Synthesis and characterization of poly(butylene terephthalate‐co‐triethylene terephthalate) copolyesters

Poly(butylene terephthalate‐co‐triethylene terephthalate) random copolymers of various compositions and molecular weights were synthesized in bulk and characterized in terms of their chemical structure and thermal and rheological properties. At room temperature all the copolymers were partially crystalline and showed good thermal stability. The main effect of copolymerization was a decrease in the melting and glass‐transition temperatures with respect to the poly(butylene tere‐ phthalate) homopolymer. The fusion temperatures were well correlated with the composition by the Baur equation and the equilibrium melting temperature and the heat of fusion extrapolated values for poly(butylene terephthalate) were in good agreement with those reported elsewhere. Triethylene terephthalate units were found to influence the rheological behavior in the melt, the viscosity being significantly higher than that of the poly(butylene terephthalate‐co‐diethylene terephthalate) copolymers investigated previously. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 981–990, 2001     

Synthesis and characterisation of telechelic poly(2,6-dimethyl-1,4-phenylene ether) for copolymerisation

Telechelic poly(2,6-dimethyl-1,4-phenylene ether) (PPE) segments are interesting starting materials, for example for copolymerisation. A good method to make partly bifunctional PPE-2OH is by redistribution or depolymerisation of high molecular weight commercial PPE with tetramethyl bisphenol A. The product has a bimodal molecular weight distribution because only ∼70-80% of high molecular weight starting material is depolymerised. The phenolic endgroups can be modified easily by a fast and complete reaction with methyl chlorocarbonyl benzoate. The product after endgroup modification is called PPE-2T and has two terephthalic methyl ester endgroups and a molecular weight of 2000-4000 g/mol. The functionality of these PPE-2T products is around 1.8. The bimodal PPE-2OH and PPE-2T products can be separated in a high and low molecular weight fraction by selective precipitation. The low molecular weight fraction has a narrow molecular weight distribution with a polydispersity between 1.2 and 1.5.     

Efficient method for recycling poly(ethylene terephthalate) to poly(butylene terephthalate) using transesterification reaction

A method of recycling postconsumer poly(ethylene terephthalate (PET) using transesterification was studied. Shredded flakes of postconsumer PET waste were transesterified with higher diols, such as 1,4‐butanediol, 1,4‐cyclohexane dimethanol, and 1,6‐hexanediol, to yield copolyesters in the presence of Ti(iPrO)₄ and Sb₂O₃ as catalysts. The extent of the formation of undesirable tetrahydrofuran side products was dependent on the molar ratio of PET to1,4‐butanediol and the time of reflux during transesterification. Quantitative insertion of the butylene moiety into PET could be achieved under appropriate reaction conditions. The mechanical properties of PBT obtained by a transesterification reaction of PET with 1,4‐butanediol were comparable to those of virgin PBT (obtained by direct reaction of dimethyl terephathalate with 1,4‐butanediol). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3720–3729, 2004     

Mechanical,thermal, and structural characterization of poly(ethylene terephthalate) and poly(butylene terephthalate) blend systems by the addition of postconsumer poly(ethylene terephthalate)

The focus of this study was mainly on the use of scrap poly(ethylene terephthalate) (PET) in poly(butylene terephthalate)‐rich blend systems. A good combination of tensile and impact properties was observed in the newly formed blend system with scrap PET. The morphology depicted controlled and well‐dispersed phases. The thorough mixing of the constituents was observed in the thermal study. For this innovative blend system, an attempt to correlate the mechanical, thermal, structural, morphological properties and the chemistry of the blend system seemed to be technoeconomical. This study contributed to the recycling of waste material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and thermal characterization of poly(butylene terephthalate-co-thiodiethylene terephthalate) copolyesters

Poly(butylene terephthalate-co-thiodiethylene terephthalate) copolymers of various compositions were synthesized and characterized in terms of chemical structure and molecular weight. The thermal behavior was examined by thermogravimetric analysis and differential scanning calorimetry. All the polymers under investigation show a good thermal stability. At room temperature they appear as semicrystalline materials: the main effect of copolymerization was a lowering in the amount of crystallinity and a decrease of melting temperature with respect to homopolymers. A pure crystalline phase has been evidenced at high content of butylene terephthalate or thiodiethylene terephthalate units and Baur's equation was found to describe well the T_m-composition data. Amorphous samples (containing 50-100 mol% of thiodiethylene terephthalate units) showed a monotonic decrease of T_g as the content of sulfur-containing units is increased, due to the presence of flexible C-S-C bonds in the polymeric chain. Finally, the Fox equation described well the T_g-composition data.     

