Surface crystallization of poly(ethylene terephtalate) studied by atomic force microscopy

Poly(ethylene terephtalate) (PET) crystallization was shown by atomic force microscopy (AFM) to occur at 85 °C in the first few nanometers near the polymer-air interface. The surface was fully transformed into spherulites after 30 min, while no signs of bulk crystallization were observed by FTIR. All the observed spherulites presented a nucleation centre, indicating that the crystallization process started at the surface of the film. Tapping mode AFM confirmed that the spherulites were not covered by an amorphous layer. The most probable explanation is a decrease of T_g near the surface. Due to the poor crystallization conditions, the constitutive units of the spherulites were small crystalline blocks. By changing the annealing time, it was possible to produce PET surfaces with different surface fractions consisting of semi-crystalline material (spherulites) and amorphous matrix. This provided a controlled surface heterogeneity on the submicrometer scale, with a contrast in terms of stiffness, roughness and swelling by organic solvents.     

Effect of CO2 on crystallization kinetics of poly(ethylene terephthalate)

The effect of CO₂ on the isothermal crystallization kinetics of poly(ethylene terephthalate), PET, was investigated using a high‐pressure differential scanning calorimeter (DSC), which performed calorimetric measurements while keeping the polymer in contact with presurized CO₂. It was found that the crystallization rate followed the Avrami equation with values of the crystallization kinetic constant dependent on the crystallization temperature and concentration of CO₂ in PET. The presence of CO₂ in the PET increased its overall crystallization rate. CO₂ also decreased the glass transition temperature, T_g, and the melting temperature, T_m. As a result, the observed changes in crystallization rate caused by CO₂ can be qualitatively predicted from the magnitude of T_g depression and that of the equilibrium melting temperature, T_m⁰.     

High-performance semi-interpenetrating polymer networks based on acetylene-terminated sulfone. II. Phase separation and morphology

The dynamic mechanical behavior, phase separation, and morphology of high-performance semi-interpenetrating polymer network (semi-IPN) obtained from acetylene-terminated sulfone (ATS-C) and high-performance thermoplastics have been studied by torsional braid analysis (TBA) and scanning electron microscopy (SEM). All the ATS-C/thermoplastic blends studied are compatible before curing. The addition of ATS-C results in a dramatic reduction in the glass transition temperature (T_g) of the thermoplastic. As the reaction of cure proceeds, the initially compatible blend passes through a stage of partial compatibility to achieve a fully incompatible semi-IPN. SEM observation of the fracturedetched surface reveals the formation of a co-continuous two-phase structure in the semi-IPNs. The connected globule and network morphology of the cured ATS-C phase are dispersed in a matrix of the thermoplastic phase. The size of dispersed particles decreases with increasing T_g of the thermoplastic. The mechanism of phase separation is discussed. © 1994 John Wiley & Sons, Inc.     

Effect of Pre-Melting Time on Crystallization of Poly(ethylene terephthalate)

In this study poly(ethylene terephthalate) (PET) was melted at 300°C, approximately 46°C above the crystalline melting point, T _m, for different times, i.e., Δt _m,=5, 8, and 10 min, and then quenched to different isothermal crystallization temperatures, T _c, ranging from 190°C to 230°C. The effect of pre-melting time, Δt _m, at 300°C on the degree of crystallinity and on crystalline morphology were investigated by differential scanning calorimetry (DSC) and polarized-light microscopy (PLM). After crystallization at low T _c, PLM data revealed the PET contained usual, positive, and unringed spherulites. After crystallization at high T _c PET contained unusual, ringed, and double-extinction spherulites. The experimental results reveal that increasing the pre-melting time Δt _m at 300°C causes an increment in T _c for usual–unusual, unringed–ringed, and positive–double-extinction transitions of the PET spherulites. The experimental results also show that PET with a pre-melting time Δt _m=8 min had higher crystallinity than those with pre-melting times Δt _m=5 and 10 min. These crystallization phenomena were attributed to the different numbers of residual unmelted PET crystallites as a result of the variation in pre-melting time, Δt _m, at 300°C.     

