Novel composites by hot compaction of fibers

The production of solid section products from highly oriented fibers by a novel compaction procedure is described for melt-spun and gel-spun polyethylene fibers, poly(ethylene terephthalate) and polypropylene fibers and Vectran liquid crystalline copolyester fibers. Differential scanning calorimetry and electron microscopy have been used to study the structure of the compacted polymers. For the most successful compaction, selective surface melting of a small fraction of each fiber enables the formation of a fiber composite of high integrity, where the matrix phase is formed by epitaxial crystallization of the melted fraction on the initial fibers, retaining a high proportion of their initial strength and stiffness. A wide range of potential applications is envisaged for the composites produced by hot compaction. In many cases these composites will be produced by thermoforming. In addition to the obvious advantages of high stiffness and strength, in several instances the unrestricted exploitation of unique properties of the fibers such as transparency to microwave radiation or low thermal expansion coefficients offer additional incentives for the use of these hot compacted materials rather than conventional fiber/resin composites.     

The preparation of oriented morphologies of the thermotropic aromatic copolyester of poly(ethylene terephthalate) and 80 mole percent p-acetoxybenzoic acid

Highly oriented morphologies of poly(ethylene terephthalate) and 80 mole percent p-acetoxybenzoic acid were prepared by shearing in an optical plate-plate rheometer and by melt fiber drawing in a temperature range at which the copolyester was either in the semicrystalline state or liquid crystalline phase. The optical, thermal, and mechanical properties of the oriented films and drawn fibers depended significantly on the processing temperature.     

Optothermal properties of fibers. XIII. Evaluation of the form birefringence and some other structural parameters due to thermal annealing for polyester (PET) fibers

In this work, changes in the structure of polyester [poly(ethylene-terephtalate) (PET)] fibers after annealing at constant temperature (120 and 140°C) and different times were studied interferometrically. The density of annealed PET fibers were measured by a system based on vibrating string. The Pluta polarizing interference microscope was used to determine the optical parameters of these fibers. The density and optical results were used to calculate the degree of crystallinity, the form birefringence, the number of monomeric units per unit volume, harmonic mean polarizability of the dielectric, harmonic mean specific refractivity, and the virtual refractive index. The behavior of fiber crystallinity at different annealing conditions were discussed with different optical parameters. Hermans optical orientation function have been compared with the generalized Lorentz–Loranz equation given by de Vries. Microinterferograms and curves are given for illustration. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:1955–1963, 1998     

取向PET/PEG共聚酯纤维的非等温结晶动力学

研究了取向ＰＥＴ／ＰＥＧ共聚酯纤维的非等温结晶动力学，提出了解析结晶动力学参数的新方法。结果表明，随ＰＥＧ含量的增加共聚酯纤维的结晶扩散活化能降低，结晶速率加快。与各向同性试样比较，取向试样的结晶峰明显向低温方向扩散。取向试样在较低温度下的结晶速率高于各向同性试样，而在较高温度下的结晶速率低于各向同性试样。     

Opto‐thermal properties of fibers. XV. A study of the drawing behavior of quenched poly(ethyleneterephthalates) fibers

Studies of the mechanical and optical properties of undrawn uniaxially stretched polyester PET (Egyptian manufacture) fibers by annealing and cold drawing were performed. The optical properties and strain produced in PET fibers at different conditions were measured interferometrically at room temperature. A two‐beam interferometric technique was used to determine refractive indices and birefringence of the investigated PET samples with strain produced by different stresses. Using a microstrain device attached to a microscope stage and through the application of the appropriate mathematical equations, the refractive indices and the birefringence values were determined as a function of the draw ratios. The resulting data were utilized to calculate the polarizability per unit volume, the number of molecules per unit volume, Poisson's ratio, the strain optical coefficient, and several other parameters and constants. Also, some structural parameters are determined, such as form birefringence, the virtual refractive index, the harmonic mean polarizability of the dielectric, the harmonic mean specific refractivity, and the isotropic refractive index. The generalized Lorentz–Lorenz equation given by de Vries is used to determine PET fiber structure parameters. Comparison between the results have been compared with Hermans' optical orientation function. Relationships between the various optical parameters and the draw ratios are plotted, and the effect of draw ratio on the refractive index profile is studied. Microinterferograms are given for illustration. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1869–1880, 1999     

Structures and properties of easily dyeable copolyesters and their fibers respectively modified by three kinds of diols

