声速值都呈现出先上升后下降的趋势,在拉伸温度为220℃、拉伸倍数为3.0时,PEI纤维力学性能最好,其断裂强度达到2.6 cN/dtex;PEI纤维初始热分解温度为460.3℃,800℃时纤维的质量保持率为54.74%,具有良好的热稳定性。     

多级热拉伸对PPS纤维结构与性能的影响

将相对分子质量为55 000的聚苯硫醚(PPS)干燥,熔融纺丝,通过4级拉伸与热定型装置制备了不同拉伸倍数的PPS纤维,采用差示扫描量热仪、声速仪、广角X射线衍射仪、二维广角X射线衍射仪、电子单纱强力仪等研究了PPS纤维的结构与性能。结果表明:在纤维成形过程中,拉伸倍数对PPS纤维的结构与性能有较大的影响;随着拉伸倍数的增加,结晶度和取向度呈线性增大,最大增加幅度分别为50.6%和59.6%,其断裂强度逐渐增大,最大可达3.47 c N/dtex,最大增加幅度为39.4%,断裂伸长率逐渐降低,最大降低幅度为55.3%,干热收缩率和沸水收缩率均逐渐降低,最大降低幅度分别为56.2%和72.1%。     

聚醚醚酮薄膜的性能研究

采用挤出流延法制备了一系列聚醚醚酮（PEEK）薄膜,通过拉力机、差示扫描量热仪、紫外分光光度计、透光率雾度仪等对PEEK薄膜的基本性质、光学性能、力学性能进行了研究。结果表明,PEEK薄膜的透光率随结晶度的升高而降低;拉伸速率对拉伸强度、断裂伸长率的影响不大,拉伸速率快,屈服强度明显提高;拉伸强度随流延辊速度的增加而提高;双向拉伸的方法可使薄膜拉伸强度达到203 MPa;增加薄膜厚度、提高结晶度的方法可以提高薄膜的抗紫外性能。     

沸水再拉伸速率对聚丙烯腈纤维结构与性能的影响

以1-丁基-3-甲基咪唑氯盐([BMIM]Cl)为溶剂溶解聚丙烯腈(PAN)制成PAN纺丝原液,采用干喷湿法纺丝,经过凝固、预拉伸、沸水拉伸制得PAN纤维,对所得PAN纤维进行沸水再拉伸处理,研究了沸水再拉伸速率对PAN纤维结构和性能的影响。结果表明:PAN纤维中残留质量分数为4.38%的离子液体,为沸水再拉伸起到了增塑作用;随着沸水再拉伸速率的增大,PAN纤维的力学性能提高,断裂强度由2.69cN/dtex提高到4.33 cN/dtex,而断裂伸长率由26%减小到20%,纤维的玻璃化转变温度、晶区取向度、双折射率、结晶度、晶粒尺寸均增大。     

拉伸对非晶态聚醚醚酮结晶取向行为的影响

借助差示扫描量热仪(DSC)和广角X射线衍射仪(WAXD),研究了不同拉伸工艺对非晶态聚醚醚酮(PEEK)结晶取向行为的影响。结果表明:在较高的温度、较低的拉伸速率及拉伸比下,拉伸后样品为非晶体;样品拉伸后的冷结晶温度向较低温度移动。     

拉伸对熔纺聚乙烯醇纤维结构形态的影响

采用含水的复合改性剂增塑聚乙烯醇(PVA),制备熔纺PVA纤维原丝。经冷拉伸3倍后,分别在160、220℃下进行热拉伸。研究了拉伸对纤维结构和表面、截面形貌的影响。结果表明:拉伸使纤维分子取向,结晶度升高;熔纺PVA纤维截面为圆形,拉伸后在纤维表面产生沿轴向的微孔,增加了纤维表面的粗糙度。     

热定型对嵌段聚醚酯弹性纤维结构与性能的影响

研究了热定型时间、温度和方式对嵌段聚醚酯弹性纤维的结构和性能的影响 ,采用 DSC、X-射线衍射测定了纤维热定型前后结晶结构及结晶度的变化 ,同时测定了纤维的断裂强度、断裂伸长、回弹率和热水收缩率的变化 ,结果表明 ,热定型处理使嵌段聚醚酯纤维的结晶结构发生了变化并使结晶度提高 ,从而提高了纤维的回弹性能和力学性能 ,纤维的热水收缩率与氨纶相当     

Mechanical properties of poly(ether-ether-ketone) for engineering applications

An outline of the characteristics of PEEK and the versatility of its compositional forms (micro and macro composites) are given to illustrate its wide potential for success in engineering applications. Although it is necessary to have particular tabulations of mechanical properties for engineering design, these are seldom available and consequently it is argued that an understanding of stiffness, toughness and strength properties are required to fully exploit available manufacturer's data and thus develop the full potential of PEEK and its composites. Stiffness characteristics are considered in terms of a modulus function which is dependent on time under load and temperature. In its composite forms, whether reinforced with short or continuous fibres, stiffness anistropy can be both considerable and complex, but some empirical ground-rules are apparent. For continuous fibre composites even in the form of complex lay-ups, it is also possible to attempt some stiffness prediction from certain pseudo-elastic constants. Toughness of PEEK and its composites is described in terms of both comparative and intrinsic properties. Instrumented falling weight impact data, particularly as a function of temperature enable some insight into ductile-brittle transitions for the unreinforced material, but crack initiation and crack propagation processes for the various fibre reinforced forms. Intrinsic toughness is described in terms of linear elastic fracture mechanics theory. Strength properties are described for static and dynamic loading configurations. In particular, PEEK and its composites are evaluated for increasing test severities for strength characteristics; stress concentration, loading form and test temperature are considered.     

