Water sorption in poly(ethylene furanoate) compared to poly(ethylene terephthalate). Part 2: Kinetic sorption

Diffusion coefficients for water in amorphous poly(ethylene furanoate) (PEF) and poly(ethylene terephthalate) (PET) were studied at 35 °C over the entire water activity range. PEF exhibits a ∼5× reduction in diffusion coefficient averaged over the entire concentration interval compared to PET. Fickian diffusion was observed for water in both polyesters up to ∼0.6 activity, after which the presence of non-Fickian relaxations required treatment using the Berens–Hopfenberg modeling framework. Penetrant plasticization at high activity was found for both PEF and PET, as evidenced by a positive correlation between diffusion coefficient and increasing water concentration. Arrhenius interpretation of diffusion coefficients measured at 15, 25, 35, and 45 °C allowed calculation of the activation energies of diffusion for PEF and PET, which were similar at 47.1 ± 2.8 kJ/mol and 46.4 ± 3.0 kJ/mol, respectively. This study complements prior work pertaining to the equilibrium water sorption properties in both polyesters, and subsequently provides a detailed investigation of the water diffusion process in these materials.     

Water sorption in amorphous poly(ethylene terephthalate)

The water sorption characteristics of poly(ethylene terephthalate) (PET) amorphous samples of 250 μm thickness have been studied at various temperatures in a saturated atmosphere. Concerning diffusivity, one can distinguish the following two domains characterized by distinct values of the activation energy: E_D ≈ 36 kJ mol⁻¹ at T > 100°C, and E_D ≈ 42 kJ mol⁻¹ at T < 60°C, with a relatively wide (60–100°C) intermediary domain linked to the glass transition of the polymer. The crystallization of this latter occurs in the time scale of diffusion above 80°C but doesn't change the Fickian character of sorption curves. The equilibrium concentration m_∞ is an increasing function of temperature, but the solubility coefficient S decreases sharply with this latter, with the apparent enthalpy of dissolution ΔH_s being of the order of −28 kJ mol⁻¹ at T < 80°C and −45 kJ mol⁻¹ at T > 80°C. Density measurements in the wet and dry states suggest that water is almost entirely dissolved in the amorphous matrix at T < 80°C but forms partially a separated phase at T > 80°C. Microvoiding can be attributed to crystallization-induced demixing. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1131–1137, 1999     

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     

Oxygen sorption and transport in amorphous poly(ethylene furanoate)

Oxygen transport in amorphous poly(ethylene furanoate) (PEF) was studied at various temperatures using complementary permeation and pressure-decay sorption techniques. A significant reduction in oxygen permeability of ∼11× was observed at 35 °C for PEF compared to poly(ethylene terephthalate) (PET), and is attributed primarily to reduction in chain segment mobility for PEF resulting from a hindrance of furan ring flipping. A custom-built high accuracy sorption system allowed determination of temperature-dependent so-called dual-mode parameters that have not been reported for oxygen in any polyester. Energetic parameters, i.e. the enthalpy of sorption and activation energies of diffusion and permeation, were measured for oxygen in PEF and discussed in the context of PET and related polyesters. The current work presents the first detailed study of penetrant transport in PEF, which demonstrates the impressive performance enhancements of PEF compared to PET.     

Mechanical properties of poly(ethylene terephthalate) modified with functionalized polymers

This study examined the effect of blending poly(ethylene terephthalate) (PET) with 5% of a functionalized polymer. The blends were characterized by particle size and size distribution, unnotched tensile behavior, toughness, and notch sensitivity. The improved properties of blends that incorporated a functionalized elastomer were consistent with in situ formation of a graft copolymer by reaction with PET end groups. Triblock copolymers were examined that had styrene end blocks and an ethylene/butylene midblock (SEBS) with grafted maleic anhydride. The present study extended previous investigations that focused on level of grafting to examine the effects of component molecular weight and PET hydroxyl‐to‐carboxyl end‐group ratio. Increasing the molecular weight of the SEBS and decreasing the hydroxyl‐to‐carboxyl ratio of the PET increased the effectiveness of the SEBS. In addition, a mix of an unfunctionalized SEBS with a functionalized SEBS was more effective than a single SEBS with the same total anhydride content. The same elastomers were the most effective for modifying a lower molecular weight PET (intrinsic viscosity 0.73) and a higher molecular weight PET (intrinsic viscosity 0.95). Some functionalized polypropylenes included in the study did not enhance the properties of PET. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 203–219, 1999     

