刚性链嵌段共聚物的研究（Ⅲ）──PEEK／HTA有规嵌段共聚物的合成与性能

采用ＰＥＥＫ和ＨＴＡ齐聚物的溶液缩聚法制备了ＨＴＡ含量不同的刚性链嵌段共聚物系列样品，用ＩＲ、ＤＳＣ、ＴＧＡ、ＷＡＸＤ和动态粘弹谱等手段对共聚物进行表征并研究了热性能和结晶行为。结果表明，该组成范围的共聚物未发生微相分离，共聚物的结晶结构与ＰＥＥＫ相同，结晶度随ＨＴＡ含量增加而迅速下降。含ＨＴＡ３７．２４％的共聚物Ｔ_ｇ＝１８３℃，比纯ＰＥＥＫ高４０℃。新型嵌段共聚物的熔点稍低于ＰＥＥＫ，具有良好的力学性能。     

Anisotropic linear thermal expansivity of poly(ether-ether-ketone)

This paper deals with anisotropic behavior of thermal expansivity (α) of poly(ether-ether-ketone) (PEEK) sample prepared by compression molding above the melting point of polymer. The α was determined using thermo mechanical analyzer (TMA) for the temperature interval 50-250 °C in expansion mode. It is found that out-of-plane thermal expansivity (α_z) is 3.8-fold of the in-plane thermal expansivity (α_xy) below the glass transition temperature (T_g) of PEEK while α_z is decreased to 1.8-fold of the α_xy above the T_g. Moreover, the average α_z over the range studied is about 2.2-fold of the α_xy. This anisotropic behavior may be attributed to the alignment of polymer spherulites and chains along in-plane direction due to compressive forces under hot compression molding.     

Experimental investigation and constitutive modeling of the deformation behavior of Poly-Ether-Ether-Ketone at elevated temperatures

The present study investigates the deformation behavior of Poly-Ether-Ether-Ketone (PEEK) at elevated temperatures and low strain rates through a combination of experiments and simulations. Uniaxial tension tests at elevated temperatures (293–543 K) and strain rates (8.3 × 10⁻³ to 3.3 × 10⁻¹ s⁻¹) were performed, and the temperature- and rate-dependencies of the deformation behavior and mechanism of PEEK were discussed in detail. The Erichsen test was performed at temperatures varying from 473 to 533 K and a fixed speed of 1 mm/s. Based on an investigation of numerous constitutive models, a phenomenological model called DSGZ was employed in ABAQUS/Explicit to characterize the deformation behavior of PEEK at elevated temperatures, and the deviation between experimental and simulation data was less than 10% at large deformations. Moreover, the simulation results accurately predicted the necking and cold drawing phenomena in the tension test as well as the deformation in the Erichsen test.     

Study of the carbon fiber–poly(ether–ether–ketone) (PEEK) interfaces, 2: relationship between interfacial shear strength and adhesion energy

In the second part of this general study, the carbon fiber–PEEK interfacial shear strength is measured by means of a fragmentation test on single-fiber composites. Different thermal treatments (continuous cooling from the melt, isothermal treatments and long melting temperature time) are applied to these model composites prior to testing. The results are systematically compared with the previously determined reversible work of adhesion between carbon fiber and PEEK. It is shown that physical interactions at the interface determine, to a large extent, the magnitude of the interfacial shear strength between both materials. However, it appears that the magnitude of the stress transfer from the matrix to the fiber is affected either by the existence of an interfacial layer or by a preferential orientation of the polymer chains near the fiber surface. The results obtained on systems that have been subjected to isothermal treatments (isothermal crystallization of PEEK) seem to confirm the existence of a transcrystalline interphase, the properties of which are dependent upon the crystallization rate of the matrix and the interfacial adhesion energy.     

含有脂肪族侧链的聚醚醚酮的合成、表征及结构与性能关系

以苯酚和含有不同链长的长链脂肪酮作为原料, 制备了与双酚A结构相似的双酚单体, 并与4, 4'-二氟二苯酮共聚, 合成了几种含有不同长度脂肪族侧链结构的聚醚醚酮类(PEEKs)聚合物. 利用元素分析和核磁共振氢谱(1H NMR)对所合成的双酚单体进行了表征, 并用红外光谱(FTIR)\, 示差量热扫描仪(DSC)、热失重分析仪(TGA)和电子拉力机对所合成的聚合物结构和性能的关系进行了研究.     

