Thermal and DMA Characterization of PTFE-PMMA Nanocomposites from Core-Shell Nanoparticles

The thermal and dynamic-mechanical characteristics of three PTFE/PMMA nanoparticle samples are described. The shell forming PMMA, once isolated from the PTFE cores, exhibits a lower thermal stability than the PMMA component in the corresponding nanocomposite under both thermal and oxidative degradation conditions thus indicating a definite, though moderate, thermal reinforcement due to the morphology of the nanocomposites. An increase in the thermal stability under nitrogen atmosphere was observed as the PTFE amount increases. However under air, no difference is observed in the various systems. These observations suggest that only a physical shield can be exerted by the PTFE cores to the PMMA matrix possibly due to a weak interface between PTFE and the PMMA. This hypothesis is also substantiated by the DMA analysis.     

Thermal degradation behavior of multi-walled carbon nanotubes/polyamide 6 composites

This paper focuses on the thermal degradation behavior of multi-walled carbon nanotubes (MWNTs)/polyamide 6 (PA6) composites under air and nitrogen atmosphere using thermogravimetric analysis (TGA). The results show that the dispersion of amino-functionalized MWNTs (f-MWNTs) in PA6 is more homogeneous than purified MWNTs (p-MWNTs). The presence of MWNTs improves the thermal stability of PA6 under air obviously, but has little effect on the thermal degradation behavior of PA6 under nitrogen atmosphere. The activation energies for degradation under air, E_a, estimated by Kissinger method, are 153, 165 and 169 kJ/mol for neat PA6, p-MWNTs/PA6 and f-MWNTs/PA6 composites, respectively. The p-MWNTs/PA6 composites show two-step degradation not only under air but also under nitrogen atmosphere, however, neat PA6 and the f-MWNTs/PA6 composites exhibit two-step degradation only under air.     

Phthalocyanine polymers. III. Poly(nickel phthalocyanine)benzimidazole as a novel high-temperature-resistant polymer

A new type of poly(nickel phthalocyanine)benzimidazole was prepared by the condensation reaction between nickel (11) 4,4′,4″,4″′-phthalocyanine tetracarboxylic acid dihydrate and 3, 3′-diaminobenzidine. The reaction was investigated by both the melt and solution condensation methods. This polymer showed good thermal and thermo-oxidative stability. Also noteworthy is its high thermal stability with a char yield of 88% at 800°C in nitrogen. No catastrophic decomposition was observed up to 1100°C. A qualitative study of decomposition in both air and nitrogen is presented. Elemental analyses agreed well with the proposed structure. Infrared (IR) and thermogravimetric analysis (TGA) studies were performed to characterize this polymer, and isothermal gravimetric analysis was done to determine its long-term thermal stability. The apparent activation energies for the thermal degradation in air and nitrogen are given.     

新型侧基含磷共聚酯的阻燃和热降解动力学

利用动态热重分析法(TG)研究了聚酯(PET )及侧基含磷共聚酯(FR-PET)在不同升温速率下的热稳定性及热降解动力学, 并通过极限氧指数法(LOI)考察了FR-PET的阻燃性能; 采用Flynn-Wall-Ozawa方法分析了PET和FR-PET的热降解表观活化能; 利用Coast-Redfern方法通过对不同机理模型的选取, 确定了PET和FR-PET热降解动力学机理及其模型, 得出了主降解阶段的非等温动力学方程及热降解速率曲线图. 研究结果表明, 侧基含磷单元的引入提高了聚酯的阻燃性能, 侧基上的P—C和P—O键易断裂, 从而降低了聚酯的热稳定性. PET和FR-PET的热降解表观活化能(0.1≤α≤0.85)分别为194-227和184-209 kJ/mol; PET和FR-PET热降解反应均属于受减速形α-t曲线控制的反应级数机理, 其机理函数为f(α)=3(1-α)2/3(0.1≤α≤0.85). 侧基含磷单元的引入对PET的主降解阶段的热降解速率并无实质上的影响. 侧基含磷共聚酯的凝聚相阻燃作用有限, 可能以气相阻燃机理为主发挥阻燃作用.     

