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     

Optothermal properties of fibers. IX. Study changes of optical parameters by multiple-beam technique due to thermal annealing for natural silk fibers

Multiple-beam Fizeau fringes were used for studying the effect of the annealing process on the refractive indices and birefringence of natural silk fibers (best yellow Italian silk, Ford & Co. Ltd). Silk fibers were annealed at a constant time of 2 h with different annealing temperatures ranging from 60 to 160 ± 1°C. A scanning electron microscope was used for measuring the cross-sectional shape and a longitudinal view of the natural silk fibers. The Becke-line method was used for measuring the skin refractive indices and the birefringence of the natural silk fibers. The thermal coefficient of the refractive index, Cauchy dispersion constants, dispersive power, dielectric constant at infinity, polarizability per unit volume, isotropic polarizability, and isotropic refractive index were determined interferometrically. Microinterferograms and curves are given for illustration. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1495–1504, 1998     

Optothermal properties of fibers. VI. Effect of annealing on some of the optical and dynamic mechanical parameters of polyester fibers

Changes in the structure of annealed polyester fibers (Egyptian manufacture) at a constant time of 5 h and different temperatures (80–190°C) were studied interferometrically. The Pulta polarizing interference microscope was used for determining the mean refractive indices and mean birefringence of these fibers. The multiple-beam Fizeau fringes in transmission was also used for determining the refractive indices of the skin and core of these fibers. Also, the acoustic method was used for measuring the density and mechanical loss factor of these fibers. Relations between the mean refractive indices, birefringences polarizabilities per unit volume, and mechanical parameters of annealed polyester fibers with different temperatures are discussed to clarify the thermal effects. Illustrations are given using graphs and microinterferograms. © 1996 John Wiley & Sons, Inc.     

Optothermal properties of fiber morphology on nylon 66 fibers due to annealing and drawing processes

The changes produced by the effects of annealed and drawn fibers on the microstructure and macrostructure of nylon 66 fibers are considered. The optical properties and strain produced in nylon 66 fibers under different conditions are measured interferometrically at room temperature. Structural parameters are calculated such as the average work per chain, the work per unit volume, the reduction in entropy due to elongation, and the work stored in the body as strain energy. The evaluation of the density aided the calculation of the crystallinity, the mean square density fluctuation, the isotropic refractive index, the harmonic mean polarizability of the dielectric, and the harmonic mean specific refractivity. In addition, the resulting data are utilized to calculate the optical stress coefficient and the optical configuration and to apply the Mooney–Rivlin equation to determine its constants. Also, the number of crystals per unit volume and the average orientation angle for uniaxial stretching are calculated by the extension ratio. The relations between the optical, mechanical, and thermal changes with different parameters are given for the studied fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 916–928, 2002; DOI 10.1002/app.10107     

Opto-thermal properties of fibers. XI. The effect of thermal annealing of drawing behavior for Egyptian polyester fibers on the crystallinity and some optical parameters

The structure developed of annealed Egyptain poly(ethyleneterephthalate) (PET) fibers is studied interferometerically due to the drawing process. Using a two-beam Pluta polarizing interference microscope connected to a device to dynamically study the draw ratio with the birefringence changes, the relations of drawing changes with some optical parameters are given. The evaluation of density, the mean square density fluctuation η², crystallinity, amorphous orientation, crystalline orientation functions, number of chains per unit volume N_c, and number of random links between the network junction points N has been found. The results obtained clarify the effect of annealing time and temperature with different draw ratios on the structure of PET fibers. Empirical formula is suggested to correlate the changes in f_θ, θ, Δn_a, and A with the draw ratio. Microinterferograms and curves are given for illustration. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 68: 1371–1386, 1998     

