Novel poly(butylene terephthalate)/poly(vinyl butyral) blends prepared by in situ polymerization of cyclic poly(butylene terephthalate) oligomers

Blends of in situ polymerized PBT from cyclic oligomers (c-PBT) and PVB were prepared with varying compositions and compared with mechanical blends of conventional PBT and PVB. The materials were characterized by a variety of techniques including DSC, DMTA, DETA, FTIR, NMR and GPC. It was found that the in situ prepared blend of c-PBT/PVB has one glass transition temperature and shows evidence of miscibility. In contrast, the conventional blend of PBT/PVB shows incompatibility after blending. The cause of miscibility in the in situ prepared PBT/PVB blends is thought to be the formation of a graft copolymer. These results show that there are unique possibilities for in situ processing by combining polymerization of cyclic polyester oligomers with blending.     

Chain extension of poly(butylene terephthalate) by reactive extrusion

The chain extension reaction in poly(butylene terephthalate) (PBT) melt was studied in detail. A high‐reactivity diepoxy, diglycidyl tetrahydrophthalate, was used as a chain extender that can react with the hydroxyl and carboxyl end groups of PBT at a very fast reaction rate and a relatively high temperature. A Haake mixer 600 was used to record the torque during the chain extension reaction. The data show that this chain extension reaction could be completed within 2 to 3 min at temperatures above 250°C, and the reaction time decreased very fast with an increase in the temperature. Shear rate also had some effects on the reaction rate. The effect of the diepoxy chain extender on the flowability, thermal stability, and mechanical properties of PBT were investigated. The melt flow index (MFI) of the chain‐extended PBT dramatically decreased as the diepoxy was added to PBT. In addition, the notched Izod impact strength and elongation‐at‐break of the chain‐extended PBT also increased. The chain‐extended PBT is more stable thermally. Compared with the conventional solid post‐polycondensation method, this approach is simpler and cheaper to obtain high‐molecular‐weight PBT resins. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1827–1834, 1999     

Synthesis of poly(butylene succinate‐co‐butylene terephthalate) (PBST) copolyesters with high molecular weights via direct esterification and polycondensation

In this article, biodegradable poly(butylene succinate‐co‐butylene terephthalate) (PBST) copolyesters with high molecular weights were synthesized by direct esterification and polycondensation route. The reaction conditions and catalytic systems were investigated in detail. Through balancing the reaction efficiency and the costs of reactants, the proper molar ratio of diol to diacid was determined. Titanium tetraisopropoxide (TTiPO) was found to be an effective catalyst both in esterification and polycondensation reaction, and its content was optimized based on the esterification ratio and amount of formed by‐products. The complex reaction was determined to be the dominant catalytic reaction mechanism. By importing the additives of metal oxides coupled with TTiPO, the weight‐average molecular weights of PBST increased sharply from 8.51 × 10⁴ to 14.38 × 10⁴, manifesting the additives promoted the polymerization reaction greatly. The enhancement of carbonyl polarization and provision of suitable reaction space arose from the metal oxides were the reasons for promoting the polymerization reaction. With respect to thermal properties, the same melting point and heat of fusion were found, while thermal stability increased with the import of additives. The result was prone to be interpreted by the higher molecular weights of PBST in the presence of additives. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Sequence analysis of poly(ethylene terephthalate)/poly(butylene terephthalate) copolymer prepared by ester-interchange reactions

The molecular structure of the copolyester formed through the interchange reaction in poly(ethylene terephthalate)/poly(butylene terephthalate) blends was investigated with ¹³C-NMR spectroscopy. The molar fractions of heterolinkage triads in the copolyesters were lower than the values calculated by Bernoullian statistics; this indicates that the sequence of heterolinkages was far from a random distribution at the initial stage of the interchange reaction. However, the randomness increased and the number-average sequence length decreased with reaction time. The solubility of the blend decreased with increasing sequence length, resulting from the formation of block copolymers with long sequence lengths at the initial stage of the interchange reaction. The solubility of the copolyester formed by a dibutyltin dilaurate (DBTDL)-catalyzed reaction was higher than that of the copolyester formed by a titanium tetrabutoxide-catalyzed reaction; this is related to the fact that alcoholysis prevailed in the DBTDL-catalyzed reaction. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 159–168, 2001     

Simultaneous plasticization and blending of isolate soy protein with poly[(butylene succinate)‐co‐adipate] by one‐step extrusion process

This article focuses on the preparation of isolated soy protein plasticized by a glycerol and water mixture/poly[(butylene succinate)‐co‐adipate] blends by an original single step extrusion process. Prepared blends were injection‐molded and characterized for their molecular interaction, morphology, rheological, thermal, dynamic mechanical, and mechanical properties. The comparison of these results with those obtained using a more regular two‐step compounding process validates the technical efficiency of this cost‐effective one‐step approach. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46442.     

