Surface modification of superfine tourmaline powder with titanate coupling agent

The effects of surface modification of the superfine tourmaline powder with a titanate coupling agent were discussed by investigating its hydrophobicity and distribution in poly (ethylene terephthalate) (PET). The modified tourmaline powder became hydrophobic, which resulted in better distribution in the PET matrix. The mechanism of the surface modification was analyzed.     

Characterization of the effects of compressed gas annealing on semicrystalline polymers

The effects of annealing semicrystalline polymers in the presence of plasticizing agents is an area of considerable current interest, given the potential to modify the degree and nature of crystallinity. These effects were studied for two semicrystalline polymers, custom‐synthesized methyl‐substituted poly(aryl ether ether ketone) (MePEEK) and industrial‐grade poly(ethylene terephthalate) (PET). Small‐angle X‐ray scattering (SAXS) was used to characterize the microstructure of both amorphous and preannealed materials. Differential scanning calorimetry (DSC), wide‐angle X‐ray scattering, and density measurements were also performed for the PET samples, and reference is made to similar analysis work done for MePEEK. A distinct morphological effect could be identified from SAXS measurements of MePEEK annealed in a stepwise fashion in the presence of high‐pressure CO₂ with the polar cosolvent CH₃OH. This result was absent in MePEEK similarly annealed in air and supports earlier DSC measurements. A very different morphological effect of pressure alone was observed in PET annealed in pure CO₂ (170 and 510 atm) at a temperature of 150 °C, well above the glass transition. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2457–2467, 2000     

Poly(ethylene terephthalate) copolymers containing 5‐nitroisophthalic units. II. Crystallization studies

The microstructure and crystallization behavior of a set of poly(ethylene terephthalate‐co‐5‐nitroisophthalate) copolymers (PETNI) containing 5‐nitroisophthalic units in the 10–50 mol % range were examined and compared to those of poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate‐co‐isophthalate) (PETI) copolymers. A ¹³C NMR analysis of PETNI copolymers in a trifluoroacetic acid solution indicates that they are random copolymers with average sequence lengths in accordance with ideal polycondensation statistics. Differential scanning calorimetry (DSC) studies show that PETNI containing 5‐nitroisophthalic units up to 20 mol % are able to crystallize and that crystallization takes place in these copolymers at much slower rates than in PET. Wide‐angle X‐ray diffraction from powder and fibers reveals that crystallizable PETNI adopts the same triclinic crystal structure as PET, with the nitroisophthalate units being excluded from crystallites. Fourier transform infrared in combination with cross‐polarization/magic‐angle spinning ¹³C NMR spectroscopy demonstrates the occurrence of a gauche–trans conversion encompassing the crystallization process. A correlation between DSC and spectroscopic data leads us to conclude that the content of trans conformer in the noncrystallized phase of PETNI is higher than in both PET and PETI copolymers and suggests that secondary crystallization in the homopolymer must proceed by a mechanism different than that in copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1553–1564, 2001     

Microstructure and mechanical properties of hot‐air drawn poly(ethylene terephthalate) fibers

Hot‐air drawing method has been applied to poly(ethylene terephthalate) (PET) fibers in order to investigate the effect of strain rate on their microstructure and mechanical properties and produce high‐performance PET fibers. The hot‐air drawing was carried out by blowing hot air controlled at a constant temperature against an as‐spun PET fiber connected to a weight. As the hot air blew against the fibers weighted variously at a flow rate of about 90 ℓ/min, the fibers elongated instantaneously at a strain rate in the range of 2.3–18.7 s⁻¹. The strain rate in the hot‐air drawing increased with increasing drawing temperature and applied tension. When the hot‐air drawing was carried out at a drawing temperature of 220°C under an applied tension of 27.6 MPa, the strain rate was the highest value of 18.7 s⁻¹. A draw ratio, birefringence, crystallite orientation factor, and mechanical properties increased as the strain rate increased. The fiber drawn at the highest stain rate had a birefringence of 0.231, degree of crystallinity of 44%, tensile modulus of 18 GPa, and dynamic storage modulus of 19 GPa at 25°C. The mechanical properties of fiber obtained had almost the same values as those of the zone‐annealed PET fiber reported previously. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1703–1713, 1999     

一种离子导电PET纤维的制备

通过含有KI的聚乙二醇(PEG)与PET熔融共混制得导电聚合物,其在常温下电阻率可达到105Ω.cm左右,电阻率随温度升高而降低,具有离子导电的特性.通过FTIR、DSC和偏光显微镜研究其形态结构和热性能,结果表明该导电聚合物中PEG和PET主要是物理共混,晶区不相容,非晶区具有部分相容性,熔融降温发生相分离,KI/PEG形成连续的一相.该导电聚合物作为导电母粒与PET切片以不同的配比共混纺丝制备出颜色较浅的导电PET纤维.当纤维中导电母粒的质量分数超过10 wt%时,制得的导电纤维的电阻率为106Ω.cm左右,具有较好的耐水洗性.该导电纤维具有双连续相结构,连续的KI/PEG导电相因形成导电通路使纤维具有导电性能;连续的PET相使纤维基本保持PET纤维的力学性能.     

