Neat PTT Research Articles

Influence of intercalated organoclay on the phase structure and physical properties of PTT–PTMO block copolymers

Poly(trimethylene terephthalate-block-tetramethylene oxide) (PTT–PTMO) copolymer/organoclay nanocomposites were prepared by in situ polymerization. They showed an intercalated silicate structure, as determined by X-ray diffraction and transmission electron microscopy. The influence of intercalated organoclay on the two-phase structure and mechanical properties of PTT–PTMO block copolymer was examined by using DSC and tensile tests. The DSC results imply that the silicate layers (Nanofil 32) in PTT–PTMO act as nucleation agents and accelerate the crystallization of PTT hard phase during the cooling down process from the melt. The introduction of silicate layers does not have great effect on the glass transition temperature of PTMO-rich soft phase, melting temperature of PTT hard phase, and degree of crystallinity of the nanocomposites. As the organoclay loading in the nanocomposites increase, the enhanced tensile modulus and yield stress was observed. The cyclic tensile tests showed that obtained nanocomposites have values of permanent set comparable to the neat PTT–PMO copolymer.

Mechanical Property, Crystal Morphology, and Nonisothermal Crystallization Kinetics of Poly(Trimethylene Terephthalate)/Maleinized Acrylonitrile-Butadiene-Styrene Blends

The mechanical properties, morphology, crystallization, and melting behaviors and nonisothermal crystallization kinetics of poly (trimethylene terephthalate)(PTT)/maleinized acrylonitrile-butadiene-styrene (ABS-g-MAH) blends were investigated by an impact tester, polarized optical microscopy, and differential scanning calorimetry (DSC). The results suggested that the ABS-g-MAH component served as both a nucleating agent for increasing the crystallization rate and as a toughening agent for improving the impact strength of PTT. When the ABS-g-MAH content was 5wt.%, the blend had the best toughness and a high crystallization rate. The blends showed different crystallization rates and subsequent melting behaviors due to their different ABS-g-MAH contents. The Ozawa theory and the method developed by Mo and coworkers were used to study the nonisothermal crystallization kinetics of the blends. The kinetic crystallization rate parameters suggested that the proper contents of ABS-g-MAH can highly accelerate the crystallization rate of PTT, but this effect nearly reaches saturation for ABS-g-MAH contents over 5%. The Ozawa exponents calculated from the DSC data suggested that the PTT crystals in the blends have similar growth dimensions as those in neat PTT, although they are smaller and/or imperfect. The effective activation energy calculated by the method developed by Kissinger also indicates that the blends with higher ABS-g-MAH content were easier to crystallize.

Non-isothermal crystallization of poly(trimethylene terephthalate)/single-walled carbon nanotubes nanocomposites

In this work, non-isothermal crystallization behavior of nanocomposites based on poly(trimethylene terephthalate) (PTT) and single-walled carbon nanotubes (SWCNTs) and neat PTT was studied in order to determine the effects of SWCNTs on its crystallization behavior. Nanocomposites with 0.3 and 0.5 wt. % of SWCNTs were studied. Using of SAXS and DSC methods, the nanostructure of PTT/SWCNTs nanocomposites and neat PTT was investigated in real time in the process of crystallization from the melt. The correlation function approach was used to analyze SAXS data. Changes in long period values, thickness of crystalline lamellae, thickness of amorphous layers, degree of crystallinity during cooling from the melt were discussed.

Banded spherulites of electrospun poly(trimethylene terephthalate)/carbon nanotube composite mats

AbstractThe crystallization of poly(trimethylene terephthalate) (PTT) composites containing carbon nanotubes (CNTs) were studied in this work. The electrospinning technology was employed successfully to fabricate thin film samples with well‐embedded CNTs for spherulite observations using atom force microscopy. The results show that the composites present a higher overall crystallization rate than that of the neat PTT due to the nucleation effect of the CNTs. Banded spherulites can be observed on both the neat PTT and the composites. The presence of CNTs does not change the twisting mode of PTT crystal, but reduces band spacing and twist period. This is attributed to the enhanced fold staggering level of lamellae caused by the narrowed lamellae size and accelerated spherulite growth, which is further confirmed by analysis through secondary nucleation theory. Copyright © 2011 Society of Chemical Industry

Preparation and characterization of nanocomposites based on COOH functionalized multi-walled carbon nanotubes and on poly(trimethylene terephthalate)

