Degradation study on the thermally stable nickel phthalocyanine sheet polymer

Poly (nickel phthalocyanine) which has exceptional thermal stability is synthesized. Knowledge of modes of degradation of this polymer is found to be necessary for its high temperature applications. This polymer showed very high thermal stability with maximum polymer decomposition temperatures (PDT_max) of 500 °C in air and 890 °C in N₂, with char yield 93% at 800 °C. Because of its excellent thermal stability, degradation study with MS as well as GC–MS techniques were found to be very difficult. The present publication deals with MS and GC–MS studies of nickel phthalocyanine sheet polymer at high temperatures ranging from 700 to 1000 °C. Tentative mechanisms are proposed for its modes of fragmentations and based on GC–MS studies, the most probable degradation products are identified.     

Thermal degradation of biodegradable edible films based on xanthan and starches from different sources

Films based on xanthan/wheat starch and xanthan/maize starch were prepared in different proportions and analysed in terms of thermal stability in relation to the degradation reaction in an inert atmosphere. The main gaseous decomposition products were identified by infrared spectroscopy. Xanthan was found to be less thermally stable than starch from different sources. The starch addition to xanthan induced an increase in the film thermal stabilities. The thermal degradation mechanism of xanthan starts with scission of the side chain groups with subsequent scission of the main chain. Starches from maize and wheat presented a constant mechanism of thermal degradation. The proportion of xanthan/starch (50/50) presented a synergistic behaviour which may be associated with changes in the mechanism of the thermal degradation process. The FTIR spectra of the gaseous products during thermal degradation of xanthan showed a broad absorption in the 2750–3300 cm⁻¹ region, probably indicating decomposition of β-d-mannopyranosyl groups, present in xanthan side chains. For pure starches, absorptions related to alcohol O–H stretching (3500–3750 cm⁻¹), CO stretching of CO₂, CO and carbonyl compounds (2361, 2177 and 1743 cm⁻¹, respectively) were observed. For xanthan/starch mixtures (50/50) the same compounds as those for the pure polymer degradation were evolved. However, a shift of the CO to higher wavenumber values indicates that new carbonyl compounds are being formed due to changes in the thermal degradation mechanism.     

Thermal behavior of nitrided TiO2/In2O3 by TG–DSC–MS combined with PulseTA

TiO₂/InN (In/(Ti + In) = 6.5:100 mol) was prepared by nitridation of TiO₂/In₂O₃ by NH₃ at 580 °C for 8 h. Only the anatase TiO₂ phase was detected in the XRD measurements. The highly dispersed InN clusters on the surface of anatase TiO₂ nanocrystals were beyond the detection limit of XRD. In order to confirm the existence of InN in the products of nitridation, thermogravimetry–differential scanning calorimetry–mass spectrometry (TG–DSC–MS) coupling techniques were used for a simultaneous characterizing study of the changes of mass, enthalpy and determination of the evolved gases during the thermal decomposition of the InN and the nitrided TiO₂/In₂O₃ samples. Moreover, pulse thermal analysis (PulseTA) was combined with TG–DSC–MS for the quantitative calibration of the evolved nitrogen formed during the thermal decomposition of the InN and the nitrided TiO₂/In₂O₃. The applied technique enabled identification and quantification of the InN in the products of the nitridation of TiO₂/In₂O_3.     

Calorimetry and thermogravimetry as tools for the assessment of the thermal stability of polyoxide-based nonionic surfactants

Differential scanning calorimetry (DSC) and thermogravimetry (TGA) have been used to evaluate the thermal stability of nonionic surfactants. We have studied monofunctional diblock copolymers of poly(ethylene oxide-propylene oxide) (R-PEO–PPO–OH, where R length is linear C₄ or C_12–14) as nonionic surfactants. It was observed that the thermal stability was dependent on the copolymer structure. Moreover, the higher the EO/PO ratio in the copolymers the higher the oxidative thermal stability. The autoxidation exhibits exothermic behaviour and the enthalpy related to the process depends on the EO/PO ratio. The initial temperatures of degradation obtained from DSC and TGA were in agreement.     