Thermal behavior of bismaleimide resin

The cure of a bismaleimide (BMI) neat resin modified with an aromatic diamine and a siloxane elastomer, has been studied by ¹³C solid state nuclear magnetic resonance. Two chemical reactions occur during the cure cycle; at a low temperature, Michael's reaction predominates, while at a high temperature the polymerization of the double bond maleimide creates the network. The degradation of this BMI material was characterized with isothermal and dynamic thermogravimetric analyses in air and in nitrogen. The BMI thermal stability is lower in nitrogen than in air. This behavior is an indication of oxygen participating in reactions at high temperatures. The activation energy (E_a) of thermal degradation was determined from isothermal data using an Arrhenius equation (In V vs. 1/T). The global E_a for the weight loss in air was found to be 91 kJ/mol. The nature and the evolution of the thermal degradation products were the combined analyzed by techniques of pyrolysis, gas chromatography and mass spectrometry. The major thermal decomposition products obtained in the temperature range of 300–700°C are identified as benzene, methyl formamide, aniline, toluene and isocyanate-derived products.     

聚对苯二甲酸乙二醇酯/碳酸钙纳米复合材料的制备和表征

以聚乙二醇磷酸酯1000为表面处理剂, 采用碳化法合成了方解石型碳酸钙纳米粒子, 进一步制备了聚对苯二甲酸乙二醇酯/碳酸钙纳米复合材料. 采用透射电子显微镜(TEM)、 X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR), 场发射扫描电子显微镜(FESEM)和热重分析(TGA)对样品进行了分析. 结果表明, 聚乙二醇磷酸酯1000成功地修饰到碳酸钙的表面, 并得到平均直径为60 nm, 形貌为立方体的纳米碳酸钙晶体. 与碳酸钙(空白)样品相比, 表面处理碳酸钙的复合材料表现出更好的分散性和热稳定性. 采用Friedman方法计算了复合材料热分解的活化能. 聚对苯二甲酸乙二醇酯、 聚对苯二甲酸乙二醇酯/空白碳酸钙和聚对苯二甲酸乙二醇酯/表面处理碳酸钙的活化能分别为200.58, 214.86和219.50 kJ/mol, 进一步说明了表面处理碳酸钙更好地改善了聚对苯二甲酸乙二醇酯的热稳定性.     

Kinetics study of thermal decomposition of epoxy resins containing flame retardant components

Hyperbranched polyphosphate ester (HPPE) and phenolic melamine (PM) were blended in different ratios with a commercial epoxy resin to obtain a series of flame retardant resins. The thermal decomposition mechanism of their cured products in air was studied by thermogravimetric analysis and in situ Fourier-transform infrared spectroscopy. The degradation behaviours of epoxy resins containing various flame retardant components were found to be greatly changed. The incorporation of phosphorus and nitrogen compounds improved the thermal stability at elevated temperature. The kinetics of thermal decomposition was evaluated by Kissinger method, Flynn-Wall-Ozawa method and Horowitz-Metzger method. The results showed that the activation energy at lower degree of the degradation decreased by the incorporation of flame retardant components, while increased at higher degree of the degradation.     

Thermal Studies on Chlorinated Atactic Polypropylene

Thermal behavior of chlorinated atactic polypropylene (CAPP) obtained by thermal chlorination of atactic polypropylene was evaluated by thermogravimetric analysis and differential thermal analysis (DTA). It was found that the initial decomposition temperature, integral procedural decomposition temperature, activation energy, and char yield increase with an increase in chlorine content. The thermal stability of CAPP was found to be lower in air than in nitrogen. This has been ascribed to thermooxidative degradation in air. DTA study shows that onset decomposition temperature, glass transition temperature, and polymer melting temperature increase with increasing degree of chlorination. The possible reasons for the phenomena are discussed.     

