Structure-properties relationship of poly(ethylene terephthalate) wool-type fibres

Two PET wool-type fibres were studied for this research, i.e. a normal wool-type and a low-pilling modification. The structural morphology and crystalline orientation of the fibres were investigated by means of wide-angle x-ray scattering (WAXS), density measurements and infrared (IR) spectroscopy. The degree of crystallinity, crystallite orientation, apparent crystallite dimensions and micro-void system were determined by x-ray scattering. Birefringence measurements were used to study the average molecular orientation and the orientation of macromolecular chain segments in the amorphous regions. In addition, PET samples were conventionally dyed and the effect of the structure on colour was followed using colorimetry. Significant differences between the two PET wool fibre types were observed; i.e. crystallinity is higher for the standard PET wool fibre type, the crystallites are slightly larger and better oriented, long periods are larger, the orientation of molecular segments in non-crystalline phase is higher, and bigger voids are formed. The observed structure gives rise to fibres higher tenacity and higher bending stiffness.     

Miscibility and crystallization behaviors of poly(trimethylene terephthalate)/poly(ethylene naphthalate) blends

Poly(trimethylene terephthalate) (PTT)/poly(ethylene naphthalate) (PEN) blends of various compositions were prepared by the solution-blending and melt-blending methods. The changes in miscibility and crystallization behaviors of the blends upon thermal treatment above the melting temperature of the blends at 280°C were investigated by using DSC, DMA,¹H NMR, and SAXS analyses. Without any thermal treatment, the blend systems were not miscible, and the thermal transitions, such as glass transition, cold crystallization, and crystal melting of the individual components were observed in the DSC and DMA analyses. With thermal treatment, though, they became miscible as the thermal transitions of each component disappeared and single glass transition peaks were observed in the thermal analysis. The chain randomness determined using¹H NMR spectroscopy revealed that thermal treatment at 280°C for more than 30 min brought about transesterification reactions between the PTT and PEN segments resulting in an increase in their miscibility. These results were confirmed by the small angle X-ray analysis conducted to determine the long period (L), the thickness of the crystalline lamella stack (l _c ), and the thickness of the amorphous region (l _a ). After short thermal treatment, the melt-blended sample followed the values for the individual components. However, with extended thermal treatment, the blend became homogeneous, possessing different crystalline morphologies which resulted in different values ofL, l _c , andl _a .     

Copper metallization of poly(ethylene terephthalate) fabrics via intermediate polyaniline layers

Poly(ethylene terephthalate) fabrics were metallized through electroless plating of copper. The copper plating was performed on palladium-decorated polyaniline surfaces, and polyaniline was present as an intermediate layer on fabrics to facilitate palladium formation. Different oxidation states of polyaniline were tested in their efficacy in Pd (II) reduction and subsequent Cu plating. X-ray photoelectron spectroscopy was used to monitor the surface changes along the metallization procedure, and surface resistance was measure to probe the electrical properties of the metallized fabrics.     

Crystallization and molecular relaxation of poly(ethylene terephthalate) annealed in supercritical carbon dioxide

Poly(ethylene terephthalate) was annealed at different temperature and pressure of supercritical carbon dioxide (CO₂) using samples quenched from the melt. Crystallization and molecular relaxation behavior due to CO₂-annealing of samples were investigated using differential scanning calorimetric and dynamic mechanical measurements. The glass transition and crystallization temperatures significantly decreased with increasing temperature and pressure of CO₂. The dynamic mechanical measurement of samples annealed at 150 °C in supercritical CO₂ showed three relaxation peaks, corresponding to existence of different amorphous regimes such as rigid, intermediate, and mobile domains. As a result, the mobile chains were likely to facilitate crystallization in supercritical state. It also led to the decreased modulus of CO₂-annealed samples with increasing pressure.     

