The impact of cupric ion on thermo‐oxidative degradation of chitosan

The thermal degradation of chitosan and chitosan–cupric ion compounds in air was studied using thermogravimetric and differential thermal analyses in the temperature range 30–600 °C. The impact of cupric ion on the thermo‐oxidative degradation of chitosan was investigated. Fourier transform infrared and X‐ray diffraction analyses were utilized to determine the microstructure of the chitosan–cupric ion compounds. Kinetic parameters such as activation energy, pre‐exponential factor, Gibbs energy, and enthalpy and entropy of activation were determined using the Coats–Redfern equation. The results show that the thermo‐oxidative degradation of chitosan and chitosan–cupric ion compounds is a two‐stage reaction. The impact of cupric ion on the thermo‐oxidative degradation of chitosan is significant, and all thermodynamic parameters indicate that the thermo‐oxidative degradation of chitosan and chitosan–cupric ion compounds is a non‐spontaneous process and proceeds via a mechanism involving nucleation and growth, with an Avrami–Erofeev function (A₄) with the integral form [?ln(1 ? α)]⁴. Copyright © 2010 Society of Chemical Industry     

气氛对壳聚糖及其铜离子混合物热降解的影响

利用热重分析(TGA)和差热分析(DTA)研究了壳聚糖及其铜离子混合物在氮气气氛和空气气氛中的热降解行为,探讨了气氛对壳聚糖及其铜离子混合物热降解的影响,并采用FTIR、X-射线衍射对壳聚糖铜离子混合物进行了表征.结果显示,壳聚糖及其铜离子混合物的热降解和热氧降解分三个阶段进行:第一阶段为材料失水,为吸热反应;第二阶段为主链脱乙酰和糖苷键的裂解,为放热反应;第三阶段为吡喃环的裂解和炭化残渣的分解,为放热反应.气氛对壳聚糖第一、第二阶段的降解影响较小,对第三阶段的降解影响较大.     

Thermogravimetric analysis of chitosan

The thermal degradation of chitosan at different heating rates B in nitrogen was studied by thermogravimetric analysis. The results indicate that the thermal degradation of chitosan in nitrogen is a one‐step reaction. The degradation temperatures increase with B. Experimentally, the initial degradation temperature (T₀) is (1.049B + 326.8)°C; the temperature at the maximum degradation rate, that is, the peak temperature on a differential thermogravimetry curve (T_p), is (1.291B + 355.2)°C; and the final degradation temperature (T_f) is (1.505B + 369.7)°C. The degradation rates at T_p and T_f are not affected by B, and their average values are 50.17% and 72.16%, respectively, the maximum thermal degradation reaction rate, that is, the peak height on a differential thermogravimetry curve (R_p), increases with B. The relationship between B and R_p is R_p = (1.20B + 2.44)% min^?1. The thermal degradation kinetic parameters are calculated with the Ozawa–Flynn–Wall method. The reaction activation energy (E) and frequency factor (A) change with an increasing degree of decomposition, and the variable trends of the two kinetic parameters are similar. The values of E and A increase remarkably during the initial stage of the reaction, then keep relatively steady, and finally reach a peak during the last stage. The velocity constants of the thermal degradation vary with the degree of decomposition and increase with the reaction temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and characterization of the copolymer containing N‐pyridyl bi(methacryl)imide unit

The copolymer of methacrylic acid anhydride and N‐2‐pyridyl bi(methacryl)imide was prepared based on the reaction of polymethacrylic acid with 2‐pyridylamine. The molecular structure was characterized by ¹H‐NMR, FTIR, UV–Vis, and circular dichroism techniques. The physical properties of polymethacrylic acid change significantly after an introduction of 6 mol % N‐2‐pyridyl bi(methacryl)imide unit. In particular, the thermal degradation of the polymer was systematically studied in flowing nitrogen and air from room temperature to 800°C by thermogravimetry at a constant heating rate of 10°C/min. In both atmospheres, a four‐stage degradation process of the copolymer of methacrylic acid anhydride and N‐2‐pyridyl bi(methacryl)imide was revealed. The initial thermal degradation temperature T_d, and the first, second, and third temperatures at the maximum weight‐loss rate T_dm1, T_dm2, and T_dm3 all decrease with decreasing sample size or changing testing atmosphere from nitrogen to air, but the fourth temperature at the maximum weight‐loss rate T_dm4 increases. The maximum weight‐loss rate, char yield at elevated temperature, four‐stage decomposition process, and three kinetic parameters of the thermal degradation were discussed in detail. It is suggested that the copolymer of methacrylic acid anhydride and N‐2‐pyridyl bi(methacryl)imide exhibits low thermal stability and multistage degradation characteristics. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1673–1678, 2002     

