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.     

Thermal degradation and cyclodepolymerization of poly(ethylene terephthalate-co-isophthalate)s

The thermal degradation of poly(ethylene terephthalate-co-isophthalate)s (PETIs) is investigated by using isothermal thermogravimetric analysis at the temperature range of 280–310°C. The degradation rate of PETIs is increased as the mole ratio of ethylene isophthaloyl (EI) units in PETIs increases. The activation energies for the thermal degradation of poly(ethylene terephthalate), PETI(5/5), and poly(ethylene isophthalate) are 33.4, 16.6, and 8.9 kcal/mole, respectively. The degradation rate of PETIs is influenced by their volatile cyclic oligomer components formed during the polymerization and the thermal degradation. It is simulated by the rotational isomeric state model that the content of cyclic dimer in PETIs, which is the most volatile cyclic oligomer component, increases with the EI units in PETIs.     

Theoretical analysis of the melt spinning process of poly(trimethylene terephthalate) fibers

Profiles development of the melt spinning process of poly(trimethylene terephthalate) (PTT) was simulated by a numerical method. The spinning speed of 3 km/min to 5 km/min was analyzed and the characteristic of PTT spinning process was compared with that of poly(ethylene terephthalate) (PET). Velocity development of PTT was slower than that of PET. Although PTT’s spinning temperature was lower than PET’s, the PTT solidified slower because of a smaller super-cooling and the large specific heat capacity. The diameter profile of PTT decreases gradually in comparison with that of PET. PTT’s strain rate has a broader distribution than PET’s and its maximum ranged from 541 to 570 s⁻¹ for PET and 136 to 149 s⁻¹ for PTT. PTT’s tensile stress was smaller than PET’s.     

Studies on the ternary blends of liquid crystalline polymer and polyesters

Thermotropic liquid crystalline polymer made up of poly(p-hydroxybenzoate) (PHB)-poly(ethylene terephthalate) (PET) 8/2 copolyester, poly(ethylene 2,6-naphthalate) (PEN) and PET were mechanically blended to pursue the liquid crystalline phase of ternary blends. Complex viscosities of blends decreased with increasing temperature and PHB content. DSC thermal analysis indicated that glass transition temperature (Tg) and melting temperature (Tm) of blends increased with increasing PHB content. Both tensile strength and initial modulus increased with raising PHB content and take-up speed of monofilaments. In the WAXS diagram, only PEN crystal reflection at 2Θ=15.5^o appeared but PET crystal reflection was not shown in all compositions. The degree of transesterification and randomness of blends increased with blending time but sequential length of both PEN and PET segment decreased.     

Use of 1,6-diaminohexane-functionalized glycidyl methacrylate-g-poly(ethylene terephthalate) fiber for removal of acidic dye from aqueous solution

In this study, removal of Congo red (CR) from aqueous solution by 1,6-diaminohexane-functionalized glycidyl methacrylate-g-poly(ethylene terephthalate) (HMDA-GMA-g-PET) fiber was investigated. A new aminated fibrous adsorbent was prepared by a reaction between amine and epoxy group in GMA-g-PET fiber prepared by grafting GMA monomer onto poly (ethylene terephthalate) (PET) fiber. Effects of various parameters such as pH, treatment time, initial, dye concentration, and reaction temperature on the adsorption amount of dye onto reactive fiber were investigated. The adsorption rates of CR were much higher on the HMDA-GMA-g-PET fiber than on GMA-g-PET and ungrafted PET fiber. The effective pH was 2.0 for adsorption on grafted PET fiber. It was found that the sufficient time to attain equilibrium was 60 min. The maximum adsorption capacity of the reactive fiber for CR is 16.6 mg/g fiber. The rates of adsorption were found to conform to the pseudo-second order kinetics with good correlation. It was found that the adsorption isotherm of CR fitted Freundlich type isotherm.     