Thermal stability of poly(N-vinyl-2-pyrrolidone-co-methacrylic acid) copolymers in inert atmosphere

The thermal stability of poly(N-vinyl-2-pyrrolidone-co-methacrylic acid) copolymers was studied by thermogravimetry and infrared spectroscopy in inert atmosphere. The thermogravimetric curves suggested that the effective degradation of both systems occurred in the temperature range 350–500 °C with more than 60% mass loss. At this temperature, the activation energy was in the range 160–200 kJ mol⁻¹ (average values), suggesting that the degradation occurred by a random scission of the chain. The FTIR results indicated that the main volatile products of degradation are CO₂, CO and hydrocarbons (unsaturated structures) with low molecular weight. Pure PVP also showed the formation of NH₃ which was apparently suppressed in the copolymer by the formation of large amounts of CO₂ and CO. The results suggested that the thermal stability of the copolymers was essentially associated with the N-vinyl-2-pyrrolidone monomer, losing stability when the percentage of methacrylic acid in the copolymer system was increased.     

界面聚合法制备PANI/g-C3N4复合催化剂及其热稳定性和可见光催化性能

利用界面聚合法, 成功将聚苯胺(PANI)纳米棒生长在石墨型氮化碳(g-C₃N₄)片层上, 制备了PANI/g-C₃N₄复合光催化剂. 采用傅里叶变换红外(FTIR)光谱、X射线衍射(XRD)、扫描电镜(SEM)、紫外-可见(UV-Vis)光谱、热重分析(TGA)和电化学工作站表征手段考察样品的结构、形貌及性能, 以可见光催化降解亚甲基蓝为模型考察样品的可见光催化活性. 实验结果表明, 在复合材料中的g-C₃N₄能很好地分散成层状, 并在层间与PANI纳米棒形成复合物, 这种特殊的复合结构不仅利于片状g-C₃N₄对PANI链段运动的限制及对其降解产物的物理屏蔽, 从而可以提高复合材料的热稳定性, 而且具有优越的可见光催化性能.     

Thermal Kinetics and Decomposition Mechanism of Methylphenylphosphinic Acid and Diphenylphosphinic Acid

Thermal degradation and degradation kinetics of methylphenylphosphinic acid（MPPA） and diphenyl- phosphinic acid（DPPA） were investigated via thermogravimetric analysis（TGA） technique under non-isothermal conditions. The activation energies of the decomposition process for the two compounds were calculated through the Friedman and Kissinger-Akahira-Sunose（KAS） methods. The thermal decomposition mechanism was investigated by the Criado method based on a set of TGA data obtained at different heating rates. It was shown that the activation energies calculated from the decomposition reaction by different methods were consistent with each other. The results show that the probable model for the degradation of MPPA and DPPA agreed with the two-dimensional（D2） and three-dimensional（D4） diffusion models, respectively. Moreover, the thermodynamic functions（△H, △S, △G） of the two decomnosition reactions were also calculated.     

Flammability characteristics and flame retardant mechanism of phosphate-intercalated hydrotalcite in halogen-free flame retardant EVA blends

The flammability characteristics and flame retardant mechanism of phosphate-intercalated hydrotalcite (MgAl-PO₄) in the halogen-free flame retardant ethylene vinyl acetate (EVA) blends have been studied by X-ray diffraction (XRD), Fourier transfer infrared (FTIR) spectroscopy, cone calorimeter test (CCT), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), limiting oxygen index (LOI) and UL-94 tests. The results show that the hydrotalcite MgAl-PO₄ intercalated by phosphate possesses the enhanced thermal stability and flame retardant properties compared with ordinary carbonate-intercalated hydrotalcite MgAl-CO₃ in the EVA blends. The CCT tests indicate that the heat release rate (HRR) and mass loss rate (MLR) values of the EVA/MgAl-PO₄ samples are much lower than those of the EVA/MgAl-CO₃ samples. The TGA data show that the thermal degradation rates of MgAl-PO₄ and EVA/MgAl-PO₄ samples are much slower and leave more charred residues than those of MgAl-CO₃ and its corresponding EVA blends. The LOI values of EVA/MgAl-PO₄ samples are 2% higher than those of the corresponding EVA/MgAl-CO₃ samples at the range of 40–60 wt% loadings, while the EVA sample with 55 wt% MgAl-PO₄ can reach the UL-94 V-1 rating. The dynamic FTIR spectra reveal that the flame retardant mechanism of MgAl-PO₄ can be ascribed to its catalysis degradation of the EVA resin, which promotes the formation of charred layers with the P–O–P and P–O–C complexes in the condensed phase. The SEM observations give further evidence of this mechanism that the compact charred layers formed from the EVA/MgAl-PO₄ sample effectively protect the underlying polymer from burning.     