Miscibility and melting behavior of poly(ethylene terephthalate)/poly(trimethylene terephthalate) blends

The miscibility and melting behavior of binary crystalline blends of poly(ethylene terephthalate) (PET)/poly(trimethylene terephthalate) (PTT) have been investigated with differential scanning calorimetry and scanning electron microscope. The blends exhibit a single composition‐dependent glass transition temperature (T_g) and the measured T_g fit well with the predicted T_g value by the Fox equation and Gordon‐Taylor equation. In addition to that, a single composition‐dependent cold crystallization temperature (T_cc) value can be observed and it decreases nearly linearly with the low T_g component, PTT, which can also be taken as a valid supportive evidence for miscibility. The SEM graphs showed complete homogeneity in the fractured surfaces of the quenched PET/PTT blends, which provided morphology evidence of a total miscibility of PET/PTT blend in amorphous state at all compositions. The polymer–polymer interaction parameter, χ₁₂, calculated from equilibrium melting temperature depression of the PET component was ?0.1634, revealing miscibility of PET/PTT blends in the melting state. The melting crystallization temperature (T_mc) of the blends decreased with an increase of the minor component and the 50/50 sample showed the lowest T_mc value, which is also related to its miscible nature in the melting state. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Characterization and properties of sPS/PET/SsPS‐K engineering plastic alloys

The compatibility, crystallization behavior, and mechanical properties of syndiotactic polystyrene (sPS)/polyester (PET)/potassium salt of sulfonated syndiotactic polystyrene (SsPS‐K) were investigated. DMA results showed that all the alloys showed one T_g and the half‐peak width of the sPS/PET/SsPS‐K alloys became narrower compared with that of sPS/PET alloys, which decreased with an increasing content of the SsPS‐K ionomer. The results of DSC showed that the T_m of sPS and PET of the alloys was similar to those of the pure materials and did not change with the content of the SsPS‐K ionomer, while the initial crystallization temperature (T₀) and crystallization temperature at peak (T_p) increased. The crystallization velocity of PET increased with an increasing content of SsPS‐K. The TMA results showed that the alloys could retain the perfect heat proof property of sPS. SEM micrographs showed that the addition of SsPS‐K could reduce the PET domain dimension and enhance the adhesion between the PET domains and the matrix. With an increasing content of SsPS‐K, the PET domain dimension was reduced continuously and dispersed more evenly. The ternary alloys had better mechanical properties and significantly higher unnotched Izod impact strength than those of the alloys without SsPS‐K. When the weight ratio of sPS/PET/SsPS‐K was 85/15/4, the impact strength reached a maximum of 11.5 kJ/m², which was about three times that of pure sPS, and still had a higher tensile strength, flexural strength, and storage modulus, which were 38.8, 54.2, and 1.55 × 10⁴ MPa, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 656–661, 2002     

Isothermal crystallization kinetics in binary miscible blend of poly(ε‐caprolactone)/tetramethyl polycarbonate

The crystallization kinetics of pure poly(ε‐caprolactone) (PCL) and its blends with bisphenol‐A tetramethyl polycarbonate (TMPC) was investigated isothermally as a function of composition and crystallization temperature (T_c) using differential scanning calorimetric (DSC) and polarized optical microscope techniques. Only a single glass‐transition temperature, T_g, was determined for each mixture indicating that this binary blend is miscible over the entire range of composition. The composition dependence of the T_g for this blend was well described by Gordon–Taylor equation with k = 1.8 (higher than unity) indicating strong intermolecular interaction between the two polymer components. The presence of a high T_g amorphous component (TMPC) had a strong influence on the crystallization kinetics of PCL in the blends. A substantial decrease in the crystallization kinetics was observed as the concentration of TMPC rose in the blends. The crystallization half‐time t_0.5 increased monotonically with the crystallization temperature for all composition. At any crystallization temperature (T_c) the t_0.5 of the blends are longer than the corresponding value for pure PCL. This behavior was attributed to the favorable thermodynamics interaction between PCL and TMPC which in turn led to a depression in the equilibrium melting point along with a simultaneous retardation in the crystallization of PC. The isothermal crystallization kinetics was analyzed on the basis of the Avrami equation. Linear behavior was held true for the augmentation of the radii of spherulites with time for all mixtures, regardless of the blend composition. However, the spherulites growth rate decreased exponentially with increasing the concentration of TMPC in the blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3307–3315, 2007     