Thermal degradation of amino-group-modified polydimethylsiloxane

Degradation behaviors of amino-group-modified polydimethylsiloxane (APS) under nitrogen and air atmosphere were studied by thermogravimetric analysis, pyrolysis–gas chromatography-mass spectrometry, and infrared spectroscopy, and the effect of amino-group content on the thermal stability of the tested APS was investigated. Results showed that the existence of amino-group in APS molecule decreased its thermal stability, and the degradation behavior and mechanism of APS in nitrogen and air atmosphere were different.     

Thermal degradation and pyrolysis study of brominated butyl rubber‐based damping material

This paper deals with the thermal stability and decomposition behavior of brominated butyl rubber‐based damping material (BRP). The raw materials, butyl rubber matrix (IIR) and brominated phenolic resin (PF), were also investigated as control. IIR shows one decomposition stage, while PF shows four weight loss stages. Flynn‐Wall‐Ozawa calculation indicates that BRP has thermal stability between IIR and PF. Thermogravimetric analysis–Fourier transform infrared (TGA‐FTIR) and pyrolysis–gas chromatography/mass spectrometry (GC/MS) were used to investigate the volatile products under nitrogen atmosphere. As expected, BRP shows combined thermal decomposition behavior of both IIR and PF. The degradation mechanism of BRP was proposed, which is not significantly influenced by the incorporation of PF. The application stability of BRP is worth to be noticed since the post‐cure effect, that is, the free radicals remained from vulcanization would cause additional cross‐linking when stored at 80°C to 120°C.     

Polymorphism and Thermal Behaviour of Syndiotactic Poly(propylene)/Carbon Nanotube Composites

Summary: Nanocomposite materials were obtained by blending multi‐wall carbon nanotubes (CN), obtained by acetylene catalytic chemical vapour deposition (CVD) on Co/Fe‐modified NaY zeolite, with syndiotactic poly(propylene) (sPP). The nanotubes, well dispersed in the polymer matrix, favour the crystallization of the sPP helical chains and significantly improve the sPP thermal stability either in nitrogen or in air. The morphology of the sPP affects the behaviour of the sPP degradation in air.

Thermogravimetric analysis in air of pure sPP and the nanocomposite material.     

Phthalocyanine polymers. V. Novel type of thermally stable polyimides derived from metal phthalocyanine tetraamines and pyromellitic dianhydride

New poly(metal phthalocyanine) pyromellitimides of copper, cobalt, nickel, and zinc were synthesized and elemental, IR, TGA, and inherent viscosity measurement studies were done to characterize these polymers. They showed exceptional thermal and thermo-oxidative stability with char yields at 800°C ranging from 75 to 87% in a nitrogen atmosphere. The ratio of the polymer decomposition temperatures in air and nitrogen (PDT) (air)/PDT (N₂) varied from 0.91 to 0.97, which indicated that the onset of degradation of these polymers is greatly affected by the presence of an oxidizing atmosphere. Isothermal studies were done to evaluate the long-term thermal stability of these polymers.     

Effect of the catalyst MCM-41 on the kinetic of the thermal decomposition of poly(ethylene terephthalate)

The aim of this work is to determine the activation energy for the thermal decomposition of poly(ethylene terephthalate)—PET, in the presence of a MCM-41 mesoporous catalyst. This material was synthesized by the hydrothermal method, using cetyltrimethylammonium as template. The PET sample has been submitted to thermal degradation alone and in presence of MCM-41 catalyst at a concentration of 25% in mass (MCM-41/PET). The degradation process was evaluated by thermogravimetry, at temperature range from 350 to 500 °C, under nitrogen atmosphere, with heating rates of 5, 10 and 25 °C min^?1. From TG, the activation energy, determined using the Flynn–Wall kinetic method, decreased from 231 kJ mol^?1, for the pure polymer (PET), to 195 kJ mol^?1, in the presence of the material (MCM-41/PET), showing the catalyst efficiency for the polymer decomposition process.     

