Polyurethanes Based on Castor Oil: Kinetics,Chemical, Mechanical and Thermal Properties

Polyurethanes based on vegetable oil were synthesized with castor oil and toluene diisocyanate, isophorone diisocyanate or hexamethylene diisocyanate, using dibutyltin dilaurate as a catalyst. The effects of the nature of the diisocyanate on the evolution of the kinetics, as well as the physical and mechanical properties and the thermal stability, of the different synthesized polyurethanes were investigated, and these complement data from the literature on equivalent systems. The polymerization kinetics, degree of swelling and mechanical properties were greatly affected by the diisocyanate nature, whereas the rheological properties and thermal stability were found to be similar for all polyurethanes.

     

Thermal stability of polyhydroxyalkanoates

In this study, we examined the thermal decomposition of polyhydroxyalkanoates (PHAs) such as the homopolymer poly(3‐hydroxybutyrate) and the copolymer poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate). They are biodegradable polymers that can replace plastics produced from nonrenewable resources, such as polypropylene. The biopolymers we analyzed were commercial PHAs [obtained by means of pure cultures, with hydroxyvalerate (HV) contents of 0 and 10.4 mol %] and biopolymers produced in our laboratories (by means of an enriched activated sludge at two different organic loads, 8.5 and 20 gCOD/L, with a HV content of 20 mol %). To process these biopolymers, it is important to know their thermal stability. For this reason, thermal degradation in air by means of dynamic thermogravimetry (TG) was carried out. The TG data were adjusted to the nth‐order general analytical equation to evaluate the best order of the reaction, the temperatures of the onset and end of thermal decomposition, and the kinetic parameters. The latter were also calculated by means of other integral and differential methods and compared to those obtained by the general analytical solution. Finally, the influence of the preparation method (pure and mixed cultures and HV content within the biopolymer) on thermal stability was analyzed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2111–2121, 2006     

Mechanical and Thermal Performances of Roselle Fiber-Reinforced Thermoplastic Polyurethane Composites

The aim of this paper is to present research findings on the measurements of mechanical, morphological, and thermal properties of Roselle fiber-reinforced thermoplastic polyurethane composites. The Roselle fiber/thermoplastic polyurethane composites were prepared with fibers of different sizes such as 125?µm and lower, 125–300 and 300–425?µm by internal mixer and hot press at 170°C. The results show that mechanical properties (tensile, flexural, and impact properties) of the composites were improved with the increase in fiber sizes. The highest tensile (10.45?MPa), flexural strength (6.93?MPa), and impact strength (20.22 kJ/m²) was obtained from composites with 300–425?µm fiber size of Roselle fiber/thermoplastic polyurethane composites. Morphological properties of dispersion fiber and tensile fracture surfaces were studied using scanning electron microscope. Thermal properties of the composites were studied using thermogravimetric analyses and results showed that the thermal decomposition effect was almost similar for all compositions.     

Fluorescence method using labeled chromophores to study the curing kinetics of a polyurethane system

A fluorescence method using labeled chromophores to study the curing kinetics of a polyurethane (PU) system was developed. A PU system based on fluorescent‐labeled hexamethylene diisocyanate and a polyol (polyether/polyester) was cured at different temperatures (25, 40, 50, and 65°C). The fluorescent response from the 5‐dimethylaminonaphtalene‐1‐(N‐2‐aminoethyl)sulfonamide and 4‐methacryloylamino‐4′‐nitrostilbene moieties chemically bonded to the PU system was monitored as a function of the curing time. With the fluorescence data, it was possible to model the kinetics of the curing process. Methods based on the fluorescence intensity ratio and the first moment of the fluorescent band emission were applied to determine the degree of curing of the PU system. In addition, it was possible to calculate an apparent activation energy for the curing process, and a value of 17 kJ/mol was obtained. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2992–3000, 2002     

葛粉的热分析与热分解动力学的研究

利用热重差热综合热分析仪(TG/DTA),在不同升温速率(5,10,15,20℃/min)下,采用Freeman-Carroll、Kissinger、Flynn-Wall-Ozawa和Friedman四种热分析方法,对葛粉的热行为及其热分解的动力学参数进行了研究。结果表明,葛粉的热行为包括自由水脱附(30～150℃)和分解(200～400℃)两个阶段,对应的失重率分别约为6%和70%。其热解反应的动力学方程为:dα/dt=1.424×1018[exp(-(193.70±8.97)×103/RT)](1-α)(2.28±0.04)。     