Sequence analysis and fiber properties of a blend of poly(ethylene terephthalate) and poly(ethylene terephthalate‐co‐4,4′‐bibenzoate)

Blends of poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate‐co‐4,4′‐ bibenzoate) (PETBB) are prepared by coextrusion. Analysis by ¹³C‐NMR spectroscopy shows that little transesterification occurs during the blending process. Additional heat treatment of the blend leads to more transesterification and a corresponding increase in the degree of randomness, R. Analysis by differential scanning calorimetry shows that the as‐extruded blend is semicrystalline, unlike PETBB15, a random copolymer with the same composition as the non‐ random blend. Additional heat treatment of the blend leads to a decrease in the melting point, T_m, and an increase in glass transition temperature, T_g. The T_m and T_g of the blend reach minimum and maximum values, respectively, after 15 min at 270°C, at which point the blend has not been fully randomized. The blend has a lower crystallization rate than PET and PETBB55 (a copolymer containing 55 mol % bibenzoate). The PET/PETBB55 (70/30 w/w) blend shows a secondary endothermic peak at 15°C above an isothermal crystallization temperature. The secondary peak was confirmed to be the melting of small and/or imperfect crystals resulting from secondary crystallization. The blend exhibits the crystal structure of PET. Tensile properties of the fibers prepared from the blend are comparable to those of PET fiber, whereas PETBB55 fibers display higher performance. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1793–1803, 2004     

Thermal,mechanical, and barrier properties of polyethylene terephthalate‐platelet nanocomposites prepared by in situ polymerization

This study used in situ polymerization to prepare polyethylene terephthalate (PET) nanocomposites incorporating Ethoquad‐modified montmorillonite (eMMT), unmodified hectorite (HCT), or phenyl hectorite (phHCT) particles to study the impact of platelet surface chemistry and loading on thermal, mechanical, and gas barrier properties. eMMT platelets reduced the PET crystallization rate without altering the ultimate degree of crystallinity. In contrast, HCT and phHCT platelets accelerated the polymer's crystallization rate and increased its crystallinity. DMA results for thermally‐quenched samples showed that as T increased past glass transition temperature (T_g), HCT and phHCT nanocomposites (and control PET) manifested precipitous drops in G′ followed by increasing G′ due to cold crystallization; in contrast, eMMT nanocomposites had much higher G′ values around T_g. This provides direct evidence of eMMT reinforcement in thermally‐quenched eMMT nanocomposites. These results suggest that eMMT has a strong, favorable interaction with PET, possibly through Ethoquad‐PET entanglement. HCT and phHCT have a fundamentally different interaction with PET that increases crystallization rate and T_g by 11 to 17°C. Water barrier improvement in eMMT nanocomposites agrees with previously published oxygen barrier results and can be rationalized in terms of a tortuous path gas barrier model. POLYM. ENG. SCI., 52:1888–1902, 2012. © 2012 Society of Plastics Engineers     

Low temperature melting behavior of CO2 crystallized modified PETs

Differential scanning calorimetry (DSC) analysis has been performed on modified and commericial amorphous samples of poly(ethylene terephthalate) (PET) crystallized by high pressure carbon dioxide (CO²). Two endothermic peaks are present in the DSC scans of all the carbon dioxide-treated samples. A qualitatively analogous behavior has been detected in the case of amorphous samples heat treated at temperatures slightly exceeding the glass transition temperature of virgin material. Wide angle X-ray scattering analysis has confirmed the structural analogies between samples CO₂ crystallized at 50°C and thermally crystallized slightly above T_g. A differential scanning calorimeter capable of working at high pressure of CO₂ has been adopted in order to examine the effect of carbon dioxide on the crystallization temperature range.     