Online wide‐angle X‐ray diffraction/small‐angle X‐ray scattering measurements for the CO2‐laser‐heated drawing of poly(ethylene terephthalate) fiber

Fiber‐structure‐development in the poly(ethylene terephthalate) fiber drawing process was investigated with online measurements of wide‐angle and small‐angle X‐ray scattering with both a high‐luminance X‐ray source and a CO₂‐laser‐heated drawing system. The intensity profile of the transmitted X‐ray confirmed the location of the neck‐drawing point. The diffraction images had a time resolution of several milliseconds, and this still left much room for improvement. Crystal diffraction appeared in the wide‐angle X‐ray images almost instantaneously about 20 ms after necking, whereas a four‐point small‐angle X‐ray scattering pattern appeared immediately after necking. With the elapse of time after necking, the four‐point scattering pattern changed into a meridional two‐point shape. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1090–1099, 2005     

Effect of the chemical nature and length of spacer arms on the covalent grafting of fluorinated molecular probes at the surface of poly(ethylene terephthalate) membrane

A series of fluorinated molecular probes were synthesized that are characterized by spacer arms of various lengths and polarities. Previous molecules ( 1 , 2a , 2b , 2c , 3a , 3b ) were covalently fixed on the surface of poly(ethylene terephthalate) (PET) membranes via activated hydroxyl chain endings. X‐ray photoelectron microscopic analysis of the grafted samples allowed us to quantify the PET surface reactivity; the results were within 40–50 pmol/cm² of fixed probes, independent of the length and hydrophilicity of the spacer arms. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 770–781, 2002; DOI 10.1002/pola.10156     

Initial stage of fiber structure development in the continuous drawing of poly(ethylene terephthalate)

The initial stage of fiber structure development in the continuous neck‐drawing of amorphous poly(ethylene terephthalate) fibers was analyzed by in situ wide‐angle X‐ray diffraction, small‐angle X‐ray scattering, and fiber temperature measurements. The time error of the measurements (<600 μs) was obtained by synchrotron X‐ray source and laser irradiation heating. A highly ordered fibrillar‐shaped two‐dimensional (smectic‐like) structure was found to be formed less than 1 ms after necking. By analyzing its (001′) and (002′) diffractions, the length of the structure 60–70 nm were obtained. A three‐dimensionally ordered triclinic crystal began to form with the vanishing of the structure around 1 ms after necking. The amount and size of the crystal were almost saturated within several milliseconds of necking, during which time a mainly exothermic heat of crystallization was also observed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2126–2142, 2008     

Confirmation of a nanohybrid shish‐kebab (NHSK) structure in composites of PET and MWCNTs

Here, the confirmation of an oriented nanohybrid shish‐kebab (NHSK) crystalline structure in a series of composites of poly(ethylene terephthalate) (PET) and multiwall carbon nanotubes (MWCNTs) is reported. The combined use of small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) and thermal analysis has been used to investigate the morphology development in PET‐MWCNT nanocomposites under hot isothermal crystallization conditions. The MWCNTs act as both heterogeneous nucleating agents and surfaces (oriented shish structures) for the epitaxial growth of PET crystallites (kebabs) giving an oriented crystalline morphology. In contrast, the PET homopolymer does not show any residual oriented crystalline morphology during isothermal crystallization but gave a sporadic nucleation of a classic unoriented lamellar structure with slower crystallization kinetics. The results provide a valuable insight into the role of MWCNTs as nanoparticulate fillers in the morphology development and subsequent modification of physical properties in engineering polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 132–137     

Study of molecular orientation in poly(ethylene terephthalate) fibers by fluorescence polarization

Molecular orientation in poly(ethylene terephthalate) (PET) fibers was studied by polarized fluorescence. The observed amorphous orientation of the spun as fiber was not random but uniaxial along the fiber axis. This orientation increased with draw ratio up to about 2 and then remained fairly constant. The amorphous regions of PET fibers were disoriented when the fibers were heated while unconstrained. The fluorescence data obtained were correlated with shrinkage measurements. Fluorescence data indicated that spin drawing had more effect upon orientation than subsequent drawing of the fiber, whereas birefringence data indicated the opposite. The reason for this behavior is discussed.     

