碱处理竹纤维对聚酰胺6结构和性能的影响

采用10 ％的（质量分数,下同）NaOH碱溶液对竹纤维进行了处理,通过双螺杆挤出和注射成型制备了聚酰胺6（PA6）/竹纤维复合材料。用扫描电子显微镜﹑差示扫描量热仪、X射线衍射仪和热失重分析仪等表征了材料的形貌、结构和热性能,测试了熔体流动速率和力学性能。研究表明,碱处理可清除竹纤维中的胶质物,增大其比表面积,有利于改善PA6和竹纤维间的界面结合。PA6与竹纤维之间具有较好界面结合,相界面间无明显间隙。竹纤维使复合材料中PA6晶相的完整程度降低,使复合材料刚性增加,冲击强度、熔体流动性和热稳定性下降。在挤出和注射过程中,PA6/竹纤维复合材料较好的熔体流动性和一定的热稳定性使其具有熔体加工性能。     

截面形状对聚酰胺6/石墨烯复合纤维性能的影响

通过母粒共混熔融纺丝法制备了圆形、三角形和十字形截面的聚酰胺6/石墨烯复合纤维。采用光学显微镜观察了纤维的截面形貌并计算其异形度,采用负离子测试仪、远红外发射率测试仪、恒温恒湿干燥箱表征了不同截面纤维的负离子释放性能、远红外辐射性能和纤维吸湿及其干燥速度。研究表明:圆形、三角形和十字形截面纤维的异形度分别达到6.31%、34.80%和58.29%。相对而言,异形度增大,会明显影响纤维的负离子释放浓度、吸湿速度及干燥速度,其中十字形截面纤维的负离子释放浓度最高达到1 820个/cm~3;另一方面,异形度的变化不会对纤维远红外辐射能力产生明显的影响,其远红外发射率在0.90～0.93,远红外辐射温升约为1.70℃。     

纺丝原料对高强高模聚乙烯醇纤维结构性能的影响

研究了纺丝原料聚合度、转化率对聚乙烯醇(PVA)纤维高强高模化的影响。结果表明:高聚合度有利于减少端基缺陷,提高纤维性能;低转化率PVA相对高转化率PVA具有高的聚合度和线性程度,所得纤维力学性能更高。同时发现,低转化率原料纺得纤维在高倍拉伸后有强度模量较高的横纹丝产生,因此适合制备高强高模纤维。     

凝固浴温度对超高相对分子质量聚酰胺6冻胶纺纤维结构和性能的影响

以氯化钙为络合剂,采用冻胶纺丝技术制备超高相对分子质量（UHMW）聚酰胺（PA）6纤维,重点研究凝固浴温度对UHMW PA6冻胶纺纤维结构和性能的影响,以期获得高强高模PA6纤维。试验结果表明：在较低凝固浴温度（4～8 ℃）下得到的纤维表面较为光滑;凝固浴温度越低,分子间排列越规整,取向度越好,成品丝条的双折射率越高,越易形成α晶型,结晶度越高,所得纤维的强度和模量也较大。综合考虑力学性能测试结果和室温的影响,凝固浴温度选为8 ℃。     

卷绕速度对PTT初生纤维结构与性能的影响

PTT特性粘数0.935 dL/g,卷绕速度2 500-4 000m/min,熔融纺丝制备PTT初生纤维(PTT/POY),研究了卷绕速度对其结构和性能的影响。结果表明:提高卷绕速度,PTT/POY的玻璃化温度、结晶度和密度提高,冷结晶温度和过热度降低;晶面距和晶粒尺寸略有增加,双折射先逐渐增加,达到最大值后降低,声速取向因子则逐渐增加,但非晶区取向大分子链的取向度随之减小。随卷绕速度的提高,PTT/POY的断裂强度和初始模量增加,而断裂伸长率和断裂比功降低。热拉伸倍数与卷绕速度有关,2 500~4 000 m/min时,应取1.18~1.57。     

树枝形聚酰胺胺对尼龙6性能影响的研究

研究4．0代树枝形聚酰胺胺（PAMAM）对尼龙6拉伸性能、冲击性能及熔体流动速率的影响。结果发现，在尼龙6中添加PAMAM后，尼龙6的拉伸强度、断裂伸长率、缺口冲击强度及熔体流动速率均有所提高，PAMAM添加量为1．0％时效果最佳。PAMAM与尼龙6之间强烈的相互作用，以及两相界面上形成的密实薄层，是尼龙6力学性能提高的原因。     