High resolution solid-state NMR and DSC study of poly(ethylene glycol)-silicate hybrid materials via sol-gel process

Hybrid materials incorporating poly(ethylene glycol) (PEG) with tetraethoxysilane (TEOS) via a sol-gel process were studied for a wide range of compositions of PEG by DSC and high resolution solid-state ¹³C- and ²⁹Si-NMR spectroscopy. The results indicate that the microstructure of the hybrid materials and the crystallization behavior of PEG in hybrids strongly depend on the relative content of PEG. With an increasing content of PEG, the microstructure of hybrid materials changes a lot, from intimate mixing to macrophase separation. It is found that the glass transition temperatures (T_g) (around 373 K) of PEG homogeneously embedded in a silica network are much higher than that (about 223 K) of pure PEG and also much higher in melting temperatures T_m (around 323 K) than PEG crystallites in heterogeneous hybrids. Meanwhile, the lower the PEG content, the more perfect the silica network, and the higher the T_g of PEG embedded in hybrids. An extended-chain structure of PEG was supposed to be responsible for the unusually high T_g of PEG. Homogeneous PEG-TEOS hybrids on a molecular level can be obtained provided that the PEG content in the hybrids is less than 30% by weight. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 139–147, 1998     

Crystallization of poly(ethylene terephthalate) modified with codiols

The nucleation of poly(ethylene terephthalate) (PET) by codiols and olefinic segments was studied. The codiols 1,5‐pentanediol, 1,8‐octanediol, 2,5‐hexanediol, and 1,3‐dihydroxymethyl benzene were copolymerized into PET in a concentration range of 0–10 mol %. The melting (T_m), crystallization (T_c), and glass‐transition (T_g) temperatures were studied. These codiols were found to be able to nucleate PET at low concentrations, probably by lowering the surface free energy of the chain fold. However, the codiols also disturbed the structural order of the polymer, resulting in a decrease in both the T_m and T_c values. The optimum codiol concentration was found to be at around 1 mol %, which is lower than previously reported. A diamide segment N,N′‐bis(p‐carbo‐methoxybenzoyl)ethanediamine (T2T) was found to be a more effective nucleator than the codiols; however, no synergy was observed between the nucleating effect of the diamide segment T2T and that of the codiol. An olefinic diol (C₃₆‐diol) with a molecular weight of 540 g/mol was also copolymerized into PET in a concentration range of 0–21 wt %. Only one T_g was observed in the resulting copolymers, suggesting that the amorphous phases of PET and the C₃₆‐diol are miscible. The main effect of incorporating the C₃₆‐diol into PET was the lowering of the T_g; thus, the C₃₆‐diol is an internal plastifier for PET. The C₃₆‐diol had little effect on the T_m value; however, the T_c value actually increased in the 11.5 wt % copolymer. As the T_g decreased and the T_c increased, the crystallization window also increased and thereby the likelihood of crystallization. Therefore, the thermally stable C₃₆‐diol appears to be an interesting compound that may be useful in improving the crystallization of PET. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2676–2682, 2001     

Phase structure and properties of poly(ethylene terephthalate)/high‐density polyethylene based on recycled materials

Blends based on recycled high density polyethylene (R‐HDPE) and recycled poly(ethylene terephthalate) (R‐PET) were made through reactive extrusion. The effects of maleated polyethylene (PE‐g‐MA), triblock copolymer of styrene and ethylene/butylene (SEBS), and 4,4′‐methylenedi(phenyl isocyanate) (MDI) on blend properties were studied. The 2% PE‐g‐MA improved the compatibility of R‐HDPE and R‐PET in all blends toughened by SEBS. For the R‐HDPE/R‐PET (70/30 w/w) blend toughened by SEBS, the dispersed PET domain size was significantly reduced with use of 2% PE‐g‐MA, and the impact strength of the resultant blend doubled. For blends with R‐PET matrix, all strengths were improved by adding MDI through extending the PET molecular chains. The crystalline behaviors of R‐HDPE and R‐PET in one‐phase rich systems influenced each other. The addition of PE‐g‐MA and SEBS consistently reduced the crystalline level (χ_c) of either the R‐PET or the R‐HDPE phase and lowered the crystallization peak temperature (T_c) of R‐PET. Further addition of MDI did not influence R‐HDPE crystallization behavior but lowered the χ_c of R‐PET in R‐PET rich blends. The thermal stability of R‐HDPE/R‐PET 70/30 and 50/50 (w/w) blends were improved by chain‐extension when 0.5% MDI was added. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Processing characteristics,structure development,and properties of uni and biaxially stretched poly(ethylene 2,6 naphthalate) (PEN) films