聚醚砜纤维及织物性能研究

将聚醚砜(PES)进行熔融纺丝,制得PES纤维,并织成布样,对纤维及其织物的性能进行了研究。结果表明:PES纤维的力学性能不稳定,放置一定时间,其强度下降,需经140℃高温热定型加以改善。纤维回潮率为2．33%;织物极限氧指数为26．9%,紫外吸光度低于1．6,体积比电阻为8．13×10~(13)Ω·cm,摩擦静电压为7 272 V,1 min后衰减电压为5 519 V。     

拉伸与热定型对聚苯硫醚长丝结构性能的影响

以国产聚苯硫醚(PPS)树脂为原料,用熔融法纺丝制得PPS长丝。采用差示扫描量热仪、热重分析仪研究了后处理对纤维结晶和热性能的影响;利用声速取向测量仪研究了拉伸对纤维取向的影响;用单纱电子强力仪测量了纤维力学性能。结果表明:热拉伸倍数增大,PPS纤维取向度、结晶度增加,纤维的断裂强度增加,断裂伸长减小;拉伸倍数大于5,会出现较多毛丝和断头;控制热拉伸温度85～105℃,热定型温度100℃以上;纤维的结晶主要在热拉伸过程中基本完成,热定型进一步完善结晶结构;高温下氧气的存在,会使PPS纤维发生严重的氧化降解。     

熔融纺丝法制备聚醚砜纤维

将聚醚砜(PES)树脂进行熔融纺丝,制得PES纤维,对PES树脂的可纺性、PES纤维的拉伸条件、力学性能、热性能、阻燃性能进行了研究。结果表明：PES树脂在熔融温度380℃,卷绕速度300m/min的条件下,可纺性较好;PES纤维适合在较低温度和较低速度下拉伸,在30℃下低速拉伸,PES纤维可拉伸3倍,其强度可达2．30cN/dtex;PES纤维的热稳定较好,其初生纤维的起始分解温度为442．15℃;PES纤维的阻燃性能较好,极限氧指数为26．9%。     

Effect of physical aging on the microstructure and dynamic mechanical properties of poly(ether sulfone) copolymer

Effects of physical aging on the submicroscopic structure and dynamic mechanical properties of amorphous poly(ether sulfone) copolymer film were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and electron‐microscopy measurements. Heat flow responses were measured after annealing the amorphous samples obtained, by quenching the melt into an ice‐water bath close to but below the glass transition temperature. The extent of aging is related to the supercooling from the glass transition temperature and to the aging time. The activation energy of the aging process was estimated by the Williams–Watt expression (Williams and Watts, Trans Faraday Soc 1970, 66, 80). A systematic study of the influence of aging on the dynamic mechanical properties of poly(ether sulfone) copolymer has also been made. During isothermal annealing, the increase of the temperature of tan δ peak for the α and β′ relaxation with aging time has been observed. The aging in the zone of the β peak has also been investigated and an interpretation of the results was proposed on the basis of foregone theories. The result of electron‐microscopy investigation indicates that poly(ether sulfone) copolymer has formed a local order structure during the physical aging. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 530–534, 2006     

预氧化拉伸对PAN基碳纤维结构和性能的影响

借助X射线衍射、元素分析等表征手段,研究了聚丙烯腈(PAN)纤维在预氧化过程中拉伸对纤维孔隙结构、预氧丝氧含量和最终碳纤维力学性能的影响。结果表明:随着拉伸倍数的增大,PAN预氧丝的平均孔径和孔隙率均减小;经一定拉伸后PAN基碳纤维的强度和模量均有所增加,但当拉伸到一定程度后,PAN预氧丝的氧含量呈下降趋势,纤维未形成稳定的耐热梯形结构,PAN基碳纤维力学性能显著下降。     

高强度聚乙烯醇纤维结构与性能研究

继超高相对分子质量聚乙烯(UHMW-PE)纤维得到较快发展以来,有关高强度聚乙烯醇纤维的研究与开发也受到人们重视,介绍和讨论了高强度聚乙烯醇纤维的研究和开发现状,包括制备方法、纤维结构与性能、应用等方面的情况。     

Enhancing mechanical properties of poly(vinyl alcohol) blown films by drawing and surface crosslinking

Thermal blowing of poly(vinyl alcohol) (PVA) film was successfully realized based on molecular complexation. Ways to enhance the performance of the PVA blown films (drawing and surface crosslinking) were studied. The experimental results showed that water exists in PVA films in different states through hydrogen bonds with PVA and other modifiers and influences the drawability of PVA films, as well as the structure and properties of the stretched films. When the initial water content of the film was higher than 35.0%, the draw ratio of the PVA film was quite large because of the effects of the bound water with PVA, as well as the plasticization of free water. With the increase of the initial water content in PVA, the free water content and draw ratio of the films increased but the strength of the films decreased because of the higher residual water in the films. Surface crosslinking can improve the stretchability of PVA films because more water remains in the films and disrupts the hydrogen bonding of PVA. In addition, crosslinking enhances the mechanical properties of stretched PVA films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 774–779, 2005