聚醚型水性聚氨酯热分解动力学的研究

以聚醚N-210为原料,利用丙酮法合成了水性聚氨酯,使用热重分析技术考察了聚醚型水性聚氨酯分别在氮气条件和氧气条件下的热稳定性,并采用"无模式法"研究了在不同气氛氛围下的热分解动力学,同时计算了不同热分解阶段反应的活化能Ea、指前因子A等动力学参数。结果表明:合成的聚醚型水性聚氨酯的热分解过程在氮气条件和氧气条件下均为二阶段过程,第一阶段为硬段链的分解,第二阶段为软段链的分解,同时氧气的存在促进了水性聚氨酯主链上C—C和C—O键的断裂。     

Kinetic investigations of trimethylolpropane–diisocyanate reactions

Trimethylolpropane (TMP) is frequently used as a trifunctional branching and chain‐extending agent in polyurethane production. This article deals with the analysis of the reactivities of the three primary hydroxyl groups of TMP during reactions with two exemplary diisocyanates: aromatic diphenylmethane‐4,4′‐diisocyanate and aliphatic m‐tetramethylxylylene diisocyanate. The method of examination is online attenuated total reflection/Fourier transform infrared spectroscopy. With this method, reactions in progress can be monitored simultaneously. It is shown that the addition of an isocyanate (here phenyl isocyanate) to the alcohol affects the rate of subsequent reactions. The higher the substitution degree is, the smaller the rate constant is of the reaction between the remaining free hydroxyl groups and the diisocyanates. This effect is largely determined by the type of diisocyanate. For reactions with very reactive aromatic diisocyanates, steric hindrance plays a significant role. For aliphatic diisocyanates, the substitution shows only minor effects because of the slowly reacting isocyanate groups. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4090–4097, 2006     

氟橡胶F2314黏结剂的热分解动力学

根据F2314黏结剂在升温速率分别为5,10,20K／min时的DSC-TG曲线,在20～500C温度范围内对F2314黏结剂的热分解过程进行了研究,用Coats-Redfern方法获得F2314黏结剂的热分解动力学参数和机理函数。结果表明,在不同升温速率的TG曲线上,F2314黏结剂热失重的起始温度大致相同,而结束温度随升温速率的增大而升高。同时,升温速率为10K／min的DSC曲线由一个熔化吸热峰和一个分解放热峰组成,在低于360℃时具有良好的热稳定性。得到F2314黏结剂热分解的活化能为294．76kJ／mol,指前因子为10^21.62s^-1,机理函数为f（α）=（1-α）^3/4。     

可生物降解热塑性聚氨酯弹性体的合成与性能研究

以中等分子量聚碳酸亚丙酯多元醇作为软段,并与过量的甲苯二异氰酸酯生成预聚物,用1,4–丁二醇进行扩链制备热塑性聚氨酯弹性体,整个反应体系保持—NCO/—OH=1.2。研究了硬段含量变化对材料结构与性能的影响。结果表明,所得弹性体的拉伸性能随着硬段含量的增加而增大,这是微相分离变化的结果;弹性体具有较好的生物降解性,可用于潮湿恶劣环境。     

Preparation,curing kinetics,and thermal properties of bisphenol fluorene epoxy resin

Diglycidyl ether of 9,9‐bis(4‐hydroxyphenyl) fluorene (DGEBF) was synthesized to introduce more aromatic structures into an epoxy resin system. The structure of DGEBF was characterized with Fourier transform infrared and ¹H‐NMR. 4,4′‐Diaminodiphenylmethane (DDM) was used as the curing agent for DGEBF, and differential scanning calorimetry was applied to study the curing kinetics. The glass‐transition temperature of the cured DGEBF/DDM, determined by dynamic mechanical analysis, was 260°C, which was about 100°C higher than that of widely used diglycidyl ether of bisphenol A (DGEBA). Thermogravimetric analysis was used to study the thermal degradation behavior of the cured DGEBF/DDM system: its onset degradation temperature was 370°C, and at 700°C, its char yield was about 27%, whereas that of cured DGEBA/DDM was only 14%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Enhanced Thermal and Mechanical Properties in Polyurethane/Au Nanocomposites

