Poly(ethylene terephtalate) films modified with N,N‐dimethylacrylamide: Incorporation of disperse dye

Poly(ethylene terephtalate), PET, can be modified with N,N‐dimethylacrylamide to obtain a better incorporation of disperse dye (Disperse Blue 79). Minimal variations in the decomposition at 10% level, melting, and glass transition temperatures, show that the thermal stability of modified PET films does not change when compared to nonmodified PET. The atomic force images show nanopeaks formation on the surface due to the modification. Modified PET films show a decrease in the contact angle and then, an increase in the superficial tension measurements, when compared to the value of 37 ± 1 dynes · cm⁻¹(nonmodified), with values liying in the range of 42–46 ± 0.5 dynes · cm⁻¹. The data obtained by photoacoustic spectroscopy (PAS) for dyed PET films show a dye peak at 580 nm. The data analysis of the peak area show that PET films modified with N,N‐dimethylacrylamide for 15 min at 85°C, dyed for 6 h at 85°C with a dye concentration of 0.333 g/L, incorporate three times more dye than the nonmodified films dyed in the same conditions. By the data obtained from PAS, it was possible to calculate the depth profile of dyeing with values around 54 μm. Factorial analyses show that the dyeing time was the most important variable. The major amount of incorporated dye was obtained by the following combination of variables: temperature and time of modifier treatment were, respectively, 72.5°C and 15 min; time and temperature of dyeing were, respectively, 90°C and 195 min for a dye concentration of 0.133 g/L. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 269–282, 2000     

Spinning of poly(ethylene terephthalate) fibers incorporated with modified calcium silicate

The spinning of poly(ethylene terephthalate) (PET) filaments in laboratory‐scale was studied. The objective was to study the effect of modified calcium silicate (CS) with vinyltriethoxysilane (VTES) on the melt spinning of PET fibers. The CS was modified with VTES (2% v/v) in diethyl ether at room temperature for 24 h. The modification of CS with VTES improved agglomeration of CS, hydrophobic, and heat‐resistance properties. These properties were expected that modified CS could be used as the filler in melt spinning of PET. The incorporation of modified CS in PET was spinnable. The addition of CS in PET improved its heat resistance. Also, the filler had an effect on the mechanical properties of polyester fibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Correlation of solubility data of azo disperse dyes with the dye uptake of poly(ethylene terephthalate) fibres in supercritical carbon dioxide

Solubility data of disperse azo dyes in supercritical carbon dioxide are presented for dyeings of poly(ethylene terephthalate) fibres with CI Disperse Red 167:1, carried out at 200–300 bar and 80–120 °C, with varying amounts of adulterants. The same dyeings were also carried out in water for comparison. Scanning electron micrographs were taken of the dyes which show a growth of dye crystals during treatment in supercritical carbon dioxide. The paper reports that at 120 °C, melting of the pure dye CI Disperse Red 167:1 is observed. The presence of adulterants in the dye formulations help prevent agglomeration by acting as spacers between the dye molecules. Dyeings of PETP carried out under conditions of the highest solubility of the dye in supercritical carbon dioxide do not necessarily result in a very high dye uptake. This was shown by pressure- and temperature-dependent dyeing experiments of PETP in supercritical carbon dioxide.     

Effect of drawing temperature on mesomorphic transitions of oriented poly(ethylene terephthalate) fibers exposed to supercritical CO2

Samples of partially oriented yarn (POY) PET fibers were uniaxially drawn at 23, 68 °C (cold drawing) and 100 °C (hot drawing) and then exposed to the supercritical carbon dioxide (scCO₂) without tension at a temperature of 80 °C and a pressure of 220 bar. The effect of drawing temperature on the evolution of mesomorphic phases and the structural changes under exposure to scCO₂ were investigated by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), and wide-angle X-ray diffraction. The orientation factor of the samples was measured using a polarizing microscope. A good correlation was obtained between the results of various analyses. The results illustrate that evolution of structure strongly depends on both process temperature and post-treatment by scCO₂ exposure. The latter process leads to plasticization and reduced glass transition temperature of the samples, thus inducing structural changes in the fibers.     