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     

模拟退火算法在岩土热物性参数确定中的应用

岩土的热物性是土壤源热泵系统设计的重要参数,需要在工程地点实施热响应试验才能确定。针对现场热响应试验中恒加热功率难以保证的实际情况提出了利用模拟退火算法确定变热流状况下热物性参数的新方法。该方法以竖直U形地埋管换热器的柱热源(CSM)模型为基础,引入格林函数加快了热响应试验系统模型确定换热器进出水温度的计算速度,利用RMSE分布图解决了传热反分析中参数识别的非适定问题,保障了模拟退火算法的有效实施。在结合具体算例实施热物性参数识别的过程中,变热流情况下模拟退火算法对应的退火温度降温速度快,确定的岩土热导率和容积比热容的相对误差分别为4.1%和1.3%,而且计算了地埋管换热器的有效热阻。研究结果可为确定岩土热物性参数和指导地埋管换热器系统设计提供参考。     

Interferometric determination of the birefringence of thermo-tropic polyester fibers and its copolymers of structure (PCPT-co-CPO)

The aim of this study is to determine the optical anisotropy of three different samples of thermo-tropic polyester fibers of structure Poly(chloro-1,4-phenylene terephthalate-co-4,4′-oxybisbenzoate) and its copolymers (PCPT-co-CPO). The molar fraction of disruptor units ([CPO]) ranging from 0.40 to 0.60. The variable wavelength interferometry, VAWI technique, was used to determine the birefringence and spectral dispersion properties of such of these fibers. The Cauchy's dispersion formula and its related constants were determined using the spectral dispersion curves of the birefringence. A mathematical formula was derived for direct measurement of the birefringence profile of highly birefringent polymer fibers using VAWI technique. The effect of varying copolymer molar fractions of the three samples of thermo-tropic polyester fibers was investigated throughout the spectral dispersion curves, the Cauchy's formula constants and the birefringence profiles. Microinterferograms are given for illustration. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The role of dry and wet isothermal annealing treatment on the structure and the mechanical properties of isotactic polypropylene fibers

Dry and wet annealing of isotactic polypropylene fibers was carried out under constant length at 120°C in air and in glycerine environments with annealing times ranging from 1 to 30 h. A detailed analysis of the infrared spectrum of samples annealed, especially in air, showed clear evidence of the surface oxidation as indicated by the appearance of oxygen containing functional groups. Annealing was found to lead to an improved structural organization as indicated by the crystallinity, crystallite size, and orientation measurements using X‐ray diffraction and infrared spectroscopy methods. Analysis of the X‐ray diffraction measurements showed a gradual transformation of metastable smectic phase to a more stable α‐monoclinic phase with increasing annealing time. Crystallinity, crystallite size, and orientation measurements performed for the samples annealed in air and in glycerine environments showed no distinct difference. Mechanical properties of the annealed samples were influenced by the annealing environment. Annealing in an air environment resulted in a continuous loss of tensile strength up to the annealing time of 12 h due to an oxidation related chain scission mechanism. On the other hand, annealing in glycerine environment resulted in a continuous and gradual increase of tensile strength without loss of physical form up to the annealing time of 30 h. It is suggested that wet annealing in glycerine environment should be used to obtain improved tensile strength values. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Optothermal properties of fibers. I. Relations between optical properties and change of the density and mechanical loss factor for annealed polyester fibers

Polyester (Egyptain manufacturers) fibers were annealed in the temperature range 80–190°C for time intervals from 1 to 10 h. The density of the annealed fibers was measured by a system based on the theory of vibrating strings. The fiber diameter was also determined, using the laser forward diffraction technique. Refractive indices and birefringence for annealed fibers at different temperatures and constant time, 1 h, were measured by the polarizing interference microscope. The behavior of fiber density and the mechanical loss factor at different annealing temperatures and times were discussed at different optical parameters. The results obtained clarify the effect of annealing time and temperatures on the optical, density, and mechanical loss factor behavior of polyester fibers. Microinterferograms are given for illustration. © 1995 John Wiley & Sons, Inc.     

