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     

Thermal curing reaction and heat‐resistance of methyl‐di(M‐ethynylphenyl‐amino)silane

Methyl‐di(m‐ethynylphenyl‐amino)silane (MEAS) is a new kind of silazane with ethynylphenyl groups in the end of the molecule. The studies about the curing reaction kinetics and curing reaction mechanism are important for its application and performance. In this article, differential scanning calorimeter was used to study the curing reaction kinetics of MEAS. The results showed that both of the apparent activation energy (E_a) and the reaction order (n) that were evaluated with the method of Kissinger (113.4 kJ/mol, 0.93) agreed well with those using the method of Ozawa (116.1 kJ/mol, 0.95). According to structural changes during curing characterized using Fourier‐transform infrared spectra, it was inferred that MEAS resin underwent the main four kinds of cross‐linking reaction under the condition of heating. Thermogravimetric analysis was used to characterize the heat‐resistance of MEAS thermoset. The results showed that the temperature of 5% weight loss based on the initial weight (T_d5) of the thermoset was 632.4°C and the residue yield at 900°C was 86.4% in nitrogen. The thermoset sintered at 1450°C in argon transformed into a ceramic with yield of 71%, which was studied by scanning electron microscopy and X‐ray diffraction. The sintered products were smooth and hard solid and its chemical composition was made up of β‐SiC, α‐Si₃N₄ ceramic and free carbon. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis,cure and pyrolysis behavior of heat‐resistant boron‐silicon hybrid polymer containing acetylene

The synthesis and characterization of a novel heat‐resistant boron‐silicon hybrid polymer containing acetylene (PBSA) and its conversion to a highly crosslinked thermoset were discussed. The polymer was synthesized from phenylboron dichloride using Grignard reagent method. The structure of PBSA was characterized by using Fourier transform infrared spectra, ¹H‐NMR, ¹³C‐NMR, and gel permeation chromatography. PBSA was thermosetting, highly heat‐resistant, high‐viscous, orange liquid at room temperature and good solubility in common organic solvents. Differential scanning calorimetry and thermogravimetric analysis analyses showed that the PBSA had excellent thermal and oxidative stability and the temperature of 5% weight loss (Td₅) were 650 and 638°C under nitrogen and air, respectively, and the residue at 1000°C were 93.3 and 91.3%, respectively, which indicated that the incorporation of boron and silicon into polymeric backbone was found to improve thermal and oxidative properties. X‐ray diffraction and scanning electron microscope were also used to analyze the formation of pyrolytic products. The results showed that the pyrolysis of PBSA resin was made up of β‐SiC and graphite. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Novel heat resistant methyl‐tri(phenylethynyl)silane resin: Synthesis,characterization and thermal properties

Methyl‐tri(phenylethynyl)silane (MTPES) was successfully synthesized by the reaction of lithium phenylacetylide with methyltrichlorosilane. The structure was characterized by HRMS, FTIR, ¹H‐NMR, ¹³C‐NMR, ²⁹Si‐NMR, and elementary analysis. Thermal cure process was monitored by DSC, DMA, and FTIR. MTPES was heated to free flowing liquid around 130°C and thermally polymerized at 327–377°C to form thermoset. Thermal and oxidative properties were evaluated by TGA analysis. Thermoset exhibits extremely high heat‐resistance and TGA curve in nitrogen shows the temperature of 5% weight loss (Td₅) of 695°C and total weight loss at 800°C of 7.1%. TGA shows a high Td₅ of 565°C even in air, although the total weight loss at 800°C was 56.1% of the initial weight, much higher than that in nitrogen. The high heat resistance of MTPES was ascribed to crosslinking reaction concerning ethynyl groups. Aging studies performed at elevated temperatures in air on a thermoset showed that MTPES is oxidatively stable to 300°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2488–2492, 2006     

Bismaleimide‐modified methyl‐di(phenylethynyl)silane blends and composites: Cure characteristics,thermal stability,and mechanical property