Imidazolium poly(butylene terephthalate) ionomers with long-term antimicrobial activity

Imidazolium poly(butylene terephthalate) ionomers with ionic groups located randomly along the polymer chain or selectively as end-groups (telechelic) have been prepared in order to determine their antimicrobial (AM) activity. Two different approaches have been followed for the linkage of the imidazolium to the polymer backbone: a covalent bond and an ionic aggregation to sulfonated groups covalently bonded to the polymer. The ionic groups have been linked to the polymer in order to improve the long-term AM activity since the low molecular weight additives commonly used tends to migrate toward the surface during use. We have found that imidazolium ionomers present AM activity comparable with that of commercial antimicrobial agents such as Triclosan. The AM activity depends on the polymer architecture, the telechelic approach being more active compared to the random approach. We have proved that imidazolium ionomers retain their high AM activity even after 6 days in water at 60 °C while Triclosan consistently loses his activity.     

Crystallization kinetics of poly(butylene terephthalate) and its talc composites

Crystallization kinetics of poly (butylene terephthalate) (non‐talc‐PBT) and its 0.1 wt % talc composites (talc‐PBT) was determined for a wide range of cooling rates and isothermal temperatures. The critical cooling rate to suppress crystallization is 2000 K s^?1 for non‐talc‐PBT and 7000 K s^?1 for talc‐PBT. The cooling rate dependence of the total enthalpy change and heating rate dependence of enthalpy of cold crystallization are quantitatively discussed on the basis of the Ozawa's method. For isothermal crystallization, the annealing‐temperature (T _iso) dependence of crystallization half‐time (t _1/2) shows a bimodal curve with two minima. Talc shortens the t _1/2 at T _iso above 340 K and acts as a heterogeneous nucleation agent. Tammann's approach revealed that the t _1/2 is shortened by pre‐nucleation for non‐talc‐PBT but not for talc‐PBT. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44739.     

Blends of poly(ethylene terephthalate) and poly(butylene terephthalate)

Commercial grade poly(ethylene terephthalate), (PET, intrinsic viscosity = 0.80 dL/g) and poly(butylene terephthalate), (PBT, intrinsic viscosity = 1.00 dL/g) were melt blended over the entire composition range using a counterrotating twin‐screw extruder. The mechanical, thermal, electrical, and rheological properties of the blends were studied. All of the blends showed higher impact properties than that of PET or PBT. The 50:50 blend composition exhibited the highest impact value. Other mechanical properties also showed similar trends for blends of this composition. The addition of PBT increased the processability of PET. Differential scanning calorimetry data showed the presence of both phases. For all blends, only a single glass‐transition temperature was observed. The melting characteristics of one phase were influenced by the presence of the other. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 75–82, 2005     

Synthesis and applications of triblock and multiblock copolymers using telechelic oligopropylene

Isotactic polypropylene (iPP)-polystyrene (PS) and iPP-poly(methyl methacrylate) (PMMA) multiblock copolymers were synthesized by atom transfer radical coupling (ATRC) of PS-iPP-PS and PMMA-iPP-PMMA triblock copolymers obtained by atom transfer radical polymerization (ATRP) of styrene (St) and methyl methacrylate (MMA), respectively, using α,ω-dibromoisobutyrateoligopropylene (iPP-Br) as a bifunctional macroinitiator. The iPP-Br was prepared by hydroxylation and subsequent esterification of telechelic oligopropylene having terminal vinylidene double bonds at both ends obtained by controlled thermal degradation of iPP. ATRP of St and (meth) acrylic monomers using iPP-Br formed the corresponding triblock copolymers. It was confirmed that the PMMA-iPP-PMMA triblock copolymer was effective as the compatibilizer for the iPP/PMMA blend. An iPP-PS multiblock copolymer (M_n: 25?000 g/mol and M_w/M_n: 4.1) was prepared by ATRC of PS-iPP-PS triblock copolymer (M_n: 8900 g/mol and M_w/M_n: 1.3). ATRC with St of PMMA-iPP-PMMA triblock copolymer (M_n: 13?000 g/mol and M_w/M_n: 1.4) provided an iPP-PMMA multiblock copolymer containing St chains (M_n: 39?000 g/mol and M_w/M_n: 2.8).     

Crystallization of poly(butylene terephthalate)

This article provides a thorough analysis of the crystallization process of poly(butylene terephthalate) (PBT). Isothermal crystal growth rates have been experimentally measured between 459 and 491 K, and analyzed according to the Hoffman and Lauritzen theory. A II–III regime transition occurs at 484 K, accompanied by a change in crystal morphology. By means of a non‐linear fitting procedure, precise values of the nucleation constant K_g were obtained. The lateral surface free energy σ was calculated and, from this, the α parameter of the Thomas‐Staveley expression was obtained.     