Evaluation of the tensile properties and thermal stability of ultrahigh‐molecular‐weight polyethylene fibers

The thermal stability of ultrahigh‐molecular‐weight polyethylene (UHMWPE) should be paid attention in its applications, although the fiber has excellent flexible tensile properties. The measurements for two kinds of UHMWPE fibers, Dyneema SK65 (The Netherlands) and ZHF (Beijing, China), were carried out at different annealing temperatures and for different aging times. Experimental and regression analysis results showed that the aging behavior of the fibers followed an exponential attenuation with the annealing temperature and aging time. The critical temperature for the safe use of the fibers was equal to or lower than 70°C and depended on the glass‐transition temperature; this was validated by tensile tests. The difference between the two fibers in the thermal properties resulted from the intrinsic supermolecular structures of the two fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 310–315, 2005     

一种新型聚酯大单体的合成及其热交联膜性能的研究

以聚己二酸异丁二酯(PMPA)、异佛尔酮二异氰酸酯(IPDI)、甲基丙烯酸羟乙酯(HEMA)等为原料,合成了一种新型的功能性不饱和聚酯大单体,并将其热交联固化成膜。通过对合成温度、合成时间等参数的研究,确定了最佳的合成反应条件,并用红外光谱对大单体的结构进行了表征。详细研究了大单体的热交联成膜过程,讨论了交联时间及交联温度对成膜的影响。对膜的溶胀率、接触角、耐高温性能等性质进行了研究。     

The influence of annealing on the thermal properties of poly(ethylene terephthalate) fibers I. The heat capacity of annealed PET fibers

The influence of annealing of PET fibers on their specific heat capacity has been examined. The annealing has been performed in air in the loose state of the fibers within the temperature range 130–210°C for 2,5,10, and 30 min. The obtained results give evidence that three temperature intervals of annealing may be distinguished. The ascertained variation of c_p has been discussed on the basis of established morphological and fine structure changes in the fibers caused by the applied annealing.     

二茂铁甲酸封端不饱和聚酯的固化及热性能研究

以乙二醇、反丁烯二酸为原料合成的不饱和聚酯作为主链,二茂铁甲酸(FCA)作为封端剂,合成了含二茂铁基的不饱和聚酯(RFc),采用红外光谱对产物结构进行了表征。采用DSC及TGA研究了不同二茂铁甲酸含量对不饱和聚酯树脂固化性能和热稳定性的影响。结果表明,随着二茂铁甲酸含量的增加,RFc树脂固化反应活性减弱,热稳定性下降。其最高放热峰温度在171～173℃,且具有比较宽的加工温度范围(152～195℃),符合模塑料固化工艺要求。树脂的耐热性较好,初始热分解温度约为340℃,N2气氛下600℃残炭率可达19.76%。     

Physical and mechanical properties of unsaturated polyester resin matrix from recycled PET (based PG) with corn straw fiber

In this study, composites of unsaturated polyester resin (UPR), synthesized from recycled polyethylene terephthalate (PET), with 10 to 40% in volume of corn straw fiber (CSF), were elaborated and studied the effect of fiber content on their physical and mechanical properties. The content of cellulose (48.97%), hemicellulose (24.06%), and lignin (6.59%) were determined by chemical characterization of CSF. The characteristic bonds of the UPR were identified as a cross-linking network between the styrene monomer (ST) and the unsaturated polyester (UP) through FTIR. Two decomposition stages were observed by TGA–DTG. The results of physical and mechanical properties showed that as the fiber content increased in the UPR, the water absorption increased (0.6% to 2.56%), on the other hand, the density (1218.23 to 1150.28 kg/m³), flexural strength (50.58 to 26.98 MPa), flexural modulus (2.66 to 2.29 GPa), tensile strength (8.62 to 3.65 MPa), tensile modulus (1.18 to 0.43 GPa), and hardness (81.67 to 65.67 Shore D), they decreased. SEM analysis showed some defects in the fiber distribution in the UPR, which affected the mechanical properties of the composites. This research contributes to the development of new material from use of two waste materials for the benefit of the environment.     

