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     

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     

Syntheses and characterization of poly(butylene terephthalate) copolyesters modified with p‐acetoxybenzoic acid

Poly(butylene terephthalate) (PBT) copolyesters modified with seven compositions of p‐acetoxybenzoic acid (PABA) ranging from 10 to 70 mol % were prepared. The X‐ray diffraction patterns, the polarizing microscopy behaviors, and thermal analysis showed that the modified PBT contained more PABA homopolymer units (PABA–PABA) than PBT–PABA units in the copolyesters. On increasing PABA mole percenage, PBT crystallinity decreased and thermal stability increased. It was found that although the PBT copolyesters did not exhibit a clear liquid crystalline texture like the copolyester of poly(ethylene terephthalate) modified with PABA did, the PBT copolyester containing 70 mol % of PABA exhibited the typical shear thinning behavior of a liquid crystalline polymer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1085–1095, 2001     

Properties of uncompatibilized and compatibilized poly(butylene terephthalate)–LLDPE blends

In this work, blends of poly(butylene terephthalate) (PBT) and linear low‐density polyethylene (LLDPE) were prepared. LLDPE was used as an impact modifier. Since the system was found to be incompatible, compatibilization was sought for by the addition of the following two types of functionalized polyethylene: ethylene vinylacetate copolymer (EVA) and maleic anhydride‐grafted EVA copolymer (EVA‐g‐MAH). The effects of the compatibilizers on the rheological and mechanical properties of the blends have been also quantitatively investigated. The impact strength of the PBT–LLDPE binary blends slightly increased at a lower concentration of LLDPE but increased remarkably above a concentration of 60 wt % of LLDPE. The morphology of the blends showed that the LLDPE particles had dispersed in the PBT matrix below 40 wt % of LLDPE, while, at 60 wt % of LLDPE, a co‐continuous morphology was obtained, which could explain the increase of the impact strength of the blend. Generally, the mechanical strength was decreased by adding LLDPE to PBT. Addition of EVA or EVA‐g‐MAH as a compatibilizer to PBT–LLDPE (70/30) blend considerably improved the impact strength of the blend without significantly sacrificing the tensile and the flexural strength. More improvement in those mechanical properties was observed in the case of the EVA‐g‐MAH system than for the EVA system. A larger viscosity increase was also observed in the case of the EVA‐g‐MAH than EVA. This may be due to interaction of the EVA‐g‐MAH with PBT. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 989–997, 1999     

Microstructure and crystallization of melt‐mixed poly(ethylene terephthalate)/poly(ethylene isophthalate) blends

Physical blends of poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI), abbreviated PET/PEI (80/20) blends, and of PET and a random poly(ethylene terephthalate‐co‐isophthalate) copolymer containing 40% ethylene isophthalate (PET₆₀I₄₀), abbreviated PET/PET₆₀I₄₀ (50/50) blends, were melt‐mixed at 270°C for different reactive blending times to give a series of copolymers containing 20 mol % of ethylene isophthalic units with different degrees of randomness. ¹³C‐NMR spectroscopy precisely determined the microstructure of the blends. The thermal and mechanical properties of the blends were evaluated by DSC and tensile assays, and the obtained results were compared with those obtained for PET and a statistically random PETI copolymer with the same composition. The microstructure of the blends gradually changed from a physical blend into a block copolymer, and finally into a random copolymer with the advance of transreaction time. The melting temperature and enthalpy of the blends decreased with the progress of melt‐mixing. Isothermal crystallization studies carried out on molten samples revealed the same trend for the crystallization rate. The effect of reaction time on crystallizability was more pronounced in the case of the PET/PET₆₀I₄₀ (50/50) blends. The Young's modulus of the melt‐mixed blends was comparable to that of PET, whereas the maximum tensile stress decreased with respect to that of PET. All blend samples showed a noticeable brittleness. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3076–3086, 2003     

Structure and mechanical properties of poly(sulfone of bisphenol A)/poly(butylene terephthalate) blends