Phase equilibrium characteristics of supercritical CO2/poly(ethylene terephthalate) binary system

The solubility of carbon dioxide in poly (ethylene terephthalate) (PET) at high pressure and elevated temperature conditions was investigated for a better understanding of the phase equilibrium characteristics of supercritical CO₂/PET binary system and useful data for the process development of the supercritical fluid dyeing. Based on the principle of pressure decaying, a novel experimental apparatus suitable to high pressure and high temperature measurement was established. The solubilities of CO₂ in PET were measured with the apparatus at temperatures of 110, 120, and 130°C and pressures up to 30.0 MPa. The results show that the solubility of CO₂ in PET increases with the increase of pressure and CO₂ density, respectively, at a constant temperature, whereas it decreases with the increase of temperature at a constant pressure. The Sanchez‐Lacombe equation of state (S‐L EOS) was used to correlate the experimental data. The calculated results are in good agreement with the experimental ones. The average absolute relative derivation (AARD) is less than 3.91%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Microcellular injection molding of in situ modified poly(ethylene terephthalate) with supercritical nitrogen

The microcellular injection molding (commercially known as MuCell) of in situ polymerization‐modified PET (m‐PET) was performed using supercritical nitrogen as the physical blowing agent. Based on the design of experiment matrices, the influence of operating conditions on the mechanical properties of molded samples was studied systematically for two kinds of m‐PETs, namely, n‐m‐PET and m‐m‐PET synthesized using pentaerythritol and pyromellitic dianhydride (PMDA) as modifying monomers, respectively. Optimal conditions for injection molding were obtained by analyzing the signal‐to‐noise (S/N) ratio of the tensile strength of the molded samples. The specific mechanical properties, especially the impact strength, of the microcellular samples under those optimal conditions increased significantly. Scanning electron microscope analyses showed a uniform cell structure in the molded specimens with an average cell size of around 35 µm. The m‐m‐PET modified with PMDA generated a slightly finer cell structure and a higher cell density than the n‐m‐PET. POLYM. ENG. SCI., 54:2739–2745, 2014. © 2013 Society of Plastics Engineers     

Comparison of disperse dye exhaustion,color yield,and colorfastness between polylactide and poly(ethylene terephthalate)

Ten popular disperse dyes with different energy levels and chemical constitutions were used to compare their exhaustion, color yield, and colorfastness on polylactide (PLA) and poly(ethylene terephthalate) (PET). Only two out of the 10 dyes had exhaustions higher than 80% on PLA at 2% owf. Five out of the 10 dyes had exhaustions less than 50%. All 10 dyes had more than 90% exhaustion on PET, whereas six of them had exhaustions of 98% or higher. There was no obvious pattern as for which energy level or which structure class provided dye exhaustion better than that of others. Although PLA had lower disperse dye exhaustion than that of PET, it had higher color yield. Based on the 10 dyes examined, the color yield of PLA was about 30% higher than that of PET. This means that even with low dye uptake, PLA could have a similar apparent shade depth as that of PET if the same dyeing conditions are applied. Our study supported that the lower reflectance, or reflectivity, of PLA contributes to the higher color yield of PLA than that of PET. A quantitative relation between the shade depth of PLA and PET based on their dye sorption was developed. Disperse dyes examined had lower washing and crocking fastness on PLA than on PET. The differences in class were about 0.5 to 1.0. If the comparison was based on the same dye uptake, the differences might be larger. The differences in light fastness between the two fibers were smaller than that in washing and crocking fastnesses. The light fastness of disperse dyes on PLA is expected to be even better if the comparison is based on the same dye uptake on both fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3285–3290, 2003     

Effects of tension on mesomorphic transitions and mechanical properties of oriented poly(ethylene terephthalate) fibers under supercritical CO2 exposure

Samples of partially oriented yarn PET fibers were uniaxially drawn below the glass transition temperature (cold-drawing) before exposure to supercritical carbon dioxide (scCO₂) in the absence and presence of tension at a temperature of 80 °C and a pressure of 220 bar. The effects of draw ratio, scCO₂ exposure, and tension on structural changes and on mechanical properties in particular were investigated using differential scanning calorimetry, tensile deformation, and birefringence and density measurements. A good correlation was obtained among the results obtained from various techniques. Results indicate that exposure to scCO₂ not only induces structural changes but also develops crystallization in the samples. Tension under scCO₂ exposure also produces significant effects in terms of causing structural changes and transforming the oriented chains in the mesophase into the crystalline or noncrystalline domains. PET fibers exposed to scCO₂ under no tension yields lower values of crystallinity, orientation, tenacity, and Young’s modulus but higher values of breaking elongation compared to samples exposed under tension. This is an indication of higher plasticity of the chains in the amorphous domains in samples exposed under no tension. It is also found that mechanical measurements confirm the structural changes taking place in exposed PET samples.     