One-pot synthesis of cyclodextrins, modified with poly(ethylene oxide)

A new series of bouquet-like molecules based on cyclodextrins (CD) is described. They result from the polymerization of ethylene oxide initiated by hydroxyl groups of cyclodextrins, that constitutes the organizing core. Analysis of the structure and composition of the conjugates based on α-, β- and γ-CDs was done using ¹³C-NMR and data of molecular mass of conjugates. Glass transition behavior of conjugates shows that they are amorphous compounds. Received: 29 April 1996/Revised: 2 January 1997/Accepted: 23 January 1997     

Water sorption in poly(ethylene furanoate) compared to poly(ethylene terephthalate). Part 1: Equilibrium sorption

Equilibrium water sorption properties of amorphous poly(ethylene furanoate) (PEF) and amorphous poly(ethylene terephthalate) (PET) were studied at 35 °C over the entire water activity range. PEF exhibits a largely increased equilibrium water sorption capacity of ∼1.8× averaged over the entire concentration range compared to PET, resulting from substitution of the non-polar phenyl ring in PET with the polar furan ring in PEF. Both polyesters exhibit dual-mode sorption up to ∼0.6 activity, after which the onset of swelling produces a noticeable upturn in concentration vs. activity for both polyesters. Excellent agreement was observed between three independent sorption measurement techniques, thereby providing a consistency check for the reported data. Sorption measurements performed at 15, 25, 35, and 45 °C allowed estimation of the effective enthalpy of water sorption for both polyesters, which were similar to the enthalpy of condensation for pure water. The current work demonstrates the importance of structure on sorption and transport properties in these two important polyesters.     

Water absorbency of poly(sodium acrylate) superabsorbents crosslinked with modified poly(ethylene glycol)s

A series of novel crosslinkers, polyethylene glycol diacrylate (PEGDA) with different molecular weights, were prepared, consisting of acryloyl end groups and the PEG backbones. The corresponding poly(sodium acrylate) superabsorbents of 60 mol % neutralization degree were synthesized by using ammonium persulfate and dimethylaminoethyl methacrylate as redox initiators in aqueous solution. PEGDA was characterized by FTIR and ¹H‐NMR. The maximum of water absorbency (Q) of superabsorbents occurred at a specific mole fraction of crosslinker; Q‐values increased with increasing molecular weight of PEGDA at the same mole fraction, whereas the water absorption rate was the opposite, in which Q‐values decreased gradually with time (>24 h). Compared with superabsorbents containing methylene bisacrylamide crosslinker with PEGDA, the Q‐value of the former was significantly less than that of the latter, although levels of the residual monomer and the soluble polymer were opposite. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1851–1856, 2003     

Nonisothermal crystallization kinetics and morphology of poly(ethylene terephthalate) modified with poly(lactic acid)

The nonisothermal crystallization kinetics of poly(ethylene terephthalate) (PET) copolymers modified with poly(lactic acid) (PLA) were investigated with differential scanning calorimetry, and a crystal morphology of the samples was observed with scanning electron microscopy. Waste PET (P100) obtained from postconsumer water bottles was modified with a low‐molecular‐weight PLA. The PET/PLA weight ratio was 90/10 (P90) or 50/50 (P50) in the modified samples. The nonisothermal melt‐crystallization kinetics of the modified samples were compared with those of P100. The segmented block copolymer structure (PET‐b‐PLA‐b‐PET) of the modified samples formed by a transesterification reaction between the PLA and PET units in solution and the length of the aliphatic and aromatic blocks were found to have a great effect on the nucleation mechanism and overall crystallization rate. On the basis of the results of the crystallization kinetics determined by several models (Ozawa, Avrami, Jeziorny, and Liu–Mo) and morphological observations, the crystallization rate of the samples decreased in the order of P50 > P90 > P100, depending on the amount of PLA in the copolymer structure. However, the apparent crystallization activation energies of the samples decreased in the order of P90 > P100 > P50. It was concluded that the nucleation rate and mechanism were affected significantly by the incorporation of PLA into the copolymer structure and that these also had an effect on the overall crystallization energy barrier. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Micromechanical behavior of impact modified poly(ethylene terephthalate)