Poly(ethylene 2,6, naphthalene dicarboxilate), PEN, is very similar to poly(ethylene terephthalate), PET, in its chemical structure and was, therefore, expected to exhibit similar processing characteristics. We, however, observed a few problems during stretching of PEN, the most important of which was necking behavior at 145°C, which is between T_g (117°C) and T^cc (195°C). This is usually observed in PET only when it is stretched close to or below T_g. At temperatures between T_g and T_cc (cold crystallization temperature) PET stretches rather uniformly. The temperature window for film stretching appears to be rather wide, but our results indicate that this is not the case. Films stretched to high stretch ratios become uniform due to propagation and final disappearance of necks as a result of stress hardening. Our attempts at stretching these films at higher temperatures indicated that necking is eliminated, but so is stress induced crystallization, which causes stress hardening (unless high stretching rates are employed). The presence of stress hardening is essential for obtaining high quality, uniform films of these polymers. In addition, at high temperatures thermally activated crystallization which starts dominating the structure development, detrimentally affects the general appearance of the films. In brief, the PEN films we investigated have a narrower processing window than was anticipated based on their thermal behavior alone. At elevated temperatures the films are sensitive to the rate of stretching even more than typical PET processed at comparable conditions. The uniformity of the films depends on the stretch ratio, stretching mode, ratio(s) and rates and temperature. WAXS studies on the films indicate that the macromolecules packed into the low temperature crystal modification. In addition, WAXS pole figure studies suggest that naphthalene planes preferentially orient parallel to the film surface during biaxial stretching. The biaxially stretched films were observed to exhibit a bimodal chain orientation as evidenced by pole figure analysis of the (010) planes.     

Effect of moisture on the crystallization behavior of PET from the quenched amorphous phase

The dependence on the moisture content of the glass transition temperature (T_g) and of the crystallization temperature from the quenched amorphous phase (T_c) for poly(ethylene terephthalate) (PET) samples is studied by differential scanning calorimetry. For low moisture contents, very large and reversible decreases of T_c but small decreases of T_g are observed. This indicates that the strong increase of nucleation rate observed for PET in the presence of moisture is not related to the plasticizing effect that produces significant T_g changes.     

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.     

Influence of composition,crystallization conditions and melt phase structure on solid morphology,kinetics of crystallization and thermal behavior of binary polymer/polymer blends

Results of an investigation on the morphology, the crystallization and the thermal behavior of several binary crystallizable blends are reported. The composition, molecular mass and crystallization conditions strongly influence the crystallization and the thermal behavior as well as the overall morphology of crystallizable binary blends. Quantities such as nucleation density (N), radial growth rate (G) of spherulites, overall rate of crystallization (K), and equilibrium melting temperature (T_m) are strongly dependent upon composition, crystallization conditions, and molecular mass of components. The type of dependence is to be related to the physical state of the melt, which, at the crystallization temperature, is in equilibrium with or coexists with the developing solid phase. In the ease of compatible blends such as poly(ethylene oxide)/poly(methyl methacrylate) the depression observed for G and T_m is mainly to be attributed to the diluent effect of the non-crystallizable component. For such a blend it is found that, after crystallization, the non-crystallizable component is trapped in intralamellar regions increasing the distance between adjacent lamellae. Depression of G, in the case of incompatible blends such as isotactic polypropylene/rubbers is mainly accounted for by rejection and deformation of rubber drops. The coexistence during crystallization of different processes such as molecular fractionation and segregation, preferential inclusion or dissolution of molecules with lower molecular mass and/or high degree of steric disorder of the crystallizable component in the phase rich in non-crystallizable component and vice versa may explain some minima observed in the plots of T and T^m, vs. composition in the case of blends semicompatible in the melt. It was found that the addition of a second non-crystallizable component causes drastic variations on some morphological and structural quantities of the semicrystalline matrix (isotactic polypropylene or nylon 6) such as the shape, dimensions, and regularity of spherulites and interspherulite boundary regions and lamella and interlamella thickness. In some cases the formation of new boundary lines connecting occluded particles are also observed. Such phenomena may have great importance on crack propagation and on impact behavior as well as on the tensile mechanical properties of binary blends characterized by a semicrystalline polymer component with a relatively high T^g and a rubber-like component with a lower T^g.     