Hydrolysis of poly(butylene terephthalate)

The hydrolytic stability of poly(butylene terephthalate) (PBT) resins and compounds was studied. Rates of reaction were determined by measuring changes in melt flow rate. Hydrolysis was slightly accelerated by contact of PBT with glass containers and reduced by incorporation of some flame retardant additives. Melt flow rates were related to tensile elongation ofunfilled PBT and tensile strength ofthe glass fiber reinforced polymer and used as failure criteria. Reaction rates were used to predict failure times at various conditions.     

Crystallization and melting behaviour of poly(butylene terephthalate) in poly(butylene terephthalate)/polyarylate blends

Summary The crystallization and melting behaviour of poly(butylene terephthalate) has been studied in the pure state and in its blends with a polyarylate of bisphenol A and isophthalic/terephthalic acids. Differential scanning calorimetry has been used as experimental technique and the effects of different thermal treatments have been analyzed. Results show the hindrance for the crystallization of poly(butylene terephthalate) imposed by the presence of polyarylate, as well as the existence of multiple melting after isothermal crystallization. Explanations are given for the observed behaviours.     

Poly(butylene terephthalate)/poly(ethylene glycol) blends with compatibilizers

Polymer blend systems offer a versatile approach for tailoring the properties of polymer materials for specific applications. In this study, we investigated the compatibility of polybutylene terephthalate (PBT) and poly(ethylene glycol) (PEG) blends processed using a twin-screw extruder, with the aim of enhancing their compatibility. Phthalic anhydride (PAn) and phthalic acid (PAc) were used as potential compatibilizers at different concentrations to improve interfacial interactions between PBT and PEG. Blend morphologies were characterized using scanning electron microscopy, which revealed improved interfacial compatibility and reduced phase separation with the incorporation of small amounts of PAn and PAc. Differential scanning calorimetry analysis indicated changes in the melting temperature (T_m) and glass transition temperature (T_g) of the blends owing to the compatibilizing effects of PAn and PAc. Dynamic mechanical analysis further corroborated the influence of the compatibilizers on the T_g and viscoelastic behavior. Thermogravimetric analysis demonstrated enhanced thermal stability with the addition of either PAn or PAc. Rheological measurements indicated an increase in complex viscosity with increasing compatibilizer content, indicating improved compatibility. The degradation point (T_d) of PBT/PEG blend increased from 158 to 200 and 319°C with the incorporation of 5 phr PAn and 2 phr PAc, respectively. Mechanical properties, including tensile strength, Young's modulus, and Izod impact strength, were evaluated. For instance, the tensile strength of PBT/PEG blend was enhanced from 43.5 to 48.7 and 49.7 MPa by incorporating 5 phr PAn and 2 phr PAc, respectively. However, the impact strength of PBT/PEG blend increased from 3.0 to 4.3 and 4.2 kJ/m² with the addition of 1 phr PAn and 1 phr PAc, respectively. The findings demonstrated that adding 5 phr PAn or 2 phr PAc to the PBT/PEG blends was advantageous, achieving a harmony of performance benefits and compromises. Rheological observations contributed significantly to the mechanical and thermal properties. Overall, the study highlights the significance of utilizing PAn and PAc as effective compatibilizers for enhancing the properties of PBT/PEG blends, making them potential candidates for various applications.     

Crystallization in blends of poly(ethylene terephthalate) and poly(butylene terephthalate)

Blends composed of poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) were melt-mixed in a Brabender cam mixer at different mixing speeds. The glass transition (T_g) and the crystallization behavior of the blends from glassy state were studied using DSC. It was found that although the blends had the same composition and exhibited the similar T_g, their properties of crystallization could be different; some exhibited a single crystallization peak and some exhibited multiple crystallization peaks depending upon experimental conditions. Results indicated that the behavior of crystallization from glassy state were influenced by entanglement and transesterification of chains. The crystallization time values were obtained over a wide range of crystallization temperature. From curve fitting, the crystallization time values and the temperature, at which the crystallization rate reaches the maximum, were found.     

Synthesis, characterization, and properties of poly(ethylene terephthalate)/poly(1,4-butylene succinate) block copolymers

Reactive blending at 290 °C of a series of mixtures of poly(ethylene terephthalate) (PET) and poly(1,4-butylene succinate) (PBS) led to the formation of block PET/PBS copolyesters. The block lengths of the resulting copolymers decreased with the severity of the treatment. Copolyesters with PET/PBS molar compositions of 90/10, 80/20, 70/30, and 50/50 were prepared by this method and their composition and microstructure were characterized by ¹H and ¹³C NMR, respectively. The T_g, T_m, and crystallinity of the copolymers decreased as the content in PBS and the degree of randomness increased. The elastic modulus and tensile strength of the copolymers decreased with the content of PBS, whereas, on the contrary, the elongation at break increased. The PET/PBS copolymers exhibited a pronounced hydrolytic degradability, which increased with the content in 1,4-butylene succinic units. Hydrolysis mainly occurred on the aliphatic ester groups.     

