Two-stage crystallization kinetics modeling of a miscible blend system containing crystallizable poly(butylene terephthalate)

A modified two-stage kinetic model is proposed to describe the crystallization/solidification from the melt state of a miscible binary blend system comprising amorphous poly(ether imide) (PEI) and crystallizable poly(butylene terephthalate) (PBT). Differential scanning calorimetry (DSC) was employed to monitor the isothermal melt-crystallization of the PBT/PEI blends. A nonlinear regression method was adopted for estimating the kinetic parameters in accordance with the modified two-stage series-parallel model in comparison with the Avrami model. The results suggested that the crystallization of the PEI/PBT blends could be more precisely described by using the modified model, which properly takes into account the changing mechanisms from early to later stage of crystallization. For practical applications, an optimal temperature window for solidifying PEI/PBT miscible blends may be determined by utilizing this model.     

The vibration welding of poly(butylene terephthalate) and a polycarbonate/poly(butylene terephthalate) blend to each other and to other resins and blends

Vibration welding is used to assess the weldability of poly(butylene terephthalate) (PBT) and a polycarbonate/poly(butylene terephthalate) blend (PC/PBT) to each other and to other resins and blends: PBT to PC/PBT, PBT to modified poly(phenylene oxide) (M-PPO), PBT to polyetherimide (PEI) and PEI to a 65 wt% mineral-filled polyester blend (65-PF-PEB), PBT to a poly(phenylene oxide)/polyamide blend (PPO/PA), PC/PBT to M-PPO, and PC/PBT to PPO/PA. Based on the tensile strength of the weaker of the two materials in each pair, the following relative weld strengths have been demonstrated: PBT to PC/PBT,98%; PBT to PEI, 95%; 65-PF-PEB to PEI, 92%; and PC/PBT to M-PPO, 73%. PBT neither welds to M-PPO nor to PPO/PA, and PC/PBT does not weld to PPO/PA.     

Study of the effect of processing conditions on the co‐injection of PBS/PBAT and PTT/PBT blends for parts with increased bio‐content

This work studies the effect of processing parameters on mechanical properties and material distribution of co‐injected polymer blends within a complex mold shape. A partially bio‐sourced blend of poly(butylene terephthalate) and poly(trimethylene terephthalate) PTT/PBT was used for the core, with a tough biodegradable blend of poly (butylene succinate) and poly (butylene adipate‐co‐terephthalate) PBS/PBAT for the skin. A ½ factorial design of experiments is used to identify significant processing parameters from skin and core melt temperatures, injection speed and pressure, and mold temperature. Interactions between the processing effects are considered, and the resulting statistical data produced accurate linear models indicating that the co‐injection of the two blends can be controlled. Impact strength of the normally brittle PTT/PBT blend is shown to increase significantly with co‐injection and variations in core to skin volume ratios to have a determining role in the overall impact strength. Scanning electron microscope images were taken of co‐injected tensile samples with the PBS/PBAT skin dissolved displaying variations of mechanical interlocking occurring between the two blends. © 2014 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41278.     

Toughening effects of poly(butylene terephthalate) with blocked isocyanate‐functionalized poly(ethylene octene)

BACKGROUND: Blocked isocyanate‐functionalized polyolefins have great potential for use in semicrystalline polymer blends to obtain toughened polymers. In this study, poly(butylene terephthalate) (PBT) was blended with allyl N‐[2‐methyl‐4‐(2‐oxohexahydroazepine‐1‐carboxamido)phenyl] carbamate‐functionalized poly(ethylene octene) (POE‐g‐AMPC). RESULTS: New peaks at 2272 and 1720 cm^?1, corresponding to the stretching vibrations of NCO and the carbonyl of NH? CO? N, respectively, in AMPC, appeared in the infrared spectrum of POE‐g‐AMPC. Both rheological and X‐ray photoelectron spectroscopy results indicated a new copolymer was formed in the reactive blends. Compared to uncompatibilized PBT/POE blends, smaller dispersed particle sizes with narrower distribution were found in the compatibilized PBT/POE‐g‐AMPC blends. There was a marked increase in impact strength by about 10‐fold over that of PBT/POE blends with the same rubber content and almost 30‐fold higher than that of pure PBT when the POE‐g‐AMPC content was 25 wt%. CONCLUSION: The blocked isocyanate‐functionalized POE is an effective toughener for semicrystalline polymers. Super‐toughened PBT blends can be obtained when the POE‐g‐AMPC content is equal to or more than 15 wt%. Copyright © 2009 Society of Chemical Industry     