The effect of PVAc on the efficiency of thermal reactions in PS/PVAc blends in relation to the atmosphere

The thermal stability of polystyrene (PS) blends with polyvinyl acetate (PV Ac) has been investigated. It was found that PV Ac acts as a sensitizer of the thermal degradation of these blends when the process takes place in a nitrogen atmosphere. In air PV Ac acts as a stabilizer, and the temperature of the decomposition of these blends is higher than that of pure PS. This stabilization is caused by PV Ac favoring an oxidation reaction without breaking the polymer chains.     

THERMAL DEGRADATION KINETICS OF THERMOTROPIC COPOLY (P-OXYBENZOATE-ETHYLENE TEREPHTHALATE-VANILLATE) BY A HIGH-RESOLUTION THERMOGRAVIMETRY

Thermotropic liquid crystalline terpolymers consisting of three units of p-oxybenzoate (B), ethylene terephthalate (E), and vanillate (V), were studied through a high-resolution thermogravimetry to ascertain their thermostability and kinetics parameters of thermal decomposition in nitrogen and air. Overall activation energy data of the major decomposition have been calculated through four calculating techniques. The thermal degradation occurs in three steps in nitrogen, but in four steps in air due to an additional thermo-oxidative step. The thermal degradation temperatures are higher than 436°C in nitrogen and 424°C in air and increase with increasing B-unit content at a fixed V-unit content of 5 mol%. The temperatures at the first maximum weight-loss rate are higher than 444°C in nitrogen and 431°C in air and increase slightly with an increase in B-unit content. The first, second, and third maximum weight-loss rates almost maintain at 10–11, 10–11, and 3.6–5.3%/min regardless of copolymer composition and testing atmosphere. The char yields at 500°C in both nitrogen and air are larger than 40 wt% and increases with increasing B-unit content. But the char yields at 800°C in nitrogen and air are quite different, i.e., 18–25 wt% in nitrogen and 0 wt% in air. The activation energy and Ln (pre-exponential factor) for the major decomposition are higher in nitrogen than in air and decrease slightly with an increase in B-unit content at a given V-unit content 5 mol%. There is no regular variation in the decomposition order with the variation of copolymer composition and testing atmosphere. It is found that the most V-unit-containing terpolymer exhibited the lowest degradation temperature, lowest activation energy, and lowest Ln (pre-exponential factor). The activation energy, decomposition order, and Ln (pre-exponential factor) of the thermal degradation for the terpolymers, are situated in the ranges of 121–248 kJ/mol, 1.5–2.8, 19–38 min^?1, respectively. These results indicate that the terpolymers exhibit high thermostability. The isothermal decomposition kinetics of the terpolymer at 450°C have also been discussed and compared with the results obtained based non-isothermal high-resolution thermogravimetry.     

Flame‐retardant poly (ethylene terephthalate) enabled by a novel melamine polyphosphate nanowire

A novel strategy was developed for the preparation of melamine polyphosphate (MPP) nanowires to achieve a superior flame‐retardant poly (ethylene terephthalate) (PET). Thanks to the well‐designed nanostructure, the prepared MPP nanowires exhibited great thermal stability and flame retardance. Herein with incorporation of only 1‐wt% MPP nanowires (PET/FR1.0 nanocomposite), the limiting oxygen index (LOI) value was dramatically increased to 29.4% from 20.5%, showing self‐extinguishing behavior. Moreover, PET/FR1.0 nanocomposite passed V‐0 UL‐94 rating in the vertical combustion test. However, PET containing 5‐wt% commercial MPP powder (PET/FR_C5.0) only showed a LOI of 27.9% and ignited the absorbent cotton with flammable melt‐droplets. Cone results also presented that introducing 1‐wt% MPP nanowires brought about a crucial decrease in fire hazard of PET, for instance, 11.1% and 7.7% maximum reduction in heat release rate and total heat release, respectively. Thermogravimetric analysis/infrared spectrometry (TG‐FTIR) result indicated that the main pyrolysis volatiles generated from PET degradation including benzoic acid, aromatic compounds, and carbon dioxide were apparently suppressed after introducing MPP nanowires into PET matrixes, suggesting the outstanding obstructing effect of graphited char residue formed in the combustion. This enhanced flame retardancy rooting in addition of MPP nanowires can be attributed to the combined dilution effect in gaseous phase and catalytic carbonization effect in condensed phase.     