Poly(trimethylene terephthalate) nanocomposites containing COOH functionalized multi-walled nanotubes were synthesized with in situ polymerization method. The microstructure of the nanocomposites was studied by SEM, in terms of the dispersion state of the nanotubes and the polymer-nanotube interface. The thermal behaviour, mechanical properties and conductivity of these resultant PTT/MWCNTs nanocomposites were studied. The effect of the presence of MWCNTs on cold crystallization of PTT was monitored by dielectric spectroscopy. From thermal analysis study, it is found that the melting temperature and glass transition temperature are not significantly affected by the addition of MWCNTs. The crys- tallization temperature of PTT matrix is affected by the presence of CNTs. Nanocomposites have slightly higher degree of crystallinity than neat PTT and their thermo-oxidative stability is not significantly affected by the addition of MWCNTs. The study of the isothermal cold crystallization of amorphous PTT and its nanocomposites monitored by dielectric spec- troscopy reveals that the presence of MWCNTs have influence on crystallization rate, especially at higher concentration (0.3 wt%). In comparison with neat PTT, the MWCNTs reinforced nanocomposites posses higher tensile strength and Young's modulus at low MWCNTs loading (0.05-0.3 wt%). In addition, all nanocomposites show reduction of brittleness as compared to the neat PTT. The electrical percolation threshold was found between 0.3 and 0.4 wt% loading of MWC- NTs.

Phase structure of electrospun poly(trimethylene terephthalate) composite nanofibers containing carbon nanotubes

Nanofibrous composite mats were prepared by electrospinning of poly(trimethylene terephthalate), PTT, with multi-walled carbon nanotubes (PTT/MWCNT). Tri- fluoroacetic acid (TFA) and methylene chloride (MC) with volume ratio of 50/50 is a good solvent for PTT and was used as the electrospining solution. Scanning electron microscopy was used to investigate the morphology of electrospun (ES) nanofibers with 0, 0.2, 1.0, or 2.0 wt% of MWCNTs. Crystal structure of the ES mats was deter- mined from wide angle X-ray diffraction. Thermal prop- erties were investigated using heat capacity measurements from differential scanning calorimetry (DSC) using the three-runs method for baseline correction, heat flow amplitude calibration, and sample heat capacity determi- nation. A model comprising three phases, a mobile amor- phous fraction (MAF), rigid amorphous fraction (RAF), and crystalline fraction (C), is appropriate for ES PTT/ MWCNT fibers. The phase fractions, Wi (for i = RAF, MAF or C) were determined by DSC. Crystallinity decreases very slightly with the amount of MWCNT. At the same time, a large increase in RAF was observed: WRAF of PTT fiber with 2% MWCNT is twice that of neat PTT fiber. The addition of MWCNTs enhanced the PTT chain alignment and increased RAF as a result. Changes of vibrational band absorbance at 1358 and 1385 cm -1 , cor- responding to characteristic groups, were obtained with infrared spectroscopy. The increased absorbance at 1358 cm -1 and decreased absorbance at 1385 cm -1 , with the addition of MWCNTs, strongly supports the three- phase model for ES PTT/MWCNT nanocomposites.

Crystallization and spherulitic growth kinetics of poly(trimethylene terephthalate)/polycarbonate blends

AbstractThe macroscopic and microscopic melt‐crystallization kinetics of poly(trimethylene terphthalate) (PTT)/polycarbonate (PC) blends have been measured by differential scanning calorimetry (DSC), and optical microscopy (OM). The results are analyzed in terms of the Avrami equation and the Hoffman–Lauritzen crystallization theory (HL model). Blending with PC did not change the crystallization mechanism of PTT, but reduced the crystallization rate compared with that of neat PTT at the same crystallization temperature. The crystallization rate decreased with increasing crystallization temperature. The spherulitic morphology of PTT was influenced apparently by the crystallization temperature and by the addition of PC. X‐ray diffraction shows no change in the unit cell dimension of PTT was observed after blending. Through the HL theory, the classical regime II→III transition was detected for the neat PTT and the blends. The nucleation parameter (Kg), the fold‐surface free energy (σe), and the work of chain folding (q) were calculated. Blending with PC decreased all the aforementioned parameters compared with those of neat PTT. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers

Crystallization kinetics and structure of poly(trimethylene terepthalate)/monolayer nano-mica nanocomposites