Synthesis of modified poly(ethylene terephthalate) fibers with antibacterial properties and their characterization

Poly(ethylene terephthalate) (PET) fibers were grafted with vinyl monomers by utilizing benzoyl peroxide. Grafted PET fibers were modified in optimized conditions with several functional groups such as amine, chlorine, hydrogen peroxide_, and triclosan to gain antibacterial feature. The second part of this study comprised examination of the antibacterial features of PET fibers via use of Staphylococcus aureus (ATCC 29213) and Escherichia coli (ATCC 25922) bacteria. Kirby-Bauer test is used to study antibacterial properties. The longest zone diameter for Trc-GMA-g-PET fibers was 56?mm for E. Coli whereas the biggest diameter for S. aureus bacteria was 130?mm with Trc-MMA-g-PET fibers.     

Crystallization of poly(ethylene terephthalate) modified with codiols

The nucleation of poly(ethylene terephthalate) (PET) by codiols and olefinic segments was studied. The codiols 1,5‐pentanediol, 1,8‐octanediol, 2,5‐hexanediol, and 1,3‐dihydroxymethyl benzene were copolymerized into PET in a concentration range of 0–10 mol %. The melting (T_m), crystallization (T_c), and glass‐transition (T_g) temperatures were studied. These codiols were found to be able to nucleate PET at low concentrations, probably by lowering the surface free energy of the chain fold. However, the codiols also disturbed the structural order of the polymer, resulting in a decrease in both the T_m and T_c values. The optimum codiol concentration was found to be at around 1 mol %, which is lower than previously reported. A diamide segment N,N′‐bis(p‐carbo‐methoxybenzoyl)ethanediamine (T2T) was found to be a more effective nucleator than the codiols; however, no synergy was observed between the nucleating effect of the diamide segment T2T and that of the codiol. An olefinic diol (C₃₆‐diol) with a molecular weight of 540 g/mol was also copolymerized into PET in a concentration range of 0–21 wt %. Only one T_g was observed in the resulting copolymers, suggesting that the amorphous phases of PET and the C₃₆‐diol are miscible. The main effect of incorporating the C₃₆‐diol into PET was the lowering of the T_g; thus, the C₃₆‐diol is an internal plastifier for PET. The C₃₆‐diol had little effect on the T_m value; however, the T_c value actually increased in the 11.5 wt % copolymer. As the T_g decreased and the T_c increased, the crystallization window also increased and thereby the likelihood of crystallization. Therefore, the thermally stable C₃₆‐diol appears to be an interesting compound that may be useful in improving the crystallization of PET. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2676–2682, 2001     

Dichroism of poly(ethylene terephthalate)-disperse dye system

As an approach to the basic study on the orientation behavior of amorphous region, the dichroic orientation factor, D, of poly(ethylene terephthalate), PET, fiber or film dyed with disperse dyes was investigated in relation to Δn, birefringence of the crystalline and amorphous regions, and Δn_a, birefringence of the amorphous region. It was found that D versus Δn plot belonged to a linear relationship passing through the origin but breaking slightly toward the D axis at Δn ? 0.14, while D versus Δn_a plot was expressed by a straight line passing similarly through the origin but with no break. D₀, the value of D at the ideal parallel orientation, was obtained by extrapolating the latter plot of the samples stretched with no relaxation: 1.00 and 0.73 for the PET–C.I. Disperse Yellow 7 and PET–C.I. Disperse Red 17 systems respectively. When the sample had been relaxed, the D versus Δn_a was also linear; however, D₀'s obtained were smaller than the above mentioned respective values. Even in these cases D for Disperse Yellow 7 versus the corresponding D for Disperse Red 17 belonged to a linear relationship with the slop 1:0.73. As the result it was concluded that the transition moment of molecule of C.I. Disperse Yellow 7 coincided with the molecular axis and the dye molecule combined parallel to PET chain, while as to C.I. Disperse Red 17 any definite conclusion could not be determined. However, in the both cases the mode of combination of dye molecules with PET is definite and kept unchanged during stretching and heating.     