Summary: We have prepared waterborne polyurethane (WBPU) thin films containing gold nanoparticles by casting WBPU/Au solutions. The effect of the Au nanoparticle contents on the microstructure and properties of the composite films was investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), field emission scanning electron microscopy (FESEM), transmittance electron microscopy (TEM), FTIR spectroscopy (FTIR) and dynamic mechanical analysis (DMA). The Au nanoparticles initially in the WBPU solution were well dispersed in the WBPU films cast and dried at 60 °C. The thermostability and mechanical properties of the polymer increased with Au contents up to 4.35 × 10^?2 wt.‐%, which was believed to be a result of induced crystallization in the presence of Au nanoparticles. The Au/WBPU nanocomposite containing with 6.5 × 10^?2 wt.‐% of Au resulted in the aggregation of Au particles, which leads to a worsening of the thermal and mechanical properties.

TEM micrograph of nanocomposites filled with 4.35 × 10^?2 wt.‐% of Au nanoparticles.     

Preparation and properties of one epoxy system bearing fluorene moieties

Diglycidyl ether of bisphenol fluorene (DGEBF) and 9,9‐bis(4‐aminophenyl) fluorene (BPF) were synthesized to introduce more aromatic structures into an epoxy system, and their chemical structures were characterized with Fourier transform infrared spectroscopy, NMR, and mass spectrometric analysis. The dynamic curing behavior of the DGEBF/BPF system was investigated with differential scanning calorimetry. DGEBF was cured with BPF, diaminodiphenylsulfone (DDS), and diaminodiphenylmethane (DDM), and E‐44 (bisphenol A epoxide) was also cured with BPF for comparison. The thermal properties of the obtained polymers were evaluated with dynamic mechanical thermal analysis and thermogravimetric analysis. The cured DGEBF/BPF system showed a remarkably higher glass‐transition temperature, better thermal stability and lower moisture absorption in comparison with the general bisphenol A epoxy resin/BPF system but approximated the heat resistance of the DGEBF/DDS and DGEBF/DDM systems. Such properties make this epoxy system very promising for heat‐resistant applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Kinetic study of the urethane and urea reactions of isophorone diisocyanate

Kinetic studies of the catalyzed urethane reactions between isophorone diisocyanate (IPDI) and alcohols and of the urea reactions between an isocyanate‐terminated prepolymer [IPDI–PPG2000–IPDI, where PPG2000 is poly(propylene glycol) with a number‐average molecular weight of 2000 g/mol] and water in the bulk state were performed with Fourier transform infrared (FTIR) spectroscopy. Dibutyltin dilaurate was used as the catalyst for the urethane reaction, and various tertiary amines were used as catalysts for the urea reactions. The reactions were followed through the monitoring of the change in the intensity of the absorbance band for NCO stretching at 2270 cm^?1 in the FTIR spectra; the activation parameters were determined through the evaluation of the kinetic data obtained at various temperatures (within the range of 30–60°C). The kinetic data indicated that the catalyzed isocyanate/alcohol and isocyanate/water reactions both followed second‐order kinetics during their initial stages but later followed third‐order kinetics resulting from the autocatalytic effects of hydrogen bonding between the hydroxyl groups and the newly formed urethane and urea groups. Furthermore, activation energies of 64.88 and about 80 kJ/mol for the isocyanate/alcohol and isocyanate/water reactions, respectively, indicated that the urea‐forming reactions were more sensitive to the reaction temperature than the urethane‐forming reactions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

新型硬质聚氨酯泡沫的热分解行为及动力学

利用热重分析法比较研究了新型硬质聚氨酯泡沫[超支化聚氨酯多元醇型(HBPU型)]和硬质聚氨酯泡沫(RPUF)在氮气中的热分解行为,探讨了HBPU型RPUF在不同升温速率下的热分解动力学,运用Kissinger最大失重率法和Flynn-Wall-Ozawa等失重百分率法计算获得了其热分解过程的活化能。研究结果表明,HBPU型RPUF的初始分解温度(T5%)为205℃,半寿温度(T50%)为361℃,略低于传统的RPUF。Kissinger法得到的HBPU型RPUF的热分解表观活化能为159.8 kJ/mol;Flynn-Wall-Ozawa法得到的热分解过程分为三个阶段:第一阶段的平均活化能为82.8 kJ/mol,第二阶段的平均活化能为140.7 kJ/mol,第三阶段的平均活化能为111.3 kJ/mol,HBPU型RPUF具有较好的热稳定性。     