In this work, the structure of poly(trimethylene terepthalate) (PTT)/monolayer nano-mica (MNM) nanocomposites are investigated by wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS) and scanning electron microscope (SEM). In the PTT nanocomposites, the crystallization induces the segregation of MNM in which three morphologies, including interlamellar, interfibrillar, and interspherulitic segregations, are observed with changing the MNM content. Avrami analysis of isothermal crystallization demonstrates that MNM enhances the bulk crystallization rate in the nanocomposites. Moreover, the non-integral values of Avrami exponent n between 2 and 4 with increasing crystallization temperature indicate the mixed growth and nucleation mechanisms. The analysis of secondary nucleation theory for neat PTT and the PTT nanocomposites exhibit the same regime transition of crystallization behaviour in which the classical transition temperatures of regime I to II and regime II to III take place at 488 K and 468 K, respectively. The growth rate of spherulites of the PTT nanocomposites is twofold larger than that of neat PTT in regime III, implying that MNM plays an effective role as a nucleating agent, since the addition of MNM enormously reduces the activation energy of nucleation, folding surface free energy and average work of chain folding for PTT nucleation. However, experimental results show that the MNM content below 1 wt% is the most effective for nucleation of PTT crystallization.

The morphology and non-isothermal crystallization characteristics of poly(trimethylene terephthalate)/BaSO 4 nanocomposites prepared by in situ polycondensation

A simple method was developed for preparing nano-BaSO 4 suspension by reacting H 2SO 4 with Ba(OH) 2 in 1,3-propanediol (PDO). The zymotechnics 1,3-propanediol and newly prepared nano-BaSO 4 suspension were used for fabricating PTT/BaSO 4 nanocomposites by in situ polymerization. The size distribution curves revealed that most of the nano-BaSO 4 particles in PDO have a diameter of 15–23 nm. Transmission electron microscopy (TEM) showed that BaSO 4 disperses uniformly in PTT matrix when BaSO 4 content was no more than 12 wt%. The non-isothermal crystallization behavior was studied quantitatively by modified Avrami equation and Ozawa theory. Both theories can successfully describe the non-isothermal crystallization of pure PTT and PTT/nano-BaSO 4 composites. The crystallinity and crystallization rate of nanocomposites was greatly increased by addition of BaSO 4. The maximum enhancement of crystallization rate for the nanocomposites was observed in nanocomposites containing about 12 wt% BaSO 4 with a range of 2–16 wt%, which was confirmed by both Avrami crystallization rate parameter ( Z c) and Ozawa crystallization rate parameter log K( T). The Avrami and Ozawa mechanism exponents, n and m of the nanocomposites, were higher than those of neat PTT, suggesting more complicated interaction between molecular chains and the nanoparticles that caused the changes of the nucleation mode and the crystal growth dimension. Effective activation energy calculated from the Friedman formula was reduced as nano-BaSO 4 content increased, suggesting that the nano-BaSO 4 made the molecular chains of PTT easier to crystallize during the non-isothermal crystallization process. The polarizing micrographs showed that much smaller or less perfect crystals formed in composites due to the interaction between molecular chains and nano-BaSO 4 particles.

Rheological, morphological, thermal, and mechanical properties of blends of vectra A950 and poly(trimethylene terephthalate): A study on a high-viscosity-ratio system

Poly(trimethylene terephthalate) (PTT) and a liquid crystalline polymer, Vectra A950 (VA), were melt-blended and subjected to capillary rheometry. Effects of VA content, shear rate and temperature on viscosity and flow activation energy ( E a) were investigated. Partial fibrillation was found even though the viscosity ratio was greater than one, leading to the formation of in-situ composites. Thermal and thermogravimetric analysis of the blends suggested that they were immiscible and their thermal stabilities were enhanced. From tensile tests, the incorporation of VA improved tensile modulus, slightly decreased tensile strength, and drastically lowered elongation at break, compared to neat PTT. It was found that the blend with the best VA dispersion can be achieved at the minimum VA content (10 wt%) and lowest processing temperature (250 °C). Not only did this blend exhibit improved mechanical properties comparable to those of blends processed at temperatures closer to the crystalline-to-nematic transition of VA (∼280 °C), it also shows enhanced processibility through the reduction of both melt viscosity and E a.