Reactive blends of organic‐inorganic hybrid monomer, methyl‐di(phenylethynyl)silane (MDPES) and a modified bismaleimide resin (BMI/DBA) have been prepared. The thermal and oxidative stabilities of MDPES‐BMI/DBA blends were characterized by thermogravimetric analysis, derivative thermogravimetry, differential thermal analysis, dynamic mechanical analysis, and flexural strength retention at 240°C. Scanning electron microscopy was employed to study the surface morphology of MDPES‐BMI/DBA composite after thermal oxidative treatment. With the increase of concentration of BMI/DBA, flexural strength of composites increased from 78 to 331 MPa. The results showed that MDPES‐BMI/DBA blends exhibited excellent thermal and thermal oxidative properties, and the interface between MDPES and glass fiber was improved by the incorporation of BMI/DBA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of phosphorus‐containing polyhedral oligomeric silsesquioxanes via hydrolytic condensation of a modified silane

A simple route to synthesize a new type of phosphorus‐containing polyhedral oligomeric silsesquioxanes (DOPO–POSS) in high yield, by the hydrolytic condensation of a modified silane, is reported. The starting material was a phosphorus‐containing triethoxy silane (DOPO–VTES), which was synthesized by addition reaction between 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) and vinyl triethoxy silane (VTES). This product was subjected to hydrolytic condensation using an HCl catalyst in methanol. The new types of phosphorus‐containing POSS were obtained and characterized using ¹H, ¹³C, ²⁹Si‐NMR, MALDI‐TOF MS, XRD, DSC, and FTIR. All of these results suggested that the DOPO–POSS were amorphous mixtures of T₈, T₉(OH), and TGA curve of DOPO–POSS shows that the cage‐like compound has high thermal stability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Study of thermal stability and ablation behavior of carbon/epoxy‐novolac composites

The use of carbon/epoxy‐novolac composites as advanced ablative materials for insulation of exit cone of solid‐propellant rocket nozzles are studied. In this article, three types of carbon fabrics are used and their composites are prepared by use of impregnation and hand lay‐up methods. To study the thermal stability and ablation behavior, these composites are tested by thermal tests such as thermogravimetric analysis (TGA) and oxyacetylene standard flame tests; the latter test is one of the most important standard tests of ablative materials. The test apparatus is made according to American standard, ASTM‐E‐285‐80, and over 33 polymeric composites and 3 steel specimens were carried out according to its standards. It is found that the composites that are made up of C‐9750 fabric (high‐strength carbon fabric) in comparison with steel and the other types of carbon fabric specimens have the highest thermal stability and the best ablation behavior. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2455–2461, 2003     

Synthesis of single component element‐block materials based on siloxane‐based cage frameworks

This mini‐review focuses on recent efforts to prepare single component element‐block materials based on siloxane‐based cage frameworks, a promising approach to control the sequence of organic and inorganic segments in organic–inorganic hybrids at the molecular level. Polyhedral octasilsesquioxanes, denoted (RSiO_1.5)₈ or labeled T₈ cages, and octadimethylsiloxy‐Q₈ cages, denoted (RSiMe₂OSiO_1.5)₈, are used here as siloxane‐based cage frameworks. Thermoplastic optically transparent silsesquioxane materials derived from a single cage compound can be obtained with dumbbell‐ and star‐shaped cage structures, allowing precise design of their structures for tuning properties. The siloxane‐based cage core dendrimers are ideal candidates for single component element‐block materials which possess three‐dimensional, well‐defined molecular level structures. Their rigid and cubic inorganic frameworks provide unique features for siloxane‐based cage core dendrimers. These topics attract attention in both academia and industry. © 2016 Society of Chemical Industry     