Blends of poly(sulfone of bisphenol A) (PSU) with poly(butylene terephthalate) (PBT) were obtained by direct injection moulding across the composition range. The two components of the blends reacted slightly in the melt state, producing linear copolymers. The slight changes observed in the two glass transition temperatures indicate that the copolymers were present in the two amorphous phases of the blends. The observed reactions and the high viscosity of the matrix of the PSU‐rich compositions led to a very fine morphology which could not be attained in the PBT‐rich compositions due to the low viscosity of the matrix and the direct injection moulding procedure used. This procedure is fast and economically advantageous, but leads to poor mixing. The different morphologies influenced neither the modulus nor the yield stress, which tended to follow the rule of mixtures. However, the low fracture properties of the PBT‐rich compositions contrasted with the ductility behaviour, and even the impact strength of the PSU‐rich blends, which also tended to be proportional to the blend composition. Copyright © 2004 Society of Chemical Industry     

Rheological behavior of polyester blend and mechanical properties of the polypropylene–polyester blend fibers

The article deals with method of preparation, rheological properties, phase structure, and morphology of binary blend of poly(ethylene terephthalate) (PET)/poly(butylene terephthalate) (PBT) and ternary blends of polypropylene (PP)/(PET/PBT). The ternary blend of PET/PBT (PES) containing 30 wt % of PP is used as a final polymer additive (FPA) for blending with PP and subsequent spinning. In addition commercial montane (polyester) wax Licowax E (LiE) was used as a compatibilizer for spinning process enhancement. The PP/PES blend fibers containing 8 wt % of polyester as dispersed phase were prepared in a two‐step procedure: preparation of FPA using laboratory twin‐screw extruder and spinning of the PP/PES blend fibers after blending PP and FPA, using a laboratory spinning equipment. DSC analysis was used for investigation of the phase structure of the PES components and selected blends. Finally, the mechanical properties of the blend fibers were analyzed. It has been found that viscosity of the PET/PBT blends is strongly influenced by the presence of the major component. In addition, the major component suppresses crystallinity of the minor component phase up to a concentration of 30 wt %. PBT as major component in dispersed PES phase increases viscosity of the PET/PBT blend melts and increases the tensile strength of the PP/PES blend fibers. The impact of the compatibilizer on the uniformity of phase dispersion of PP/PES blend fibers was demonstrated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4222–4227, 2006     

Synthesis and characterisation of copolyesters from poly(ethylene terephthalate) and poly(hexamethylene terephthalate)

Copolyesters containing poly(ethylene terephthalate) and poly(hexamethylene terephthalate) (PHT) were prepared by a melt condensation reaction. The copolymers were characterised by infrared spectroscopy and intrinsic viscosity measurements. The density of the copolyesters decreased with increasing percentage of PHT segments in the backbone. Glass transition temperatures (T_g). melting points (T_m) and crystallisation temperatures (T_c) were determined by differential scanning calorimetry. An increase in the percentage of PHT resulted in decrease in T_g, T_m and T_c. The as-prepared copolyesters were crystalline in nature and no exotherm indicative of cold crystallisation was observed. The relative thermal stability of the polymers was evaluated by dynamic thermogravimetry in a nitrogen atmosphere. An increase in percentage of PHT resulted in a decrease in initial decomposition temperature. The rate of crystallisation of the copolymers was studied by small angle light scattering. An increase in percentage of PHT resulted in an increase in the rate of crystallisation.     