Crystallization in oriented poly(ethylene terephthalate) fibers. II. Consequences in subsequent deformation

When a melt-spun poly(ethylene terephthalate) (PET) fiber is heat treated at a temperature above its glass transition temperature, the relative rates at which the crystallization and major orientational relaxation processes occur have been shown to have a pronounced effect on the structure of the fiber and its deformability. The present study describes the consequences of this aspect, with examples from drawing of melt-spun PET fibers subsequent to their crystallization by thermal annealing. Additional features of the highly ordered PET fibers which can be produced through a combination of oriented crystallization and drawing at high temperatures are also given.     

Poly(ethylene terephthalate) reinforced by N,N′‐diphenyl biphenyl‐3,3′,4,4′‐tetracarboxydiimide moieties

Starting with 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and methyl aminobenzoate, we synthesized a novel rodlike imide‐containing monomer, N,N′‐bis[p‐(methoxy carbonyl) phenyl]‐biphenyl‐3,3′,4,4′‐tetracarboxydiimide (BMBI). The polycondensation of BMBI with dimethyl terephthalate and ethylene glycol yielded a series of copoly(ester imide)s based on the BMBI‐modified poly(ethylene terephthalate) (PET) backbone. Compared with PET, these BMBI‐modified polyesters had higher glass‐transition temperatures and higher stiffness and strength. In particular, the poly(ethylene terephthalate imide) PETI‐5, which contained 5 mol % of the imide moieties, had a glass‐transition temperature of 89.9 °C (11 °C higher than the glass‐transition temperature of PET), a tensile modulus of 869.4 MPa (20.2 % higher than that of PET), and a tensile strength of 80.8 MPa (38.8 % higher than that of PET). Therefore, a significant reinforcing effect was observed in these imide‐modified polyesters, and a new approach to higher property polyesters was suggested. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 852–863, 2002; DOI 10.1002/pola.10169     

Transverse heterogeneity in PET fibers

X-ray scattering from a series of poly(ethylene terephthalate) (PET) fibers spun at differet speeds is analyzed to probe the morphology in the direction transverse to the fiber axis. Both the apparent crystal modulus, determined from the change in wide-angle X-ray scattering angle with fiber stretching, and the transverse degree of crystallinity indicate there is a substantial interfiberillar amorphous content. In the PET fiber spun at conventional speeds, only roughly one-quarter of the fiber cross-section is actually occupied by fibrils. The transverse crystallinity increases for fibers spun at speeds sufficient to cause crystallization in the spin line. The X-ray moduli and fibril diameters are correspondingly larger in these high speed spun fibers. © 1993 John Wiley & Sons, Inc.     

Preparation,Characterization and Electromagnetic Shielding Effectiveness of Conductive Polythiophene/Poly(ethylene terephthalate) Composite Fibers

Conductive polythiophene (PTh)/poly(ethylene terephthalate) (PET) composite fibers were prepared by polymerization of thiophene in the presence of PET fibers in acetonitrile medium using FeCl₃. The effects of polymerization conditions such as oxidant/monomer mol ratio and polymerization temperature and time on PTh content and surface electrical resistivity of PTh/PET composite fiber were investigated in detail. It was observed that the usage of preswelled PET fibers in dichloromethane increased the PTh content and decreased surface resistivity of composite fiber. Composite fiber having the highest PTh content (5.7%) and the lowest surface resistivity (80 kΩ) was obtained at 20°C with 1.25 M FeCl₃ and 0.42 M thiophene concentrations. The washing effects of laundering detergent and dry cleaning liquid on surface resistivity of composite fibers were investigated. The electromagnetic shielding effectiveness (EMSE) and relative shielding efficiency by absorption and reflection of composite fibers were measured in the radio and microwave frequency range. The results show that the EMSE values decreased with increasing frequency from radio waves to microwaves with an attenuation of 21 dB to 4 dB.     

Syntheses of random PET‐co‐PTTs and some related copolyesters by entropically‐driven ring‐opening polymerizations and by melt blending: Thermal properties and crystallinity

A library of random poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT), and seven PET–PTT copolymers has been prepared in a high throughput manner by entropically‐driven ring‐opening polymerizations of the corresponding macrocyclic oligomers. The products have been investigated by differential scanning calorimetry and wide angle X‐ray diffraction. They show that the 50:50 copolymer displays a crystalline phase. The same phase can be formed by in situ transesterification when a 50:50 mixture of PET and PTT is melt blended. Poly(butylene terephthalate) (PBT)–PET and PTT–PBT 50:50 copolymers also show crystal phases. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Electrical conductivities of carbon nanotube-filled polycarbonate/polyester blends