The micromechanical behavior of poly(ethylene terephthalate), PET, modified with a metallocene polyolefin copolymer (mPE) was investigated. Uniaxial deformation tests were performed using a tensile stage in a scanning electron microscope. This technique allowed the identification of the main deformation mechanisms that are associated with energy dissipation and toughness improvement. The poly(ethylene terephthalate) was blended with 5 wt% mPE by single‐screw extrusion. Films with thicknesses ranging from 200 to 500 μm were produced. Observation of the surfaces of the films during uniaxial deformation revealed the sequence of events leading to the full yielding of the matrix. In the early stages of deformation, the particles deform together with the matrix. As the deformation is increased, cavitation inside the particles occurs and fibrillation at the particle/matrix interface is observed, as well as the onset of shear banding. In order to study the effect of interfacial adhesion of the deformation mechanisms, the PET/mPE blends were compatibilized by grafting with glycidyl methacrylate (GMA). The reduction of the particle size was significant, which is indicative of the efficiency of GMA grafting in this type of blend. In this case, the particles were difficult to detect on the surface. Cavitation and shear banding occurred simultaneously. A similar behavior was observed in the case of oriented blends.     

Porous polyurethane foams based on recycled poly(ethylene terephthalate) for oil sorption

In using recycled poly(ethylene terephthalate) (PET) as a petroleum sorbent we tried to achieve two important objectives simultaneously. PET waste was glycolized using trimethylolpropane (TMp) or pentaerytheritol (PEr) to produce suitable polyol oligomers for polyurethane (PU) foams. The glycolysis was carried out in the presence of manganese acetate as a catalyst under normal pressure in m‐cresol at 220 °C. Producing polyols, PEr degraded PET into lower molecular weights than TMp. So prepared oligomers were reacted with 2,4‐toluene diisocyanate providing several types of PU foam. The effect of various variables (polyol reactivity, water content, type of catalyst, isocyanate amount and surfactant) on the foam structure and properties were analyzed. Porosity of the PU foams was examined using environmental scanning electron microscopy. Foams based on glycolized TMp contain small uniform cells whereas other foams form less uniform cells with varying sizes including closed cells. Dynamic mechanical analysis gives much lower storage moduli for TMp‐based PUs that for those based on PEr, an effect of dangling ethylene chains in the former case. The glass transition temperatures T_g are higher when PEr rather than TMp is used. Our PU foams show good sorption properties and sufficient reusability. Copyright © 2012 Society of Chemical Industry     

Practical applications of modified poly(ethylene oxide) networks

Modified poly(ethylene oxide) (PEO) networks have been studied as phase transfer catalysts, flocculates and solvent-free polymer electrolytes. The activity of the hydrogels has been investigated with respect to the structure and crosslinking density of the networks, their degree of quaternization and amphiphilic properties (hydrophilicity coefficients). It has been found that the microenvironment of the active sites (EO segments and ammonium ions) affects the catalytic activity and sorption ability of the modified networks. Hydrophobic organic compounds such as sodium picrate and bromophenolblue are bound predominantly to the lipophilic quaternary ammonium ions. A stable level of electrical conductivity of 5.0×10⁻⁵ S cm⁻¹ was achieved without using of additives. A probable mechanism of ion transport within the networks has been proposed. Potential applications of PEO-based materials as solvent-free solid polymer electrolytes are also discussed.     

Miscibility of polystyrene with poly(ethylene oxide) and poly(ethylene glycol)

The intrinsic viscosity of polystyrene–poly(ethylene oxide) (PS–PEO) and PS–poly(ethylene glycol) (PEG) blends have been measured in benzene as a function of blend composition for various molecular weights of PEO and PEG at 303.15 K. The compatibility of polymer pairs in solution were determined on the basis of the interaction parameter term, Δb, and the difference between the experimental and theoretical weight-average intrinsic viscosities of the two polymers, Δ[η]. The theoretical weight-average intrinsic viscosities were calculated by interpolation of the individual intrinsic viscosities of the blend components. The compatibility data based on [η] determined by a single specific viscosity measurement, as a quick method for the determination of the intrinsic viscosity, were compared with that obtained from [η] determined via the Huggins equation. The effect of molecular weights of the blend components and the polymer structure on the extent of compatibility was studied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1471–1482, 1998     

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.     

