聚醚醚酮的结晶与熔融行为研究

研究了PEEK在高于熔点的温度范围内处理时的结晶行为以及结晶后的熔融行为。发现处理时熔融的PEEK将同时发生交联与结晶,交联使未结晶的部分结晶受阻,结晶使尚存的晶片增厚,从而导致PEEK在DSC上出现对应于不同晶体结构的新的熔融双峰,并在此基础上提出了处理过程中PEEK结构变化的模型。此外,还发现处理后的PEEK的熔点,可高于目前已报导的平衡熔点。     

聚醚醚酮的热交联及其对结晶的影响

本文研究了聚醚醚酮于空气中熔处理时的交联特征及其对ＰＥＥＫ结晶的影响，结果表明，交联使ＰＥＥＫ的耐溶剂性提高，交联伴随着ＰＥＥＫ主链上苯环的邻位取代发生，并有氧参与了反应。交联将对ＰＥＥＫ的结晶产生阻碍：使其结晶速率与结晶度降低；使其结晶形态及微晶尺寸改变。     

熔融温度对PPS／PEEK中PPS的结晶熔融行为的影响

用粉末干混法制备结晶／结晶共混体系ＰＰＳ／ＰＥＥＫ，并用ＤＳＣ研究了不同熔融温度下淬火ＰＰＳ及ＰＰＳ／ＰＥＥＫ共混物中ＰＰＳ的结晶熔融行为。熔融温度（Ｔｍｅｌｔ）高于３６０℃时，对ＰＰＳ的结晶熔融行为有影响，结晶温宽（ΔＴｃ）随Ｔｍｅｌｔ提高而加宽；ＰＥＥＫ加入ＰＥＥＫ含量增加，使ＰＰＳ的结晶、熔融温度下降。共混物中的ＰＰＳ的结晶熔融行为受Ｔｍｅｌｔ影响更大。     

电子束辐射对取向性聚醚醚酮性能的影响

在室温空气气氛中用电子束(EB)辐照拉伸取向后的聚醚醚酮(PEEK)片,研究了辐射对取向性PEEK片材性能的影响。采用X射线衍射(XRD)、热重分析(TGA)、差示扫描量热(DSC)和万能拉力机等手段测试了不同辐射吸收剂量对取向性PEEK片受力方向(平行方向)和垂直于受力方向(垂直方向)的结晶性能、热稳定性、力学性能和热收缩性能的影响。结果表明,在实验吸收剂量范围内,样品的结晶温度、熔融焓以及结晶度都随着吸收剂量的增加而减小;随着吸收剂量的增加样品的热稳定性降低;在空气气氛中辐照样品,其平行和垂直方向上的断裂伸长率、断裂应力均随吸收剂量的增加而减小;辐照后样品平行方向的热收缩率是垂直方向的2倍,在不同吸收剂量的条件下两方向的热收缩率都不变。     

热氧老化对聚醚醚酮结构与性能的影响

聚醚醚酮(PEEK)作为工程材料广泛应用于多个领域,研究其热氧老化规律对其材料服役优化具有重要意义.采用傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)、X射线衍射、差示扫描量热和万能拉力机等测试了PEEK片在310℃高温环境中热氧老化不同时间后化学结构及性能的变化.结果表明,在实验老化时间范围内,FT-I...     

分子量及其分布对聚丙烯力学性能和结晶行为的影响

通过机械共混的方法制备一系列不同分子量及其分布的聚丙烯，并对其力学性能和结晶行为进行了表征，研究了分子量及其分布对这些性能的影响以及力学性能和结晶行为的对应关系。通过实验发现，分子量及其分布对聚丙烯的结晶速率，结晶温度，结晶度，冲击强度，拉伸屈服强度，断裂伸长率等均有较大影响。     

结晶／结晶共混体系PPS／PEEK中PPS的多熔融行为

用ＤＳＣ研究了熔融时间和高温退火结晶时间对聚苯硫醚和结晶性聚醚醚酮对ＰＰＳ的多熔融行为的影响。２７５℃退火结晶≤３ｈ样品呈现熔融双峰，Ｔｍｌ〈退火结晶温度（Ｔａ）〈Ｔｍ２；然而，ｔａ＝１２ｈ时，熔融双峰的峰温均高于Ｔａ和无退火结晶ＰＰＳ的熔点。ＰＥＥＫ加入对ＰＰＳ玻璃态和熔体结果 起到阻碍作用，共混物在ＰＰＳ的Ｔｍ２以上形成１个高温吸热峰，其峰温在３１０℃以上，且随ａ延长而移向高温。     