Mechanical and thermal properties of recycled poly(ethylene terephthalate) reinforced newspaper fiber composites

This study presents the mechanical and thermal properties of environment-friendly composites made from recycled newspaper fibers reinforced recycled poly(ethylene terephthalate) (rPET) resin with the addition of styrene-ethylene-butylene-styrene grafted maleic anhydride (SEBS-g-MA) as compatibilizer. The effect of SEBS-g-MA addition (i.e., 10 phr) by using a twin-screw extruder to the rPET resin, followed by different fiber content (5, 10 and 15 wt.%) on the tensile, flexural and impact properties of the composites were determined. Stiffness of composites increased significantly compared to those of rPET/SEBS-g-MA blend. Fiber addition resulted in moderate increases in both tensile and flexural strength of the composites. Scanning electron microscope (SEM) photomicrographs of the impact fracture surfaces demonstrate good adhesion at 5 and 10 % fiber content. Differential scanning calorimetry (DSC) showed that the presence of newspaper fibers enhanced the nonisothermal crystallization kinetics and crystallinity. Thermal stability of the composites was improved as indicated by thermogravimetric analysis (TGA).     

Thermal and mechanical properties of modified CaCO3 filled poly (ethylene terephthalate) nanocomposites

Poly(ethylene terephthalate) (PET)/CaCO₃ and PET/modified-CaCO₃ (m-CaCO₃) nanocomposites were prepared by melt blending. The morphology indicated that m-CaCO₃ produced by reacting sodium oxalate and calcium chloride, was well dispersed in PET matrix and showed good interfacial interaction with PET compared to CaCO₃. No significant differences in the thermal properties such as, glass transition, melting and degradation temperatures, of the nanocomposites were observed. The thermal shrinkage of PET at 120 °C was 10.8 %, while those of PET/CaCO₃ and PET/m-CaCO₃ nanocomposites were 2.9–5.2 % and 1.2–2.8 %, respectively depending on filler content. The tensile strength of PET/CaCO₃ nanocomposite decreased with CaCO₃ loading, whereas that of PET/m-CaCO₃ nanocomposites at 0.5 wt% loading showed a 17 % improvement as compared to neat PET. The storage modulus at 120 °C increased from 1660 MPa for PET to 2350 MPa for PET/CaCO₃ nanocomposite at 3 wt% loading, and 3230 MPa for PET/m-CaCO₃ nanocomposite at 1 wt% loading.     

Incorporating shape memory properties in poly(ethylene terephthalate) film by isothermal crystallization

In this paper the peculiar shape memory property of semicrystalline PET films is studied. The shape memory samples were prepared through isothermal crystallization of glassy PET films at different temperatures between 120 and 230 °C for 15 and 4 minutes. It was assumed that the incorporated shape memory constitution is due to crystalline and amorphous parts and also third phase i.e. a rigid amorphous fraction (RAF) which rose by increasing the degree of crystallinity. The microstructure of samples was probed by DSC and WAXD analysis, and concluded that isothermal crystallization at temperature which spinodal decomposition mechanism is dominant, brings the formation of secondary crystal lamellas in amorphous regions between pre-existing lamellar stacks, incorporating shape recovery in the samples. As the crystallization proceeds with time or at higher temperatures, the fraction of RAF increases leading to suppression of shape memory effect.     

Helium/oxygen atmospheric pressure plasma treatment on poly(ethylene terephthalate) and poly(trimethylene terephthalate) knitted fabrics: Comparison of low-stress mechanical/surface chemical properties

Helium-oxygen plasma treatments were conducted to modify poly(trimethylene terephthalate)(PTT) and poly(ethylene terephthalate) (PET) warp knitted fabrics under atmospheric pressure. Lubricant and contamination removals by plasma etching effect were examined by weight loss (%) measurements and scanning electron microscopy (SEM) analysis. Surface oxidation by plasma treatments was revealed by x-ray photoelectron spectroscopy (XPS) analyses, resulting in formation of hydrophilic groups and moisture regain (%) enhancement. Low-stress mechanical properties (evaluated by Kawabata evaluation system) and bulk properties (air permeability and bust strength) were enhanced by plasma treatment. Increasing interfiber and interyarn frictions might play important roles in enhancing surface property changes by plasma etching effect, and then changing low-stress mechanical properties and bulk properties for both fabrics.     