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     

Syntheses and characterization of poly(ethylene terephthalate) modified with p-acetoxybenzoic acid

Though the structure and properties of a copolyester of 40 mole % of polyethylene terephthalate (PET) and 60 mole % p-hydroxybenzoic acid (PHB) (PET/60PHB) and their blends have been well documented, no work has been reported in an open literature on the systematic investigation of the PET copolymers modified with broad range of p-acetoxybenzoic acid (PABA) composition as yet. In this study, several PETA-x copolyesters having various PABA compositions from 10 to 70 mole % were prepared by the melt reaction of PABA and PET without a catalyst, where x denotes the mole % of PABA. And the modified polyesters obtained were characterized by ¹H-NMR spectrophotometry, X-ray diffraction pattern, polarizing microscopy, thermal analysis, and rheometry. The anisotropic phase appeared when x is above 50 mole % of PABA, and especially for the x's of 60 and 70 mole %, the nematic liquid crystalline texture appeared clearly on the whole matrix. As the mole % of PABA increased, melting temperature, heat of fusion, crystalline temperature, degree of crystallinity, and the glass transition temperature of the modified PET were decreased, but the thermal stabilities of those copolyesters were increased. The dependence of melt viscosity on the shear rate for PETA-50 ∼ 70 followed the typical rheological behavior of liquid crystalline polymers. Finally, it was concluded that the PETA-x copolyesters having compositions of higher than 50 mole % of PABA exhibit the behavior of thermotropic liquid crystalline polymers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1707–1719, 1999     

Cure kinetics of an epoxy/liquid aromatic diamine modified with poly(ether imide)

The cure kinetics and mechanisms of an epoxy oligomer based on diglycidyl ether of bisphenol A (DGEBA), polymerized with a liquid aromatic diamine based on diethyl toluene diamine (DETDA 80), and its blends with poly(ether imide) (PEI) at concentrations of 0–15 wt % were studied with differential scanning calorimetry under dynamic and isothermal conditions. The kinetic analyses were performed with a phenomenological approach. The reaction mechanism of the blends remained the same as that of the neat epoxy. However, the addition of PEI had a marked effect on the cure kinetics in the DGEBA/DETDA 80 system. The rate of reaction decreased with an increase in the thermoplastic content. Diffusion control was incorporated to describe the cure behavior of the blends in the latter stages. Greater diffusion control was observed as the PEI concentration increased and the cure temperature decreased. Polymer blends based on this epoxy/liquid aromatic diamine had not been previously studied from a kinetic viewpoint. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 660–672, 2005     

端脂肪氨基聚醚改性环氧树脂的性能研究

用自制的一种既含聚醚柔性链段又含苯脂肪氨基刚性链段的端脂肪氨基聚醚(APPEG)作为固化剂对环氧树脂进行增韧改性。扫描电子显微镜和力学性能测试结果表明,固化剂对环氧树脂具有明显的增强、增韧效果,且改性的环氧树脂胶粘剂具有很好的填充性能,填充比高达50%。与羰基铁粉组成的涂层材料具有优异的力学性能和热稳定性能。     

Metal chelating resins by condensation of ethylene diamine with p-dichloromethyl benzene

Polycondensation of ethylene diamine with p-dichloromethyl benzene in different molar ratios (0.8–1.5) gives mostly crosslinked polymers. These resinous polymers are water-compatible and have moderate swelling ability (swelling rate 1.6–20) in water depending on the pH of the solutions. The free amine state of the resinous polymers are capable of chelating with various transition-metal ions such as Cu(II), Ni(II), Co(II), Cd(II), and Zn(II), even in very low concentrations. Due to rapid complexation, high metal binding capacity, and ease of regenerability, these resins can be useful for the removal and recovery of transition-metal ions from water solutions. © 1996 John Wiley & Sons, Inc.     

Structural and thermal properties of modified poly(ethylene terephthalate)

High-molecular-weight copolyesters based on ethylene glycol, tetraphthalic and 4,4′-biphenyl dicarboxylic acids containing up to 10.3 mole % of a second component were synthesized in the presence of homo- and heterogeneous catalysts. It was found that synthesis of these copolymers with a heterogeneous catalyst yields polymers with a higher molecular weight. The thermochemical properties of the copolyesters obtained were investigated. The thermostabilizing effect on addition of up to 10.3 mole % ethylene-4,4′-biphenyl dicarboxylic acid units to the PET polymer substrate was demonstrated. It was hypothesized that this modifier is a mesogen with respect to poly(ethylene terephthalate). Translated from Khimicheskie Volokna, No. 1, pp. 21-23, January-February, 2009.