PET synthesis in the presence of lanthanide catalysts

Syntheses of poly(ethylene terephthalate), PET, by transesterification of dimethyl terephthalate with ethylene glycol in the presence of well-known catalysts and various lanthanide compounds were performed. Lanthanide catalysts appeared to be much more efficient in the first stage of the process (transesterification in the presence of an excess of ethylene glycol), and less active in polycondensation. PET produced with lanthanides was found to possess enhanced thermal and hydrolytic stability as compared to PET synthesized with well-known catalysts and commercial PET. © 1995 John Wiley & Sons, Inc.     

Poly(ethylene terephthalate)/poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate)/clay nanocomposites: Effects of biaxial stretching

In this study, we fabricated poly(ethylene terephthalate) (PET)/clay, PET/poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate) (PETG), and PET/PETG/clay nanocomposite plates and biaxially stretched them into films by using a biaxial film stretching machine. The tensile properties, cold crystallization behavior, optical properties, and gas and water vapor barrier properties of the resulting films were estimated. The biaxial stretching process improved the dispersion of clay platelets in both the PETG and PET/PETG matrices, increased the aspect ratio of the platelets, and made the platelets more oriented. Thus, the tensile, optical, and gas‐barrier properties of the composite films were greatly enhanced. Moreover, strain‐induced crystallization occurred in the PET/PETG blend and in the amorphous PETG matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42207.     

Processing characteristics of poly(ethylene terephthalate): hydrolytic and thermal degradation

The effects of poly(ethylene terephthalate) (PET) resin moisture content and temperature exposure have been investigated in terms of material changes resulting from the injection moulding process. Two resins with initial carboxyl contents of 10 µeq/g PET and 20 µeq/g PET have been analysed. Preforms processed at different resin moisture contents and processing temperatures of 280, 290 and 300 °C were evaluated in terms of carboxyl end‐group concentration using a titration method. Intrinsic viscosities of the performs were also measured by solution viscosity. Mathematical models describing the relationships of carboxyl end‐group concentration and intrinsic viscosity to the processing conditions were generated from the experimental data. Carboxyl end‐groups formed were compared for both resins and shown to be dependent on initial carboxyl content in the resin. Reducing the initial carboxyl content in the resin has been shown to increase its hydrolytic stability. The hydrolytic effect on the overall molecular weight drop was separated from the thermal/thermal‐oxidative degradation and shown to be dependent on both the processing temperature and the resin moisture content. © 2002 Society of Chemical Industry     

Preparation and performance of a transparent poly(3,4‐ethylene dioxythiophene)–poly(p‐styrene sulfonate‐co‐acrylic acid sodium) film with a high stability and water resistance

Poly(p‐styrene sulfonate‐co‐acrylic acid sodium) (PSA) from the copolymerization of acrylic acid sodium and p‐styrene sulfonate monomers were used to dope poly(3,4‐ethylene dioxythiophene) (PEDOT) to generate PEDOT–PSA antistatic dispersions. Compared to those of the PEDOT–poly(p‐styrene sulfonate sodium) (PSS), the physical and electrical properties of the PEDOT–PSA conductive liquids were much better. The PEDOT–PSA films possessed a better water resistance without a decrease in the conductivity. The sheet resistance of the PEDOT–PSA–poly(ethylene terephthalate) (PET) films was about 1.5 × 10⁴ Ω/sq with a 100 nm thickness, the same as the PEDOT–PSS–PET films. The transmittance of the PEDOT–PSA–PET films exceeded 88%. Furthermore, the environmental dispersity of the PEDOT–PSA antistatic dispersion was apparently improved by the dopant PSA so that the stability was extraordinarily promoted. Meanwhile, the water resistances of the PEDOT–PSA–PET and PEDOT–PSA films were also enhanced. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45163.     