Reactive blending of poly(ethylene terephthalate) with a liquid crystalline copolyester and polyhydroxyether

Poly(ethylene terephthalate) modified with a dianhydride (PET–anhydride) was melt‐blended with a liquid crystalline copolyester (Vectra A) in the presence of a small amount of a liquid crystalline polyhydroxyether. The mechanical properties of a blend consisting of PET–anhydride/Vectra A/polyhydroxyether were drastically improved compared to blends without polyhydroxyether or without anhydride. Melt‐spun fibers of PET–anhydride/Vectra A/polyhydroxyether in a 80/20/0.75 weight ratio displayed a much higher tensile modulus (17 GPa) and tensile strength (214 MPa) than did a 80/20 PET–anhydride/Vectra A blend (4 GPa and 60 MPa, respectively). A similar increase in modulus and strength was found for a 90/10/0.75 relative to a 90/10 blend. The tensile moduli of the blends can well be described by the Tsai–Halpin equation. A better fibril formation was observed, which was attributed to an improved viscosity ratio. Reactions between the various functional groups during melt processing were indicated by viscosity measurements. The polyhydroxyether may act as a reactive compatibilizer which improves the interfacial adhesion, chemically and/or physically. WAXD recordings of both blends showed a crystalline and highly oriented Vectra phase. The PET phase was unoriented and amorphous in a PET/Vectra blend and semicrystalline and weakly oriented in a PET/Vectra/polyhydroxyether blend. Postdrawing of the various blend fibers to λ = 4 increased the modulus by about 40% and the tensile strength by more than 100%, mainly through orientation of the PET phase. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1107–1123, 1999     

Properties of poly(ethylene terephthalate) and maleic anhydride-grafted polypropylene blends by reactive processing

The properties of poly(ethylene terephthalate) (PET) and polypropylene (PP) blends and PET/maleic anhydride-grafted PP (MAgPP) reactive blends were investigated. Two blend systems were immiscible based on tan δ measured by dynamic mechanical analyzer (DMA). In case of PET/MAgPP blends, the reaction of ester groups of PET and MA sites on MAgPP occurred during melt mixing at 280°C for 30 min. The reaction was confirmed by a new peak between the glass transition temperatures of PET-rich and MAgPP-rich phase on tan δ curves, as well as from the rheological properties. From the morphology, the improvement of the dispersibility in PET/MAgPP reactive blends was observed. The modulus of PET/MAgPP blends was higher than that of PET/PP blends, and the strength of PET/MAgPP blends showed the good adhesion compared with the PET/PP blends. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 389–395, 1998     

Crystallization kinetics of poly(1,4‐butylene‐co‐ethylene terephthalate)

The crystallization kinetics of poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and their copolymers poly(1,4‐butylene‐co‐ethylene terephthalate) (PBET) containing 70/30, 65/35 and 60/40 molar ratios of 1,4‐butanediol/ethylene glycol were investigated using differential scanning calorimetry (DSC) at crystallization temperatures (T_c) which were 35–90 °C below equilibrium melting temperature . Although these copolymers contain both monomers in high proportion, DSC data revealed for copolymer crystallization behaviour. The reason for such copolymers being able to crystallize could be due to the similar chemical structures of 1,4‐butanediol and ethylene glycol. DSC results for isothermal crystallization revealed that random copolymers had a lower degree of crystallinity and lower crystallite growth rate than those of homopolymers. DSC heating scans, after completion of isothermal crystallization, showed triple melting endotherms for all these polyesters, similar to those of other polymers as reported in the literature. The crystallization isotherms followed the Avrami equation with an exponent n of 2–2.5 for PET and 2.5–3.0 for PBT and PBETs. Analyses of the Lauritzen–Hoffman equation for DSC isothermal crystallization data revealed that PBT and PET had higher growth rate constant G_o, and nucleation constant K_g than those of PBET copolymers. © 2001 Society of Chemical Industry     

Effect of poly(ethylene glycol) on the solid‐state polymerization of poly(ethylene terephthalate)

Poly(ethylene glycol) (PEG) and end‐capped poly(ethylene glycol) (poly(ethylene glycol) dimethyl ether (PEGDME)) of number average molecular weight 1000 g mol^?1 was melt blended with poly(ethylene terephthalate) (PET) oligomer. NMR, DSC and WAXS techniques characterized the structure and morphology of the blends. Both these samples show reduction in T_g and similar crystallization behavior. Solid‐state polymerization (SSP) was performed on these blend samples using Sb₂O₃ as catalyst under reduced pressure at temperatures below the melting point of the samples. Inherent viscosity data indicate that for the blend sample with PEG there is enhancement of SSP rate, while for the sample with PEGDME the SSP rate is suppressed. NMR data showed that PEG is incorporated into the PET chain, while PEGDME does not react with PET. Copyright © 2005 Society of Chemical Industry     