Intrinsic UV reflection and fluorescence studies for water sorption in polycarbonate, polyurethane and poly(ethylene terephthalate) films

Intrinsic UV reflection and fluorescence behaviors of polycarbonate, polyurethane and poly(ethylene terephthalate) films were investigated in order to characterize the interaction of water in these films. During water sorption process, UV reflection spectra of polycarbonate and polyurethane films showed little peak position changes. Fluorescence emission spectra of polycarbonate films showed red spectral shifts from 332 nm with water immersion time. This red-shifted peak could be due to phenyl-2-phenoxybenzoate, which is one of the major thermal degradation products in polycarbonate. Fluorescence peaks of polyurethane films appeared at two different positions and the ratio of these peak intensities increased with increasing immersion time. In the case of PET films, the UV reflection spectrum showed the peak intensity around 340 nm to change in response to water sorption. The fluorescence near 388 nm probably due to ground state dimer exhibited sensitivity with water sorption, when excited at 340 nm.     

Eco-friendly dyeing of poly(trimethylene terephthalate) with temporarily solubilized azo disperse dyes based on pyridone derivatives

Dispersant-free PTT dyeing of temporarily solubilized azo disperse dyes based on pyridone moiety which contain β-sulfatoethylsulfonyl group was investigated. The dyes were successfully applied to PTT without the use of dispersants. The color yields of the dyes on PTT fabric were dependent on dyeing pH as well as dyeing temperature. The optimum results were obtained at pH 5–6 and 110 °C. The dyes showed alkali-clearing property and exhibited good to excellent fastness on the PTT fabric. The COD levels of the dyeing effluent from the temporarily solubilized disperse dyes were much smaller than those from commercial disperse dye.     

Removal of benzidine-based azo dye from aqueous solution using amide and amine-functionalized poly(ethylene terephthalate) fibers

In this study, amide and amine groups bound to poly(ethylene terephthalate) fibers are used to remove the colored toxic Congo red dye from aqueous solution. The effects of process variables like pH, contact time, graft yield, and initial dye concentration on the adsorption were investigated. The maximum adsorption of Congo red to amide and amine groups was observed at pH 3 and 5 respectively. Equilibrium was attained at approximately 60 min for the amine group. The adsorption capacity of amine group on the poly(ethylene terephthalate) fiber was 46.5 mg g⁻¹ at 25 °C, which was higher than that of the amide group on the poly(ethylene terephthalate) fiber. Desorption was done using 0.1 M NH₃, and recovery was measured at 58.2 %. The used adsorbent was regenerated and recycled six times. The results showed that the amine-functionalized fiber could be considered as potential adsorbents for removal of Congo red from aqueous solution.     

Miscibility of flame retardant epoxy resin with poly(ethylene terephthalate) and the characterizations of the blends

Epoxy resin containing bromine compound was melt blended with PET to obtain flame retardant polymer. The blend product was characterized by DSC, SEM, intrinsic viscosity and melt index measurements. The reaction between the epoxy group of DGEBBA (diglycidyl ether of brominated bisphenol A) and the carboxyl (or hydroxyl) end group of PET led to cross-linking of PET chains, and the intrinsic viscosity and melt index (MI) were increased in the range of equivalent amount of epoxy resin (within 1 %). DSC data revealed that the epoxy resin was not located in the crystalline region but was appeared in the amorphous region of PET matrix. Good miscibility of epoxy resin resulted in the decrease of crystallization temperature and glass transition temperature of PET. The blend was spun into fiber without any problems such as swelling or draw resonance, however, the mechanical properties were decreased as the amount of the DGEBBA was increased.     