Thermal characteristics and pyrolysis of methyl‐di(phenylethynyl)silane resin

Thermal stability of a recently synthesized polymeric methyl‐di(phenylethynyl)silane (MDPES) resin was studied using a number of thermal and spectrometric analytical techniques. The polymer exhibits extremely high thermal stability. Thermogravimetric analysis (TGA) shows that the temperature of 5% weight loss (T_d5) was 615°C and total weight loss at 800°C was 8.9%, in nitrogen atmosphere, while in air, T_d5 was found to be 562°C, and total weight loss at 800°C was found to be 55.8% of the initial weight. Differential thermal degradation (DTG) studies show that the thermal degradation of MDPES resin was single‐stage in air and two‐stage in nitrogen. The thermal degradation kinetics was studied using dynamic TGA, and the apparent activation energies were estimated to be 120.5 and 114.8 kJ/mol in air, respectively, by Kissinger and Coats–Redfern method. The white flaky pyrolysis residue was identified to be silicon dioxide by FTIR and EDS, indicating that the thermal stability of polymer may be enhanced by the formation of a thin silicon dioxide film on the material surface. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 103: 605–610, 2007     

Characterization of PVC cable insulation materials and products obtained after removal of additives

Organic solvents cyclohexane, dichloromethane, hexane, and tetrahydrofuran were tested to separate the dioctylphthalate (DOP) as plasticizer from the poly(vinyl chloride) (PVC)‐based materials. It was found that the efficiency of ultrasound‐enhanced hexane extraction of the DOP from PVC is 70% and the efficiency of the separation of the DOP and other compounds from the PVC by dissolution in THF followed by subsequent precipitation was 98–99%. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to characterize the thermal behavior of PVC materials before and after extraction of plasticizers. It was found that during heating in the range 20–800°C the total mass loss measured for the nontreated, extracted, and precipitated PVC samples was 71.6, 66.6, and 97%, respectively. In the temperature range 200–340°C, the release of DOP, HCl, and CO₂ was observed by simultaneous thermogravimetry (TG)/FTIR. The effect of plasticizers on thermal behavior of PVC‐based insulation material was characterized by DSC in the range ?40–140°C. It was found that, concerning the PVC cable insulation material before treatment, the value of the glass transition temperature (T_g) was 1.4°C, whereas for the PVC sample extracted by hexane, the value of T_g was 39.5°C and for the PVC dissolved in THF and subsequently precipitated, the value of T_g was 80.4°C. Moreover, the PVC samples after extraction of plasticizers, fillers, and other agents were tested to characterize their thermal degradation. The TG and FTIR results of chemically nontreated, extracted, and precipitated samples were compared. The release of DOP, HCl, CO₂, and benzene was studied during thermal degradation of the samples by FTIR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 788–795, 2006     

Synthesis and properties of castor oil-based polyurethane containing short fluorinated segment

This study successfully incorporated a short-segment fluorine-containing chain extender (2,2,3,3-tetrafluoro-1,4-butanediol [TF]) into castor oil-based polyurethane (COPU) to synthesize TF/COPUs. The interactions between TF and COPU components were identified by Fourier transform infrared and X-ray photoelectron spectroscopies, the results revealed that the increase in the TF content increased the van der Waals forces in C F…CO and the hydrogen bonding force in C F…H N. Atomic force microscopy indicated that the addition of more TF contributed to a higher level of microphase separation in the TF/COPUs. Thermogravimetric analysis showed that the TF component can enhance the thermal resistance of TF/COPUs. Differential scanning calorimetry and dynamic mechanical analysis indicated that the glass transition temperature (T_g) of TF/COPUs increased with the TF content. The stress–strain testing showed that the tensile strength and elongation at break values decreased with the TF content. This tensile behavior may be due to the molecular weight of a TF/COPU decreased with the TF content as evidenced by the gel permeation chromatography results. The hydrolytic degradation tests of dipping TF/COPUs in 3 wt% NaOH solution indicated that TF could lower the surface free energy and enhance the degradation stability of TF/COPUs.     