Nonisothermal crystallization behavior and crystals morphology of poly(trimethylene terephthalate)/nano‐calcium carbonate composites

AbstractNonisothermal crystallization behavior and crystal morphology of poly(trimethylene terephthalate) (PTT) composites filled with modified nano‐calcium carbonate (CaCO3) had been investigated by using differential scanning calorimetry and polarized optical microscopy. The modified Avrami equation and Ozawa theory were used to investigate the nonisothermal crystallization, respectively. The particles of nano‐CaCO3, acting as a nucleation agent in composites, accelerated the crystallization rate by decreasing the half‐time of crystallization or increasing the parameters of Zc and K(T). Moreover, the nano‐composite with 2 wt% nano‐CaCO3 exhibited the highest crystallization rate. The Avrami and the Ozawa exponents, n and m of the nano‐composites, were higher than those of neat PTT, suggesting more complicated interaction between molecular chains and the nanoparticles that cause the changes of the nucleation mode and the crystal growth dimension. The effective activation energy calculated from the Friedman formula was reduced as nano‐CaCO3 content increased, suggesting that the nano‐CaCO3 made the molecular chains of PTT easier to crystallize during the nonisothermal crystallization process. The optical micrographs showed that much smaller or less perfect crystals were formed in composites because of the presence of the nano‐CaCO3 particles. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Melting behaviors, isothermal crystallization kinetics, and morphology of poly(trimethylene terephthalate)/stainless steel fiber composites

AbstractThe melting behavior and crystallization kinetics of poly(trimethylene terephthalate) (PTT)/stainless steel fiber (SSF) composites were investigated with differential scanning calorimetry. The morphology was studied with scanning electron microscopy and polarized optical microscopy. Differential scanning calorimetry analysis revealed that the crystallization temperature increased by 27°C with the addition of 1 vol % SSF to the matrix. The Avrami exponents, analyzed in isothermal crystallization kinetics, were determined to be 2–3 for both neat PTT and PTT/SSF composites. SSF, as a nucleating agent in the composites, greatly increased the crystallization rate. The activation energies of the composites were obviously lower than that of pure PTT, and this indicated much easier crystallization of the composites. All these samples exhibited banded spherulites, and the spherulite size gradually decreased with the SSF loading increasing. Subsequent melting behaviors revealed that all of these samples, especially of the composites, exhibited triple melting peaks at all crystallization temperatures studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Crystal morphology, melting behaviors and isothermal crystallization kinetics of SCF/PTT composites

AbstractIsothermal crystallization kinetics, subsequent melting behavior, and the crystal morphology of short carbon fiber and poly(trimethylene terephthalate) composites (SCF/PTT) were investigated by using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The crystal morphology of the composites isothermally crystallized at Tc = 205°C is predominantly banded spherulites observed under polarizing micrographs, while the pattern of banded spherulites changed from ring to serration as the SCF content added into the PTT. Moreover, nonbanded spherulites formed at Tc = 180°C. The commonly used Avrami equation was used to fit the primary stage of the isothermal crystallization. The Avrami exponents n are evaluated to be 1.6–2.0 for the neat PTT and 2.7–3.0 for SCF/PTT composites, and the SCF acting as nucleation agents in composites accelerates the crystallization rate with decreasing the half‐time of crystallization and the sample with SCF component of 2% has the fastest crystallization rate. The crystallization activation energy calculated from the Arrhenius formula suggests that the adding SCF component improved the crystallization ability of the PTT matrix greatly, and the sample with of 2% SCF component has the most crystallization ability. Subsequent melting scans of the isothermally crystallized composites all exhibited triple melting endotherms, in which the more the component of SCF, the lower temperature of the melting peak, indicating the less perfect crystallites formed in those composites. Furthermore, the melting peaks of the same sample are shifted to higher temperature with increasing Tc, suggesting the more perfect crystallites formed at higher Tc. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Thermal properties and phase morphology of melt‐mixed poly(trimethylene terephthalate)/poly(hexamethylene isophthalamide) blends

AbstractThis work examines the thermal properties and phase morphology of melt‐mixed poly(trimethylene terephthalate) (PTT)/poly(hexamethylene isophthalamide) (PA 6I) blends. Two temperatures, i.e., 250 and 260°C, are used to prepare the blends, respectively. Differential scanning calorimetry results indicate the immiscible feature of the blends. It is thus concluded that the ester‐amide interchange reaction hardly occurred in the PTT/PA 6I blends. Depending on the composition and mixing temperature, the crystallization ability of PTT in the blends is either enhanced or hindered. Basically, a lower PA 6I content shifts the PTT melt crystallization to a higher temperature, whereas a higher PA 6I content causes an opposing outcome. The original complex melting behavior of neat PTT becomes more regular after the incorporation of 60 wt % or 80 wt % of PA 6I. Thermogravimetry analyses (TGA) show that the thermal stability of the blends improves as the PA 6I content increases. The two‐phased morphology of the blends is examined by scanning electron microscopy (SEM). Polarized light microscopy (PLM) results reveal that the PTT spherulites become coarser with the inclusion of PA 6I; only smaller/dispersed crystallites are observed in the blend with 20 wt % of PTT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Isothermal crystallization kinetics and melting behaviors of nanocomposites of poly(trimethylene terephthalate) filled with nano‐CaCO3