Effects of blend ratio and heat treatment on the properties of the electrospun poly(ethylene terephthlate) nonwovens

Semicrystalline poly(ethylene terephthalate) (cPET)/amorphous poly(ethylene terephthalate) with isophthalic acid (aPET) blends with 100/0, 75/25, 50/50, 25/75, and 0/100 by weight ratios were dissolved in a mixture of trifluoroacetic acid (TFA)/methylene chloride (MC) (50/50, v/v) and electrospun via the electrospinning technique. Solution properties such as solution viscosity, surface tension and electric conductivity were determined. The solution viscosity slightly decreased as aPET content increased, while there was no difference in surface tension with respect to aPET composition. The characteristics of the electrospun cPET/aPET blend nonwovens were investigated in terms of their morphology, pore size and gas permeability. All these measurements were carried out before and after heat treatment for various blend weight ratios. The average diameter of the fibers decreased with increasing aPET composition due to the decrease in viscosity. Also, the morphology of the electrospun cPET/aPET blend nonwovens was changed by heat treatment. The pore size and pore size distribution varied greatly from a few nanometers to a few microns. The gas permeability after heat treatment was lower than that before heat treatment because of the change of the morphology.     

Dyeing properties of 4-amino-4′-fluorosulfonylazobenzene disperse dyes on poly(ethylene terephthalate)

Dyeing properties of a series of 4-amino-4′-fluorosulfonylazobenzene disperse dyes on poly(ethylene terephthalate) (PET) were investigated. Build-up properties and color properties on PET were examined. In particular, the 4-aminoazobenzene dyes containing a nitro group instead of a fluorosulfonyl group at 4′-position were also synthesized in order to compare their dyeing properties on PET with that of 4′-fluorosulfonyl analogues.     

Preparation and characterization of high molecular weight poly(trimethylene terephthalate) by solid-state polymerization

Solid-state polymerization of poly(trimethylene terephthalate)(PTT) was carried out to obtain high molecular weight polymers. Two kinds of commercial PTT chips were polymerized in the solid state by the heat treatment at 190∼220°C for various times and they were characterized by end group content, molecular weight, thermal analysis, and X-ray diffraction. In the solid-state polymerization of PTT, the overall reaction rate was governed by the solid-state polymerization temperature and time, and pellet size. The content of carboxyl end groups decreased during the solid-state polymerization with increasing solid-state polymerization temperature and time. The melting temperature and crystallinity of the PTT were higher for the ones treated at higher temperature and longer time. The activation energy for the solid-state polymerization of PTT was in the range of 24∼25 kcal/mol for both chips. Through the solid-state polymerization of commercial PTT chips, high molecular weight polymers up to an intrinsic viscosity of 1.63 dl/g was obtained, which corresponded to about a 117,000 weight-average molecular weight.     

Improvement of mechanical and electrical properties of poly(ethylene glycol) and cyanoresin based polymer electrolytes

Ionic conductivity and mechanical properties of a mixed polymer matrix consisting of poly(ethylene glycol) (PEG) and cyanoresin type M (CRM) with various lithium salts and plasticizer were examined. The CRM used was a copolymer of cyanoethyl pullulan and cyanoethyl poly(vinyl alcohol) with a molar ratio of 1:1, mixed plasticizer was ethylene carbonate (EC) and propylene carbonate (PC) at a volume ratio of 1:1. The conductive behavior of polymer electrolytes in the temperature range of 298∼338 K was investigated. The PEG/LiClO₄ complexes exhibited the highest ionic conductivity of ∼10⁻⁵ S/cm at 25°C with the salt concentration of 1.5 M. In addition, the plasticized PEG/LiClO₄ complexes exhibited improvement of ionic conductivity. However, their complexes showed decreased mechanical properties. The improvement of ionic conductivity and mechanical properties could be obtained from the polymer electrolytes by using CRM. The highest ionic conductivity of PEG/CRM/LiClO₄/(EC-PC) was 5.33×10⁻⁴ S/cm at 25°C.     

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.     

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.     

Synthesis and evaluation of a series of novel monoazo disperse dyes derived from N-carboxylic acid-1,8-naphthalimide on poly(ethylene terphthalate)