Characterization and biodegradability of poly(butylene adipate‐co‐succinate)/poly(butylene terephthalate) copolyester

Characterization of poly(butylene adipate‐co‐succinate) (PBAS)/poly(butylene terephthalate) (PBT) copolyesters resulting from the intermolecular ester‐exchange reaction between molten PBAS and PBT have been analyzed using ¹H‐NMR spectroscopy, differential scanning calorimetry, wide‐angle X‐ray diffraction, and total organic carbon lab analyzer. Using the assignment of proton resonance due to homogeneous and heterogeneous dyads, the average block lengths were investigated over the entire range of copolymer composition. A decrease in melting temperature was observed with the increase of a terephthalate unit in the composition. The result of X‐ray diffraction curve matches well with that of average block length and thermal property. When a rich component is crystallized, the poor component is excluded completely in a crystal formation. The biodegradability in copolyesters also depended on the terephthalate unit in the composition and average block length of the aromatic unit. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 593–608, 1999     

Characterization of poly(trimethylene/butylene terephthalate) copolymer prepared by the copolycondensation of bis(3‐hydroxypropyl terephthalate) and bis(4‐hydroxybutyl terephthalate)

Homopolymers and copolymers were synthesized by polycondensation and copolycondensation, with varying feed ratios of bis(3‐hydroxypropyl terephthalate) (BHPT) and bis(4‐hydroxybutyl terephthalate) (BHBT) at 270°C. In addition, in the mol ratio of 1:1, copoly(trimethylene terephthalate/butylene terephthalate) [P(TT/BT)], with reaction times of 5, 10, 20, 30, and 60 min, was synthesized to identify the chain‐growth process of the copolymers. From differential scanning calorimetry (DSC) data, it was found that a random copolymer might be formed during copolycondensation. The molecular structure of copolymers, formed through the interchange reaction of BHPT and BHBT, was investigated using carbon nuclear magnetic resonance spectroscopy (¹³C‐NMR). We calculated the sequence‐length distributions of trimethylene and butylene sequences and randomness in the copolymers using ¹³C‐NMR data. From the values of the number‐average sequence length calculated, it was determined that a random copolymer was produced: This result coincides with previous DSC data. The lateral spacing of the unit cell of the copolymer increased slowly when the mol percent of one monomer was increased to that of the other monomer, indicating broadening of the unit cell by lateral distortion. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2200–2205, 2003     

Structure formation in stretched sheets of poly(butylene terephthalate)

Crystalline and amorphous sheets of poly(butylene terephthalate) (PBT) were drawn in the temperature range of 20–150°C. The molecular orientation and the relative amount of α- and β-form crystals in the stretched sheets were studied by wide-angle X-ray diffraction (WAXD) and density measurements. When crystalline PBT sheets are drawn at lower temperatures, α-form crystals are partially transformed into β-form crystals. Both α- and β-form crystals are formed by drawing amorphous PBT sheets. The relative amount of α- and β-form crystals is much more sensitive to drawing temperature than to draw ratio. The α-form crystallinity is higher at higher drawing temperature and increases slightly with increasing draw ratio. The second moments of orientation functions of α- and β-form crystals increase with increasing draw ratio, and the increase of the orientation function is suppressed at higher draw ratio. The orientation function of α-form crystals is higher than that of β-form crystals in a same sample.     

Phase separation in poly(butylene terephthalate)-based materials prepared by solid-state modification

The morphology of a series of poly(butylene terephthalate) (PBT)/fatty acid dimer diol (FADD)-based copolyesters prepared by solid-state modification (SSM) was studied. It was shown that in copolyesters containing less than 10 wt% FADD two different phases, i.e. a PBT crystalline phase and a PBT-rich amorphous phase, are present. The FADD residues were more or less homogeneously distributed throughout the interlamellar regions. For copolymers containing more than 10 wt% of FADD, a three-phase morphological model has to be used due to phase separation of a FADD-rich amorphous phase from the PBT-rich matrix, as confirmed by solid-state nuclear magnetic resonance spectroscopy and transmission electron microscopy. The final morphology was dependent on the morphology of the PBT/FADD-based physical mixtures prior to SSM. In addition, it was shown that FADD diffusion during SSM influences the final morphology.     

