Preparation and properties of borosiloxane gels

Hybrid gels were synthesized from modified silicon alkoxides (R‐Si(OEt)₃, R?H, Me, Vi) and triiso‐butylborate (B(O? R′)₃, R′ = isoBu). The obtained gels were characterized by Fourier‐transform infrared (FTIR), nuclear magnetic resonance (NMR), elemental analyses, X‐ray diffraction (XRD), and scanning electron microscopy (SEM). Boron atoms in the precursors were homogeneously dispersed in the siloxane network via Si? O? B bonds. The effect of the boron load on oxidation resistance of the gels, and the pyrolysis behavior of the borosiloxane gels with different substituents on silicon, were investigated using various techniques. The experimental results suggest that the addition of a proper fraction of boron alkoxide to the precursors can improve the oxidation stability of the gels, and decrease the weight loss of the samples to 6.9 wt % at 1000°C under air. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 719–724, 2006     

A new modified silicone–TiO2 polymer composite film and its photocatalytic degradation

The photodegradation of the silicone surfactant–TiO₂ composite films was characterized by FTIR, Raman spectroscopy, and scanning electron microscope. After photocatalytic degradation, the FTIR Si? O? Si peak intensity of the composite film remained unchanged, implying no cleavage of Si? O? Si bond. The above Si? O? Si peak intensity is sensitive to the polyoxyethylene chain length of the composite. The PEG10000‐silicone composite is more resistant to photodegradation than those composites with lower molecular weight of constituent PEGs. The wetting rates of the silicone surfactant–TiO₂ composites showed that modified silicone composite films exhibited hydrophobic nature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3341–3344, 2006     

Organic–inorganic hybrid boron‐containing phenol–formaldehyde resin/SiO2 nanocomposites

The organic–inorganic hybrid boron‐containing phenol–formaldehyde (BPFR) resin/SiO₂ nanocomposites was synthesized in‐situ from boric acid, phenol, and tetramethoxysilane. The structure of BPFR modified and the distributions of silicon element were studied by Fourier‐transform infrared spectroscopy, energy dispersive X‐ray spectrometry, and transmission electron microscope, respectively. The glass transition temperature (T_g) was determined by torsional braid analysis. The results show that silicon element distribution is homogeneous, and the size of nanosilica is about 40–60 nm. The thermal stability and kinetics parameters of thermal degradation were determined by thermogravimetry analysis (TGA). TGA results show that the resin modified has higher heat resistance property when the additive quantity of SiO₂ was 3 wt%. The temperature of 5% weight loss is 487.7°C, which is 12.4°C higher than that of common BPFR. The residual ratio of 3 wt% SiO₂/BPFR was 62.3% at the temperature of 900°C, which is 11.2% higher than that of common BPFR. The mechanics loss peak T_p of 3% SiO₂/BPFR is 33°C higher than common BPFR. Fiberglass‐reinforced BPFR modified by 3 wt% SiO₂ has better mechanical and dielectric properties than that of common BPFR. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers     

Synthesis and effects of MDT silicone resin on PMPS‐based ablative composites

A novel methylphenyl silicone resin, with M, D, and T units, was synthesized by cohydrolysis and cocondensation method from dimethyldimethoxysilane (Me₂Si(OMe)₂), phenyltrimethoxysilane (PhSi(OMe)₃), hexamethyldisiloxane, and 1,3‐divinyl‐1,1,3,3‐tetramethyldisiloxane in toluene/water mixture catalyzed by hydrochloric acid and trifluoromethanesulfonic acid. The vinyl end‐capped MDT silicone resins were chosen for reinforcement filler to enhance the mechanical properties of silicone‐based ablative composites. The effects of resins with various R/Si ratios, vinyl content, and loadings on mechanical properties of PMPS rubbers were investigated. It was revealed that on the premise of good fluidity and processing performance, MDT resin showed excellent reinforcing effect and thermal stability compared with silica. MDT reinforced ablative composite showed satisfactory mechanical and antiablative properties. The linear ablation rate was 0.01 mm/s, which maybe associated with high yield of charred residue in thermogravimetric analysis results. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41571.     