Rheology and morphology of some thermoplastic blends with a liquid crystalline copolyester

Liquid crystalline polymers (LCPs) are known for their high performance properties. However, owing to their high cost, research efforts are much oriented to their use as reinforcements for different thermoplastics. In this study, we investigated the morphology, mechanical and dynamic rheological properties of blends of a 60/40 para hydroxybenzoic acid–ethylene terephthalate copolyester LCP (PHB/PET) with poly(butylene terephthalate) (PBT), poly(hexamethylene terphthalate) (PHMT), and polycarbonate (PC). Addition of up to 30 wt% of LCP to the different thermoplastics was performed in a Haake Rheomix mixer at 300°C. The dynamic rheological properties of the blends showed significant changes upon the addition of LCP, but no improvement in the mechanical properties was observed. The rheological properties of the blends below the nematic transition temperature of the LCP (210°C) were similar to those of solid filled thermoplastics. At 270°C, at which the LCP is in the nematic phase, the viscosity of LCP blends with PC blends decreased, whereas that obtained with PBT blends was increased. This is interpreted as being due to the differences in viscosity and interfacial tension between the components and to a possible reaction between the LCP and the thermoplastics.     

Crystallization behavior and mechanical properties of poly(aryl ether ether ketone)/poly(ether imide) blends

Crystallinity and mechanical properties of blends with different amounts of semicrystalline poly(aryl/ ether ether ketone) (PEEK) and amorphous poly(ether imide) (PEI) polymers have been studied. The blends, prepared by melt mixing, have been investigated by differential scanning calorimeter (DSC) to analyze the miscibility between the components and the final crystalline content. Moreover, for the 20/80 PEEK/PEI blend, crystallization in dynamic and isothermal conditions has been carefully investigated in order to find proper conditions for maximum development of crystallinity. Mechanical tests (static and dynamic) have been performed to evaluate the properties of the as-molded and crystallized blends and to compare them with those of crystalline PEEK and amorphous PEI neat resins. Finally, a few SEM observations have been performed to compare the fractured surface of the blend with those of the pure constituents.     

Rheological and thermal properties of blends of modified poly(ethylene terephthalate) with p‐acetoxybenzoic acid and poly(butylene terephthalate)

Blending of thermotropic liquid crystalline polyesters (LCPs) with conventional polymers could result in materials that can be used as an alternative for short fiber‐reinforced thermoplastic composites, because of their low melt viscosity as well as their inherent high stiffness and strength, high use temperature, and excellent chemical resistance and low coefficient of expansion. In most of the blends was used LCP of 40 mol % of poly(ethylene terephthalate) (PET) and 60 mol % of p‐acetoxybenzoic acid (PABA). In this work, blends of several copolyesters having various PABA compositions from 10 to 70 mol % and poly(butylene terephthalate) (PBT) were prepared and their rheological and thermal properties were investigated. For convenience, the copolyesters were designated as PETA‐x, where x is the mol % of PABA. It was found that PET‐60 and PET‐70 copolyesters decreased the melt viscosity of PBT in the blends and those PBT/PETA‐60 and PBT/PETA‐70 blends showed different melt viscosity behaviors with the change in shear rate, while blends of PBT and PET‐x having less than 50 mol % of PABA exhibited totally different rheological behaviors. The blends of PBT with PETA‐50, PETA‐60, and PETA‐70 showed the morphology of multiple layers of fibers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1797–1806, 1999     