Carbon nanotube (CNT)-filled polycarbonate (PC)/poly(butylene terephthalate) (PBT) and polycarbonate (PC)/poly(ethylene terephthalate) (PET) blends containing 1 wt% CNTs over a wide range of blend compositions were prepared by melt mixing in a torque rheometer to investigate the structure-electrical conductivity relationship. Field emission scanning electron microscopy was used to observe the blend morphology and the distribution of CNTs. The latter was compared with the thermodynamic predictions through the calculation of wetting coefficients. It was found that CNTs are selectively localized in the polyester phase and conductive blends can be obtained over the whole composition range (20 wt%, 50 wt% and 80 wt% PBT) for CNT-filled PC/PBT blends, while conductive CNT-filled PC/PET blends can only be obtained when PET is the continuous phase (50 wt%, 80 wt% PET). The dramatic difference in the electrical conductivity between the two types of CNT-filled PC/polyester blends at a low polyester content (20 wt%) was explained by the size difference of the dispersed phases on the basis of the transmission electron microscope micrographs.     

Modification of poly(ethylene terephthalate) and nylon 66 surfaces by using organometallic polymerization catalysts

Zirconium hydrocarbyl catalysts react with nylon and poly(ethylene terephthalate) (PET) fibers to produce a supported species which may be used to polymerize a sheath of polyethylene around the fiber. Very high catalyst activities have been achieved over very short reaction periods on PET spinning threadlines. It is also possible to use these reagents to produce strongly adhered oxide and sulfide surface coatings. Infrared evidence is given for a mechanism in the case of reaction between catalyst and PET.     

Attachment of bis‐(trifluoromethyl)aryl labels onto the chain ends of poly(ethylene terephthalate) (PET) track‐etched membranes and films by surface wet chemistry

Organic chemistry performed at the solid–liquid interface allowed us to achieve the selective chain‐end functionalization of poly(ethylene terephthalate) (PET) membranes and films with perfluorinated labels. The carboxyl endings were activated with water‐soluble carbodiimide and were coupled to 3,5‐bis(trifluoromethyl)benzylamine (1) in aqueous acetonitrile, whereas the hydroxyl endings were activated by tosylation and were also coupled to 1. 3,5‐Bis(trifluoromethyl)phenyl isocyanate (2) was directly fixed on the hydroxyl endings of the polymer substrates in dry organic media. All the derivatized materials were analyzed by X‐ray photoelectron spectroscopy, allowing the quantitative determination of the amounts of surface‐grafted labels. Yields were between 10 and 100 pmol/cm². These surface reactivity assays mimic at best the experimental conditions that would be applied for the covalent anchorage of biologically active molecules onto PET substrates used in cell culture systems. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3510–3520, 2000     

Flame‐retardant poly (ethylene terephthalate) enabled by a novel melamine polyphosphate nanowire

A novel strategy was developed for the preparation of melamine polyphosphate (MPP) nanowires to achieve a superior flame‐retardant poly (ethylene terephthalate) (PET). Thanks to the well‐designed nanostructure, the prepared MPP nanowires exhibited great thermal stability and flame retardance. Herein with incorporation of only 1‐wt% MPP nanowires (PET/FR1.0 nanocomposite), the limiting oxygen index (LOI) value was dramatically increased to 29.4% from 20.5%, showing self‐extinguishing behavior. Moreover, PET/FR1.0 nanocomposite passed V‐0 UL‐94 rating in the vertical combustion test. However, PET containing 5‐wt% commercial MPP powder (PET/FR_C5.0) only showed a LOI of 27.9% and ignited the absorbent cotton with flammable melt‐droplets. Cone results also presented that introducing 1‐wt% MPP nanowires brought about a crucial decrease in fire hazard of PET, for instance, 11.1% and 7.7% maximum reduction in heat release rate and total heat release, respectively. Thermogravimetric analysis/infrared spectrometry (TG‐FTIR) result indicated that the main pyrolysis volatiles generated from PET degradation including benzoic acid, aromatic compounds, and carbon dioxide were apparently suppressed after introducing MPP nanowires into PET matrixes, suggesting the outstanding obstructing effect of graphited char residue formed in the combustion. This enhanced flame retardancy rooting in addition of MPP nanowires can be attributed to the combined dilution effect in gaseous phase and catalytic carbonization effect in condensed phase.     

MONOMERIC INTERACTION BETWEEN ETHYLENE-TEREPHTHALATE AND CAPROLACTONE

The miscibility of poly (ethylene terephthalate (ET) -- caprolactone (CL) (TCL)/poly(ethylene terephthalate) (PET) blends were examined by Differential Scanning Calorimeter(DSC). In these blends, a miscibility limit specified by ET content in the TCL was found tobe about 70 (wt%). In the blends of TCL/TCL with different ET contents, a miscibilitywindow defined by ET content was also found to range from 82 to 58 (wt%). Based on theexperimental miscibility limits and the mean field binary interaction model, the interactionparameter between monomeric units of ET and CL was obtained.