AbstractThe isothermal crystallization and subsequent melting behavior of poly(trimethylene terephthalate) (PTT) composites filled with nano‐CaCO3 were investigated at designated temperatures with differential scanning calorimetry. The Avrami equation was used to fit the isothermal crystallization. The Avrami exponents were determined to be 2–3 for the neat PTT and PTT/CaCO3 composites. The particles of nano‐CaCO3, acting as nucleating agents in the composites, accelerated the crystallization rate, with the half‐time of crystallization decreasing or the growth rate constant (involving both nucleation and growth rate parameters) increasing. The crystallization activation energy calculated from the Arrhenius formula was reduced as the nano‐CaCO3 content increased from 0 to 2%, and this suggested that nano‐CaCO3 made the molecular chains of PTT easier to crystallize during the isothermal crystallization process. Subsequent melting scans of the isothermally crystallized composites exhibited triple or double melting endotherms: the greater the content was of nano‐CaCO3, the lower the temperature was of the melting peak. The degree of crystallization deduced from the melt enthalpy of composites with the proper concentration of nano‐CaCO3 was higher than that of pure PTT, but it was lower when the nano‐CaCO3 concentration was more than 2%. The transmission electron microscopy pictures suggested that the dispersion state of nano‐CaCO3 particles in the polymer matrix was even when its concentration was no more than 2%, whereas some agglomeration occurred when its concentration was 4%. Polarized microscopy pictures showed that much smaller or less perfect crystals formed in the composites because of the interaction between the molecular chains and nano‐CaCO3 particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Effect of small amount of poly(ethylene naphthalate) on isothermal crystallization and spherulitic morphology of poly(trimethylene terephthalate)

The effect of a small amount of poly(ethylene naphthalate) (PEN) in its blends with poly(trimethylene terephthalate) (PTT) on isothermal melt-crystallization kinetics and spherulitic morphology of the blends was thoroughly investigated. The maximum PEN content in the blends was 9 wt%. Due to the single composition-dependent glass transition temperature ( T g) that was observed for each blend, these blends appeared to be miscible in the amorphous state. After isothermal crystallization from the melt state, the neat PTT and its blends with PEN exhibited either double or triple melting endotherms. The triple endothermic peaks were observed in both the neat PTT and the blends when being crystallized at crystallization temperatures ( T c) of less than or equal to ∼195 °C. The equilibrium melting temperature ( T m 0 ) for the neat PTT was determined based on the linear Hoffman–Weeks extrapolative method to be ∼248 °C. Such values for the blends were found to decrease with the addition and increasing amount of PEN. Both the neat PTT and the blends were isothermally crystallized over the T c range of 190–205 °C. At a given T c, the 97PTT/3PEN blend exhibited a half-time of crystallization ( t 0.5) value that was lower, while it exhibited reciprocal half-time ( t 0.5 - 1 ), Avrami rate constant ( K A), and spherulitic growth rate ( G) values that were greater, than those of the neat PTT. With further increase in the PEN content, the t 0.5 value increased, while the t 0.5 - 1 , K A, and G values decreased. Analysis of the G values based on the Lauritzen–Hoffman's (LH) secondary nucleation theory showed that the neat PTT and the 91PTT/9PEN blend exhibited a regime II→III transition at ∼194 °C (∼467.2 K), while no regime transition was observed for the other two blends. The lateral and the fold surface free energies ( σ and σ e) and the work of chain folding ( q) for the neat PTT and the blends were 19.4, 30.2–46.3 erg cm −2, and 2.4–3.6 kcal mol −1, respectively. Lastly, the effect of both the T c and the PEN content on morphology and texture of the PTT spherulites was also investigated and the results showed that the texture of the spherulites became coarser with increasing T c and PEN content.