Study on in situ reinforcing and toughening of a semiflexible thermotropic copolyesteramide in PBT/PA66 blends

Ternary in situ composites based on poly(butylene terephthalate) (PBT), polyamide 66 (PA66), and semixflexible liquid crystalline polymer (LCP) were systematically investigated. The LCP used was an ABA30/PET liquid crystalline copolyesteramide based on 30 mol % of p‐aminobenzoic acid (ABA) and 70 mol % of poly(ethylene terephthalate) (PET). The specimens for thermal and rheological measurements were prepared by batch mixing, while samples for mechanical tests were prepared by injection molding. The results showed that the melting temperatures of the PBT and PA66 phases tend to decrease with increasing LCP addition. They also shifted toward each other due to the compatibilization of the LCP. The torque measurements showed that the ternary blends exhibited an apparent maximum near 2.5–5 wt % LCP. Thereafter, the viscosity of the blends decreased dramatically at higher LCP concentrations. Furthermore, the torque curves versus the PA66 composition showed that the binary PBT/PA66 blends can be classified as negative deviation blends (NDBs). The PBT/PA66/LCP blends containing up to 15 wt % LCP were termed as positive deviation blends (PDBs), while the blends with the LCP ≥25 wt % exhibited an NDB behavior. Finally, the tensile tests showed that the stiffness and tensile strength of ternary in situ composites were generally improved with increasing LCP content. The impact strength of ternary composites initially increased by the LCP addition, then deteriorated when the LCP content was higher than 10 wt %. The correlation between the mechanical properties and morphology of the blends is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1975–1988, 2000     

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     

Acetaldehyde scavengers and their effects on thermal stability and physical properties of poly(ethylene terephthalate)

The acetaldehyde (AA) scavenging abilities of poly(ethylene terephthalate) (PET) blends containing various concentrations of anthranilamide, meta-xylenediamine (MXDA), or alpha-cyclodextrin have been evaluated. It was found that higher AA scavenger concentrations generally resulted in greater reductions in detectable AA in terms of both the AA generation rates and residual AA contents. As little as 100 ppm, by weight, of anthranilamide and MXDA were respectively shown to reduce residual AA detected in PET preforms by 46% and 36%. Melt-blending 500 ppm of alpha-cyclodextrin, into PET, reduced preform residual AA concentration by 42%. The scavengers acted as PET nucleating agents causing more rapid crystallization while heating the blends from the glassy state and when cooling from the melt; however, they caused no changes in the glass transitions, melting characteristics, or oxygen permeation behaviors of the blends. Addition of optimal scavenger concentrations had minimal effects on preform intrinsic viscosity and color changes. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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     

Influence of branching on the properties of poly(ethylene terephthalate) fibers

A series of branched poly(ethylene terephthalate) samples was prepared by employing 0.07–0.42 mol % trimethylolpropane (TMP) for melt polycondensation. These polymers were characterized with respect to molar mass, intrinsic viscosity, and melt viscosity. Spinning into fibers took place at spinning speeds ranging from 2500 to 4500 m/min. The molecular orientation of the fibers as measured by birefringence and polarized fluorescence decreases with growing amounts of TMP, as does crystallinity. Thus with slightly branched polymers, higher spinning speeds than with a linear polymer can be used to achieve a certain property profile. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 728–734, 1999     

Improvement of compatibility of poly(ethylene terephthalate) and poly(ethylene octene) blends by γ‐irradiation