Synthesis and characterization of dendritic poly(amidoamine)‐silica gel hybrids

Novel dendrimer‐silica gel hybrids were prepared from amino‐terminated poly(amidoamine) generation 3 (32 cascade) and its partly ester‐terminated derivatives with tetraethoxysilane in the presence of a coupling agent 3‐glycidoxypropyltrimethoxysilane by in situ sol‐gel process. The scanning electron micrograph spectra showed that these transparent hybrids have the nanocomposite structure. Their transparent and thermal properties were characterized by ultraviolet, thermogravimetric analysis. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2186–2190, 2000     

Evaluation of poly(methylsilane‐carbosilane) synthesized from methyl‐dichlorosilane and chloromethyldichloromethylsilane as a precursor for SiC

A new poly(methylsilane‐carbosilane) (PMSCS) for silicon carbide precursor was synthesized by Wurtz‐type copolycondensation of methyldichlorosilane (MeHSiCl₂) with chloromethyldichloromethylsilane (ClCH₂MeSiCl₂) and terminated with vinylmagnesium chloride (ViMgCl). The use of insufficient sodium made the reaction more economic and safe. By changing the ratios of two monomers and the end‐block agent, the properties of the obtained PMSCS and the C/Si ratio of its derived ceramic could be tuned. Upon pyrolysis at 1000 °C under argon, silicon carbide with nearly stoichiometric C/Si ratio and low oxygen content was obtained in 64% of ceramic yield. PMSCS showed high potential as an economical SiC ceramic precursor for the fabrication of SiC matrix, coating, and adhesives. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46610.     

Ultraviolet‐curing behavior of an epoxy acrylate resin system

Ultraviolet (UV)‐curing behavior of an epoxy acrylate resin system comprising an epoxy acrylate oligomer, a reactive diluent, and a photoinitiator was investigated by Fourier transform infrared (FTIR) spectroscopy. The conversion changes of the resin system containing 20 phr of 1,6‐hexanediol diacrylate as a reactive diluent and 2‐hydroxy‐2‐methyl‐1‐phenyl‐propan‐1‐one as a photoinitiator were measured under different UV‐curing conditions. The fractional conversion was calculated from the area of the absorption peak for the vinyl group vibration occurring at 810 cm^?1. The effects of photoinitiator concentration, total UV dosage, one‐step or stepwise UV irradiation, UV intensity, atmosphere, and temperature on the curing behavior of the resin system were investigated. The conversion of the resin system increased rapidly at the initial stage of the UV‐curing process but increased very slowly after that. The final conversion of the resin system was mainly affected by total UV dosage. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1180–1185, 2005     

Thermal cure behavior of unsaturated polyester/phenol blends

Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to detect and simulate the cure behavior of unsaturated polyester (UP), phenol, and UP/phenol blends and to calculate and predict the cure rate, cure temperature, conversion, and changes in the glass‐transition temperature along with various cure orders in order to obtain the optimum parameters for processing. With dynamic scanning and isothermal DSC procedures and Borchardt–Daniels dynamic software, cure data for the UP resin were obtained, 90% of the conversion rate at 100°C being achieved after 15 min. However, for the phenol and UP/phenol blends, gradually increasing the temperature was found to be best for curing according to the DSC and DMA test results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1041–1058, 2004     

Novel trifluoromethyl‐containing poly(amide–imide)s: Organosolubility,optical behavior,thermostability, and crystallinity

A new dicarboxylic acid monomer, 2,6‐bis(1,3‐dioxo‐5‐carboxyisoindolin‐2‐yl)‐4,4′‐bis(trifluoromethyl)‐1,1′‐diphenyl ether (IFDPE), bearing two preformed imide rings was synthesized via a three‐step manner from 4‐(trifluoromethyl)phenol and 4‐chloro‐3,5‐dinitrobenzotrifluoride. The monomer IFDPE was then used to prepare a series of novel trifluoromethyl‐containing poly(amide–imide)s via a direct phosphorylation polycondensation with various aromatic diamines. The intrinsic viscosities of the polymers were found to be in the range 0.86–1.02 d/g. The weight‐ and number‐average molecular weights of the resulting polymers were determined with gel permeation chromatography. The polymeric samples were readily soluble in a variety of organic solvents and formed low‐color, flexible thin films via solution casting. The values of the absorption edge wavelength were determined by ultraviolet–visible spectroscopy, and all of the resulting poly (amide–imide)s films exhibited high optical transparency. The resulting polymers showed moderately high glass‐transition temperatures in the range 295–324°C and had 10% weight loss temperatures in excess of 524°C in nitrogen. The crystallinity extents were qualitatively investigated with wide‐angle X‐ray diffraction measurements. Scanning electron microscopy images revealed an agglomerated bulk with nonuniformity on the surface. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Addition‐curable propargyl‐containing novolac‐type phenolic resin: Its synthesis,characterization, cure,and thermal properties