Curing behavior and thermal properties of multifunctional epoxy resin with methylhexahydrophthalic anhydride

The curing behavior and thermal properties of bisphenol A type novolac epoxy resin (bisANER) with methylhexahydrophthalic anhydride (MHHPA) at an anhydride/epoxy group ratio of 0.85 was studied with Fourier‐transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetry. The results showed that the FTIR absorption intensity of anhydride and epoxide decreased during the curing reaction, and the absorption peak of ester appeared. The dynamic curing energies were determined as 48.5 and 54.1 kJ/mol with Kissinger and Flynn–Wall–Ozawa methods, respectively. DSC measurements showed that as higher is the curing temperature, higher is the glass transition. The thermal degradation of the cured bisANER/MHHPA network was identified as two steps: the breaking or detaching of ? OH, ? CH₂? , ? CH₃, OC? O and C? O? C, etc., taking place between 300 and 450°C; and the carbonizing or oxidating of aromatic rings occurring above 450°C. The kinetics of the degradation reaction was studied with Coats–Redfern method showing a first‐order process. In addition, vinyl cyclohexene dioxide (VCD) was employed as a reactive diluent for bisANER (VCD/bisANER = 1 : 2 w/w) and cured with MHHPA, and the obtained network had a higher T_g and a slight lower degradation temperature than the undiluted system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2041–2048, 2007     

Energetics and Structure of Polymer‐Derived Si–(B–)O–C Glasses: Effect of the Boron Content and Pyrolysis Temperature

The structure and properties of polymer‐derived Si–(B–)O–C glasses have been shown to be significantly influenced by the boron content and pyrolysis temperature. This work determined the impact of these two parameters on the thermodynamic stability of these glasses. High‐temperature oxide melt solution calorimetry was performed on a series of amorphous samples, with varying boron contents (0–7.7 at.%), obtained by pyrolysis of precursors made by a sol–gel technique. Thermodynamic analysis of the calorimetric results demonstrated that at a constant pyrolysis temperature, adding boron makes the materials energetically less stable. While the B‐containing glasses pyrolyzed at 1000°C were energetically less stable than the competitive crystalline components, increasing the pyrolysis temperature to 1200°C led to their enthalpic stability. ²⁹Si and ¹¹B MAS nuclear magnetic resonance (NMR) spectroscopy measurements on selected samples confirmed a decrease in the concentrations of mixed Si‐centered SO_iC_4?i and B‐centered BO_jC_3?j bonds at the expense of formation of SiO₄ and B(OSi)₃ species (indicating a tendency toward phase separation) when the boron content and pyrolysis temperature increased. In light of the findings from calorimetry and NMR spectroscopy, we propose a structure–energetic relationship in Si–(B–)O–C glasses.     

Synthesis and optical and thermal properties of poly[methyl(2,9‐diphenyl‐ 7,8‐benzophenanthryl)silylene‐co‐1,4‐bis(methylphenylsilyl)phenylene]

Poly[methyl(2,9‐diphenyl‐7,8‐benzophenanthryl)silylene‐co‐1,4‐bis(methylphenylsilyl)phenylene] (PMBS‐co‐BSP) was synthesized by the condensation reaction of dichloromethyl(2,9‐diphenyl‐7,8‐benzophenanthryl)silane and 1,4‐bis(chloromethylphenylsilyl)benzene with sodium in toluene. Optical and thermal behavior of the polymer was investigated. Because of the introduction of substituted benzophenanthryl groups into the Si atoms of the polymer, the UV absorption wavelength of the PMBS‐co‐BSP red‐shifted significantly in the UV region, and a strong photoluminescence band was observed in the visible region other than the near‐UV photoluminescence typical of normal polysilane. The photochemical behavior was examined both in solution and in thin film by fluorescence and UV spectroscopy. Irradiation of the PMBS‐co‐BSP with a low‐pressure mercury lamp in solution resulted in homolytic scission of silicone–silicone bonds; the fluorescence emission intensities decreased gradually with increasing UV irradiation time and the maximum emission wavelength blue‐shifted significantly. Irradiation of thin solid films of the PMBS‐co‐BSP in air led to the formation of photoproducts containing Si? OH and Si? O? Si groups. The PMBS‐co‐BSP began to weigh less at about 300 °C and the weight loss of the polymer at 700 °C was calculated to be 75% of the initial weight in N₂. Copyright © 2006 Society of Chemical Industry     

Kinetics of thermal degradation of nanometer calcium carbonate/linear low‐density polyethylene nanocomposites