Coating of modified poly(ethylene terephthalate) fibers with sericin-capped silver nanoparticles for antimicrobial application

Polymer Bulletin - In this work, a kind of amine-type PET fibers was synthesized by reacting hexamethylenediamine (HMDA) with methacrylic acid-g-poly(ethylene terephthalate) (PET-g-MAA) fibers for...     

Integrated process of supercritical CO2-assisted melt polycondensation modification and foaming of poly(ethylene terephthalate)

An integrated process of melt polycondensation modification and foaming of poly(ethylene terephthalate) (PET) was performed in a high pressure vessel assisted by supercritical carbon dioxide (scCO₂). ScCO₂ was firstly employed to sweep PET melt, i.e., high pressure CO₂ continuously flows through the vessel at a fixed flow rate to remove small molecules for higher molecular weight PET, then this modified PET melt was directly foamed through a rapid depressurization process using scCO₂ as blowing agent. In this integrated process, PET with high melt strength after polycondensation modification could be foamed directly in molten state. Therefore, re-molten process of solid modified PET pellets was canceled to avoid its degradation and CO₂ saturation time could be saved in foaming process, thus processing time could be shortened and energy efficiency could be improved. The influences of scCO₂ sweeping treatment time, pressure and flow rate on properties of the modified PETs and cell morphologies of the foamed PETs were investigated respectively. The results showed that CO₂ sweeping treatment could effectively enhance PET melt polycondensation modification process, which was superior to that of N₂ treatment. PET foams with average cell diameter of 32–62 μm and cell density of 1 × 10⁷ to 4 × 10⁷ cells/cm³ have been obtained in the integrated process. Compared with the process of only foaming modified PET by scCO₂ or performing scCO₂ assisted modified PET further melt polycondensation process and scCO₂ foaming process separately, this integrated process produced better cell morphology.     

Visible dichroism of the poly(ethylene terephthalate)–disperse dye system at high temperatures

The dichroic behavior of PET film dyed at 70°C with Disperse Red 17 or Disperse Yellow 7 was investigated in the temperature range 20–200°C with a view to studying the changes in amorphous region of PET at high temperatures. The dichroic orientation factor D versus temperature plot is expressed by a straight line with negative slope; two breaks appear at 80 (T_g) and 120°C. So long as the amorphous structure does not change irreversibly, the values of D change reversibly with the temperature. Hence, if a change in D after heating is observed at room temperature, it is evidence that an irreversible change occurred in the amorphous structure during the heating. The break at 120°C is a new amorphous transition point of PET existing along with T_g, although the T_g can hardly be observed after the cold crystallization; some phenomena reported in the literature are proposed as evidence.     

Crystallization of poly(ethylene terephthalate) and poly (butylene terephthalate) modified by diamides

Poly(ethylene terephthalate) (PET) and poly (butylene terephthalate) have been modified by diamide units (0.1–1 mol%) in an extrusion process and the crystallization behavior studied. The diamides used were: for PET, T2T‐dimethyl (N, N′‐bis(p‐carbomethoxybenzoyl)ethanediamine) and for PBT, T4T‐dimethyl (N, N′‐bis(p‐carbomethoxybenzoyl)butanediamine). The above materials were compared to talc (0.5 wt%), this being a standard heterogeneous nucleator, and to diamide modified copolymers obtained by a reactor process. Two PET materials were used: a slowly crystallizing recycled grade obtained from soft drink bottles and a rapidly crystallizing injection molding grade. The crystallization was studied by differential scanning calometry (DSC) and under injection molding conditions using wedge shaped specimens; the thermal properties were studied by dynamic mechanical analysis. T2T‐dimethyl is effective in increasing the crystallization of PET in both of the extrusion compounds as well as in the reactor materials. It was also found that the crystallization temperature of poly(butylene terephthalate) could be slightly increased by the addition of nucleators.     