Blends of poly(ethylene terephthalate) (PET) and poly(ethylene octene) (POE) were prepared by melt blending with various amounts of trimethylolpropane triacylate (TMPTA). The mechanical properties, phase morphologies, and gel fractions at various absorbed doses of γ‐irradiation have been investigated. It was found that the toughness of blends was enhanced effectively after irradiation as well as the tensile properties. The elongation at break for all studied PET/POE blends (POE being up to 15 wt %) with 2 wt % TMPTA reached 250–400% at most absorbed doses of γ‐irradiation, approximately 50–80 times of those of untreated PET/POE blends. The impact strength of PET/POE (85/15 wt/wt) blends with 2 wt % TMPTA irradiated with as little as 30 kGy absorbed dose exceeded 17 kJ/m², being approximately 3.4 times of those of untreated blends. The improvement of the mechanical properties was supported by the morphology changes. Scanning electron microscope images of fracture surfaces showed a smaller dispersed phase and more indistinct inter‐phase boundaries in the irradiated blends. This indicates increased compatibility of PET and POE in the PET/POE blends. The changes of the morphologies and the enhancement of the mechanical properties were ascribed to the enhanced inter‐phase boundaries by the formation of complex graft structures confirmed by the results of the gelation extraction and Fourier Transform Infrared analyses. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Fast crystallization of liquid crystalline copolyesters based on poly(ethylene terephthalate)

Crystallization of a series of liquid crystalline copolyesters prepared from p‐hydroxybenzoic acid (HBA), hydroquinone (HQ), terephthalic acid (TA), and poly(ethylene terephthalate) (PET) was investigated by using differential scanning calorimetry (DSC). It was found that these copolyesters are more crystalline than copolyesters prepared from PET and HBA. Insertion of HQ–TA disrupts longer rigid‐rod sequences formed by HBA and thus enhances molecular motion and increases the crystallization rate. The effects of additives on the crystallization of the copolyesters were also studied. Sodium benzoate (SB) and sodium acetate (SA) increase the crystallization rate of the copolyesters at low temperature, but not at high temperature. It is most likely that liquid crystalline copolyesters do not need nucleating agents, and small aggregates of local‐oriented rodlike segments in nematic phase could act as primary nuclei. Chain scission of the copolyesters caused by the reaction with the nucleating agents was proved by the determination of intrinsic viscosity and by the IR spectra. Diphenylketone (DPK) was shown to effectively promote molecular motion of chains, leading to an increase in the crystallization rate at low temperature, but it decreased the crystallization rate at high temperature. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 497–503, 2001     

Influence of the degree of grafting on the morphology and mechanical properties of blends of poly(butylene terephthalate) and glycidyl methacrylate grafted poly(ethylene‐co‐propylene) (EPR)

Poly(ethylene‐co‐propylene) (EPR) was functionalized to varying degrees with glycidyl methacrylate (GMA) by melt grafting processes. The EPR‐graft‐GMA elastomers were used to toughen poly(butylene terephthalate) (PBT). Results showed that the grafting degree strongly influenced the morphology and mechanical properties of PBT/EPR‐graft‐GMA blends. Compatibilization reactions between the carboxyl and/or hydroxyl of PBT and epoxy groups of EPR‐graft‐GMA induced smaller dispersed phase sizes and uniform dispersed phase distributions. However, higher degrees of grafting (>1.3) and dispersed phase contents (>10 wt%) led to higher viscosities and severe crosslinking reactions in PBT/EPR‐graft‐GMA blends, resulting in larger dispersed domains of PBT blends. Consistent with the change in morphology, the impact strength of the PBT blends increased with the increase in EPR‐graft‐GMA degrees of grafting for the same dispersion phase content when the degree of grafting was below 1.8. However, PBT/EPR‐graft‐GMA1.8 displayed much lower impact strength in the ductile region than a comparable PBT/EPR‐graft‐GMA1.3 blend (1.3 indicates degree of grafting). Morphology and mechanical results showed that EPR‐graft‐GMA 1.3 was more suitable in improving the toughness of PBT. SEM results showed that the shear yielding properties of the PBT matrix and cavitation of rubber particles were major toughening mechanisms. Copyright © 2006 Society of Chemical Industry