To improve the thermal properties of linear low‐density polyethylene (LLDPE), the CaCO₃/LLDPE nanocomposites were prepared from nanometer calcium carbonate (nano‐CaCO₃) and LLDPE by melt‐blending method. A series of testing methods such as thermogravimetry analysis (TGA), differential thermogravimetry analysis, Kim‐Park method, and Flynn‐Wall‐Ozawa method were used to characterize the thermal property of CaCO₃/LLDPE nanocomposites. The results showed that the CaCO₃/LLDPE nanocomposites have only one‐stage thermal degradation process. The initial thermal degradation temperature T₀ increasing with nano‐CaDO₃ content, and stability of LLDPE change better. The thermal degradation activation energy (E_a) is different for different nano‐CaCO₃ content. When the mass fraction of nano‐CaCO₃ in nanocomposites is up to 10 wt %, the nanocomposite has the highest thermal degradation E_a, which is higher (28 kJ/mol) than pure LLDPE. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and properties of optically clear silicone resin/epoxy resin hybrids

Optically clear silicone/epoxy hybrid resins were synthesized. The silicone resin (SiR) carrying Si? H, Si? CH?CH₂ and Si? OH groups was prepared by hydrolytic condensation. The blends of SiR and diglycidyl ether of hydrogenated bisphenol A (DGEHBA) were cured through platinum‐catalyzed hydrosilylation and aluminium acetylacetonate‐catalyzed polymerization. The curing process was studied using differential scanning calorimetry and rigid‐body pendulum rheometry. It was found that the ratio of SiR to DGEHBA plays a major role in the curing process. The Si? OH groups of SiR assist polymerization of DGEHBA, and react with the epoxy resin to prevent phase separation. The cured hybrid resins are single‐phase materials with a transmittance of about 87% at 400 nm for a thickness of 3 mm using air as reference. UV resistance and thermal stability of the hybrids are largely dependent on the composition. The adhesive strength of the SiRs can be significantly improved by a small fraction of DGEHBA, with a marginal influence on UV resistance. However, increasing the epoxy proportion has a marked negative influence on thermal stability. Compounding stabilizers, especially thermal stabilizers, are essential, in particular for high epoxy content, if the hybrids are to be used for high‐brightness light‐emitting diode packaging. Copyright © 2011 Society of Chemical Industry     

Thermal degradation kinetics of poly(O,O‐diethyl‐O‐allylthiophosphate‐co‐acrylonitrile) in nitrogen

The nonisothermal degradation kinetics of the copolymer poly(O,O‐diethyl‐O‐allylthiophosphate‐co‐acrylonitrile), which was synthesized with O,O‐diethyl‐O‐allylthiophosphate and acrylonitrile, were studied by thermogravimetry/derivative thermogravimetry techniques. The kinetic parameters, including the activation energy and the pre‐exponential factor of the copolymer degradation process, were calculated by the Kissinger and Flynn–Wall–Ozawa methods. The thermal degradation mechanism of the copolymer was also studied with the Satava–Sestak method. The results show that the activation energies were 138.17 kJ/mol with the Kissinger method and 141.63 kJ/mol with the Flynn–Wall–Ozawa method. The degradation of the copolymer followed a kinetic model of a phase boundary reaction and the kinetic equation could be expressed as G(α) = 1 ? (1 ? α)⁴ [where G(α) is the integral function of conversion and α is the extent of conversion of the reactant decomposed at time t]. The reaction order was 4. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical and thermal enhancements of benzoxazine‐based GF composite laminated by in situ reaction with carboxyl functionalized CNTs

An easy and efficient approach by using carboxyl functionalized CNTs (CNT‐COOH) as nano reinforcement was reported to develop advanced thermosetting composite laminates. Benzoxazine containing cyano groups (BA‐ph) grafted with CNTs (CNT‐g‐BA‐ph), obtained from the in situ reaction of BA‐ph and CNT‐COOH, was used as polymer matrix and processed into glass fiber (GF)‐reinforced laminates through hot‐pressed technology. FTIR study confirmed that CNT‐COOH was bonded to BA‐ph matrices. The flexural strength and modulus increased from 450 MPa and 26.4 GPa in BA‐ph laminate to 650 MPa and 28.4 GPa in CNT‐g‐BA‐ph/GF composite, leading to 44 and 7.5% increase, respectively. The SEM image observation indicated that the CNT‐COOH was distributed homogeneously in the matrix, and thus significantly eliminated the resin‐rich regions and free volumes. Besides, the obtained composite laminates showed excellent thermal and thermal‐oxidative stabilities with the onset degradation temperature up to 624°C in N₂ and 522°C in air. This study demonstrated that CNT‐COOH grafted on thermosetting matrices through in situ reaction can lead to obvious mechanical and thermal increments, which provided a new and effective way to design and improve the properties of composite laminates. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Octa(aminophenyl) polyhedral oligomeric silsesquioxane/boron‐containing phenol–formaldehyde resin nanocomposites: Synthesis,cured, and thermal properties