煤矸石填充聚酰胺6复合材料的结构与性能研究

采用熔融共混法制备了聚酰胺6／煤矸石复合材料，研究了复合材料的力学性能、微观结构、结晶行为和流变性能。结果表明：煤矸石的加入使聚酰胺6的的拉伸强度、弹性模量、弯曲强度和弯曲模量分别增加了约53．8％、66．1％、37．1％和63．4％，而冲击韧性基本保持，煤矸石最佳填充量为25％；煤矸石在聚酰胺6基体中分散均匀，复合材料具有韧性断裂特征；煤矸石使聚酰胺6的结晶温度由187．0℃升高到191．3℃，过冷度由33．6℃降至18．9℃，结晶温度范围变窄，即煤矸石提高了聚酰胺6的结晶速率，对聚酰胺6具有异相成核作用；在所研究的剪切速率范围内，聚酰胺6及其复合材料的流变行为表现为假塑性，煤矸石的加入使非牛顿指数减小，聚酰胺6对剪切敏感性下降。     

聚酰胺6/碳纳米管复合材料的电学性能研究

对碳纳米管(CNTs)进行有机化处理之后,采用原位聚合法制备了聚酰胺（PA）6/ CNTs复合材料。研究了CNTs含量、温度、频率等因素对复合材料电学性能、介电性能和电磁屏蔽性能的影响。结果表明,随着CNTs含量的增加,复合材料的体积电阻率和表面电阻率均下降,最显著情况分别下降了2、3个数量级;随着温度的升高复合材料的介电常数增大,增大趋势随CNTs含量的增加而急剧减小;复合材料的介电常数和介电损耗随着频率的升高变化幅度增大,频率在105.5～109 Hz范围内复合材料有一定的电磁屏蔽效能,随着频率的增大电磁屏蔽效果急剧减小,109 Hz以上几乎没有电磁屏蔽效果。     

高强纤维结构优化初探

简要分析了提高合成纤维强度的基本条件和必要因素 ,需要避免和克服的不利因素以及实用要求的某些制约条件。列举了当前经过优化工艺和纤维结构而制得的最高强度无机纤维 (PAN基碳纤维 )和有机纤维 (超强聚乙烯纤维 )的具体制备方法及采取的手段。指出今后随着科技的进步 ,纤维的强度还可能进一步提高     

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。     

聚酰胺纤维异形化对纤维性能的影响

考察了聚酰胺纤维异形化对于纤维拉伸性能、热性能和动态力学性能的影响。结果表明 ,将平直纤维加工成凸端短纤维和竹节状短纤维 ,对纤维拉伸性能的影响不大 ,但纤维的热收缩减小 ,并使纤维的动态力学性能发生一定程度的变化。主要是凸端短纤维的储能模量降低 ,动态力学损耗因子加大     

Additive manufacturing of high-strength polyamide 6 composites reinforced with continuous carbon fiber prepreg

The additive manufacturing of continuous fiber reinforced thermoplastics (CFRTPs) paves way for the high-strength, light-weight components for variety of load-bearing applications. In this work, the continuous carbon fiber reinforced PA6 (CCF-PA6) composites was successfully printed from the prepreg filament. The prepreg filament was prepared in-house by impregnating the heat-and-acid treated 1 K carbon fiber bundle with the molten PA6. The tensile strength of the prepreg filament, which contained with 40 vol% CF, reached 984 MPa. The unidirectional CCF-PA6 specimens were subsequently 3D-printed with the prepreg filament, and the mechanical strength of those 3D-printed specimens were tunable by adjusting a set of printing parameters, such as layer thickness, hatch spacing and printing temperatures. The highest tensile strength of the specimen reached 555 MPa. Those specimens also exhibited outstanding mechanical strength at elevated temperatures, still reaching 184 MPa at 150°C. The mechanical strength of those specimens was dependent on the content of the fiber. This study can hopefully provide new insights for feedstock design and spur novel ideas in tailoring the mechanical properties of the 3D-printed CFRTPs.     

Influence of fiber orientation,temperature and relative humidity on the long-term performance of short glass fiber reinforced polyamide 6

As a result of processing of short fiber reinforced thermoplastics, the fiber orientation varies throughout a product giving rise to a pronounced anisotropic mechanical response. Different flow conditions in a product result in spatial variation in both short- and long-term mechanical properties. In this study, a modeling approach is presented to evaluate the lifetime of short fiber reinforced polyamide 6, both in plasticity- and crack growth controlled regions of failure. In the plasticity-controlled region, a viscoplastic model based on separation of the load angle (by means of Hill's equivalent stress formulation) and time dependence of the yield stress is used in the form of an associative flow rule. The influence of temperature and relative humidity on the magnitude of the plastic flow rate is described by using an apparent temperature approach combined with a Ree-Eyring formulation. The depression of the glass transition temperature in the polyamide 6 matrix with increasing amount of absorbed moisture was used to predict the anisotropic deformation kinetics in a humid environment. Similar to the plasticity controlled failure, in slow crack growth controlled failure region the effect of temperature, relative humidity, and load angle on the lifetime under a fatigue load is investigated. The apparent temperature approach could also be successfully applied to predict the slow crack growth failure, while the load angle dependence is shown to scale similar to the plasticity-controlled failure with the Hill's equivalent stress.     