Evaluation of improvement of physical and mechanical properties of bamboo fibers due to alkali treatment

Bamboo strips treated with caustic solutions of different concentrations, e.g., 5%, 10%, 15%, 20%, 25%, and 50%, were subjected to mechanical testing giving stresses on tensile strength, percent elongation at break, flexural strength, flexural modulus, and toughness. The change in average density was ?15%, and the weight loss value shows a maximum of 21.94% at 50% alkali treatment. The mechanical properties of bamboo strips increase steadily with increasing concentration of caustic soda, showing a comparable increased value at 15 and 20%, and then exhibiting a gradual fall. The percent elongation at break corroborates these observations showing a continuous decreasing trend. The properties under investigation exhibit a clear transition in between 15 and 20% alkali concentration. The morphology of strips was studied by scanning electron microscope and polarizing light microscope. The crystal structure of both untreated and treated strips was compared by XRD analysis. In both cases, the breakdown of the crystal structures of the cellulose fibers and the recrystallization or reorientation of the degraded chains that are devoid of hemicellulose are quite apparent. However, at a very high concentration (to the extent of 25%) the breakdown of structure predominates much more over the reorientation or recrystallization. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of thermal annealing on surface morphology and physical properties of poly(3-octylthiophene) films

An unusual morphology observed in poly(3-octylthiophene) (P3OT) films, solution grown at room temperature, which is previously shown by highly regioregular-poly(3-alkylthiophenes) (rr-P3ATs), is reported. Upon thermal annealing a rare well-arranged corrugated-rod-type (CRT) morphology, comes up gradually. It is observed by soft-heat treatment of pristine P3OT films, which is not reported for any members of polythiophenes family. This novel CRT morphology, observed by scanning electron microscopy (SEM), is supported by photoluminescence (PL) quenching, red shift of λ_max (π-π* absorption) in UV-vis spectra, and increase in conductivity. These improvements in physical properties are perhaps due to the increase in the planarity and 3D-π-π stacking of polymer chains by gradual soft-thermal annealing. It is worthwhile to mention here that the P3OT synthesized for the present investigation, with changed polymerization parameters, is comparable with its rr-P3ATs counterparts. The improvement in the quality of P3OT may induce self-assembling nature in former which results due to increased π-π interactions.     

The influence of annealing on the thermal properties of poly(ethylene terephthalate) fibers II. The thermal volume expansivity of annealed pet fibers

The influence of annealing of PET fibers on their thermal volume expansivity has been examined. The annealing has been performed in air in the loose state of the fibers within the temperature range 130–210°C for 2,5,10, and 30 min. The established volume expansivity coefficients α₂₅ give rise to the conclusion that three temperature intervals of annealing may be distinguished. The ascertained variation in α₂₅ has been discussed on the basis of established morphological and fine structure changes caused in the fibers by the applied annealing.     

Anionic copolymers of octanelactam with laurolactam (nylon 8/12 copolymers)—v. Effect of annealing on thermal properties and crystalline structure

The effects of different annealing time/temperature regimes on the thermal and crystalline behaviour of a series of statistical copolyamides (nylon 8/nylon 12), prepared by activated anionic polymerization of octanelactam/laurolactam (OL/LL), were determined by DSC, X-ray (WAXS), density and viscosity measurements. The melting temperature and the heat of melting increased with annealing time and temperature. The results were correlated with the molar composition of the copolyamides and showed a gradual increase in percentage crystallinity with time.     

Effect of winding speed on the structure and properties of as‐spun poly(trimethylene 2,6‐naphthalenedicarboxylate) fibers as compared to poly(ethylene terephthalate) fibers

We present a comparative study of melt spinning of poly(trimethylene 2,6‐naphthalenedicarboxylate) (PTN) and poly(ethylene terephthalate) (PET) fibers with respect to the effect of winding speed (2000–6000 m/min): Structural changes were followed by X‐ray analysis, calorimetry, and measurements of density, boiling water shrinkage, and birefringence. As‐spun PTN fibers exhibited a low degree of crystallinity at relatively low speeds (< 2000 m/min). An increase in winding speed up to 6000 m/min only resulted in a minor enhancement of crystallinity and orientation. The small change of structural parameters accounted for the fact that tenacity and modulus did not rise significantly with increasing winding speed, contrary to the PET fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2489–2497, 2002