Catalytic degradation of polyethylene using thermal gravimetric analysis and a cycled-spheres-reactor

Commercial samples of pure polyethylene were decomposed over H-ZSM-5 and Y-type zeolites using thermal gravimetric analysis (TGA) and a laboratory-scale-plant, so-called the cycled-spheres-reactor. By the TGA measurements, the activity and the deactivation behavior of the zeolite catalysts were determined. The plastic to catalyst ratio was varied to find out the optimal value for catalyst screening and for the operation of the cycled-spheres-reactor. In addition, the deactivation behavior of the zeolite catalysts was investigated. Y-type zeolites revealed lower activity and faster deactivation behavior than H-ZSM-5. Higher module of H-ZSM-5 and Y-type zeolite showed slower deactivation, but lower activity than lower module of those. Experiments in the cycled-spheres-reactor proved the results of the TGA measurements in terms of activity. The main products in the non-catalytic degradation were waxes, and when catalysts were applied, a high yield of oils was obtained at the expense of waxes. The product spectra of product oils obtained with catalysts lay mainly in the range C₄–C₁₀.     

Thermal oxidation of oxynitride perovskites in different atmospheres

Oxynitride perovskites with bright and variable colour have the potential to be employed as non-toxic pigments, and to substitute colourants that contain harmful heavy metals. For this application it is extremely important to have a precise knowledge about the materials stability. The thermal stability of oxynitride perovskites in different atmospheres was measured by thermogravimetry in combination with mass spectroscopy (MS). The studied compounds, namely LaTiO₂N, SrNbO₂N and SrTaO₂N, were heated up to 1200 °C in argon–oxygen mixtures with varying oxygen contents. It was found that the thermal behaviour of the studied oxynitrides changes drastically with the oxygen concentration. When heated up in pure argon the oxynitrides transform to oxides containing transition metals of lower oxidation state and/or binary nitrides. For oxygen contents between 0.5% and 20% the samples were completely oxidised. The oxidation rate increases with oxygen content. MS analysis of the gaseous products (including N₂, NO and NO₂) reveals a complex reaction mechanism, which is strongly modified by the composition of the atmosphere.     

Effect of layered double hydroxides on the thermal degradation behavior of biodegradable poly(l-lactide) nanocomposites

This study elucidates the thermal degradation behavior of biodegradable poly(l-lactide) (PLLA)/layered double hydroxide (LDH) nanocomposites was explored using thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass spectroscopy (Py-GC/MS) in an inert atmosphere. PLLA/LDH nanocomposites were fabricated using PLLA and organically-modified magnesium/aluminum layered double hydroxide (P-LDH) in tetrahydrofuran solution. According to the TGA results, the thermal stability of PLLA/P-LDH nanocomposites was significantly lower than that of pure PLLA matrix, perhaps because P-LDH provides thermal acceleration of the degradation of the underlying polymer from the heat source. The identification of the thermal degradation products by Py-GC/MS evidently shows that introducing P-LDH into PLLA leads to a remarkable change during the thermal degradation process. The main reaction route of neat PLLA was through inter- and intra-transesterification to generate lactides and oligomer. The primary volatile products obtained from PLLA/P-LDH nanocomposites were lactides regardless of the temperature of degradation. These results suggest that the thermal degradation behavior of PLLA/P-LDH nanocomposites is governed by the preferential formation of lactide by the unzipping depolymerization reaction, which is catalyzed by Mg and Al components in P-LDH.     

Characterization of radiation-induced aging in silica-reinforced polysiloxane composites

Changes in crosslink density and chemical structure of silica-reinforced silicone polymer composites due to aging in gamma radiation environments were examined in this study. Solvent swelling was utilized to determine the individual contributions of the matrix polymer and filler phase to the overall crosslink density of silica-reinforced silicone polymer composites. The results show how polymer–filler hydrogen bonding dominates the overall crosslink density of the material. Air-irradiated samples displayed decreased hydrogen bonding at the polymer–filler interface, while vacuum irradiation revealed the opposite effect. These results were supported by solid-state NMR experiments that correlated the motional dynamics of the polymer chains with crosslink density through T₂ relaxation time measurements. GC/MS analysis was used to identify degradation products formed as a result of irradiation and speculate upon likely degradation mechanisms.     