Long‐term investigation on hydrolytic degradation and morphology of poly(ethylene glycol terephthalate)‐b‐poly(butylene terephthalate) copolymer films

Poly(ethylene glycol terephthalate)‐b‐Poly(butylene terephthalate) copolymer (PEGT‐b‐PBT) films with different copolymer compositions were incubated in phosphate buffered saline under pH 7.4 at 37°C to study hydrolytic degradation and morphology up to 300 days. With the fall of intrinsic viscosity and mass of degraded films, SEM micrographs show that a set of particular and highly interconnected porous morphologies closely related to the content of PBT hard segments in copolymer is developed. Moreover, the variation in PBT crystallinity for copolymer films with weight ratio of 70/30 fluctuates with the development of degradation profiles, and PEGT content for copolymer films with weight ratio of 80/20 and 70/30 gradually decreases. The hydrolytic experiments demonstrate that the degradation of PEGT‐b‐PBT copolymer results from the cleavage of ester bonds between hydrophilic PEG and terephthalate. At the beginning period of degradation, PEGT‐b‐PBT copolymer films follow a typical mechanism of bulk degradation, and then undergo both bulk degradation and surface erosion, all of which finally generate the particular porous morphologies for copolymer films. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Double bubble tubular film extrusion of polybutylene terephthalate–polyethylene terephthalate blends

A technology has been developed to produce biaxially oriented films of blends of polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) using double bubble tubular film extrusion. The mechanical instabilities and the mechanisms associated with their sources of occurrence are described. Bubble stability varies substantially with deformation and composition. The films have been structurally characterized with wide angle X‐ray diffraction and optical techniques. The individual phases in the blends oriented differently. We have proposed a model of crystalline morphology in biaxially oriented PBT/PET blend films. The structure of the film is related to processing conditions.     

Structural investigations of poly(ethylene terephthalate)‐graft‐polystyrene copolymer films

Structural investigations of poly(ethylene terephthalate)‐graft‐polystyrene (PET‐g‐PS) films prepared by radiation‐induced grafting of styrene onto commercial poly(ethylene terephthalate) (PET) films were carried out by FTIR, X‐ray diffraction (XRD), and differential scanning calorimetry (DSC). The variation in the degree of crystallinity and the thermal characteristics of PET films was correlated with the amount of polystyrene grafted therein (i.e., the degree of grafting). The heat of melting was found to be a function of PET crystalline fraction in the grafted films. The grafting is found to take place by incorporation of amorphous polystyrene grafts in the entire noncrystalline (amorphous) region of the PET films and at the surface of the crystallites. This results in a decrease in the degree of crystallinity with the increase in the degree of grafting, attributed to the dilution of PET crystalline structure with the amorphous polystyrene, without almost any disruption in the inherent crystallinity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1949–1955, 2002; DOI 10.1002/app.10515     

Creep and shrinkage behavior of improved ultrathin polymeric films

Long‐term creep‐deformation and shrinkage characteristics of improved ultrathin polymeric films for magnetic tapes are presented. These films include poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN), and aromatic polyamide (ARAMID). PET film is currently the standard substrate used for magnetic tapes, and thinner tensilized‐type PET, PEN, and ARAMID have recently been used as alternate substrates with improved material properties. The thickness of the films ranges from 6.2 to 4.8 μm. More dimensional stability is required for advanced magnetic tapes, and the study of creep and shrinkage behavior is important for estimating the dimensional stability. Creep measurements were performed on all available substrates at 25, 40, and 55°C for 100 h. Based on these data, master curves were generated using time–temperature superposition to predict dimensional stability after several years. The amount of creep deformation is considerably smaller for ARAMID and tensilized‐type PET than for PEN, although Standard PET shows the largest amount of creep. In addition, creep measurements under high humidity also show similar trends. Shrinkage measurements at 55°C for 100 h show that the shrinkage of ARAMID is lower than that of PET and PEN. The relationship between the polymeric structure and dimensional stability are also discussed. Based on the creep and shrinkage behavior, ARAMID and tensilized‐type PET seem to be suitable for advanced magnetic tapes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1477–1498, 2002; DOI 10.1002/app.10012     

Hydrolytic degradation of poly(1,4‐butylene terephthalate‐co‐tetramethylene oxalate) copolymer