超支化聚酰胺对聚丙烯及其纤维的性能影响

研究了超支化聚酰胺对聚丙烯(PP)的热性能、漉变性能和力学性能及其纤维的染色性能影响。结果表明:超支化聚酰胺在PP中分散均匀;超支化聚酰胺的加入,改善了PP纤维的染色性,当加入超支化聚酰胺质量分数为8%时,分散蓝的上染率可达70%,改性PP纤维的织物染色牢度均在4级以上;随着超支化聚酰胺含量增大,改性PP表观粘度下降,加工性能得到改善,其力学性能变化不大。     

PA6/蒙脱土熔融插层复合材料结构与性能分析

通过熔融共混法插层复合制备了聚酰胺(PN)6／蒙脱土纳米复合材料，测试了力学性能并对不同蒙脱土含量的PA 6／蒙脱土纳米复合材料进行了对比。实验表明，通过熔融插层可使PN 6基体插层于蒙脱土中，所得到的复合材料的性能较PN 6有很大提高。蒙脱土特殊的层状结构使得利用熔融共混在机械力的作用下插层到纳米级复合材料成为可能。     

Improving mechanical and thermal properties of short carbon fiber/polyamide 6 composites through a polydopamine/nano-silica interface layer

Carbon fiber (CF) reinforced matrix composites have been applied widely, however, the interfacial adhesion of composites is weak due to smooth and chemically inert of CF surface. To solve this problem, A polydopamine/nano-silica (PDA-SiO₂) interfacial layer on carbon fiber surface was constructed via polydopamine and nano- SiO₂ (CF-PDA-SiO₂) by a facile and effective method to reinforce polyamide 6 composites (CFs/PA6). The effects of PDA-SiO₂ interfacial layer on crystallization structure and behavior, thermal properties, and mechanical properties of CFs/PA6 composites were investigated. Furthermore, interfacial reinforcement mechanism of composites has been discussed. This interfacial layer greatly increased the number of active groups of CF surface and its wettability obviously. The tensile strength of CF-PDA-SiO₂/PA6 composites increased by 28.09%, 19.37%, and 26.22% compared to untreated-CF/PA6, CF-PDA/PA6, and CF-SiO₂/PA6 composites, respectively, which might be caused by the increased interfacial adhesion between CF and PA6 matrix. The thermal stability, crystallization temperature, crystallinity, and glass transition temperature (T_g) of CF-PDA-SiO₂/PA6 composites improved correspondingly, attributing to the heterogeneous nucleation of nano-SiO₂ in the crystalline area and hydrogen bonds with molecular chains of PA6 in the amorphous area. This work provides a novel strategy for the construction of interfaces suitable for advanced CF composites with different structures.     

聚酰胺酸纤维热酰亚胺化的研究

采用聚酰胺酸纤维热酰亚胺化处理方法制备聚酰亚胺纤维,研究了不同热处理条件对聚酰亚胺纤维性能的影响。结果表明,采用定长处理和持续升温方式,真空氛围,热处理温度420℃,得到的聚酰亚胺纤维性能较好,其断裂强度达5.06 cN/dtex。     

Synthesis and properties of hydroxyapatite nanorod‐reinforced polyamide 6 nanocomposites

BACKGROUND: Polyamide 6 (PA6)/hydroxyapatite (HA) nanocomposites, which combine the bioactivity and biocompatibility of HA and the excellent mechanical performance of PA6, have emerged as new biomaterials with potential applications in the clinical setting. It has been shown that these nanocomposites show good similarity to natural bone in terms of chemistry and mechanical properties. RESULTS: In this study, highly crystallized hydroxyapatite nanorods (HANR) were used to fabricate PA6/HA nanocomposites via in situ hydrolytic ring‐opening polymerization of ε‐caprolactam. The effect of the HANR on the thermal stability, crystallization behavior and hydrogen bonding of PA6 was investigated using thermogravimetric analysis, differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy, respectively. It was found that HANR can obviously increase the crystallization temperature and decrease the degree of supercooling. In addition, the thermal degeneration temperature of PA6 is also increased by the incorporation of HANR. FTIR analysis of the hydrogen bonded N? H stretching vibration revealed that, with increasing HANR loading, the hydrogen bonded N? H stretching band shifts to higher frequency and decreases in intensity. CONCLUSION: The thermal stability and crystallization ability of PA6 are improved considerably by the incorporation of HANR. However, the hydrogen bonding strength is weakened and the degree of ordering of hydrogen bonding is reduced by the incorporation of HANR, which can be explained by the formation of hydrogen bonds at the interface between ? OH groups of HANR and the ? N? H or ? C?O groups of PA6. Copyright © 2009 Society of Chemical Industry