Orientation-induced crystallization of poly(ethylene terephthalate) fibers with controlled microstructure

Orientation-induced crystallization of PET fibers was studied by the in-situ wide-angle X-ray diffraction (WAXD) utilizing synchrotron radiation source combined with thermomechanical analysis. The noncrystalline as-spun fiber spun was heat-treated at 150, 165, 180 and 195 °C for 0.1 s under constrained condition. The heat-treatment allowed the fibers to have various amount of isotropic amorphous (IA), oriented noncrystalline (ON), and crystalline (Cr) phase. The structure evolution accompanying the crystallization of the fibers was then examined upon elevating temperature while the fiber length was held constant. The X-ray results clearly showed that the crystallization takes place first by ON phase (extended-chain crystallization) and then followed by the crystallization of IA phase (folded-chain crystallization). The on-set of extended-chain crystallization was dependent on the amount and degree of orientation of ON phase in the fiber that was derived from the various heat-treatment temperatures. It is also noted that the IA phase transforms into not only the CR phase but also the ON phase. The crystallization on the surface of preformed extended-chain crystals appeared to induce the spontaneous orientation of the chains. The thermomechanical data indicated that a stress emerges rapidly on fiber above glass transition temperature (T_g), which is associated with the entropic relaxation of the ON phase. The stress emerged on fiber then dropped drastically as the temperatures of fibers reached the temperatures of extended-chain crystallization, indicating that the stress drop is closely related with the extended-chain crystallization. The fibers heat-treated at the highest temperature showed the highest initial crystallinity but showed the slowest crystallization rate, resulting in the lowest final crystallinity among the fibers.     

Benzoyl-peroxide-initiated graft copolymerization of poly(ethylene terephthalate) fibers with acrylamide

In this study the grafting of acrylamide onto poly(ethylene terephthalate) fibers with the help of benzoyl peroxide and the effects of the temperature and the concentrations of initiator and monomer were investigated. Some of the experiments were repeated several times in order to check the reproducibility. The optimum temperature for grafting was found to be 75°C. The graft yield was observed to increase with the monomer concentrations examined. The graft yield increased up to the benzoyl peroxide concentration approximately 0.05 g/50 mL, and then passed a plateau, before showing a decrease. The fiber diameter, intrinsic viscosity, and the moisture regain increased while the fiber density decreased with the graft yield.     

Effect of pressure on CO2 transport in poly(ethylene terephthalate)

The CO₂ solubility, permeability, and diffusion time lag in poly(ethylene terephthalate) are reported at 35° and 65°C for CO₂ pressures ranging from 0.07 to 20 atm. The subatmospheric time lag and permeability measurements were made with a glass system at North Carolina State University, while the measurements between 1 and 20 atmospheres, using an identical polymer sample, were made at The University of Texas with a metal system capable of tolerating gauge pressures up to 30 atm. The measured solubility, permeability, and time lag all show strong deviations from the well-known simple expressions for gases in rubbery polymers. The solubility isotherm is non-linear in pressure, and both θ and P are quite pressure dependent, with each showing tendencies to approach low and high pressure asymptotic limits. These effects decrease as temperature increases and would be expected to disappear at or near the glass transition where the amorphous regions become rubbery. The importance of reporting the pressure levels used in transport measurements is emphasized for gas/glassy polymer systems where transport process do not follow linear laws.     

Lamellar structure and properties in poly(ethylene terephthalate) fibers

The fibrillar and the lamellar structures in a range of poly(ethylene terephthalate) fibers were studied by small-angle X-ray scattering. The intensity maxima in the lamellar peaks lie on a curve that can be described as an ellipse. Therefore, the two-dimensional images were analyzed in elliptical coordinates. The dimensions of the coherently diffracting lamellar stack, the dimensions of the fibrils, the interfibrillar spacing, and the orientation of the lamellar surfaces were measured in addition to the lamellar spacing. The orientation of the lamellar planes and the size of the lamellar stacks had a better correlation with mechanical properties of the fibers than did the lamellar spacing. In particular, longer and wider lamellar stacks reduced fiber shrinkage, as did the closer alignment of the lamellar normal to the fiber axis. These structural features were also associated with lower tenacity. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2527–2538, 1998