A series of novel monoazo disperse dyes based on N-carboxylic acid-1,8-naphthalimides have been synthesized via 4-(4-amino-1,8-naphthalimido) butanoic acid as diazo components and various couplers. The synthesized dyes were characterized with elemental analysis, differential scanning colorimetry, Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and UV-visible spectroscopic techniques. The molar extinction coefficient, wavelength maxima, and solvatochromism effect were obtained using chloroform, acetone, and N,N-dimethyl formamide as solvent. The results showed that the synthesized dyes had molar extinction coefficient of 20908 to 38939 l mol⁻¹ cm⁻¹, wavelength maxima of 409–549 nm, and positive solvatochromism by changing solvent from chloroform to N,N-dimethyl formamide. The synthesized dyes were applied on poly(ethylene terephthalate) using high temperature method. Dyes 1 and 2 showed high build-up properties on poly(ethylene terephthalate), whereas dyes 3 and 4 offered medium build-up. All the dyes offered excellent heat fastness, good wash and rubbing fastnesses on poly(ethylene terephthalate) fabrics. The hydrolysis of the synthesized dyes in alkali media indicated that the presence of a carboxylic acid group within the dye molecules provides alkali-clearable potential.     

The effect of molecular weight and the linear velocity of drum surface on the properties of electrospun poly(ethylene terephthalate) nonwovens

In this study, we evaluated the effect of the molecular weight of the polymer on electrospun poly(ethylene terephthalate) (PET) nonwovens, and their mechanical properties as a function of the linear velocity of drum surface. Polymer solutions and electrospun PET nonwovens were characterized by means of viscometer, tensiometer, scanning electron microscope (SEM), wide angle X-ray diffraction measurement (WAXD) and universal testing machine (UTM). By keeping the uniform solution viscosity, regardless of molecular weight differences, electrospun PET nonwovens with similar average diameter could be obtained. In addition, the mechanical properties of the electrospun PET nonwovens were strongly dependent on the linear velocity of drum surface. From the results of the WAXD scan, it was found that the polymer took on a particular molecular orientation when the linear velocity of drum surface was increased. The peaks became more definite and apparent, evolving from an amorphous pattern at 0 m/min to peaks and signifying the presence of crystallinity at 45 m/min.     

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.     

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.     

Thrombin immobilization to Poly(Methacrylicacid) graft polymerized PET and PAN fabrics

Poly(ethylene terephthalate) and poly(acrylonitrile) fabrics are the most produced synthetic fabrics in the world. Their production and usage increase at medical textile. There is no functional group in their structure for enzyme immobilization. Hence, they are not inclined to react. However, functional groups could be added to their structure using graft polymerization. In this study, methacrylic acid was graft polymerized to poly(ethylene terephthalate) and poly(acylonitrile) fabrics. Characterization of modified fabrics was carried out and thrombin was immobilized to poly(methacrylic acid) graft polymerized poly(ethylene terephthalate) and poly(acylonitrile) fabrics using 1-Ethyl-3-(3-dimetylaminopropyl)-carbodiimide. Optimization studies were also performed for the immobilization of thrombin. Thrombin immobilized poly(methacrylic acid) graft polymerized poly(ethylene terephtalate) and poly(acrylonitrile) fabrics were reduced recalcification time 30 % and 25 %, respectively. It is the first time, an enzyme was immobilized to fabric and its in vitro applications were performed. Thrombin has not been immobilized to synthetic fabric, yet.     

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.     

Poly(trimethylene terephthalate) fiber melt-spinning: Material parameters and computer simulation

In this work, the method, in principle of the box complex algorithm was adopted to obtain stress-induced crystallization coefficient C and the strain-optical coefficientA _op with the value of 295 and 1.5×10⁻⁹, respectively, and some parametersA ₁=0.27,A ₂=5.06,a=3.5,b=1.8 relative to the elongational viscosity of poly(trimethylene terephthalate)(PTT) fiber. The vitrification distance as a function of the take-up velocity and mass throughput was also gotten. The effects of spinning conditions on filament temperature, velocity gradient, spinning tension, birefringence and crystallinity, and effect of viscoelasticity on take-up velocity had been discussed.     

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.     

Superhydrophobic PET fabrics achieved by silica nanoparticles and water-repellent agent

We report herein a superhyrodrophobic poly(ethylene terephthalate) (PET) fabric prepared through a biomimetic method of the Lotus effect. To attain the Lotus effect on the PET fabrics, physical roughness and chemical hydrophobicity were controlled by adopting silica nanoparticles and a commercial water-repellent agent, respectively. For this, narrow-size distributed silica nano-particles were prepared by a sol-gel process. The water contact angle on PET fabric treated with both silica nanoparticles and water-repellent agent reached 158°, which was much higher than 137° reached by the fabric treated with the water-repellent agent only.