Thermogravimetric analysis of methyl methacrylate‐graft‐natural rubber

The thermal degradations of methyl methacrylate‐graft‐natural rubber (MG) at different heating rates (B) in nitrogen were studied by thermogravimetric analysis. The results indicate that the thermal degradation of MG in nitrogen is a one‐step reaction. The degradation temperatures increase along with the increment of heating rates. The temperature of initial degradation (T₀) is 0.448B + 362.4°C, the temperature at maximum degradation rate, that is, the peak temperature on a differential thermogravimetric curve (T_p) is 0.545B + 380.7°C, and the temperature of final degradation (T_f) is 0.476B + 409.4°C. The degradation rate at T_p is not affected by B, and its average value is 48.9%; the degradation rate at T_f is not affected by B either, and its average value is 99.3%. The reaction order (n) is 2.1 and is not affected by B. The reaction activation energy (E) and the frequency factor (A) increase along with B, and the apparent reaction activation energy (E₀) is 254.6 kJ/mol. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2952–2955, 2002     

Thermal analyses of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

Thermal analyses of poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(HB–HV)], and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(HB–HHx)] were made with thermogravimetry and differential scanning calorimetry (DSC). In the thermal degradation of PHB, the onset of weight loss occurred at the temperature (°C) given by T_o = 0.75B + 311, where B represents the heating rate (°C/min). The temperature at which the weight-loss rate was at a maximum was T_p = 0.91B + 320, and the temperature at which degradation was completed was T_f = 1.00B + 325. In the thermal degradation of P(HB–HV) (70:30), T_o = 0.96B + 308, T_p = 0.99B + 320, and T_f = 1.09B + 325. In the thermal degradation of P(HB–HHx) (85:15), T_o = 1.11B + 305, T_p = 1.10B + 319, and T_f = 1.16B + 325. The derivative thermogravimetry curves of PHB, P(HB–HV), and P(HB–HHx) confirmed only one weight-loss step change. The incorporation of 30 mol % 3-hydroxyvalerate (HV) and 15 mol % 3-hydroxyhexanoate (HHx) components into the polyester increased the various thermal temperatures T_o, T_p, and T_f relative to those of PHB by 3–12°C (measured at B = 40°C/min). DSC measurements showed that the incorporation of HV and HHx decreased the melting temperature relative to that of PHB by 70°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 90–98, 2001     

Study on hot air aging and thermooxidative degradation of peroxide prevulcanized natural rubber latex film

The air‐aging process at 120°C and the thermooxidative degradation of peroxide prevulcanized natural rubber latex (PPVL) film were studied with FTIR and thermal gravity (TG) and differential thermal gravity (DTG) analysis, respectively. The result of FTIR shows that the ? OH and ? COOH absorption of the rubber molecules at IR spectrum 3600–3200 cm^?1, the ? C?O absorption at 1708 cm^?1, and the ? C? OH absorption of alcohol at 1105 and 1060 cm^?1 increased continuously with extension of the aging time, but the ? CH₃ absorption of saturated hydrocarbon at 2966 and 2868 cm^?1, the ? CH₃ absorption at 1447 and 1378 cm^?1, and the C?C absorption at 835 cm^?1 decreased gradually. The result of TG‐DTG shows that the thermal degradation reaction of PPVL film in air atmosphere is a two‐stage reaction. The reaction order (n) of the first stage of thermooxidation reaction is 1.5; the activation energy of reaction (E) increases linearly with the increment of the heating rate, and the apparent activation energy (E₀) is 191.6 kJ mol^?1. The temperature at 5% weight loss (T_0.05), the temperature at maximum rate of weight loss (T_p), and the temperature at final weight loss (T_f) in the first stage of degradation reaction move toward the high temperature side as the heating rate quickened. The weight loss rate increases significantly with increment of heating rate; the correlation between the weight loss rate (α_p) of DTG peak and the heating rate is not obvious. The weight loss rate in the first stage (α_f1) rises as the heating rate increases. The final weight loss rate in second stage (α_f2) has no reference to heating rate; the weight loss rate of the rubber film is 99.9% at that time. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3196–3200, 2004     