Experimentally synthesized poly(1,4‐butylene terephthalate‐co‐tetramethylene oxalate) (PBT–PTMO) monofilaments were evaluated for hydrolytic stability in salt water (SW) and distilled water (DW) at temperature below and above glass transition temperature (T_g), along with commercially available poly(hexamethylene adipamide) (NY), poly(ethylene terephthalate) (PET), and polypropylene (PP) monofilaments. There was no decrease in mechanical properties in case of NY, PET, and PP in either DW or SW below their T_g. The breaking strength, ultimate elongation, and thermal shrinkage of the PBT–PTMO, however, decreased as the ageing time increased. Total strength loss occurred after approximately 300 days at 25°C in either DW and SW. This can be attributed to the chain scission that occurs in the PBT–PTMO copolymer chain. The poor hydrolytic stability of the PBT–PTMO may be attributed to the higher moisture regain. The salinity of water did not have a significant effect on the breaking strength loss of the materials. The mode of hydrolytic degradation of aged PBT–PTMO polymer was confirmed by the increasing generation of the acid carbonyl and hydroxyl groups with concomitant increasing consumption of ester groups, regardless of ageing conditions. Above T_g, the hydrolytic rate constant (k^′_H, day⁻¹) of the PBT–PTMO, estimated by the rate of formation of acid carbonyl groups, is greater at a higher ageing temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 921–936, 1999     

Carbon nanotubes‐reinforced PET nanocomposite by melt‐compounding

Poly(ethylene terephthalate) (PET) nanocomposites with single‐walled carbon nanotubes (SWNTs) have been prepared by a simple melt compounding method. With increasing concentration (0–3 wt %) of SWNTs, the mechanical and dynamic mechanical properties improved, corresponding to effective reinforcement. Melt rheological characterization indicated the effective entanglements provided by SWNTs in the melt state as well. Thermogravimetric analysis suggested no influence of SWNTs on the thermal stability of PET. Electrical conductivity measurements on the composite films pointed out that the melt compounded SWNTs can result in electrical percolation albeit at concentrations exceeding 2 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Hydrolysis of resin-coated poly(ethylene terephthalate) yarns

A comparison of the resistance of resin coated and uncoated poly(ethylene terephthalate) (PET) yarns to steam exposure at 160°C shows that the coated yarn degrades more rapidly. The decrease in tensile strength upon steam exposure results from hydrolytic scission which is accelerated by acidic hydrolysis products. The resin coating on the yarn acts as a skin around the filaments, a skin which apparently does not retard steam penetration, but does trap hydrolysis products in the yarn structure. A comparison study of PET films substantiated these conclusions. Hydrolysis products in films and small bundles of monofilaments taken from yarns were measured by infrared spectroscopy.     

Hydrolytic degradation of poly(ethylene terephthalate)

Molecular weight is an important factor in the processing of polymer materials, and it should be well controlled to obtain desired physical properties in final products for end‐use applications. Degradation processes of all kinds, including hydrolytic, thermal, and oxidative degradations, cause chain scission in macromolecules and a reduction in molecular weight. The main purpose of this research is to illustrate the importance of degradation in the drying of poly(ethylene terephthalate) (PET) before processing and the loss of weight and mechanical properties in textile materials during washing. Several techniques were used to investigate the hydrolytic degradation of PET and its effect on changes in molecular weight. Hydrolytic conditions were used to expose fiber‐grade PET chips in water at 85°C for different periods of time. Solution viscometry and end‐group analysis were used as the main methods for determining the extent of degradation. The experimental results show that PET is susceptible to hydrolysis. Also, we that as the time of retention in hydrolytic condition increased, the molecular weight decreases, but the rate of chain cleavage decreased to some extent, at which point there was no more sensible degradation. The obtained moisture content data confirmed the end‐group analysis and viscometry results. Predictive analytical relationships for the estimation of the extent of degradation based on solution viscosity and end‐group analysis are presented. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2304–2309, 2007     