Melting behavior and crystallization kinetics of poly(butylene terephthalate‐co‐diethylene terephthalate) and poly(butylene terephthalate‐co‐triethylene terephthalate) copolyesters

The melting behavior of poly(butylene terephthalate‐co‐diethylene terephthalate) and poly(butylene terephthalate‐co‐triethylene terephthalate) copolymers was investigated by differential scanning calorimetry after isothermal crystallization from the melt. Multiple endotherms were found for all the samples, and attributed to the melting and recrystallization processes. By applying the Hoffman‐Weeks' method, the equilibrium melting temperatures of the copolymers under investigation were obtained. Two distinct peaks in the crystallization exothermic curve were observed for all the samples. Both of them appeared at higher times than that of PBT, indicating that the introduction of a comonomer decreased the crystallization rate. The observed dependence of this latter on composition was explained on the basis of the content of ether–oxygen atoms in diethylene and triethylene terephthalate units, and of the different sizes of these units. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3545–3551, 2001     

Effects of processing parameters on the in situ compatibilization of polypropylene and poly(butylene terephthalate) blends by one-step reactive extrusion

This paper concerns the effects of processing parameters on the in situ compatibilization of polypropylene (PP) and poly(butylene terephthalate) (PBT) blends by one-step reactive extrusion in a corotating intermeshing twin screw extruder. This in situ compatibilization process was characterized by a sequential arrangement for the free radical grafting of glycidyl methacrylate (GMA) onto PP and the interfacial compatibilization reaction between the GMA functionalized PP and the terminal carboxylic group of the PBT. Among the processing parameters examined were feed rate (Q), screw speed (N), and specific throughput (Q/N). Their effects were evaluated by the associated mechanical properties of final blends in terms of elongation at break and impact strength. Results showed that elongation at break and impact strength increased virtually linearly with decreasing Q or N. Moreover, for a particular Q/N, they increased with decreasing Q with a concomitant decrease in N. Further analysis of these results showed that it is through residence time that these parameters affect the performance of the above mentioned in situ compatibilization process. © 1996 John Wiley & Sons, Inc.     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/multiwalled carbon nanotubes nanocomposites prepared by in situ polymerization

Poly(butylene terephthalate)/multiwalled carbon nanotubes (PBT/MWNT) nanocomposites were prepared by in situ ring‐opening polymerization of cyclic butylene terephthalate oligomers (CBT). The nonisothermal crystallization behavior of the neat PBT and the PBT/MWNT nanocomposites was analyzed quantitatively. The results reveal that the combined Avrami/Ozawa equation exhibits great advantages in describing the nonisothermal crystallization of PBT and its nanocomposites. The presence of MWNTs has the nucleation effect promoting crystallization rate for the nanocomposites, and the maximum one is observed in the nanocomposite having 0.75 wt % MWNT content. On the other hand, the addition of MWNTs has the impeding effect reducing the chain mobility and retarding crystallization, which is confirmed by the crystallization activation energies. However, the nucleation effect of MWNTs plays the dominant role in the crystallization of PBT/MWNT nanocomposites, in other words, the incorporation of MWNTs is increasing the crystallization rate of the nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40849.     

Hybrid poly(ethylene terephthalate)/silica nanocomposites prepared by in‐situ polymerization

The nanocomposites, based on hybrid poly(ethylene terephthalate) (PET)/silica nanoparticles, were prepared via in‐situ condensation polymerization of terephthalic acid and ethylene glycol in the presence of silica nanoparticles pretreated with a silane coupling agent. Such a polymerization process ensured that the silica nanoparticles were well dispersed in PET matrix with the size ranging from 40 to 60 nm, which was confirmed by transmission electron microscope (TEM) observation. Attributed to the unique bonding between SiO₂ nanoparticle and PET, the crystallization behavior of PET was improved significantly, at a low temperature in particular. To further explore the effects of silica nanoparticles on crystallization, extensive differential scanning calorimeter (DSC) measurements were performed in an attempt to reveal the impact of the morphology of the dispersed silica nanoparticle (i.e., sphere or gel‐like) on the peak temperature during melting as well as the amount of heat involved in crystallization. The influences of the structure of polyether glycol (PEG) used for PET preparation as well as the addition of glass fibres (GF) were also investigated using DSC. It was concluded that the synergy among silica nanoparticles, modified PEG, and GFs lowers both T_g and T_m of PET, thus facilitating the injection processes in application. POLYM. COMPOS. 28:42–46, 2007. © 2007 Society of Plastics Engineers     

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.     