Chitin derivatives. II. Time–temperature–transformation cure diagrams of the chitosan amidization process

The transformation of the salts of chitosan with acetic and propionic acid, chitosonium acetate and chitosonium propionate, into chitin or the respective homolog of amidized chitosan has been described on the basis of time–temperature–transformation (TTT) cure diagrams. The time to vitrification at various isothermal cure temperatures (T_c) was determined using dynamic mechanical thermal analysis. The time to full cure was derived using a T_g–T_c cure time relationship according to the method of Peng and Gillham, as well as by an extrapolation procedure. Consequently, TTT cure diagrams describing the temperature-driven regeneration process include full cure and vitrification curves. As in thermosets, this transformation displays an S-shaped vitrification curve, and the time to full cure increases with decreasing cure temperature. The time to full cure is very remote from the time to vitrification, and this is attributed to the tendency of vitrification to prevent full cure from being attained. The activation energies for vitrification of chitosonium acetate and chitosonium propionate derived from an Arrhenius equation are similar. This suggests that the same mechanism governs glass formation in the N-acetyl and N-propionyl-glucosamine derivatives. Additionally, the morphology of amidized chitosan and native chitin was examined using X-ray diffraction and FTIR analysis. X-ray diffraction results indicate that amidized chitosan is an amorphous material, whereas native chitin is crystalline. FTIR suggests the existence of hydrogen-bonded amide groups in native chitin but not in amidized chitosan. This difference in morphology between amidized chitosan and native chitin is accounted for in terms of the influence of glass formation in the former. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1879–1889, 1999     

Thermal stability of polyurethane elastomers before and after UV irradiation

In this work, we investigated the thermal degradation behavior of segmented polyurethane (PUR) elastomers before and after UV irradiation. The thermal degradation of PUR elastomers was studied over the temperature range of 25–600°C in an atmosphere of nitrogen using thermal gravimetric analysis (TGA). Four series of PUR elastomers derived from poly(oxytetramethylene)glycol (PTMO) of 1000 and 2000 molecular weight and poly(caprolactone glycol) (PCL) of 1250 molecular weight, 4,4′‐diphenylmethane diisocyanate (MDI), and 4,4′‐dicyclohexylmethane diisocyanate (H₁₂MDI) and 1,4‐butanediol as an chain extender were synthesized by the prepolymer method. The derivative thermogravimetric (DTG) peaks observed in the experiments indicated that PUR elastomers degraded through two steps. We attributed the first step to degradation of the hard segment. The second degradation step could be ascribed to degradation of the soft segment. We found that the PUR elastomers based on poly(ester polyol) and aromatic diisocyanate exhibit better thermal stability than that of PUR elastomers based on the poly(ether polyol) soft segment in both steps of degradation. The thermal degradation is more prevalent in PUR elastomers based on cycloaliphatic diisocyanate. The higher values of the temperature of initial decomposition (Tⁱ) indicate a higher thermal stability of UV‐exposed elastomers on the beginning of degradation. This may be due to the formation of a crosslinking structure in the presence of UV irradiation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 864–873, 2001     

壳聚糖季铵盐铜配合物的热降解行为研究

采用热重分析(TG)研究壳聚糖季铵盐铜配合物在30℃～600℃的温度范围内的热降解行为,探讨壳聚糖季铵盐铜配合物的热稳定性。研究结果表明:壳聚糖季铵盐铜配合物的热降解为一步反应,取代度对壳聚糖季铵盐的热降解有明显的影响,壳聚糖季铵盐铜配合物的特征降解温度都随取代度的增加而降低。     

Studies on the thermal properties of poly(phenylene sulfide amide)