A simultaneous TG–DTA study of the thermal decomposition of 2-hydroxybenzoic acid, 2-carboxyphenyl ester (salsalate)

Simultaneous thermogravimetry–differential thermal analysis (TG–DTA) and gas and liquid chromatography with mass spectrometry detection have been used to study the kinetics and decomposition of 2-hydroxybenzoic acid, 2-carboxyphenyl ester, commercially known as salsalate. Samples of salsalate were heated in the TG–DTA apparatus in an inert atmosphere (100 ml min⁻¹ nitrogen) in the temperature range 30–500 °C. The data indicated that the decomposition of salsalate is a two-stage process. The first decomposition stage (150–250 °C) had a best fit with second-order kinetics with E_a=191–198 kJ/mol. The second decomposition stage (300–400 °C) is described as a zero-order process with E_a=72–80 kJ/mol. The products of the decomposition were investigated in two ways:

(a)Salsalate was heated in a gas chromatograph at various isothermal temperatures in the range 150–280 °C, and the exit gas stream analyzed by mass spectrometry (GC–MS). This approach suggested that salsalate decomposes with the formation of salicylic acid, phenol, phenyl salicylate, and cyclic oligomers of salicylic acid di- and tri-salicylides.

(b)One gram samples of salsalate were heated in a vessel under nitrogen to 150 °C, and the residues were analyzed by liquid chromatography–mass spectrometry (LC–MS). The major compound detected was a linear tetrameric salicylate ester.

     

Thermal degradation behaviour of aromatic poly(ester-amide) with pendant phosphorus groups investigated by pyrolysis-GC/MS

The thermal stability of a novel phosphorus-containing aromatic poly(ester-amide) ODOP-PEA was investigated by thermogravimetric analysis (TGA). The weight of ODOP-PEA fell slightly at the temperature range of 300-400 °C in the TGA analysis, and the major weight loss occurred at 500 °C. The structural identification of the volatile products resulted from the ODOP-PEA pyrolysis at different temperatures was performed by pyrolysis-gas chromatography/mass spectrometry (pyrolysis-GC/MS). The P-C bond linked between the pendant DOPO group and the polymer chain disconnected first at approximately 275 °C, indicating that it is the weakest bond in the ODOP-PEA. The P-O bond in the pendant DOPO group was stable up to 300 °C. The cleavage of the ester linkage within the polymer main chain initiated at 400 °C, and the amide bond scission occurred at greater than 400 °C. The structures of the decomposition products were used to propose the degradation processes happening during the pyrolysis of the polymer.     

The effect of humidity on thermal process of zinc acetate

The thermal decomposition of zinc acetate dihydrate Zn(CH₃CO₂)₂·2H₂O in some humidity-controlled atmospheres has been successfully investigated by novel thermal analyses, which are sample-controlled thermogravimetry (SCTG), thermogravimety combined with evolved gas analysis using mass spectrometry (TG–MS) and simultaneous measurement of differential scanning calorimetry and X-ray diffractometry (XRD–DSC). The thermal processes of anhydrous zinc acetate in dry gas atmosphere by conventional linear heating experiment initiated with the sublimation around 180 °C, followed by the fusion and the decomposition over 250 °C. SCTG was useful to interpret clearly the successive reaction because the high-temperature parallel decompositions were effectively inhibited. The thermal behavior changed dramatically by introducing water vapor in the atmosphere and the thermal process was quite different from that in dry gas atmosphere. Zinc oxide (ZnO) was formed only in a humidity-controlled atmosphere, and could be easily synthesized at temperatures below 300 °C. XRD–DSC equipped with a humidity generator revealed directly the crystalline change from Zn(CH₃CO₂)₂ to ZnO. A detailed thermal process of Zn(CH₃CO₂)₂·2H₂O and the effect of water vapor are discussed.     

Thermal degradation kinetics of g-HA/PLA composite

Thermal degradation behaviors of a composite constituted by poly(l-lactide) (PLA) and hydroxyapatite nanoparticle that was surface-grafted with l-lactic acid oligomer (g-HA) in a nitrogen atmosphere were studied using thermogravimetric analysis (TGA) and compared with PLA. The kinetic models and parameters of the thermal degradation of PLA and the g-HA/PLA composite were evaluated by the invariant kinetic parameters (IKP) method and Flynn–Wall–Ozawa (FWO) method based on a set of TGA data obtained at different heating rates. It was shown that the conversion functions calculated by means of the IKP method depend on a set of kinetic models. The g-HA particle slowed down the thermal degradation of PLA polymer matrix.     