Coloration of poly(lactic acid) with disperse dyes. 1. Comparison to poly(ethylene terephthalate) of dyeability, shade and fastness

The dyeability of poly(lactic acid) [PLA] with a range of commercial disperse dye was examined and compared to that of poly(ethylene terephthalate) [PET] in addition to the colour and fastness of the resultant dyeings. A screening exercise in which twenty dyes of differing energy types and chemical classes were applied to PLA revealed a substantial variation between the dyes in terms of dye uptake (12–88 % at 4 %o.w.f.). Nine dyes exhausted above 70 % and were selected for further study, which involved comparison of shade and fastness of PLA dyeings with those of the corresponding PET dyeings. Differences in shade depended on hue while wet fastness of each of the PLA dyeings was either the same or 0.5–1.0 point lower than its PET counterpart. In all but one case, dye photostability in PLA was found to be very similar to that in PET. Dye build-up profiles on PLA were also investigated and from these results mixtures of compatible dyes identified.     

Functinalization of poly(ethylene terephthalate) fibers by grafting of maleic acid/methacrylamide monomer mixture

Functionalized poly(ethylene terephthalate) (PET) fibers were synthesized by grafting of maleic acidmethacrylamide (MAA-MAAm) monomer mixtures by using benzoylperoxide as initiator onto PET fibers in an aqueous medium. The functionalized fibers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimeter, and scanning electron microscopy. The effects of reaction conditions, such as monomer mixture ratio, monomer mixture and initiator concentration, polymerization time, and temperature on grafting were investigated. In alone grafting of MAA, grafting was not observed. However, the use of MAAm as a comonomer increased the amount of MAA inserted to the PET fiber up to 40.7 %. An increase in the temperature between 75 and 95 °C and also, increase in monomer mixture concentration between 0.50 and 1.00 M increased the grafting rate and saturation graft yield. The graft yield has shown an increase up to an initiator concentration of 1.0×10⁻² M and decreased afterwards. The grafting increased the dyeability with disperse, acidic and basic dyes, and water absorption capacity but decreased the thermal stability of the fibers.     

Thermal properties of Poly(trimethylene terephthalate)/Poly(ethylene terephthalate) melt blends

The thermal behavior, morphology, ester-interchange reaction of Poly(trimethylene terephthalate) (PTT)/Poly(ethylene terephthalate) (PET) melt blends were investigated over the whole composition range(xPTT/(1-x)PET) using a twinscrew Brabender. The melt blends were analyzed by differential scanning calorimetry (DSC), nuclear magnetic resonance spectroscopy (¹³C-NMR), and scanning electron microscopy (SEM). Single glass transition temperature (T _g ) and cold crystallization temperature (T _cc ) were observed in all melt blends. Melt blends were found to be due to the ester-interchange reaction in PTT/PET blend. Also the randomness of copolymer increases because transesterification between PTT and PET increases with increasing blending time. This reaction increases homogeneity of the blends and decreases the degree of crystallinity of the melt blends. In PTT-rich blends, mechanical properties decrease with increase of PET content compared with that of pure PTT. And, in PET-rich blends, tensile modulus decreases with increase of PTT content, but tensile strength and elongation is similar to that of pure PET.     

Interchange reaction kinetics and sequence distribution of liquid crystalline poly(ethylene terephthalate-co-2(3)-chloro-1,4-phenylene terephthalate)

Liquid crystalline (LC) poly(ethylene terephthalate-co-2(3)-chloro-1,4-phenylene terephthalate) [copoly(ET/CPT)] was prepared using poly(ethylene terephthalate) (PET) as a flexible spacer, terephthalic acid (TPA), and chlorohydroquinone diacetate (CHQDA). All reactions involved in the copolymerization were investigated using some model compounds: TPA was used for acidolysis, diphenylethyl terephthalate (DPET) for interchange reaction between PET chains, and di-o-chlorophenyl terephthalate (DOCT) and di-m-chlorophenyl terephthalate (DMCT) for interchange reaction between PET and rigid rodlike segments. Activation energies obtained for the acidolysis of PET with TPA and for interchange reaction of PET with DPET, DOCT, and DMCT were 19.8 kcal/mole, 26.5 kcal/mole, 60.2 kcal/mole, and 45.9 kcal/mole, respectively. This result supports that the copolymerization proceeds through the acidolysis of PET with TPA first and subsequent polycondensation between carboxyl end group and CHQDA or acetyl end group, which is formed from the reaction of CHQDA and TPA. Also, it was found that ester-interchange reaction can be influenced by the steric hindrance. Copoly(ET/CPT)s obtained had ethylene acetate end groups formed from acetic acid and hydroxy ethylene end groups and showed almost the random sequence distribution for all compositions.     

