聚醚醚酮结晶度的测定

用Ｘ射线及图解积分法校正了聚醚醚酮（ＰＥＥＫ）的结晶与结晶衍射强度，导出了ＰＥＥＫ的结晶度公式，另外红外光谱法（ＩＲ），差示扫描量热法（ＤＳＣ）及密度法（ＤＭ）测定ＰＥＥＫ样品的结晶度，表明这些方法的结果有很好的可比性。     

Crystallinity of isotactic polypropylene films annealed from the quenched state

Quenched isotactic polypropylene films were annealed at 130, 140 and 155 °C for 24 h. The structural organization, after annealing, was analysed by wide-angle X-ray diffractograms (WAXD), differential scanning calorimetry (DSC), density and sorption of dichloromethane vapour at low activity. The comparison of the different methods used to obtain the crystallinity shows that, even at the highest annealing temperature, the transformation of the smectic phase into the monoclinic phase, is not complete. WAXD and DSC give the amount of monoclinic phase, whereas the amorphous fraction was derived from sorption of dichloromethane vapour at low activity. From the density, it was possible to derive the residual smectic fraction in the different samples. The results indicate that, at temperatures higher than 150 °C, there is an accelerated decrease of smectic phase and an accelerated increase in the crystal dimensions and perfection.     

Influence of the crystallinity on the transport properties of polyethylene

Transport properties of dichloromethane were analysed in high- and low-density polyethylene films, obtained with different thermal treatments, in order to correlate sorption and diffusion with the crystallinity of the samples. The crystalline fraction of all the analysed samples was evaluated from density and X-ray data; it ranged from 40%–85%. From the X-ray diffractograms the reciprocal of the width at half-height for the strongest reflection was derived for all the samples; it was considered as an order parameter. It was found that the sorption depends only on the fraction of amorphous phase; in fact, the specific sorption, normalized for the crystallinity of the sample, is constant for all the samples. However, the zero concentration diffusion coefficient,D ₀, varies with the sample crystallinity, but there is no simple correlation between these two parameters; rather a transition seems to separate two ranges in which the diffusion coefficient decreases with the crystallinity. At variance, a linear decrease of the diffusion parameter with the order parameter, derived from the X-ray diffractograms, was found in the whole range of crystallinity.     

Thermal analysis studies of poly(etheretherketone)/hydroxyapatite biocomposite mixtures

Biocomposite formulations which have the potential to combine the proven mechanical performance of poly(etheretherketone) (PEEK) with the inherent bioactivity of hydroxyapatite (HA), may have a utility as load-bearing materials in a medical implant context. The effect of thermal processing on the relevant properties of the PEEK and/or HA components in any fabricated composite structure is, however, an important consideration for their effective exploitation. This paper reports the results of a detailed thermal characterization study of a series of PEEK/HA mixtures using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and modulated differential scanning calorimetry (MDSC). The TGA analyses show minimal weight loss for all of the mixtures and for a pure PEEK sample up to 530 °C. Above this point there is a sharp on-set of decomposition for the PEEK component in each case. The temperature at which this feature occurs varies for each mixture in the approximate range 539–556 °C. This observation is supported by the presence of exotherms in the corresponding DSC scans, in the same temperature region, which are also assigned to PEEK decomposition. The temperature at which the degradation on-set occurs is found to decrease with increasing HA contribution. The use of the modulated DSC technique allows a number of important thermal events, not easily identifiable from the data obtained by the conventional method, to be clearly observed. In particular, the glass transition temperature T_g of the polymer can now be accurately determined. Using these thermal analysis data, calculations of the % crystallinity of PEEK in the mixtures have been made and compared with that of a 100% polymer sample. From these studies it is evident that the presence of HA does not adversely affect the degree of crystallinity of the PEEK component in the mixtures of interest over the thermal range studied.     

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.     

Microstructure of quenched and annealed films of isotactic polypropylene

The Microstructure of quenched and annealed iPP films was investigated by means of differential scanning calorimetry (DSC), density measurements, wide-angle X-ray diffraction (WAXD) and dynamic mechanical spectrometry (DMS). It was found that quenched iPP can be described as a biphasic material constituted of an amorphous phase strongly cross-linked by many crystalline entities exhibiting both small size and very low degree of perfection. Such microcrystallites act as true physical ties of the amorphous phase. On increasing the annealing temperature from 20 °C (quenched film) to 160 °C, the crystallinity ratio first remained constant for annealing temperatures between 20 and 93 °C and then it increased. Subsequently, both size and degree of perfection of crystalline entities progressively increased and tended towards the characteristics of the monoclinic phase. This resulted in a progressive decrease in the physical cross-linking degree of the amorphous phase, even for the samples exhibiting the highest crystallinity ratio.     