超高分子量聚乙烯的形态对高密度聚乙烯结晶行为的影响

通过熔融共混制备了高密度聚乙烯/超高分子量聚乙烯(HDPE/UHMWPE)共混物,采用高温熔融和再次剪切处理改变了UHMWPE在HDPE中的分散形态,并使用非等温结晶和连续自成核退火热分级(SSA)方法研究了UHMWPE的形态变化对HDPE的结晶行为的影响。扫描电子显微镜图片显示,经过高温熔融和再次剪切后UHMWPE的形态发生了极大的改变,由原生粒子转变为溶胀粒子,最后粒子破碎并以更小的相畴尺寸分散在HDPE中。结晶行为表明,原生粒子促进了HDPE的结晶,但结晶完善程度只有轻微的提高;溶胀粒子则阻碍了HDPE的结晶,结晶完善程度下降;更小相畴尺寸的UHMWPE对HDPE的结晶有明显的促进作用,结晶完善程度显著提高。     

分子量和冷却速率对PET熔体非等温结晶行为的影响

用DSC研究了粘均分子量((?)_η)和冷却速率(q)对PET熔体非等温结晶动力学参数、结晶峰高(h_(peak))和结晶热焓(△H_c)的影响。实验结果表明,Avrami指数都在3.0±0.5范围内;Avrami常数随增大((?)_η)而逐渐减小,随q增大而显著增大。q的变化影响结晶峰的峰温(T_(Peak)),也影响h_(Peak));用h_(Peak)对T_(Peak)作图,发现((?)_η)从8,000到29,000的h_(Peak)在162～170℃的温度范围内出现最大值;在T_(Peak)为177℃,有下述定量关系 ㏒ h_(Peak)=1.15×10~2((?)_η)~(-1/2)-2.04。而△H_ζ不仅依赖于((?)_η),还依赖于q。     

不同端基及分子量聚氧乙烯的结晶行为研究

通过偏光显微镜和DSC技术，较为详细地研究了不同端基及分子量PEO的结晶行为，当PEO的分子量大于6000g/mol时，分子量对其结晶行为的影响逐渐变得很小，当分子量介于6000g/mol-2000g/mol时，为一临界分子量区，分子量变化对其结晶能力有很大的影响。氯乙基酯端基PEO链的折叠结晶受限较大，结晶度损失较大，而且，当分子量降至临界分子量区时，PEO结晶受限对端基体积更加敏感，结晶能力大大降低，羟基端基对结晶熔融焓（ΔHf)的影响与分子量的大小有强烈的关系，Tm仅随着端基体积的变大而下降。     

Effect of carbon nanotubes on the mechanical properties and crystallization behavior of poly(ether ether ketone)

Pristine carbon nanotubes (CNTs) and noncovalently functionalized carbon nanotubes (f-CNTs) were used to prepare poly(ether ether ketone) (PEEK) composites (CNTs/PEEK and f-CNTs/PEEK) via melt blending. Noncovalently functionalized multiwalled nanotubes were synthesized using hydrogen-bonding interactions between sulfonic groups of sulfonated poly(ether ether ketone) (SPEEK) and carboxylic groups of nanotubes treated by acid (CNTs–COOH). The effects of these two kinds of nanotubes on the mechanical properties and crystallization behavior of PEEK were investigated. CNTs improved mechanical properties and promoted the crystallization rate of PEEK as a result of heterogeneous nucleation. Better enhancement of mechanical properties appeared in the f-CNTs/PEEK composites, which is ascribed to the good interaction between f-CNTs and PEEK. However, the strong interaction of f-CNTs and PEEK chains decreased the crystallization rate of PEEK for high content of f-CNTs.     

The influence of thermal history on the mechanical properties of poly(ether ether ketone) matrix composite materials

The purpose of this study is to provide insight into the microstructural factors that affect the flexural fatigue performance of carbon-fibre-reinforced poly(ether ehter ketone) (PEEK) composites. Specifically, the effect of the degree of crystallinity on the mechanical properties is examined at two crystallinity levels of the as-received composites (35%) and of quenched composites (10%). Higher static flexural strength and modulus as well as longer fatigue life are observed for the higher crystallinity level. By varying the loading angle with respect to the fibre direction it is shown that the crystallinity effect is not matrix dependent alone. Rather, a strong effect is evident in the fibre direction, which is attributed to the influence of the transcrystalline layer formed on the fibre surface in the high-crystallinity material. As a result, the longitudinal fatigue life at 1·7GPa of the 35% crystallinity material is three orders of magnitude higher than that of the 10% crystallinity composite.     

Carbon-nanofibre-reinforced poly(ether ether ketone) composites

Poly(ether ether ketone) nanocomposites containing vapour-grown carbon nanofibres (CNF) were produced using standard polymer processing techniques. Evaluation of the mechanical composite properties revealed a linear increase in tensile stiffness and strength with nanofibre loading fractions up to 15 wt% while matrix ductility was maintained up to 10 wt%. Electron microscopy confirmed the homogeneous dispersion and alignment of nanofibres. An interpretation of the composite performance by short-fibre theory resulted in rather low intrinsic stiffness properties of the vapour-grown CNF. Differential scanning calorimetry showed that an interaction between matrix and the nanoscale filler could occur during processing. Such changes in polymer morphology due to the presence of a nanoscale filler need to be considered when evaluating the mechanical properties of such nanocomposites.     