Octa(aminophenyl) polyhedral oligomeric silsesquioxane (OAP‐POSS) and boron‐containing phenol‐formaldehyde resin (BPFR) were synthesized, respectively. The BPFR nanocomposites with different OAP‐POSS content (wt%) were prepared, and their properties were characterized. The results show that the thermal degradation process of this nanocomposites can be divided into three stages, and they are all following the first order mechanism. The residual ratio and thermal degradation activation energy E_a of 9 wt% OAP‐POSS/BPFR nanocomposites are both better than others and the E_a increase gradually in three stages, which is 93.3, 134.0, and 181.9 kJ mol⁻¹, respectively. Its residual ratio at 900°C is 36.48%. The mechanical loss peak temperature T_p is 228°C for 12 wt% OAP‐POSSS/BPFR nanocomposites, which is higher 48°C than pure BPFR. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Silicone resin synthesized by tetraethoxysilane and chlorotrimethylsilane through hydrolysis–condensation reaction

Silicone pressure‐sensitive adhesives compositions contain a polydimethylsiloxane and a silicone resin, which can enhance the instant bonding ability and bonding strength of the adhesive. In this study, silicone resin was designed to have a low molecular weight and a highly nonpolar chemical structure. The silicone resin was applied to silicone pressure‐sensitive adhesives. The molecular structure of silicone resin was characterized by FT‐IR, GPC, ¹H‐NMR, and ²⁹Si‐NMR spectroscopic techniques. Properties such as thermal stability, solubility, hydrophobic, and transparent properties were researched and compared. When the chlorotrimethylsilane increased, it appeared that the amount of silanol groups, molecular weight and thermal stability decreased, while the hydrophobic and transparent properties increased. The silicone resin was completely soluble in toluene and xylene. It was also applied to silicone pressure‐sensitive adhesives, resulting in good peel adhesion. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40317.     

Modification of polyethylene–octene elastomer by silica through a sol–gel process

In this study, tetraethoxysilane (TEOS) and a metallocene polyethylene–octene elastomer (POE) were chosen as the ceramic precursor and the continuous phase, respectively, for the preparation of new hybrids by an in situ sol–gel process. To obtain a better hybrid, a maleic anhydride‐grafted polyethylene–octene elastomer (POE‐g‐MAH), used as the continuous phase, was also investigated. Characterizations of POE‐g‐MAH/SiO₂ and POE/SiO₂ hybrids were performed by Fourier transform infrared (FTIR) and ²⁹Si solid‐state nuclear magnetic resonance (NMR) spectrometers, a differential scanning calorimeter (DSC), a thermogravimetry analyzer, and an Instron mechanical tester. The results showed that the POE‐g‐MAH/SiO₂ hybrid could improve the properties of the POE/SiO₂ hybrid because the interfacial force between the polymer matrix and the silica network was changed from hydrogen bonds into covalent Si? O? C bonds through dehydration of hydroxy groups in POE‐g‐MAH with residual silanol groups in the silica network. The existence of covalent Si? O? C bonds was proved by FTIR spectra. For the POE/SiO₂ and POE‐g‐MAH/SiO₂ hybrids, maximum values of the tensile strength and the glass transition temperature were found at 9 wt % SiO₂ since a limited content of silica might be linked with the polymer chains through the covalent bond. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 966–972, 2003     

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     

Flame retardancy and thermal degradation behaviors of epoxy resins containing bisphenol a bis (diphenyl phosphate) oligomer

Bisphenol A bis(diphenyl phosphate) oligomer (BBO) as flame retardant was synthesized, whose structure was characterized by IR and NMR. In all, 20% weight mixture polyphosphoric acid (APP) and BBO was doped into epoxy resins (EPs) to get 26.0% of limiting oxygen index and UL 94 V‐0. The degradation behavior of EP‐containing BBO/APP was studied by thermogravimetry, differential thermogravimetry, scanning electron microscopy, and cone calorimeter. The activation energies for the decomposition of EP samples are obtained using the method of Kissinger. The experimental results exhibited that for EP‐containing BBO/APP, compared with EP, initial decomposition temperature, maximum temperature at the peak position (T_m), and the activation energy for the decomposition are decreased, whereas the maximum weight loss rate (R_max), char yields, and the inherent thermal stability are increased. Meanwhile, heat release, smoke production, and CO yield and CO₂ yield of EP‐containing BBO/APP are much decreased compared with those of EP. The thermal degradation mechanism of EP‐containing BBO/APP has been proposed. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Microstructure evolution of ammonia‐catalyzed phenolic resin during thermooxidative aging