Study of the Thermal Stability Properties of Pyridoxine Using Thermogravimetric Analysis

The thermal decomposition behavior and kinetics of pyridoxine in nitrogen-only and air atmospheres were studied using thermogravimetry analysis (TGA). Kinetic interpretation of thermal analysis data for pyridoxine decomposition was carried out using Ozawa and ASTM E698 isoconversional methods. The activation energy of the decomposition process varied with the degree of decomposition and was different in the nitrogen and air atmospheres. At a 5% decomposition level, the activation energy and the pre-exponential factor were found to be 28.3 kcal mol^?1 and 1.2 × 10¹⁴ min^?1, respectively, in the nitrogen-only atmosphere. Thermal stability was determined by calculating the time for 5% of the pyridoxine vitamer to decompose at 25°C. The calculated shelf life for the pyridoxine vitamer obtained via TGA was surprisingly smaller in nitrogen (0.9 years) than in air (1.5 years). This is speculated to be the result of a more complex decomposition mechanism in air, involving thermo-oxidative decomposition in the presence of oxygen.     

The study of non-isothermal degradation of acrylic ion-exchange resins

Summary The thermal behavior under non-isothermal conditions of some low-acidity carboxylic cationites with acrylic-divinylbenzene (DVB) matrix was investigated in air and nitrogen atmosphere up to 600°C. Thermal analysis (TG/DTG) combined with Mass Spectrometry (MS) and Fourier Transform Infrared Spectroscopy (FTIR) was used to characterize the resins decomposition steps and the degradation products. Five decomposition steps were observed. The first step is due to elimination of osmotic and bound water. The second decomposition step is due to dehydration of neighboring (-COOH) groups. The third and fourth mass-loss steps correspond to decarboxylation of the polyanhydrides and to some depolymerization of the polymeric matrix. The last decomposition step is associated with total degradation of the polymeric matrix. The shape and the temperature for each decomposition steps depend on the experimental conditions (heating rate and degradation atmosphere) and on the sample properties (i.e. granulation, cross-linking degree, porosity and physical form).     

聚氨酯胶粘剂的热分解动力学研究

采用热分析技术考察了通用型聚氨酯胶粘剂在空气中的热解过程, 并通过TG方法和动力学方法研究了各步反应的活化能E、指前因子A等动力学参数. 通过等失重转化率法校验了两种方法所获得的E和A值. 结果表明, 聚氨酯胶粘剂有三个主要降解阶段, 第一降解阶段的活化能为144.31-148.35 kJ·mol^-1, 第二个降解阶段的活化能为196.96-204.26 kJ·mol^-1, 第三个降解阶段的活化能为202.97-205.27 kJ·mol^-1; 热降解过程为一级反应, 随着失重百分率的增大, 热分解反应活化能增大. 此外, 聚氨酯胶粘剂具有较高的热稳定性, 预测其在35 ℃的空气中失重5%时的热老化寿命为10年.     

Morphology and thermal characterization of montmorillonite/polybenzimidazole nanocomposite

In this study, thermal and morphological properties of organically modified montmorillonite (mMMT)/poly(2,5-benzimidazole) (ABPBI) composite were investigated. The morphology and structure of mMMT/ABPBI composites were characterized by infrared, X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis techniques. At low mMMT loading levels, exfoliation was the predominant mechanism of mMMT dispersion. At high mMMT loading levels, nonintercalated microcomposite morphology is partially favored in expense of the intercalated nanocomposite. Thermal degradation of nanocomposite occured in three stages. In the second stage of thermal degradation, the onset temperature of degradation for the mMMT/ABPBI nanocomposites was lower than that of ABPBI polymer. In the last stage, the improvement in thermal stability by the introduction of mMMT into the ABPBI was different from the second stage. The activation energy for degradation of ABPBI increased from 62.6 to 77.7 kJ mol^?1 after loading of 5 mass% of mMMT into ABPBI matrix under air atmosphere.