Telechelic ionomeric poly(butylene terephthalate): Synthesis,characterization and comparison with random ionomers

Telechelic poly(butylene terephthalate) (PBT) ionomers have been prepared by melt synthesis using a new polycondensation process that involves a pre-reaction of sulfobenzoic acid sodium salt with butanediol. No side reaction occurs and the incorporation of the ionic groups is quantitative. The addition of a buffer agent, such as Na₃PO₄, to the catalyst reduces the THF formation and improves the polycondensation rate. The comparison of the thermo-mechanical and physical properties between random and telechelic ionomers is also reported. The ionic groups act as chain-extension reversible electrostatic links for telechelic ionomers while act as cross-links in random ionomers. Therefore, random ionomers present a consistently higher melt viscosity compared to telechelic ionomers and to PBT and for this reason high molecular weight random ionomers cannot be obtained by melt polycondensation. Thermal and hydrolytic stabilities of telechelic ionomers are comparable with those of commercial PBT and consistently higher respect to those of random ionomers. The presence of ionic groups decreases the translation mobility of the polymer chains thus lowering the crystallization rate.     

Mechanical properties in torsion for poly(butylene terephthalate) and a poly(ether ester) based on poly(ethylene glycol) and poly(butylene terephthalate)

The torsional behavior of poly(ether ester) (PEE) thermoplastic elastomer, based on poly(ethylene glycol) (PEG) and poly(butylene terephthalate) (PBT) was studied and compared with that of PBT itself. Two types of experiments were performed: (1) stress relaxation in torsion, and (2) measurement of intermittent couple-twist responses. It was shown that the relaxation of the torsional couple M could be represented as a sum of several exponential terms in the time, rather than as a simple exponential function. This sum might be called a Prony series on the analogy of the usual stress relaxation which occurs after stretching a sample to a certain deformation and holding it constant. The intermittent couple-twist experiments were carried out by analogy with similar experiments in elongation. For PEE the couple rises steadily with the twist, whereas for PBT it rises abruptly and remains constant within the experimental error for high twists. The residual twist, however, showed a similar trend for both PEE and PBT. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 495–502, 1998     

Synthesis of poly(ethylene terephthalate) in benzyl imidazolium ionic liquids

In order to improve the method of synthesis of poly(ethylene terephthalate) (PET), a series of ionic liquids (ILs) based on benzyl imidazolium ([YBMIM][X], Y = NO₂, CH₃, F; B = benzyl; X = Tf₂N) were used to investigate the formation of PET at low temperature and pressure. High molecular weight PET (M_w up to 2.6 × 10⁴ g mol^?1) was obtained by two‐step polycondensation in these ILs at lower temperature (230–240 °C) than with traditional melt polycondensation (270–290 °C). Moreover, the molecular weight of the resulting PET was found to depend on the activities of the catalysts used in the ILs. The catalysts (Sb₂(OCH₂CH₂O)₃, Sb(OAc)₃, Sb₂O₃) used in the preparation of PET have little effect on the thermostability of the ILs. The ILs can decrease the viscosity of the reaction system, and thus small molecules can be easily removed. Copyright © 2012 Society of Chemical Industry     

Preparation and characterization of poly(butylene terephthalate) nanocomposites with various organoclays

Layered‐silicate‐based polymer–clay nanocomposite materials were prepared depending on the surface modification of montmorillonite (MMT). Nanocomposites consisting of poly(butylene terephthalate) (PBT) as a matrix and dispersed inorganic clay modified with cetyl pyridinium chloride (CPC), benzyl dimethyl N‐hexadecyl ammonium chloride, and hexadecyl trimethyl ammonium bromide by direct melt intercalation were studied. The organoclay loading was varied from 1 to 5 wt %. The organoclays were characterized with X‐ray diffraction (XRD) to compute the crystallographic spacing and with thermogravimetric analysis to study the thermal stability. Detailed investigations of the mechanical and thermal properties as well as a dispersion study by XRD of the PBT/clay nanocomposites were conducted. X‐ray scattering showed that the layers of organoclay were intercalated with intercalating agents. According to the results of a differential scanning calorimetry analysis, clay acted as a nucleating agent, affecting the crystallization. The PBT nanocomposites containing clay treated with CPC showed good mechanical properties because of intercalation into the polymer matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009