Three kinds of modified poly(ethylene terephthalate) copolyesters were synthesized, using sodium‐5‐sulfo‐bis‐(hydroxyethyl)‐isophthalate as the third monomer, 1,3‐propanediol (PDO), 2‐methyl‐1,3‐propanediol (MPD), and 2,2‐dimethyl‐1,3‐propanediol (neopentyl glycol or NPG) as the fourth monomer, respectively. The copolyester fibers were also prepared by melt spinning and drawing processes. The effect of PDO, MPD, and NPG on the synthesis and spinning process was investigated, and the structures and properties of both copolyesters and the produced fibers were characterized. The results exhibited that the structural difference of PDO, MPD, and NPG played an important role in the synthesis and spinning process, and significantly affected the structures and properties of both copolyesters and the produced fibers, which thereby resulted in the difference in terms of dyeability improvement of copolyester fibers. The dyeing at boiling temperature under normal pressure experiments of copolyester fibers in both disperse dyebath and cationic dyebath revealed that incorporation of the fourth monomer could improve the dyeability of copolyester fiber, and copolyester fiber containing MPD unit had better dyeability due to a looser, more accessible structure when compared with the fiber containing PDO or NPG unit. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Determination of optical properties,dispersion, and structural parameters of poly(ethylene terephthalate) fibers using automatic variable wavelength interferometry technique

Automatic variable wavelength interferometry (VAWI) is used in combination with a Pluta double refracting polarizing interference microscope for measuring the spectral dispersion parameters of the refractive indices of poly(ethylene terephthalate) (PET) highly oriented yarn fibers (1000 denier/250 filaments). The resulting data are utilized to calculate the spectral dispersion and structural parameters such as Cauchy's constants, the dispersion energy, the oscillation energy, the density, the mean polarizability of the monomer unit, the number of monomer units per unit volume, the dielectric constant, the electric susceptibility, the optical orientation function, and the electric polarizability constant. Microinterferograms are given for illustration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1737–1742, 2003     

使用反相气相色谱法表征合成纤维表面润湿性

以聚丙烯纤维、聚癸二酰己二胺纤维和聚对苯二甲酸乙二醇酯纤维为研究对象,使用反相气相色谱法,以含有不同碳数的正烷烃和蒸馏水为探针分子,分别测定了合成纤维的表面自由能色散分量和水分子的净保留体积,表征其表面润湿性并分析影响因素。结果表明,纤维化学结构单元是合成纤维表面润湿性的决定性因素：具有非极性基团的聚丙烯纤维亲油性较好,具有极性基团的聚癸二酰己二胺纤维亲水性较好;纱线的线体结构影响合成纤维受热时的膨胀程度,从而显著影响表面自由能色散分量随温度的变化趋势。     

Optical properties of thermally crystallized poly(ethylene terephthalate)

The optical properties of thermally crystallized polyethylene terephthalate (PET) were investigated using the methods of small-angle light scattering, density, and haze measurements. The results indicate that the haze in crystallized PET results from scattering due to crystalline aggregates called spherulites. The formation of spherulites can lead to high levels of haze even at very low levels of crystallinity. A detailed analysis of polarized light-scattering patterns was employed in order to define the various structural parameters responsible for haze. The relationships between haze, crystallinity, spherulite size, and volume fraction of spherulites were developed for PET.     

Optically transparent self-reinforced poly(ethylene terephthalate) composites: molecular orientation and mechanical properties

Self-reinforced composites have been fabricated by compaction of oriented polyethylene terephthalate (PET) fibers under pressure at temperatures near, but below, their melting point. The originally white fiber bundles, which were about 40% crystalline, show increased crystallinity (55%) but optical translucency after processing. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) were used to study the crystallization and orientation of the fibers, revealing that the degree of crystallinity was somewhat insensitive to compaction conditions while the melting point increased substantially with increasing compaction temperature. Crystalline orientation, gauged using the Hermans orientation parameter from WAXD data, indicated that no significant loss in orientation of the crystalline fraction occurs due to compaction. Mechanical characterization revealed a stepwise decrease in flexural modulus (9.4-8.1 GPa) and concomitant increase in transverse modulus and strength on increasing the compaction temperature from 255 to 259 °C. This transition in behavior was accompanied by a loss of optical transparency and a change in the distribution of amorphous fraction from fine intrafibrillar domains to coarse interfibrillar domains as seen with electron microscopy. We argue then that the mechanical properties of PET compactions are influenced more by orientation of the amorphous phase than that of the crystalline phase. The impact properties of compacted materials, characterized using an unnotched Charpy test method, showed remarkable impact resistance after compaction, with impact toughness decreasing as compaction temperature was increased.     