Effects of miscible diluent of poly(ether imide) on ring-banded morphology of poly(trimethylene terephthalate)

The melting, crystallization, and self-packed ring patterns in the spherulites of miscible blends comprising poly(trimethylene terephthalate) (PTT) and poly(ether imide) (PEI) were revealed by optical, scanning electron microscopies (PLM and SEM) and differential scanning calorimetry (DSC). Morphology and melting behavior of the miscible PTT/PEI blends were compared with the neat PTT. Ringed spherulites appeared in the miscible PTT/PEI blends at all crystallization temperatures up to 220 °C, whereas at this high temperature no rings were seen in the neat PTT. A postulation was proposed, and interrelations between rings in spherulites and the multiple lamellae distributions were investigated. The specific interactions and the segregation of amorphous PEI were discussed for interpreting the morphological changes of 220 °C-melt-crystallized PTT/PEI samples. Interlamellar segregation of PEI might be associated with multiple lamellae in the spherulites of PTT/PEI blends; therefore, rings were more easily formed in the PTT/PEI blends at all crystallization temperatures. A postulated model of uneven lamellar growth, coupled with periodical spiraling, more properly describes the possible origin of ring bands from combined effects of both interactions and segregation between the amorphous PEI and PTT in blends.

Crystallization kinetics of poly(trimethylene terephthalate)/poly(ether imide) blends

The crystallization kinetics of a melt-miscible blend, consisting of poly(trimethylene terephthalate) (PTT) and poly(ether imide) (PEI) prepared by solution precipitation, has been investigated by means of optical polarized microscopy and differential scanning calorimeter. It was found that both the PTT spherulitic growth rate (G) and overall crystallization rate constant (kn) were depressed, with increasing PEI composition or crystallization temperature (Tc). The kinetic retardation was attributed to the decrease in PTT molecular mobility, and the dilution of PTT concentration due to the addition of PEI, which has a higher glass transition temperature (Tg). According to the Lauritzen–Hoffman theory of secondary nucleation, the crystallization of PTT in blends was similar to that of neat PTT as regime III, n = 4 and regime II, n = 2 growth processes, while the transition point of regime III to II has been shifted from 194°C for neat PTT to 190°C for blends. POLYM. ENG. SCI. 46:89–96, 2006. © 2005 Society of Plastics Engineers

Miscible blends of poly(4‐vinyl phenol)/poly (trimethylene terephthalate)

AbstractA new miscible blend of all compositions comprising poly(4‐vinyl phenol) (PVPh) and poly(trimethylene terephthalate) (PTT) was discovered and reported. The blends exhibit a single composition‐dependent glass transition and homogeneous phase morphology, with no lower critical solution temperature (LCST) behavior upon heating to high temperatures. Interactions and spherulite growth kinetics in the blends were also investigated. The Flory–Huggins interaction parameter (χ12) and interaction energy density (B) obtained from analysis of melting point depression are negative (χ12 = −0.74 and B = −32.49 J cm−3), proving that the PVPh/PTT blends are miscible over a wide temperature range from ambient up to high temperatures in the melt state. FTIR studies showed evidence of hydrogen‐bonding interactions between the two polymers. The miscibility of PVPh with PTT also resulted in a reduction in spherulite growth rate of PTT in the miscible blend. The Lauritzen–Hoffman model was used to analyze the spherulite growth kinetics, which showed a lower fold‐surface free energy (σe) of the blends than that of the neat PTT. The decrease in the fold‐surface free energy has been attributed to disruption of the PTT lamellae exerted by PVPh in an intimately interacted miscible state. Copyright © 2004 Society of Chemical Industry

Effects of crystalline and orientational memory phenomena on the isothermal bulk crystallization and subsequent melting behavior of poly(trimethylene terephthalate)

AbstractThe effects of crystalline and orientational memory phenomena on the subsequent isothermal crystallization and subsequent melting behavior of poly(trimethylene terephthalate) (PTT) were investigated by studying the effect of prior melt‐annealing temperature, Tf, on the subsequent isothermal crystallization kinetics, crystalline structure and subsequent melting behavior of neat and sheared PTT samples. On partial melting, choices of the Tf used to melt the samples played an important role in determining their bulk crystallization rates, in which the bulk crystallization rate parameters studied were all found to decrease monotonically with increasing Tf. The decrease in the values of these rate parameters with Tf continued up to a critical Tf value (ie ca 275 °C for neat PTT samples and ca 280 °C for PTT samples which were sheared at shear rates of 92.1 and 245.6 s−1). Choices of the Tf used to melt neat PTT samples had no effect on the crystal structure formed. The subsequent melting behavior suggested that the Tf used to melt both neat and sheared samples had no effect on the peak positions of the melting endotherms observed and that the observed peak values of these endotherms for all sample types studied were almost identical. Copyright © 2004 Society of Chemical Industry