Nonisothermal crystallization behavior and mechanical properties of PEEK/SCF/nano-SiO2 composites

Nonisothermal crystallization of hybrid PEEK composites reinforced with short carbon fibers (SCF) and nano-SiO₂ (1, 1.5 and 2 wt%) was investigated using DSC. Composites were fabricated by melt-mixing process at 400 °C. The Size of the nanoparticles was 13 nm. Samples were cooled from 410 °C to 25 °C with cooling rates of 10, 30, 50 and 70 °C min⁻¹. The onset, peak and end crystallization temperatures were investigated as well as absolute crystallization percentage and crystallization time. Avrami, Ozawa and Ozawa–Avrami equations were fitted to the data in order to investigate the crystallization kinetics. Mechanical behaviors of the composites were examined using nanoindentation and nanoscratching. DSC results revealed that absolute crystallization percentage increases in PEEK/SCF/1%SiO₂ and PEEK/SCF/1.5%SiO₂ samples compared to PEEK/SCF, however it decreases by adding more nano-SiO₂. Ozawa–Avrami is proved to be the best model for describing crystallization behavior of the composites while Avrami equation was suitable for describing a part of the crystallization process. The Avrami and Ozawa–Avrami constants were calculated. Besides, adding SCFs and nano-SiO₂ into PEEK results in a significant decrease in plasticity index, while increases the resistance to plastic deformation of the composite.     

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。     

Open circuit reactions complicating the electroprecipitation of poly(vinylferricinium) films from methylene chloride

We describe an electrochemical quartz crystal microbalance interfacial gravimetric study of the electroprecipitation and dissolution of PVF+ClO4- (PVF = poly(vinylferrocene)) films exposed to methylene chloride solutions. Film deposition is diffusion controlled by the supply of PVF from the solution. Film solvent content is markedly dependent upon the deposition potential. The self-exchange process between surface-bound ferricinium sites and solution-phase ferrocene sites, which is responsible for film deposition under conditions of positive applied potential, is also responsible for film dissolution under open circuit conditions. Dependent upon the deposition potential, releasing the electrode from potential control may (not) result in transient deposition processes that temporarily increase surface coverage. Under all conditions, opening the circuit ultimately leads to reductive stripping of the film by solution-phase PVF. The dissolution rate is independent of applied potential, and is not limited by electron transfer at the outer film interface or by electron (and coupled ion) transport within the film; we speculate that polymer-based processes, such as chain disentanglement, are rate limiting.     

The effect of filler particle size on the antibacterial properties of compounded polymer/silver fibers

Antibacterial activity has become a significant property of textiles used in applications such as medicine, clothing, and household products. In this study, we compounded polypropylene with either micro- or nano-sized silver powders. These polypropylene/silver compounds were prepared by direct melt-compounding using a conventional twin-screw mixer. We analyzed the characteristics of the compounds using wide-angle X-ray diffractometry (WAXS), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The DSC and WAXS results indicated that the crystallinity of the polypropylene component decreased slightly when compared with that of the pure polymer. The SEM micrographs indicated that the silver particles had good dispersibility in the matrix. We measured the mechanical properties of these materials using a universal tensile tester and evaluated the antibacterial activities of these compounds by performing quantitative antibacterial tests using the AATCC-100 test method. From these evaluations of antibacterial activity, we conclude that the compounds incorporating the silver nanoparticles exhibited superior antibacterial activity relative to the samples containing micron-sized particles.     

X-ray diffraction and ice nucleation studies of Agl-AgBr-Cul system

Lattice parameter calculations and ice nucleation studies for the Agl-AgBr-Cul system are reported in this study. Thirteen samples of different molar compositions were prepared by vacuum fusion. The X-ray powder diffractograms of these samples revealed the formation of cubic solid solutions of the above system. It is found that the 50:25:25 mol% composition of Agl, AgBr and Cul, has the highest nucleation temperature of –0.48° C, which is far greater than –2.53 and –2.26° C for pure Agi and Cul, respectively.     