Effect of interface on the morphology and properties of composites comprising poly(propylene) and short organic fibers

The effect of the fiber surface modification with an azide derivative on the morphology and properties of composites based on poly(propylene) (PP) and short poly(ethylene terephthalate) (PET) and nylon 66 (PA) fibers, has been investigated. Both organic fibers act as reinforcement of the PP, and the reinforcing effect increases with the introduction of azide groups on the chemical structure of the fibers. This effect is more sensible in PP/short PET fiber composites although PA fibers gives rise to higher improvements in toughness. Scanning electron microscopy (SEM) has shown that the azide treatment of PET fibers gives rise to a better wettability and adhesion at the fiber/matrix interface. A good correlation between SEM and mechanical behavior of the composites has been observed.     

Effect of moisture absorption on the tensile properties of short glass fiber reinforced poly(butylene terephthalate)

Injection molded short glass fiber reinforced poly(butylene terephthalate) was subjected to hygrothermal aging at two different relative humidities—81.2% and 100% RH. A single free phase model of diffusion has been used to analyze the data obtained from the kinetics of moisture absorption study. The diffusion coefficient and the equilibrium moisture content were found to be dependent on the volume fraction of fibers and relative humidity. Incorporation of short glass fibers into a poly(butylene terephthalate) matrix has led to a significant improvement in the retention and recoverability of the tensile properties. Examination of fracture surfaces using a scanning electron microscope (SEM) has revealed some evidence for the hydrolysis of the polymer matrix. The hydrolysis resulted in the formation of microvoids, the absence of a plastic deformation process, and degradation at the fiber-matrix interface.     

Antielectrostatic poly(ether ester) block copolymer of poly(ethylene terephthalate‐co‐isophthalate)–poly(ethylene glycol)

Poly(ethylene terephthalate) (PET) fiber has a low moisture regain, which allows it to easily gather static charges, and many investigations have been carried out on this problem. In this study, a series of poly(ethylene terephthalate‐co‐isophthalate) (PEIT)–poly(ethylene glycol) (PEG) block copolymers were prepared by the incorporation of isophthalic acid (IPA) during esterification and PEG during condensation. PEG afforded PET with an increased moisture affinity, which in turn, promoted the leakage of static charges. However, PET also then became easier to crystallize, even at room temperature, which led to decreased antistatic properties and increased manufacturing inconveniences. IPA was, therefore, used to reduce the crystallinity of the copolymers and, at the same time, make their crystal structure looser for increased water absorption. Moreover, PET fibers with incorporated IPA and PEG showed good dyeability. In this article, the structural characterization of the copolymers and antistatic and mechanical properties of the resulting fibers are discussed. At 4 wt % IPA, the fiber containing 1 mol % PEG with a molecular weight of 1000 considerably improved antistatic properties and other properties. In addition, the use of PEIT–PEG as an antistatic agent blended with PET or modified PET fibers also benefitted the antistatic properties. Moreover, PEIT–PEG could be used with another antistatic agent to produce fibers with a low volume resistance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1696–1701, 2003     

Optothermal properties of fibers—20—relation between physical structure and mechanical properties of cold drawn polypropylene fibers

The structure of annealed polypropylene (PP) fibers is studied interferometrically using two-beam Pluta polarizing interference microscope connected to a device to study the draw ratio with birefringence changes dynamically. Relations of drawing changes with some optical and physical parameters are given. Evaluation of average work per chain, work per unit volume, reduction in entropy caused by elongation, and the work stored in the body as strain energy were determined. Also the resulting optical data were utilized to evaluate the orientation factor, the orientation angle, the virtual refractive index, and the number of molecules per unit volume. The value of (Δα/3α₀), which depends upon the molecular structure of the polymer, remains constant. Relations between the physical and optical parameters with different strains are given for these fibers. The generalized Lorentz–Lorenz equation given by de Vries is used to determine polypropylene fiber structural parameters. Comparison between Hermans optical orientation function formula and the corrected formula by de Vries are given. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 819–831, 1999     

主要特种纤维及其复合材料的研发现状及发展前景

论述10种主要增强用特种纤维及其复合材料的研发现状与发展前景,目前碳纤维（CF）的最大市场是航空航天和国防军工约占40%,而到2020年汽车将成为CF的大型市场,达到与前者相当的约2.3×10^4 t。对位芳酰胺纤维（P-ARF）的需求将以10%的速率增长,最大用途仍是光缆、防弹和橡胶制品。超高相对分子质量聚乙烯纤维（UHMWPEF）技术上有重要突破,使防弹性能提高25%,而质量下降20%,并应用于人体医疗领域。聚酰亚胺纤维（PIMF）无论作为是耐热纤维或高强高模纤维我国都有重要进展,其中碳化硅纤维（SiCF）在我国开始迈向产业化,而玄武岩纤维（BSF）我国已迈入世界先进水平,但中间相沥青碳纤维（M-PCF）、聚苯并双噁唑纤维（PBOF）和聚芳酯纤维（APETF）则产业化步履艰难。2020年我国可望成为特种纤维及其复合材料的生产大国。     