Valence band XPS and FT-IR evaluation of thermal degradation of HVAF thermally sprayed PEEK coatings

Coatings of PEEK (poly-ether-ether-ketone) have been produced on stainless steel 304 using the High Velocity Air Fuel (HVAF) thermal spray technique. These coatings were produced using 50 and 100 mm nozzle lengths with 200, 300 and 400 mm gun to substrate distances. The thermal degradation of the PEEK during the production of the coatings was assessed with valence band X-ray Photoelectron Spectroscopy (XPS) and attenuated total reflectance Fourier Transform Infrared Spectroscopy (ATR FT-IR). Valence band XPS shows that in general there is minimal degradation of the PEEK during the HVAF thermal spraying process. The FT-IR results show that at the 200 mm gun to substrate (standoff) distance for both nozzle lengths there is more surface degradation of the PEEK coating than at the longer gun to substrate distances. Specifically absorption bands appeared at 2918 and 2850 cm⁻¹, which correspond to alkane -CH₂- asymmetric stretching modes. The reduction of the 1250 cm⁻¹ band as compared with the 1220 cm⁻¹ band, both representing the stretching modes of the ether bonds in PEEK suggests that the degradation occurs at only one of the ether bonds. The phenyl C-H vibration at 673 cm⁻¹ was split for coatings produced at gun-substrate distance of 200 and 300 mm. This indicates a structural change in the phenyl ring possibly indicating a change in the extent of crystallinity of the PEEK polymer.     

Synthesis and properties of poly(aryl ether ether ketone) copolymers with pendant methyl groups

Polyether ether ketone and polyether ether ketone copolymers were prepared by the nucleophilic substitution reaction of 4,4′-difluorobenzophenone with hydroquinone and with varying mole proportions of hydroquinone and methyl hydroquinone using sulfolane solvent in the presence of anhydrous K₂CO₃. The polymers were characterised by different physico-chemical techniques. The crystallinity of the polymers was found to decrease with increase in concentration of the methyl hydroquinone units in the polymer. Thermogravimetric studies showed that all the polymers were stable upto 430 °C with a char yield above 49% at 900 °C in N₂ atmosphere. The glass transition temperature was found to increase and the crystalline melting temperature and activation energy were found to decrease with increase in concentration of the methyl hydroquinone units in the polymer.     

A comparison of the strength of autohesion of plasma treated amorphous and semi‐crystalline PEEK films

Polyether ether ketone (PEEK) is a promising material for the encapsulation of electronic components for medical implants but a strong and hermetic joining technology is required. Autohesion is a self‐bonding method that avoids the need for adhesives. The strengths of autohesive joins using amorphous and semi‐crystalline PEEK films after surface activation using RF plasma were compared. Both types of PEEK films showed successful autohesion after activation with the bond strength of the amorphous sample being twice as high as the bond strength of the semi‐crystalline sample. Plasma treatment increased the autohesion strength of PEEK with no observed change in surface roughness (as measured by profilometer). The water contact angle was reduced by the treatment. X‐ray photoelectron spectroscopy (XPS) was carried out to determine surface chemistry. In the case of the semi‐crystalline surface, plasma treatment increased the relative percentage of C? O functional groups compared to the untreated surface. For treated surfaces nitrogen concentration correlated positively with bond strength while oxygen concentration correlated negatively with the semi‐crystalline PEEK samples and positively with the amorphous PEEK samples. The oxygen groups most likely are formed after the treatment by ambient oxidation are not conducive to bond formation, possibly because of the quenching of radicals that would otherwise form links. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and characterization of soluble copoly(ether ketone)s containing double bonds

A series of copoly(ether ketone)s containing double bonds along the polymer chains were synthesized from the condensation polymerization of hydroquinone with 4,4′‐difluorobenzophenone and 4,5‐bis(4‐fluorobenzoyl)‐1‐methylcyclohexene in sulfolane containing anhydrous potassium carbonate. The presence of methylcyclohexene in the polymer chains resulted in an improvement in the solubility of poly(ether ketone)s in organic solvents such as chloroform, chlorobenzene, and sulfolane. As a result, the conditions for synthesizing these polymers were much milder than those for poly(ether ether ketone). The new copoly(ether ketone)s also showed good tensile properties and reasonable thermal stability. New polyethers containing pyrazine unites were obtained from the cyclization reaction of these copoly(ether ketone)s with hydrazine. The hydrazine cycloderivatives led to an increase in the glass‐transition temperatures and a decrease in solubility in organic solvents. © 2002 Government of Canada. Exclusive world‐wide publication rights in the article have been transferred to Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3449–3454, 2002     

Physical background of the endurance limit in poly(ether ether ketone)

In this study, it is demonstrated that the apparent endurance (fatigue) limit for plasticity-controlled failure in poly(ether ether ketone) is related to an evolution of the yield stress. The increase of the yield stress has two separate causes: (a) stress- and temperature-accelerated physical aging of the amorphous phase and (b) strain hardening as a result of texture development. Yield stress evolution is monitored using thermomechanical treatments during which the material is exposed to temperature and load. The combined contributions of both temperature and applied stress to yield stress evolution (below T _g) can be effectively modeled using an effective time approach employing an Arrhenius temperature-activation as well as Eyring stress activation. Combination of the yield stress evolution with a previously developed model for plasticity-controlled failure allows prediction of time-to-failure under both static and cyclic load, quantitatively capturing the observed apparent endurance limit.