Thermal properties of poly(phenylene sulfide amide) (PPSA) prepared using sodium sulfide, sulfur, and thiourea as sulfur sources which reacted with dichlorobenzamide (DCBA) and alkali in polar organic solvent at the atmospheric pressure, were studied. The glass transition temperature (T_g), melting point temperature (T_m), and melting enthalpy (ΔH_m) of the related polymers were obtained by use of differential scanning calorimetry analysis. The results are: T_g = 103.4–104.5°C, T_m = 291.5–304.7°C, and ΔH_m = 104.4–115.4 J/g. Thermal properties such as thermal decomposition temperature and decomposition kinetics were investigated by thermogravimetric analysis under nitrogen. The initial and maximum rate temperatures of degradation were found to be 401.5–411.7°C and 437–477°C, respectively. The parameters of thermal decomposition kinetics of PPSAs were worked out to be: activation energy of degradation was 135 to 148 kJ/mol and the 60-s half-life temperature was 360 to 371°C. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1227–1230, 1997     

Thermal degradation of poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) as studied by TG,TG–FTIR,and Py–GC/MS

The thermal degradation kinetics of poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [poly(HB–HV)] under nitrogen was studied by thermogravimetry (TG). The results show that the thermal degradation temperatures (T_o, T_p, and T_f) increased with an increasing heating rate (B). Poly(HB–HV) was thermally more stable than PHB because its thermal degradation temperatures, T_o(0), T_p(0), and T_f(0)—determined by extrapolation to B = 0°C/min—increased by 13°C–15°C over those of PHB. The thermal degradation mechanism of PHB and poly(HB–HV) under nitrogen were investigated with TG–FTIR and Py–GC/MS. The results show that the degradation products of PHB are mainly propene, 2‐butenoic acid, propenyl‐2‐butenoate and butyric‐2‐butenoate; whereas, those of poly(HB–HV) are mainly propene, 2‐butenoic acid, 2‐pentenoic acid, propenyl‐2‐butenoate, propenyl‐2‐pentenoate, butyric‐2‐butenoate, pentanoic‐2‐pentenoate, and CO₂. The degradation is probably initiated from the chain scission of the ester linkage. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1530–1536, 2003     

Thermal studies: A comparison of the thermal properties of different oligomers by thermogravimetric techniques

Thermal properties of conventional organic oligomers and organically modified ceramic hybrid materials (Ormoresin) were characterized and compared by using thermogravimetric techniques. Thermal properties were compared in terms of initial thermal decomposition temperature (T₀, which is the temperature at which 5% weight loss occurred), the temperature at which 50% weight loss occurred (T₅₀), and the percentage of residue remained at 600°C. Organically modified ceramic resins are found to have improved thermal stability. It is also found that the type of inorganic material incorporated in organically modified ceramics resin (Ormoresin) has considerable influence on its thermal characteristics. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 977–985, 2004     

Grafting of poly(3‐hydroxyalkanoate) and linoleic acid onto chitosan

Poly(3‐hydroxy octanoate) (PHO), poly(3‐hydroxy butyrate‐co‐3‐hydroxyvalerate) (PHBV), and linoleic acid were grafted onto chitosan via condensation reactions between carboxylic acids and amine groups. Unreacted PHAs and linoleic acid were eliminated via chloroform extraction and for elimination of unreacted chitosan were used 2 wt % of HOAc solution. The pure chitosan graft copolymers were isolated and then characterized by FTIR, ¹³C‐NMR (in solid state), DSC, and TGA. Microbial polyester percentage grafted onto chitosan backbone was varying from 7 to 52 wt % as a function of molecular weight of PHAs, namely as a function of steric effect. Solubility tests were also performed. Graft copolymers were soluble, partially soluble or insoluble in 2 wt % of HOAc depending on the amount of free primary amine groups on chitosan backbone or degree of grafting percent. Thermal analysis of PHO‐g‐Chitosan graft copolymers indicated that the plastizer effect of PHO by means that they showed melting transitions T_ms at 80, 100, and 113°C or a broad T_ms between 60.5–124.5°C and 75–125°C while pure chitosan showed a sharp T_m at 123°C. In comparison of the solubility and thermal properties of graft copolymers, linoleic acid derivatives of chitosan were used. Thus, the grafting of poly(3‐hydroxyalkanoate) and linoleic acid onto chitosan decrease the thermal stability of chitosan backbone. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:81–89, 2007     