Influence of apple flavor absorption on physical and mechanical properties of poly(ethylene terephthalate) films

Poly(ethylene terephthalate) (PET) films (280‐μm film thickness), which are used in food packaging, were immersed into 160‐ and 320‐ppm apple flavor solution for 14, 28, and 56 days at 5, 25, and 40°C, respectively. At the end of this period, the changes in the PET films were investigated by measuring the mechanical and physical properties. The mechanical properties were determined by examining changes in the Young's modulus. The changes in the physical properties were investigated by Fourier transform IR spectroscopy and scanning electron microscopy (SEM). The formation of microcracks in the structure of PET films was observed by SEM. According to the results of those investigations, the apple flavor affects PET films, even at very low concentrations and temperatures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1802–1807, 2006     

Radiation‐induced crosslinking of acetylene‐impregnated polyesters. II. Effects of preirradiation crystallinity,molecular structure,and postirradiation crosslinking on mechanical properties

Electron beam‐irradiated crosslinking has been studied in a series of acetylene‐impregnated polyesters and amorphous copolyesters, including poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), poly(cyclohexane dimethylene terephthalate) (PCDT), and poly(cyclohexane dimethylene terephthalate‐co‐ethylene terephthalate) (P(CDT‐co‐ET)) having 29 and 60 wt % ethylene terephthalate (ET). The extent of crosslinking was observed by gel fraction measurements and was found to be significantly influenced by the aliphatic chain content of the polyesters (PET < PBT < PCDT). In addition, as the preirradiation crystallinity of the polyesters was reduced, the extent of acetylene‐enhanced crosslinking was greatly raised. Decreases in the postirradiation crystalline melting temperature and degree of crystallinity were observed in all the polyesters, using differential scanning calorimetry measurements. Particularly significant findings have been the shift in the glass‐transition temperatures (Tg) to higher temperatures and the decrease in loss tangents at higher temperatures, both of which confirm that crosslinking has taken place. The storage moduli (E′) in the rubbery plateau region of PCDT and P(CDT‐co‐ET) were significantly affected by irradiation dose. Increased network tightness in postirradiated PBT and PCDT films was also inferred from melt‐rheology measurements, in which stress relaxed more slowly following a stepped strain. Improvements in the mechanical properties of the irradiated polyesters and copolyesters were clearly evidenced by the increased modulus at higher temperatures, observed using dynamic mechanical thermal analysis and melt‐rheology methods. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4476–4490, 2006     

Grafting of polyacrylamide from poly(ethylene terephthalate) films

Poly(ethylene terephthalate) (PET) films were modified via the grafting of polyacrylamide (PAAM) onto the surface by surface‐initiated atom transfer radical polymerization and UV‐initiated grafting. The surface composition and morphology of the modified PET films were characterized by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and scanning electron microscopy (SEM). The results show that the surface of the PET film was grafted by PAAM, with its own surface morphology different from that of PET. The properties of the modified PET films were studied by contact‐angle, peeling force, penetrability, haze, and friction factor measurements. The results indicate that the peeling force and friction factor of the modified PET films were higher than those of the unmodified PET film. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Molecular structures and physical properties of heat‐drawn conjugate fibers

As‐spun poly(trimethylene terephthalate) (PTT)/poly(ethylene terephthalate) (PET) side‐by‐side conjugate fibers were drawn to investigate the effects of drawing conditions on structure development and physical properties. Effects of draw ratio and heat‐set temperature were observed. In the state of an as‐spun fiber, the molecular orientation of PTT was higher than PET, whereas PET molecular orientation increased remarkably over PTT with increasing draw ratio. Crimp contraction increased sharply at a draw ratio over 2.0, where the crystalline structure of the PET developed sufficiently. A heat‐set temperature of at least 140°C was required to develop sufficient crimp contraction. The crystallinity and orientation of the PET were attributed mainly to the crimp contraction of the drawn fiber. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Investigation of alkaline hydrolysis of polyethylene terephthalate by differential scanning calorimetry and thermogravimetric analysis