Effects of nematic polymer liquid crystal on crystallization and structure of PET/Vectra blends

We investigate the effects of a nematic liquid crystalline polymer, Vectra A, on the structure and properties of its blends with a semicrystalline polymer, poly(ethylene terephthalate),PET. PET/Vectra blend composition ranged from 100/0 to 60/40. Real-time, in situ studies ofisothermal and non-isothermal melt crystallizations of these blends were conducted usingsimultaneous wide and small angle X-ray scattering (WAXS and SAXS), differentialscanning calorimetry (DSC), and quantitative polarizing optical microscopy. All techniquesconfirm that the addition of Vectra nematic liquid crystal delays the onset of crystallization,and affects the degree of crystallinity and structural parameters such as Bragg long period,lamellar thickness and linear stack crystallinity. SAXS results indicate that some of theVectra component penetrates into the interlamellar regions of the crystal stacks. Vectrainterrupts the entangled polymer network making it more difficult for lamellar crystals tonucleate. Slower nucleation and growth result in increased perfection of the PET crystalsgrown isothermally, but reduces the crystallization temperature of PET crystals grownnon-isothermally causing these crystals to be less perfect.     

Physical properties of edible films based on cassava starch as affected by the plasticizer concentration

The aim of this work was to investigate the effect of glycerol contents on physical properties of cassava starch films. The films were prepared from film‐forming solutions (FFS) with 2g cassava starch/100g water and 0, 15, 30 and 45g glycerol/100g starch, and were analysed to determine its mechanical properties by tensile tests, the glass‐transition temperature (Tg) by differential scanning calorimetry (DSC) and the crystallinity by X‐ray diffraction (XRD). The infrared spectra of the films were also recorded. The resistance values of the films decreased, while those of the elasticity increased with an increase in glycerol concentration due to the plasticizer effect of glycerol, which was also observed in DSC curves. The Tg of the films prepared decreased with the glycerol content. However, for samples with 30 and 45g glycerol/100g starch, two Tg curves were observed, probably due to a phase separation phenomenon. According to the XRD diffractograms, the films with 0 and 15gglycerol/100g starch presented an amorphous character, but some tendency to show crystalline peaks were observed for films with 30 and 45g glycerol/100g starch. The results obtained with Fourier transform infrared (FTIR) corroborated these observations. Copyright © 2007 John Wiley & Sons, Ltd.     

Cooling rate influences in carbon fibre/PEEK composites. Part 1. Crystallinity and interface adhesion

The effect of cooling rate on the fibre–matrix interface adhesion for a carbon fibre/semicrystalline polyetheretherketone (PEEK) composite was characterised based on the fibre fragmentation, fibre pullout and short beam shear tests. The interface adhesion was correlated to the degree of crystallinity and the crystalline morphology, as well as the bulk mechanical properties of neat PEEK resin, all of which were in turn controlled by cooling rate. It was shown that the interface bond strength decreased with increasing cooling rate; the tensile strength and elastic modulus of PEEK resin decreased, while the ductility increased with increasing cooling rate through its dominant effect on crystallinity and spherullite size. The improvement of crystalline perfection and flattened lamella chains with high crystallinity at the interphase region were mainly responsible for the strong interface bond in composites processed at a low cooling rate. The interphase failure was characterised by brittle debonding in slow-cooled composites, whereas the amorphous PEEK-rich interphase introduced in fast cooled specimens failed in a ductile manner with extensive plastic yielding.     

Formation of defect-free latex films on porous fiber supports

We present here the creation of a defect-free polyvinylidene chloride barrier layer on the lumen-side of a hollow fiber sorbent. Hollow fiber sorbents have previously been shown to be promising materials for enabling low-cost CO(2) capture, provided a defect-free lumen-side barrier layer can be created. Film experiments examined the effect of drying rate, latex age, substrate porosity (porous vs nonporous), and substrate hydrophobicity/hydrophilicity. Film studies show that in ideal conditions (i.e., slow drying, fresh latex, and smooth nonporous substrate), a defect-free film can be formed, whereas the other permutations of the variables investigated led to defective films. These results were extended to hollow fiber sorbents, and despite using fresh latex and relatively slow drying conditions, a defective lumen-side layer resulted. XRD and DSC indicate that polyvinylidene chloride latex develops crystallinity over time, thereby inhibiting proper film formation as confirmed by SEM and gas permeation. This and other key additional challenges associated with the porous hollow fiber substrate vs the nonporous flat substrate were overcome. By employing a toluene-vapor saturated drying gas (a swelling solvent for polyvinylidene chloride) a defect-free lumen-side barrier layer was created, as investigated by gas and water vapor permeation.     

Physical characterization of polycaprolactone scaffolds

Films and sponges were prepared from a solution of Poly(ε-caprolactone) (PCL) in tetrahydrofuran (THF). The porosity, crystallinity, and mechanical properties of the samples were studied. Porosity of around 15% was obtained for the films produced by evaporation of THF at room temperature. A much more porous structure (50–70%) was found for the sponges obtained by cooling the solution at −30 °C and subsequently eliminating the solvent by freeze drying. The porosity of the samples was also observed by scanning electron microscopy (SEM). The crystallinity of the samples was studied by the calorimetric technique (DSC) before and after the compression scans. The mechanical properties of the different samples were determined by compression test, and were compared to those corresponding to the PCL in bulk. The compression scans did not affect the crystallinity of the samples. The variations observed in the results of the different scans were attributed to the differences in porosities and crystallinity.     