Various nano-silica particles affecting dyeability of poly(ethylene terephthalate)/silica nanocomposite films

Poly(ethylene terephthalate) [PET] based nanocomposites containing three differently modified silica particles were prepared by melt compounding. The influence of type of nano-silica on dispersibility, thermal and dyeing properties of the resultant nanocomposite was investigated by various analytic techniques, namely, polarized optical microscopy (POM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), reflectance spectroscopy (RS), and light fastness. Optical microscopy images illustrated that nano-silica particles tended to increase the number of spherulites in the PET matrix which were dependent on nano-silica type and content. Thermal studies of the resultant nanocomposites showed a slight decrease in the melting temperature compared to a pristine PET. Silica nanocomposites were finally dyed with a disperse dye and their reflectances were determined by the aid of reflectance spectrophotometer. Such reflectances were converted to the corresponding color coordinate values which are indicative of dyeability of such nanocomposites.     

Investigation on flame retardancy of poly(ethylene terephthalate) for plastics and textiles by combination of an organo-modified sepiolite and Zn phosphinate

Zn phosphinate, organo-modified sepiolite and poly(ethylene terephthalate) (PET) have been melt blended to develop a new flame retardant system for PET plastics and textiles. The combination of Zn phosphinate and sepiolite have been exploited in order to enhance the flame retardancy of PET for both plastics and textiles. The thermal stability of PET blends evaluated by thermogravimetric analysis and differential scanning calorimetry results remarkably affected by the loaded fillers. The combustion tests by cone calorimetry reveal a relevant decrease of combustion rate and a high increase of fire performance index for both plastics and textiles due to the presence of this novel flame retardant mixture. Analogously, limiting oxygen index has been found increased in a remarkable way.     

Thermal performance and flammability of poly(ethylene terephthalate) fabrics grafted with different monomers followed by electron beam irradiation

Electron beam irradiation grafting of acrylic acid (AAc), acrylamide (AAm), and dimethyl vinylphosphonate (DMVP) onto poly(ethylene terephthalate) (PET) fabrics was performed using a high-energy electron accelerator. Parameters affecting the graft polymerization of PET fabrics, including absorbed dose and monomer concentration, were investigated. Fourier transform infrared spectroscopy analysis confirmed that the monomers were grafted onto the PET fabrics. The thermal behavior of the grafted PET fabrics was investigated with thermogravimetric analysis. Findings showed that grafting with AAm could improve the thermal stability of PET. The limiting oxygen index values and vertical flammability test results showed that PET fabric graft-polymerized with AAc could improve the flammability and prevent melt dripping. Grafting with AAm and DMVP could improve the flame retardation property of PET fabric. Scanning electron micrographs showed that the surface morphology of the PET fabric samples was significantly influenced by graft polymerization, and that grafting with AAc could promote the formation of residual char and impart an anti-dripping quality to PET fabrics.     

The preparation and characterization of conductive poly(ethylene terephthalate)/polyaniline composite fibers using benzoyl peroxide

Conductive polyaniline (PAn)/poly(ethylene terephthalate) (PET) composite fibers were prepared by chemical polymerization of aniline in the presence of PET fibers using benzoyl peroxide (Bz₂O₂) in organic solvent/aqueous hydrochloric acid mixtures. The effects of polymerization conditions such as organic solvent/water ratio, oxidant, aniline and hydrochloric acid concentrations and temperature were investigated on the amount of PAn deposited on PET fiber and the electrical surface resistance of composite fibers. The maximum PAn content and the lowest electrical surface resistance of composite fibers were observed at HCl concentrations of 0.5 mol L⁻¹. The properties of PAn/PET composite fibers such as density, diameter, tensile strength and breaking elongation were also investigated in comparison with those of pure PET. Characterization of conductive composite fibers was carried out by FTIR, TGA, SEM techniques, surface resistance measurements, and cross section images taken by optical microscope.