The hydrolytic depolymerization of polyethylene terephthalate (PET) with alkaline hydroxides was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The reactions of the mixtures were conducted in their solid states under nitrogen atmosphere. The experimental results showed that potassium hydroxide possessed the hydrolytic activity of depolymerizing PET into small molecules such as ethylene glycol; in contrast, sodium hydroxide did not. The production rate of ethylene glycol was enhanced by increasing charge ratio of potassium hydroxide to PET. The presence of water facilitated the alkaline hydrolysis of PET; however, the presence of metal acetates decreased the hydrolysis rate. The activation energy for alkaline hydrolysis of PET determined by the thermograms was in good agreement with the value obtained from the experiments in a batch reactor. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1939–1945, 1998     

Thermal stability of surfactants with amino and imido groups in poly(ethylene terephthalate)/clay composites

Effects of thermal stability of surfactants with amino and imido groups on thermal properties of poly(ethylene terephthalate) (PET)/clay composites were studied. The imidosilane surfactant was synthesized successfully from the imide reaction between amino silane and phthalic anhydride. TGA shows that imidosilane decomposition behaviors have two major stages according to the degradations of different functional groups. After melt extrusion, the decomposition of amino functional groups in amino surfactants decreases the thermal stability of organoclay and accelerates the degradation behaviors of PET composites. Because of the enhanced thermal stability of imidosilane surfactants, PET/imido‐palygorskite (PT) composites represent enhanced thermal stability, good dispersion and low thermal expansion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Tensile and dynamic mechanical properties of improved ultrathin polymeric films

Tensile and dynamic mechanical properties of improved ultrathin polymeric films for magnetic tapes are presented. These films include poly(ethylene terephthalate) or PET, poly(ethylene naphthalate) or PEN, and aromatic polyamide (ARAMID). PET film is currently the standard substrate used for magnetic tapes; thinner tensilized‐type PET, PEN, and ARAMID were recently used as alternate substrates with improved material properties. The thickness of the films ranges from 6.2 to 4.8 μm. Young's modulus of elasticity, F5 value, strain‐at‐yield, breaking strength, and strain‐at‐break were obtained at low strain rates by using a tensile machine. Storage (or elastic) modulus, E′, and the loss tangent, tan δ, which is a measurement of viscous energy dissipation, are measured by using a dynamic mechanical analyzer at temperature ranges of ?50 to 150°C (for PET), and ?50 to 210°C (for PEN and ARAMID), and at a frequency range of 0.016 to 29 Hz. Frequency–temperature superposition was used to predict the dynamic mechanical behavior of the films over a 28 decade frequency range. Results show that ARAMID and tensilized films tend to have higher strength and moduli than standard PET and PEN. The rates of decrease of storage modulus as a function of temperature are lower for PET films than those for PEN and ARAMID films. Storage modulus for PEN films are higher than that for PET films at high frequencies, but this relationship reverses at low frequencies. ARAMID has the highest modulus and strength among the films in this study. The relationship between polymeric structure and mechanical properties are also discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2225–2244, 2002     

Poly(ethylene terephthalate)/clay nanocomposites with trisilanolphenyl polyhedral oligomeric silsesquioxane as dispersant: simultaneously enhanced reinforcing and stabilizing effects

This paper presents a new approach for the preparation of poly(ethylene terephthalate) (PET)/clay nanocomposites using surfactant‐free clay (sodium montmorillonite, Na‐MMT) with trisilanolphenyl polyhedral oligomeric silsesquioxane (Tsp‐POSS) as dispersant. The dispersion of clay in the PET/Na‐MMT/Tsp‐POSS nanocomposites is enhanced over that in PET/Na‐MMT by using a very small amount of Tsp‐POSS, which acts as functional spacer to keep clay platelets apart and pull monomers in, and, at the same time, acts as a PET chain extender. As a result, thermomechanical properties and thermo‐oxidative stability of PET/Na‐MMT/Tsp‐POSS are improved simultaneously compared with those of PET/organoclay nanocomposites. © 2013 Society of Chemical Industry