New method for producing high-performance thermoplastic polymeric foams

A new method for the production of foamed thermoplastic polymers from blends of a poly(aryl ether ketone) (PAEK) and polyetherimide (PEI) is presented. The blowing agent for the foaming process is water which is produced at elevated temperatures in an extruder, via an in situ reaction between an amine end group on the PEI, and a ketone functionality on the backbone of the PAEK chain. The effect of composition, mixing, time, and temperature are investigated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1543–1550, 1997     

Blends of poly(butylene terephthalate) with co[poly(ethylene terephthalate-p-oxybenzoate)]: Crystallization behaviors

Polyblends of poly(butylene terephthalate) (PBT) with four different types of co[poly(ethylene terephthalate-p-oxybenzoate)] copolyester, designated as P28, P46, P64, and P82, were prepared by melt-blending. The crystallization behaviors of the blends were then studied by differential scanning calorimetry and polarized optical microscopy (POM). Crystallization rate and temperature of neat PBT are increased when less than 10 wt% of P28 is blended. On the contrary, crystallization rate and temperature of neat PBT decrease when 10 wt% of P46, P64, or P82 copolyesters is blended. The crystallization behaviors of the blends are confirmed by the POM observations at the cooling cycles of the melts. On the other hand, melting endotherm onset temperature and melting peak width for all blends are comparable with those of neat PBT. These results imply that the stability and distribution of PBT crystallites in the blends are not significantly influenced by blending. The effects of POB content in the composition of the blends on the crystalline morphology were also presented. It is found that the structure of crystallites of the blends changed gradually with increasing the POB content in the composition of copolyester from lamellar to cross-like spherulite structures. © 1996 John Wiley & Sons, Inc.     

Morphology monitoring of PE/PBT blends by reactive processing

Polyethylene (PE)/poly(butylene terephthalate) (PBT) blends were in situ compatibilized during a processing operation by the addition of a partially hydroxylated ethylene vinyl acetate copolymer (EVAh). This copolymer, obtained from ethylene vinyl acetate (EVA), was as compatible with PE as EVA was before modification. In the presence of EVAh, the dispersion of PBT in the PE matrix was finer, and the interfacial adhesion was improved. These results are relevant for the compatibilization of PE/PBT blends. Moreover, such blends present good toluene barrier properties. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3568–3577, 2001     

Liquid-crystal polymer fiber production and reinforcing in ribbons of poly(ether imide)/vectra-B blends

Blends of poly(ether imide) (PEI) with a liquid-crystal polymer (Vectra-B950) were extruded into ribbon. Two PEI-rich compositions at three different draw ratios were obtained, and the miscibility and morphology of the blends analyzed. The tensile properties of the ribbons were determined, both in the processing and in the perpendicular direction and were compared with those of the pure PEI. Results showed that PEI/Vectra blends are immiscible and that complex structures were obtained as a consequence of extrusion. The blend composition and the draw ratio determined to a great extent the mechanical properties of the blends. The interfacial adhesion between blend components is low, but enough to break the LCP fibers when significant aspect ratios are attained.     

Fibers from poly(ethylene terephthalate) and poly(butylene terephthalate) blends I. Mechanical behavior

Fibers prepared from poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) blends show a sharp decrease in tensile strength and modulus when blends are on the verge of phase segregation. The modulus values differ for homopolymers for their differences in chain configuration and methylene groups and that of the blends are in proportion. The experimental strength values are higher than the predicted values according to Paul's model for incompatible polymers. At 90/10 PET/PBT blend, the modulus is high, which may be a relative factor to the smaller crystal size of the components.     

Structural and thermal behavior of PC/PBT blends

Blends of polycarbonate (PC) with poly(butylene terphthalate) (PBT) were characterized using density measurements, DSC, IR, and TGA. Addition of PBT increases the density values of blends linearly. All the blends show a single glass transition temperature, indicating the miscibility of the two polymers in the amorphous phase. With more than 6% addition of PBT to PC, PBT crystallizes as per its own crystal structure. The addition of 4% PBT to PC improves the thermal stability at higher temperature than does pure PC. IR studies shows that addition of PBT improves the intermolecular forces in PC, in particular, on the endgroup and the C? CH₃ and C?O groups as indicated in the frequencies 1020, 1370, and 1770–1790 cm^?1. © 1995 John Wiley & Sons, Inc.     