The thermooxidative aging of ammonia‐catalyzed phenolic resin for 30 days at 60–170°C was investigated in this article. The aging mechanism and thermal properties of the phenolic resin during thermooxidative aging were described by thermogravimetry (TG)–Fourier transform infrared (FTIR) spectroscopy, attenuated total reflectance (ATR)–FTIR spectroscopy, and dynamic mechanical thermal analysis. The results show that the C? N bond decomposed into ammonia and the dehydration condensation between the residual hydroxyl groups occurred during the thermooxidative aging. Because of the presence of oxygen, the methylene bridges were oxidized into carbonyl groups. After aging for 30 days, the mass loss ratio reached 4.50%. The results of weight change at high temperatures coincided with the results of TG–FTIR spectroscopy and ATR–FTIR spectroscopy. The glass‐transition temperature (T_g) increased from 240 to 312°C after thermooxidative aging for 30 days, which revealed the postcuring of phenolic resins. In addition, an empirical equation between the weight change ratio and T_g was obtained. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermal degradation study of interpenetrating polymer network based on modified bismaleimide resin and cyanate ester

Interpenetrating polymer networks (IPNs) based on different ratios of a modified bismaleimide resin (BMI/DBA) and cyanate ester (b10) have been synthesized via prepolymerization followed by thermal curing. A systematic thermal degradation study of these new BMI/DBA‐CE IPN resin systems was conducted by thermogravimetric analysis at different heating rates both in N₂ (thermal stability) and in air (thermal‐oxidative stability). The cured BMI/DBA‐CE IPN resin systems show excellent thermal stability, which could be demonstrated by 5% weight loss temperature (T_5%) ranging between 409 and 423 °C, maximum decomposition rate temperature (T_max) ranging between 423 and 451 °C, and the char yields at 800 °C ranging from 37% to 41% in nitrogen at a heating rate of 10 °C min^?1. The apparent activation energy associated with the main degradation stage of the cured BMI/DBA‐CE IPN resin systems was determined using the Kissinger method. The obtained results provide useful information in drawing correlation between thermal properties and structure. © 2003 Society of Chemical Industry     

Thermal degradation kinetics of a commercial epoxy resin—Comparative analysis of parameter estimation methods

The thermal degradation behavior of a commercial epoxy resin, EpoFix® (Struers), has been investigated by thermogravimetry (TG), differential thermal gravimetry (DTG), and differential thermal analysis (DTA) under nonisothermal conditions in an argon atmosphere. Different methods (Kissinger, Flynn–Wall–Ozawa (FWO), Friedman isoconversion methods, and nonlinear least‐squares (NLSQ) estimation method) have been used to analyze the thermal degradation process and determine the apparent kinetic parameters. The methods produce similar results in terms of activation energy estimations. Nevertheless, the NLSQ method has several advantages over the other methods in terms of both characterizing the activation energy and modeling the thermal degradation—i.e., including this model in a resin degradation process simulation. However, it is interesting to combine the NLSQ method with other isoconversion methods: they can reflect the dependence and variability of the activation energies during pyrolysis processes, while providing a good starting point for a nonlinear procedure, especially with respect to the activation energy E. This work is the first step (apparent kinetic reaction) of complete simulation of experimental oven of degradation of epoxy resin coating of impregnate nuclear fuel sample. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42201.     

Preparation and performance of high refractive index silicone resin‐type materials for the packaging of light‐emitting diodes

A novel high refractive index and highly transparent silicone resin‐type material for the packaging of high‐power light‐emitting diodes (LEDs) is introduced, which was synthesized by hydrosilylation of vinyl end‐capped methylphenyl silicone resin and methylphenyl hydrosilicone oil catalyzed by Karstedt's catalyst. The vinyl end‐capped methylphenyl silicone resins were prepared by hydrolysis?polycondensation method from methylphenyl diethoxysilane (MePhSi(OEt)₂), phenyl triethoxysilane (PhSi(OEt)₃), and vinyl dimethylethoxy silane (Me₂ViSiOEt) in toluene/water mixture catalyzed by cation‐exchange resin. The vinyl end‐capped methylphenyl silicone resins were characterized by ¹H‐NMR and Fourier‐transform infrared. The performances of the cured silicone resin‐type materials for LED packaging have been examined in detail. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013