Optothermal properties of fibers. XIV. Investigation of some optical structural parameters of annealed and cold drawn polyester fibers

Two-beam interferometry and density methods previously measured are used to study the changes in optical properties of annealed and cold drawn polyester (PET) fibers. Some structural parameters in the present work are determined, such as form birefringence, the number of molecules per unit volume, the virtual refractive index, the harmonic mean polarizability of the dielectric, the harmonic mean specific refractivity, and the isotropic refractive index. Also, the distribution of segment at an angle with respect to the draw ratio and the electric polarizability constant (Δα/3α₀) are determined. The generalized Lorentz–Lorenz equation given by de Vries is used to determine PET fiber structure parameters. Comparison between the results have been made with the Hermans optical orientation function. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 33–44, 1998     

Influence of fiber length,fiber orientation,and interfacial adhesion on poly (butylene terephthalate)/polyethylene alloys reinforced with short glass fibers

Blends of poly(butylene terephthalate) and high density polyethylene at a ratio of 80:20 wt% were reinforced with short glass fibers varying from 10 to 30 wt% to enhance mechanical properties. Considerable fiber damage occurred during injection molding, reducing the number average fiber length from the starting value of 4.5 mm to < 1 mm. This value decreased with increasing fiber content, which is also responsible for lowering the reinforcement efficiency. The variation in mechanical properties has been explained on the basis of fiber concertration. The effect of an ionomer, which was used to compatibilize the blends, on properties of corresponding composites has also been studied.     

Refractive index profile of polyethylene fiber using interactive multiple‐beam fizeau fringe analysis

A multiple‐beam interference Fizeau fringes technique is used to measure the refractive index profile of drawn polyethylene fiber. The interference fringe shift in the fiber region has been analyzed automatically using an interactive algorithm. The method takes into consideration the refraction of the light beam when crossing the fiber. Plane polarized light vibrating parallel and perpendicular to the fiber axis are used to obtain the refractive index profiles of both cases. These profiles are used to determine some optical parameters such as the birefringence, the optical orientation function, the polarizability per unit volume, and the value Δα/3α_o, which related to the material structure. The reliability of the method is tested considering the results of drawn polyethylene fiber samples using the manual technique. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3099–3106, 2000     

Fine structure and physical properties of polyethylene/poly(ethylene terephthalate) bicomponent fibers in high‐speed spinning. I. Polyethylene sheath/poly(ethylene terephthalate) core fibers

The high‐speed melt spinning of sheath/core type bicomponent fibers was performed and the change of fiber structure with increasing take‐up velocity was investigated. Two kinds of polyethylene, high density and linear low density (HDPE, LLDPE) with melt flow rates (MFR) of 11 and 50, [HDPE(11), LLDPE(50)], and poly(ethylene terephthalate) (PET) were selected and two sets of sheath/core combinations [HDPE(11)/PET and LLDPE(50)/PET bicomponent fibers] were studied. The fiber structure formation and physical property effects on the take‐up velocities were investigated with birefringence, wide‐angle X‐ray diffraction, thermal analysis, tensile tests, and so forth. In the fiber structure formation of PE/PET, the PET component was developed but the PE components were suppressed in high‐speed spinning. The different kinds of PE had little affect on the fine structure formation of bicomponent fibers. The difference in the mechanical properties of the bicomponent fiber with the MFR was very small. The instability of the interface was shown above a take‐up velocity of 4 km/min, where the orientation‐induced crystallization of PET started. LLDPE(50)/PET has a larger difference in intrinsic viscosity and a higher stability of the interface compared to the HDPE(11)/PET bicomponent fibers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2254–2266, 2000     

干湿热处理对PET/PTT纤维结构与性能的影响

通过对167dtex和111dtex聚对苯二甲酸乙二醇酯(PET)/聚对苯二甲酸丙二醇酯(PTT)双组分复合纤维的卷曲率、拉伸性能、声速取向及外观形态的测试,研究了干湿热处理对纤维结构与性能的影响。结果表明:经干、湿热处理后,纤维的断裂强度、声速值较处理前有显著下降,而卷曲率和断裂伸长率则明显著上升;湿热处理较干热处理对PET/PTT复合纤维断裂强度的影响较小。