聚氨酯/三聚氰胺甲醛树脂复合泡沫热降解动力学研究

三聚氰胺甲醛树脂脱水后和多元醇混合,然后用异氰酸酯与混合物进行交联反应,生成聚氨酯/三聚氰胺甲醛树脂复合泡沫.热重分析结果表明,复合泡沫失重分为3个阶段,二苯基甲烷二异氰酸酯(MDI)型三聚氰胺甲醛树脂复合泡沫的第2阶段的失重峰温比甲苯二异氰酸酯(TDI)型三聚氰胺甲醛树脂复合泡沫的高.采用Kissinger法研究了该...     

Studies of the curing kinetics and thermal stability of epoxy resins using a mixture of amines and anhydrides

This article describes the curing and thermal behavior of diglycidyl ether of bisphenol A with phthalic anhydride (PA)/pyromellitic anhydride/diaminodiphenyl sulfone (DDS) or a mixture of anhydrides and amines in varying ratios as curing agents. The kinetics of the curing behavior was investigated with a multiple‐rate method. The activation energy of the curing reaction as determined in accordance with Ozawa's method was found dependent on the structure of the anhydride and on the ratio of amines to anhydrides. The activation energy was highest with sample DP3 (0.25 : 0.75) and DM3 (0.25 : 0.75). We evaluated the thermal stability of epoxy resin, cured isothermally, by recording thermogravimetric traces in a nitrogen atmosphere. The char yield was highest for resins cured with a mixture of DDS and PA (0.5 : 0.5) and a mixture of DDS and pyromellitic dianhydride (0.25 : 0.75). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3919–3925, 2006     

热塑性聚氨酯弹性体合成的研究

以聚四氢呋喃醚二醇、4,4’-二苯甲烷二异氰酸酯及1,4-丁二醇为原料,采用双螺杆反应挤出机进行了生产热塑性聚氨酯弹性体的研究,对有关影响因素进行了讨论。生产规模为500t／a。该合成方法具有工艺简单、生产率高等优点,产品的性能与国外同类产品相当。     

Temperature Evolution During Processing of Thick‐Walled Anionic Polyamide 6 Composites: Experiment and Simulation

A 1‐D through‐the‐thickness transient heat transfer model is built to simulate the curing process of thick‐walled glass‐fibre‐reinforced anionic polyamide‐6 (APA‐6) composites. The temperature and the degree of polymerisation through the thickness of the composite are calculated and compared to the experimentally obtained results. The kinetic models describing the polymerisation behaviour of APA‐6 are implemented in the model. The kinetic model not taking into account the convection in the polymerisation process shows the best results. It is found that the predicted temperature profiles agree well with the experimental data.

     

印刷线路板热分解反应动力学研究

采用热重法研究了印刷线路板（FR4板）的热分解反应过程,并通过迭代的等转化率法和主曲线法求算得到了FR4板热解过程的动力学三因子。研究发现：FR4板呈一段热解,热解温度区间约为320-430℃,并在350--385℃温度区间达到最大热解速率;热解反应的活化能为139．98kJ／moL,指前因子1nA为26．36～26．70,动力学机理函数的积分形式为G（d）=（1-a）^-2。     

CL-20的催化热分解行为及非等温分解反应动力学

在程序升温条件下，用DSC、TG研究了CL-20、CL-20／PbCO3、CL—20/邻苯二甲酸铅（φ-Pb）和CL-20／2，4-二羟基苯甲酸铅（β-Pb）体系的热分解行为。采用6种微分、积分动力学分析方法计算了它们的热分解反应动力学参数。结果表明，CL-20、CL-20／φ-Pb、CL-20／β-Pb的热分解机理函数均为Avrami—Erofeev方程，其微分形式为f（a）-4（1-a）[-In（1-a）]^3/4，分解机理是随机成核和随后生长，n=1／4。