Comparison of EI and metastable atom bombardment ionization for the identification of polyurethane thermal degradation products

Polyurethanes are widely used in the manufacture of commercial products such as foams and paints. During combustion, these polymers can generate isocyanates, which induce adverse health effects. Polymer pyrolysis (Py) hyphenated with mass spectrometry (MS) allows the investigation of polymer thermal degradation over time/temperature. A diphenylmethanediisocyanate (MDI) polyurethane foam was analyzed with electron ionization (EI) and metastable atom bombardment (MAB) ionization at a pyrolysis temperature of 400 °C. The recently introduced MAB ionization source uses discrete energy stored in metastable atoms of gases to ionize the analytes. This characteristic allows modulation of the ionization energy by simply changing the ionization gas. The extensive fragmentation of molecular ions observed using EI 70 eV is not totally eliminated with EI 10 eV. However, only molecular ions are observed with MAB using N₂ as the ionization gas. Temperature gradients were used to separate the products generated during the thermal degradation of a 1,6-hexamethylenediisocyanate (HDI) polyurethane paint. The analysis of mass spectra was facilitated owing to a selective desorption of pyrolysis products. Furthermore, changing the MAB ionization gas allows elucidation of the structure of the pyrolysis products by controlling the extent of their fragmentation. During these experiments, isocyanic acid, methyleneisocyanate, ethyleneisocyanate, propylisocyanate and butylisocyanate were detected.     

Thermal characterization of Al2O3 and ZnO reinforced silicone rubber as thermal pads for heat dissipation purposes

Silicone rubber filled with thermally conductive, but electrically insulating Al₂O₃ or ZnO fillers were investigated to be used as elastomeric thermal pads, a class of thermal interface materials. The effect of Al₂O₃ or ZnO fillers on the thermal conductivity and coefficient of thermal expansion (CTE) of the silicone rubber were investigated, and it was found that with increasing Al₂O₃ or ZnO fillers, the thermal conductivity of the thermal pads increases, while the coefficient of thermal expansion (CTE) decreases. The thermal conductivity results obtained were also analyzed using the Agari model to explain the effect of Al₂O₃ or ZnO fillers on the formation of thermal conductive networks. Thermal gravimetry analysis (TGA) showed that the addition of either Al₂O₃ or ZnO fillers increases the thermal stability of the silicone rubber, while the scanning electron microscope (SEM) showed that at 10 vol.% filler loading percolation threshold has yet to be reached.     

Thermal decomposition of polymeric aminoborane (H2BNH2)x under hydrogen release

Polymeric aminoborane (H₂BNH₂)_x has been isolated during the thermal decomposition of solid borazane H₃BNH₃ at temperatures below 370 K. Polymeric aminoborane is a white noncrystalline solid, stable at room temperature and up to 380 K. In the temperature range of 380–500 K polymeric aminoborane undergoes a thermal decomposition, which was studied by differential scanning calorimetry (DSC), by thermogravimetry (TG) and by volumetric measurements. The solid residue was characterized by IR spectroscopy, by powder X-ray diffraction (XRD) analysis and by solid state ¹¹B NMR spectroscopy.

The thermal decomposition of polymeric aminoborane (H₂BNH₂)_x is an exothermic process accompanied by evolution of nearly 1 mol hydrogen per mole H₂BNH₂ unit corresponding to the volumetric measurements. The detected mass loss of the solid phase indicates the formation of further gaseous products beside hydrogen. The final mass loss increases with rising heating rate, in contrast to the final amount of evolved hydrogen, which still remains constant.     

三氟甲烷磺酸稀土盐对聚丙烯热稳定性的影响及机理

通过熔融共混将三氟甲烷磺酸镱[Yb(OTf)₃]和三氟甲烷磺酸镧[La(OTf)₃]添加至聚丙烯(PP)中, 制得PP/Yb和PP/La材料, 并对其热稳定性进行表征. 热失重分析(TGA)和差示扫描量热分析(DSC)结果显示, Yb(OTf)₃和La(OTf)₃均可以显著提高聚丙烯的热稳定性. 当Yb(OTf)₃添加量仅为1%(质量分数)时, PP的起始分解温度从275 ℃提高至305 ℃, 最大分解温度从384 ℃提高至405 ℃, 160 ℃下的氧化诱导时间从12.1 min延长至43.0 min, 热焓从1907 J/g降低至483 J/g; 而PP/La1的起始分解温度、 最大分解温度、 160 ℃下的氧化诱导时间和热焓分别为300 ℃, 409 ℃, 18.6 min和633 J/g. 结果表明, La(OTf)₃对聚丙烯热稳定性的改善作用弱于Yb(OTf)₃, 对2种稀土盐产生不同实验结果的原因进行分析并提出机制. 由于阴离子和阳离子的共同作用, Yb(OTf)₃和La(OTf)₃均可提高PP的热氧稳定性. La(OTf)₃中三氟甲烷磺酸根的自由基捕捉能力和稀土离子的配位能力发挥主要作用, 而Yb(OTf)₃中的稀土离子的高反应活性也起到关键作用.