Blends of semicrystalline and amorphous polymeric matrices for high performance composites

The compatibility and crystallization behavior of blends of semicrystalline and amorphous polymers, traditionally used as matrices of high performance composites, has been studied. The analysis has been focused on blends of semicrystalline poly(etheretherketone) (PEEK) with amorphous poly(etherimide) (PEI) prepared by melt mixing. Differential scanning calorimetry and thermogravimetric analysis have been used to analyze the influence of blend constituents and processing conditions on the compatibility, on the crystallization kinetics and on the final crystalline content. An Avrami model has been applied to the crystallization of PEEK in a PEEK/PEI 50/50 blend and the results have been compared with the behavior of the neat PEEK resin. The results of the characterization can be applied to predict the behavior of such blends when processed as matrix of composites or when used in the “amorphous bonding” procedure.     

Synthesis and properties of reactively compatibilized polyester and polyamide blends

The functionalization of poly(butylene terephthalate) (PBT) has been accomplished in a twin screw extruder by grafting maleic anhydride (MA) using a free radical polymerization technique. The resulting PBT‐g‐MA was successfully used as a compatibilizer for the binary blends of polyester (PBT) and polyamide (PA66). Enhanced mechanical properties were achieved for the blend containing a small amount (as low as 2.5 %) of PBT‐g‐MA compared to the binary blend of unmodified PBT with PA66. Loss and storage moduli for blends containing compatibilizer were higher than those of uncompatibilized blends or their respective polymers. The grafting and compatibilization reactions were confirmed using FTIR and ¹³C NMR spectroscopy. The properties of these blends were studied in detail by varying the amount of compatibilizer, and the improved mechanical behaviour was correlated with the morphology with the help of scanning electron microscopy. Morphology studies also revealed the interfacial interaction in the blend containing grafted PBT. The improvement in the properties of these blends can be attributed to the effective interaction of grafted maleic anhydride groups with the amino group in PA66. The results indicate that PBT‐g‐MA acts as an effective compatibilizer for the immiscible blends of PBT and PA66. © 2000 Society of Chemical Industry     

Melting and solidification behavior of blends of high density polyethylene with poly(butylene terephthalate)

This study focuses on the effect of various processing and cooling conditions upon the subsequent melting and solidification behavior of blends of poly(butylene terephthalate) (PBT) and high density polyethylene (HDPE). Differential scanning calorimetry (DSC) measurements have shown that the crystallization of reprocessed PBT is different from the crystallization behavior of virgin samples. Two melting endotherms for PBT were observed for reprocessed PBT and for PBT-PE blends. The nature of each PBT peak is discussed in relation to processing history, solidification conditions, and composition. The presence of two crystallization peaks for the PE component in blends of PE and PBT are thought to be associated with the restriction of molecular motion of PE in the presence of the second component. The relative magnitudes of the two exotherms of PE vary with composition and cooling rate during solidification.     

Solid state features and mechanical properties of PEI/PBT blends

Extrusion‐blended and injection‐molded PEI/PBT blends were found to be miscible whatever the composition. The processability of the blends clearly improved with the presence of PBT. The melt pressure at the exit was seen to be a parameter as representative of the processability of the blends as the torque of blending. In the blends with 80 and 90% PBT, a positive volume of mixing and the maintenance of the crystallinity of PBT were seen. However, in the rest of the blends, negative volumes of mixing and important decreases in the crystallinity of PBT were found. These solid state features gave rise to a ductility similar to that of the pure PEI and to a synergism of the modulus of elasticity and of the yield stress in the 90/10 and 80/20 blends such that the values were higher than those of either of the pure components. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 885–892, 2001     

Studying the formation mechanism of in situ poly(butylene terephthalate) microfibrils prepared by one‐step direct extrusion via orthogonal experimental design