Epoxidized dimeric acid methyl ester derived from rubber seed oil and its application as secondary plasticizer

A novel plasticizer epoxidized dimeric acid methyl ester (EDAMe) based on rubber seed oil was synthesized. Chemical structure of EDAMe was characterized by Fourier transform infrared (FTIR) and gel permeation chromatography (GPC). Effects of EDAMe as secondary plasticizer and its substitution of commercial plasticizer dioctyl terephthalate (DOTP) in soft poly(vinyl chloride) (PVC) films were studied. The thermal properties, mechanical properties and migration stabilities of PVC films were explored with DMA, TG, TG–FTIR, dynamic thermal stability analysis, tensile and migration tests. The results indicated that the epoxidized rubber seed oil based ester has significantly higher thermal stability than DOTP. When DOTP was substituted with 20% (m/m) EDAMe, the results of initial decomposition temperature (T_i), 10% and 50% mass loss temperatures (T₁₀ and T₅₀), and the first maximum weight‐loss temperature rate (T_P1) reached 267.2 °C, 263.5 °C, 307.3 °C and 298.9 °C, respectively. Furthermore, flexibility of the obtained PVC films enhanced significantly with the adding of EDAMe. The migration stabilities of EDAMe was also investigated and showed good migration resistance. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43668.     

Study on the thermal degradation of epoxidized natural rubber

The thermal degradation and thermooxidative degradation of epoxidized natural rubber (ENR) were studied by thermogravimetry (TG). In the thermal degradation of ENR, the initial temperature of weight loss T₀ = 1.20B + 348, the temperature of maximum weight loss rate T_p = 1.07B + 392, and the final temperature of weight loss T_f = 0.77B + 445. The C_p, which corresponds to the degradation rate at temperature T_p, increases along with the heating rate B and its mean value is 43%, but C_f, which corresponds to the degradation rate at temperature T_f, is not affected by the heating rate, and its average value is close to 100%. As in the thermooxidative degradation, T₀ = 1.84B + 246, T_p = 0.30B + 378, and T_f = 2.27B + 584. The value of C_p increases along with the heating rate B and its mean value is 36%, but C_f is not affected by the heating rate and the average value approximately equals 100%. The thermal degradation in nitrogen could be a one-step reaction, whereas the thermooxidative degradation has a multiple-step reaction. The reactive environment has a great effect on the thermal degradation of ENR and the difference of the mechanisms of the two reaction systems is obvious. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2207–2211, 1998     

Starch‐g‐polycaprolactone copolymerization using diisocyanate intermediates and thermal characteristics of the copolymers

Starch‐g‐polycaprolactone copolymers were prepared by two‐step reactions. The diisocyanate‐terminated polycaprolactone (NCO–PCL) was prepared by introducing NCO on both hydroxyl ends of PCL using diisocyanates (DI) at a molar ratio between PCL and DI of 2:3. Then, the NCO–PCL was grafted onto corn starch at a weight ratio between starch and NCO–PCL of 2:1. The chemical structure of NCO–PCL and the starch‐g‐PCL copolymers were confirmed by using FTIR and ¹³C‐NMR spectrometers, and then the thermal characteristics of the copolymers were investigated by DSC and TGA. By introducing NCO to PCL (M_n : 1250), the melting temperature (T_m ) was reduced from 58 to 45°C. In addition, by grafting the NCO–PCL (35–38%) prepared with 2,4‐tolylene diisocyanate (TDI) or 4,4‐diphenylmethane diisocyanate (MDI) onto starch, the glass transition temperatures (T_g 's) of the copolymers were both 238°C. With hexamethylene diisocyanate (HDI), however, T_g was found to be 195°C. The initial thermal degradation temperature of the starch‐g‐PCL copolymers were higher than that of unreacted starch (320 versus 290°C) when MDI was used, whereas the copolymers prepared with TDI or HDI underwent little change. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 986–993, 2000