Consolidation Process of PEEK/Carbon Composite for Aerospace Applications

Processing of PEEK/carbon composites into an aerospace structural part like the space arm can be very complex and necessitates repetition of the consolidation process in order to obtain a void free structure. The objective of the present work was to evaluate the effect of successive consolidations on the PEEK/carbon composite properties in order to determine optimum consolidation conditions.It is well known that the properties of the PEEK matrix in PEEK/carbon fiber composite are dependent on the processing conditions. Since each of the successive consolidations is done at a temperature of 400°C for a period of 60 minutes, it can be predicted that after a few cycles of consolidation, such thermal treatment can lead to matrix modifications. The results of the present study indicate that successive consolidations lead to modifications of the crystallization behavior of the PEEK matrix in the composite; alteration of the mechanism of nucleation of the PEEK matrix as well as the global rate of crystallization and a reduction in the recrystallizable material was observed. Modifications in the crystallization behavior of the PEEK matrix probably result from alteration of the chemical structure of the PEEK matrix when the composite is submitted to long treatment at high temperature. In particular, under oxidizing conditions, in air for example, chain scission followed by crosslinking reactions was proposed as the mechanism responsible for the matrix evolution.The evaluation of the tensile properties and the short beam shear strength of the consolidated samples also suggests that successive consolidations can affect the mechanical behavior of the PEEK/carbon composites. The mechanical characterization indicates that up to a certain level, the evolution of the PEEK structure during the consolidation process can be beneficial in terms of tensile and interfacial performance since crosslinks are strengthening structure.     

Effect of processing method on migration of antioxidant from HDPE packaging into a fatty food simulant in terms of crystallinity

Migration of additives from plastic packaging into food products is generally considered to be affected by polymer crystallinity. In the present work, migration of Irganox 1010 from high density polyethylene into a fatty food simulant (ethanol 95%) was studied for samples prepared with different percent crystallinities. For this purpose, 2 different processing techniques, injection and compression molding, were used, and the preparation conditions were changed to obtain high density polyethylene samples with crystallinities in the range of 50 to 70%. Migration analysis was carried out at 121°C for 2 hours, and then at 40°C for 238 hours using high performance liquid chromatography. In general, the injection molded specimens had lower crystallinity and higher overall migration than the compression molded ones. A similar trend for both injection and compression molded samples was observed indicating that the overall migration was a function of crystallinity degree. However, the specific migration rates of Irganox 1010 especially before 50 hours were found to be different for the 2 processing methods because of dissimilar morphologies. Theoretical modeling based on Fickian diffusion was applied to give more insights into the involved processes during specific migration. The interaction of the food simulant with the polymer was taken into account considering the food sorption into the polymer. By fitting the model on experimental data, it was possible to obtain the model parameters such as partition coefficients (K) and the swelling constant (B) as a function of sample crystallinity.     

Electrospun PVdF-PVC nanofibrous polymer electrolytes for polymer lithium-ion batteries

Nanofibrous membranes based on Poly (vinyl difluoride) (PVdF)-Poly (vinyl chloride) (PVC) (8:2, w/w) were prepared by electrospinning and then they were soaked in a liquid electrolyte to form polymer electrolytes (PEs). The morphology, thermal stability, function groups and crystallinity of the electrospun membranes were characterized by scanning electron microscope (SEM), thermal analysis (TG), Fourier transform infrared spectra (FT-IR) and differential scanning calorimetry (DSC), respectively. It was found that both electrolyte uptake and ionic conductivity of the composite PEs increased with the addition of PVC. The composite PVdF-PVC PEs had a high ionic conductivity up to 2.25 × 10⁻³ S cm⁻¹ at 25 °C. These results showed that nanofibrous PEs based on PVdF-PVC were of great potential application in polymer lithium-ion batteries.     

Influence of a dielectric medium on the phase state of carbon dioxide

The phase state of carbon dioxide gas dissolved in liquid n-heptane is determined by experimental investigations of the temperature dependences (180 < T < 250°K) of the spin-lattice relaxation time of protons, the coefficient of translational self-diffusion of n-heptane molecules and the nuclear magnetic resonance (NMR) linewidth of carbon¹³C.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 52, No. 3, pp. 402–405, March, 1987.