In this article, propargyl functionalized novolac resins (PN resins), with varying propargyl contents and varying molecular weights, were synthesized conveniently. The structural characteristics were determined by ¹HNMR and FTIR methods. Thermal cure studies revealed that the uncatalyzed thermal cure was remarkably affected by propargyl extent, while it was hardly affected by molecular weight. The processability of the as‐prepared PN resins was excellent as matrix of composite materials. The cure mechanism was complicated; postcure at high temperature was required to achieve entire crosslink formation. Both dynamic mechanical analysis and thermogravimetric analysis showed that the cured PN resins had substantially improved thermal mechanical properties and thermal stability in comparison to conventional cured phenolics. High propargyl extent was preferred for high thermal stability. The results show that PN resin is one of the ideal candidates for advanced composites matrices in thermostructural and ablative applications. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1010–1017, 2006     

Thermal,thermomechanical, and electrochemical characterization of the organic–inorganic hybrids poly(ethylene oxide) (PEO)–silica and PEO–silica–LiClO4

To study the effect of the silica content on the properties of the salt‐free and salt‐added hybrids based on poly(ethylene oxide) (PEO) and silica, two series of hybrids, PEO–silica and PEO–silica–LiClO₄ (O:Li, 9:1) hybrids were prepared via the in situ acid‐catalyzed sol–gel reactions of the precursors [i.e., PEO functionalized with triethoxysilane and tetraethyl orthosilicate (TEOS)]. The morphology of the hybrids was examined by scanning electron microscopy (SEM) of the fracture surfaces of the hybrid. The results indicated that the discontinuity develops with increasing the weight percent of silica in both hybrids. The differential scanning calorimetric (DSC) analysis indicated that effects of silica content on the glass transition temperatures (T_g) of the PEO phase were different in salt‐free and salt‐added hybrids. The T_g of PEO phase increased with increasing weight percent of silica in salt‐free hybrids, whereas the curve of T_g of PEO phase and silica content had a maximum at 35 wt % of silica content in salt‐added hybrids. For both salt‐free and salt‐added hybrids, peaks of the loss tangent, determined by dynamic mechanical analysis (DMA) were gradually broadened and lowered with increasing weight percent of silica. The storage modulus, E′, in the region above T_g increases with increasing silica content for both PEO–silica and PEO–silica–LiClO₄ hybrids. In the conductivity and composition curves for PEO–silica–LiClO₄ hybrids, the conductivity shows a maximum value of 3.7 × 10^?6 S/cm, corresponding to the sample with a 35 wt % of silica. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2471–2479, 2001     

两种甲基苯乙炔硅烷的共聚物酰亚胺改性研究

以苯乙炔与甲基二氯硅烷、甲基三氯硅烷在有机锂试剂中反应,合成了甲基二苯乙炔基硅烷(MD-PES)和甲基三苯乙炔基硅烷(MTPES)2种新型耐高温有机硅树脂。TGA和500℃烧蚀测试经酰亚胺(Imide)改性的二者共聚物的复合材料表明:其耐热保持性优异,5%热失量温度最高可达643℃,800℃质量保留率可达94.7%;材料具有较好的力学性能,弯曲强度、硬度及冲击强度可分别达到235 MPa、61和104.5 kJ/m2;复合材料介电常数与介电损耗正切值变化较小,介电性能优异;饱和吸水率在1.15%~4.79%,耐湿性能优异。     