Carbon-nanofibre-reinforced poly(ether ether ketone) fibres

Nano-reinforced fibres were spun from a semicrystalline high-performance poly(ether ether ketone) containing up to 10 wt% vapour-grown carbon nanofibres using conventional polymer processing equipment. Mechanical tensile testing revealed increases in nanocomposite stiffness, yield stress, and fracture strength for both as-spun and heat-treated fibres. X-ray and differential scanning calorimetry analyses were performed in order to investigate both the orientation of nanofibres within the polymer matrix and the matrix morphology. The carbon nanofibres were found to be well aligned with the direction of flow during processing. Significantly, the degree of crystallinity of the poly(ether ether ketone) matrix was found to increase with the initial addition of nanofibres although the crystal structure was not affected. The measured increase in composite tensile modulus is compared to injection-moulded nanocomposite samples made from the same blends. The results highlight the need to characterise the matrix morphology when evaluating nanocomposite performance and hence deducing the intrinsic properties of the nanoscale reinforcement.     

聚醚醚酮改性研究进展

聚醚醚酮(PEEK)作为一种新型高性能热塑性工程塑料,在许多工程领域有着广泛的应用.采用不同手段增强PEEK,改善其加工性能和力学性能、热性能、摩擦学性能,有利于降低材料成本和进一步拓展应用范围.本文从纤维增强PEEK、颗粒填充PEEK、PEEK表面改性、与聚合物共混等方面综述了PEEK改性研究的进展情况.     

聚芳醚酮树脂非等温结晶动力学及其复合材料湿热老化性能EI北大核心CSCD

聚芳醚酮(poly(aryl ether ketone),PAEK)热塑性复合材料因其突出的韧性、耐老化性能、耐疲劳性能,以及成型加工低成本、高效率、可回收等一系列优势,得以替代部分传统热固性复合材料,并已在国外航空等高端工业领域取得成功应用。PAEK是一种半结晶高聚物,复合材料不同的成型工艺条件导致树脂基体聚集态结构的差异,对其力学性能、耐老化性能等均存在显著的影响。对国产PAEK树脂的结晶动力学进行了研究,通过控制成型降温条件,采用模压工艺制备了树脂结晶度不同的连续碳纤维增强复合材料,并对其进行了湿热老化处理,评价了老化处理前后复合材料的弯曲性能。结果表明:采用较大的降温速率能够提高树脂的结晶速率,但会降低树脂的结晶度。在随炉冷却、空气冷却和水冷却三种不同的降温条件下,制备的复合材料结晶度分别约为36.3%,29.7%,26.5%,结晶度的显著差别导致复合材料的弯曲强度随结晶度的降低而减小。经湿热老化处理240 h后的弯曲强度保留率分别为88.8%,86.7%,86.6%,较高的结晶度能够较好地抵抗水对复合材料界面的破坏,提升复合材料的耐湿热老化性能。     

The effects of solvent sorption on the properties of poly(ether ether ketone)

A study has been carried out on the sorption of ortho-dichlorobenzene, N,N-dimethylformamide and water by poly(ether ether ketone) (PEEK). Two types of PEEK samples have been analysed; the first in the amorphous state and the second with a high crystallinity level. The sorption and desorption curves have been determined and the effect of the solvent presence on the mechanical properties has been analysed by means of the tensile test. PEEK is affected to a different extent by the solvents studied and also by the crystallinity of the polymer. Sorption takes place only in the case of amorphous PEEK. Its effect on the mechanical properties of PEEK is explained on the basis of the two concomitant processes that are the consequence of sorption, these are: plasticization and induced crystallization.     

聚醚醚酮复合材料的研究进展

复合改性是进一步提高聚醚醚酮(PEEK)使用性能、扩展其应用领域的重要途径.本文综述了PEEK在热机械性能、摩擦学性能等方面的复合改性研究进展,以及PEEK复合材料在生物假体材料领域、磺化PEEK复合材料在质子交换膜领域的应用研究进展.     

Sulphonated poly(ether ether ketone): Synthesis and characterisation

The sulphonation of commercially available PEEK in powder form (Gatone, Gharda Chemicals Limited, India) was carried out using conc. H²SO⁴ under different reaction conditions. The duration of reaction was varied from 3–5 h, polymer concentration 4–10% (w/v) and temperature 35–50C. Structural characterisation of sulphonated polymers was done by elemental analysis, FT-IR and ¹H-NMR spectroscopy. The degree of sulphonation as calculated from ¹H-NMR and elemental analysis (S-content) was found to be in the range of 50–80%. Multistep mass loss was observed in thermogravimetric traces (recorded in N² atmosphere). The first step (50–225 ± 25C) was due to loss of moisture (1–10%) and second step (250–425 ± 25C) has been attributed to volatilization of SO³ from the sulphonic group. The backbone degradation takes place above 450C. The mechanical properties and proton conductivities of various sulphonated samples was also evaluated.