Polypropylene/poly(butylene terephthalate) (PP/PBT) microfibrillar composites (MFCs) were prepared through in situ one‐step direct extrusion using a triangle‐arrayed triple‐screw extruder (TTSE) at a processing temperature between the melting points of two components. The orthogonal experimental method was designed to assess the effects of the PBT content and processing parameters (temperature, screw speed, and feed rate) on the morphology of PBT fibrils. It can be found that the most important influence factor on the fibril formation is the PBT content, followed by temperature, feed rate, and screw speed. Furthermore, the morphological evolution procedures of the dispersed phase started from spherical pellets to ellipsoids or ribbons, forming short fibrils, and consequently high‐aspect‐ratio fibrils appeared under the alternating shear‐extensional flow field. Moreover, the rheological properties of linear PP incorporating fibrillated PBT were thoroughly investigated. The relaxation time of blends with various fibrous PBT was linearly proportional to the aspect ratio of fibrils. Strain‐hardening in extensional flow was observed for blends with long fibrils, and the strain‐hardening factor grew with the fibrillar aspect ratio, indicating the formation of a physical entanglement network between fibrils and matrix. POLYM. ENG. SCI., 58:1166–1173, 2018. © 2017 Society of Plastics Engineers     

Morphology and mechanical properties of liquid crystalline copolyester and polyester elastomer blends

Blends of a polyester elastomer (PEL) having a hard segment of polyester (PBT) and soft segment of polyether (PTMG) and a liquid crystalline copolyester (LCP), poly(benzoate-naphthoate), were prepared in a twin-screw extruder. Specimens for mechanical testing were prepared by injection molding. The morphology of the LCP/PEL blends was characterized under different processing conditions. To determine what conditions were necessary for the development of a fibrillar morphology of LCP, we have studied the effect of processing method (extrusion and injection molding), injection molding temperature (below and above the melting point of LCP), and gate position in the mold (direct gate and side gate). SEM studies revealed that some extensional flow was required for the fibrillar formation of LCP and the fibrillar structure of LCP was controlled by the processing method. The morphology of the blends was found to be affected by their compositions and processing conditions. SEM studies revealed that finely dispersed spherical domains of LCP were formed in the PEL matrix and the inclusions were deformed in fibrils from the spherical droplets with increasing LCP content and injection temperature. The mechanical properties of the LCP/PEL blends were also found to be affected by their compositions and processing conditions. The mechanical properties of LCP/PEL blends were very similar to those of polymeric composite. An attempt was made to correlate the structure of the blends from the scanning electron microscope with the measured mechanical properties. All of the aspects of the morphology were possible to explain in terms of the mechanical properties of the blends. A DSC study revealed that the crystallization of PEL was accelerated by the addition of LCP in the matrix and a partial compatibility between LCP and PEL was predicted. The rheological behavior of the LCP/PEL blends was found to be very different from that of the parent polymers, and significant viscosity reductions were observed in the blend consisting of only 5 wt% of LCP.     

Non-isothermal crystallization kinetic of recycled PET and its blends with PBT modified with epoxy-based multifunctional chain extender

A fundamental understanding of crystallization behavior is essential for the processing of both virgin and recycled polymers. This research delves into the crystallization characteristics and non-isothermal crystallization kinetics of recycled polyethylene terephthalate (rPET) and its blends with poly butylene terephthalate (PBT), which have been modified using epoxy-based multifunctional chain extenders (CE). The preparation of rPET/PBT blends involved a twin-screw extruder, with varying weight ratios and different CE concentrations. Differential scanning calorimetry was employed to perform crystallization analysis on the samples. The results underscore the profound impact of blend composition on the thermal characteristics of the system, with CE exerting only a marginal influence. The glass transition temperatures (T_g) of the two polymers were measured at 49 and 79°C. During blending, the T_g values demonstrated variations relative to the proportions but did not adhere to the Fox equation. Furthermore, PBT was found to enhance the crystallization tendencies of rPET, resulting in an increase in relative crystallinity from 11% to 36%. Notably, the crystallization rate of PBT at 0.40 min⁻¹ exceeded that of rPET at 0.36 min⁻¹. PBT minimally affected the crystallization rate constant of rPET-dominant blends, while rPET significantly reduced the crystallization rate in PBT-dominant blends.