四苯乙炔基硅烷的合成及热性能研究

为得到耐热的含有苯乙炔官能团的有机硅单体,通过苯乙炔锂(由苯乙炔与丁基锂制得)与四氯硅烷的反应,合成了四苯乙炔基硅烷(TPES),通过多次重结晶获得了纯度为99.5%的TPES,并用FTIR、1HNMR、13C NMR、29Si NMR及元素分析对其结构进行了表征。对TPES及其400℃固化物的DSC、FTIR和TGA的分析表明:TPES的熔融温度范围宽达113℃(199℃~312℃);在氮气中失重5%时的温度Td5为710.8℃,800℃残炭率高达93.3%,空气中的Td5为595℃,800℃残炭率也达58.3%,耐热性能十分优异,具备作为一种耐高温聚合物材料的优秀潜质。     

Polymer–organoclay hybrids by polymerization into montmorillonite‐vinyl monomer interlayers

A different series of polymer–clay hybrid materials have been prepared by modification of the clay with different vinyl monomers, followed by polymerization of different ratios of vinyl monomers–clay with the monomers, such as methyl methacrylate, hydroxyethyl methacrylate, and styrene‐maleic anhydride. The materials were investigated by IR, which confirmed the intercalation of vinyl‐cation within the clay interlayers, and by TGA, which illustrated that phosphonium cation has high thermal stability than ammonium cation. Swelling studies of these materials in different organic solvents showed that the swelling degree increases as clay ratio decrease, and also showed higher swelling relative to vinyl–clay. X‐ray diffraction illustrated that the nanocomposites were exfoliated up to a 25 wt % content of organoclay relative to the amount of polymer. SEM and TEM examined the micrograph, which showed a good dispersion of the polymers into clay galleries, and formation of nanosize particles ranged 150–300 Å. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Phenol‐containing phthalonitrile polymers – synthesis,cure characteristics and laminate properties

Novolac–phthalonitrile polymers bearing a controlled concentration of phthalonitrile groups were synthesized by condensation of novolac with 4‐nitrophthalonitrile. The cure characteristics monitored by DSC and rheometry indicated acceleration of the cure reaction by the phenolic groups. Fourier transform infrared analysis of the cured products indicated that the cure mechanism was dependent on the extent of phthalonitrile substitution. In phenol‐rich systems, evidence was obtained for the phenol‐mediated reaction of nitrile groups resulting in the formation of isoindoline groups. The phthalonitrile‐rich system underwent crosslinking through formation of triazine and phthalocyanine groups. The phenol groups in the phthalonitrile backbone were conducive to building a stronger interphase in their carbon composites, resulting in better mechanical properties. This was corroborated by morphological studies by SEM. However, these groups were detrimental to the thermal stability of the cured resins. The polymers exhibited very high flame retardancy which improved further on increasing the degree of phthalonitrilation. Copyright © 2012 Society of Chemical Industry     

Thermooxidative degradation behavior of poly(silphenylene–siloxane)s

Copolymers of poly(silphenylene–siloxane) with dimethylsiloxane and diphenylsiloxane with various end groups were synthesized through an Si? H/Si? OR polycondensation process. The thermooxidative degradation behaviors of the copolymers were investigated by thermogravimetric analysis and IR spectrometry techniques. All of the polymers were characterized by a two‐step mass loss. The first one, which peaked at 510–545°C in differential thermogravimetric curves, was mostly caused by the main‐chain depolymerization, whereas the second one, which reached its maximum around 650°C, was caused by side‐group oxidation and Si? C bond scission. The main‐chain depolymerization occurred over a temperature range of some 470–580°C, whereas Si? C bond scission and side‐group oxidation occurred over a temperature range of about 585°C to above 720°C. The incorporation of phenyl groups in the end groups greatly retarded the temperature for the degradation onset of the main chain to 120°C higher. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010