Effects of molecular weight on phase structure of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) blends

The phase structure of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) (PET/PEN) blends was studied in relation to the molecular weight. The samples were prepared by both solution blends, which showed two glass‐transition temperatures (T_g), and melt blends (MQ), which showed a single T_g, depending on the composition of the blends. The T_g of the MQ series was independent of the molecular weight of the homopolymer, although the degree of transesterification in the blends was affected by the molecular weight. The MQ series showed two exotherms during the heating process of a differential scanning calorimetry scan. The peak temperature and the heat flow of the exotherms were affected by the molecular weight of the homopolymers. The strain‐induced crystallization of the MQ series suggested the independent crystallization of PET and PEN. Based on the results, a microdomain structure of each homopolymer was suggested. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2428–2438, 2005     

Study of the amorphous phase in semicrystalline poly(ethy1ene terephthalate) via dynamic mechanical thermal analysis

Summary Characters of amorphous phase in semicrystalline poly(ethy1ene terephthalate) (PET) were investigated systematically via dynamic mechanical thermal analysis (DMTA) in this paper. It was found that the storage modulus (E') and the glass transition temperature (T_g) of semicrystalline PET changed with the degree of crystallinity (X_c). T_g showed good linearity with X_c. However, neither reduction of E' in the T_g region (ΔlgE') nor loss tangent (tanδ) at the T_g presented linearity with X_c, which suggests that the two-phase model was not suitable for semicrystalline PET. It was also confirmed that the physical aging reduced the chain segmental mobility, producing higher T_g. Received: 22 July 2OO2/Revised version: 19 September 2002/ Accepted: 23 September 2002 Correspondence to Qingrong Fan e-mail: qrfan@pplas.icas.ac.cn, Tel.: +86-10-62563065, Fax: +86-10-62559373     

New soybean oil–styrene–divinylbenzene thermosetting copolymers. I. Synthesis and characterization

The cationic copolymerization of regular soybean oil, low‐saturation soybean oil (LoSatSoy oil), or conjugated LoSatSoy oil with styrene and divinylbenzene initiated by boron trifluoride diethyl etherate (BF₃·OEt₂) or related modified initiators provides viable polymers ranging from soft rubbers to hard, tough, or brittle plastics. The gelation time of the reaction varies from 1 × 10² to 2 × 10⁵ s at room temperature. The yields of bulk polymers are essentially quantitative. The amount of crosslinked polymer remaining after Soxhlet extraction ranges from 80 to 92%, depending on the stoichiometry and the type of oil used. Proton nuclear magnetic resonance spectroscopy and Soxhlet extraction data indicate that the structure of the resulting bulk polymer is a crosslinked polymer network interpenetrated with some linear or less‐crosslinked triglyceride oil–styrene–divinylbenzene copolymers, a small amount of low molecular weight free oil, and minor amounts of initiator fragments. The bulk polymers possess glass‐transition temperatures ranging from approximately 0 to 105°C, which are comparable to those of commercially available rubbery materials and conventional plastics. Thermogravimetric analysis (TGA) indicates that these copolymers are thermally stable under 200°C, with temperatures at 10% weight loss in air (T₁₀) ranging from 312 to 434°C, and temperatures at 50% weight loss in air (T₅₀) ranging from 445 to 480°C. Of the various polymeric materials, the conjugated LoSatSoy oil polymers have the highest glass‐transition temperatures (T_g) and thermal stabilities (T₁₀). The preceding properties that suggest that these soybean oil polymers may prove useful where petroleum‐based polymeric materials have found widespread utility. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 658–670, 2001