Synthesis and characterization of poly(butylene terephthalate)‐co‐poly(butylene succinate)‐block‐poly(ethylene glycol) segmented block copolymers

Poly(butylene terephthalate)‐co‐poly(butylene succinate)‐block‐poly(ethylene glycol) segmented random copolymers, with poly(butylene succinate) (PBS) molar fraction (M_PBS) varying from 10 to 60 %, were synthesized through a melt polycondensation process and characterized by means of GPC, NMR, DSC and mechanical testing. The number‐average relative molecular mass of the copolymers was higher than 4 × 10⁴ g mol^?1 with polydispersity below 1.9. Sequence distribution analysis on the two types of hard segments by means of ¹H NMR revealed that the number‐average sequence length of PBT decreased from 2.80 to 1.23, while that of PBS increased from 1.27 to 4.76 with increasing M_PBS. The random distribution of hard segments was also justified because of the degree of randomness around 1.0. Micro‐phase separation structure was verified for the appearance of two glass transition temperatures and two melting points, respectively, in DSC thermograms of most samples. The crystallinity of hard segments changed with the crystallizability controlled by the average sequence length and reached the minimum value at an M_PBS of about 50–60 mol%. The results can also be ascribed to the co‐crystallization between two structurally analogous hard segments. Mechanical testing results demonstrated that incorporating a certain amount of PBS moieties (less than 30 mol%), at the expense of a minute depression of the elastic modulus, that higher relative elongation and more flexibility of polymer chain could be expected. Maximum equilibrium water absorption and faster degradation rates were observed on samples with higher M_PBS values and lower crystallinity of hard segments were better hydrophilicity of the polymer chain, through in vitro degradation experiments. Copyright © 2003 Society of Chemical Industry     

Isothermal crystallization kinetics and melting behaviors of poly(butylene terephthalate) and poly(butylene terephthalate‐co‐fumarate) copolymer

The isothermal crystallization kinetics and melting behaviors after isothermal crystallization of poly(butylene terephthalate) (PBT) and poly(butylene terephthalate‐co‐fumarate) (PBTF) containing 95/5, 90/10, and 80/20 molar ratios of terephthalic acid/fumaric acid were investigated by differential scanning calorimetry. The equilibrium melting temperatures of these polymers were estimated by Hoffman–Weeks equation. So far as the crystallization kinetics was concerned, the Avrami equation was applied and the values of the exponent n for all these polymers are in the range of 2.50–2.96, indicating that the addition of fumarate does not affect the geometric dimension of PBT crystal growth. Crystallization activation energy (ΔE) and nucleation constant (K_g) of PBTF copolymers are higher than that of PBT homopolymer, suggesting that the introduction of fumarate hinders the crystallization of PBT in PBTF. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

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.     

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.     

Super‐toughness in compatibilized poly(butylene terephthalate)/poly(ethylene‐octene) copolymer blends

Poly(butylene terephthalate) (PBT)/poly(ethylene‐octene) (PEO) blends containing 1.0 wt% epoxy and from 0 to 30 wt% PEO were obtained by extrusion and injection molding. The blends were composed of two pure amorphous phases. The observed torque increases showed that epoxy reacted with PBT, leading to a fine and homogeneous morphology up to 15 wt% PEO content, which appeared larger and more heterogeneous at higher PEO contents. Toughness values fifteen‐fold those of pure PBT were obtained with only 13 wt% PEO. The tensile properties, including ductility, decreased with increasing PEO content, indicating that the adhesion level necessary for high ductility is higher than that necessary for super‐toughness. The inter‐particle distance (τ) was the main parameter that controlled toughness. The comparison of the results of this work with those of the same PBT/PEO blends with two different compatibilizers provides additional strong evidence of the adhesion at the interphase as the main parameter that controls the critical τ in these modified thermoplastic/rubber blends.     

Synthesis and properties of poly(butylene terephthalate)/multiwalled carbon nanotube nanocomposites prepared by in situ polymerization and in situ compatibilization

A novel cyclic initiator was synthesized from dibutyl tin(IV) oxide and hydroxyl‐functionalized multiwalled carbon nanotubes (MWNTs) and was used to initiate the ring‐opening polymerization of cyclic butylene terephthalate oligomers to prepare poly(butylene terephthalate) (PBT)/MWNT nanocomposites. The results of Fourier transform infrared and NMR spectroscopy confirmed that a graft structure of PBT on the MWNTs was formed during the in situ polymerization; this structure acted as an in situ compatibilizer in the nanocomposites. The PBT covalently attached to the MWNT surface enhanced the interface adhesion between the MWNTs and PBT matrix and, thus, improved the compatibility. The morphologies of the nanocomposites were observed by field emission scanning electron microscopy and transmission electron microscopy, which showed that the nanotubes were homogeneously dispersed in the PBT matrix when the MWNT content was lower than 0.75 wt %. Differential scanning calorimetry and thermogravimetric analysis were used to investigate the thermal properties of the nanocomposites. The results indicate that the MWNTs acted as nucleation sites in the matrix, and the efficiency of nucleation was closely related to the dispersion of the MWNTs in the matrix. Additionally, the thermal stability of PBT was improved by the addition of the MWNTs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010