笼型倍半硅氧烷(POSS)/环氧杂化树脂体系固化反应动力学及性能研究

为了提高环氧树脂的耐热性,采用笼型倍半硅氧烷(POSS)改性双酚A型环氧树脂E51,得到有机无机杂化树脂。采用Ozawa和Kissinger两种方法研究了杂化树脂/4,4′-二氨基苯砜(DDS)体系的固化反应动力学。TGA分析表明,POSS的加入提高了E51/DDS固化树脂体系的热性能。     

Influence of methacryl polyhedral oligomeric silsesquioxane on the thermal and mechanical properties of methylsilicone resin

A methacryl polyhedral oligomeric silsesquioxane (POSS)‐reinforced methylsilicone resin was prepared in this work. The structures of the obtained products were confirmed with Fourier transform infrared and atomic force microscopy. The influence of methacryl‐POSS on the thermal behavior of the methylsilicone resin was studied by thermogravimetric analysis and isothermal thermogravimetric analysis. The results showed that the thermal stability of the methylsilicone resin was improved, and the degree of thermooxidative degradation was lowered; this was due to the retardation of polymer chain motion and the formation of a protective layer of SiO₂. The interlaminar shear strength and flexural strength of quartz fiber/methylsilicone resin composites were tested to determine the effects of methacryl‐POSS on the mechanical properties of methylsilicone resin. The results revealed that the mechanical properties of the methylsilicone composites also increased obviously after the incorporation of methacryl‐POSS because of the increase in the cure degree and rigidity of the resin. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal pressure coefficient of a polyhedral oligomeric silsesquioxane (POSS)‐reinforced epoxy resin

The thermal pressure coefficients of a neat, unfilled, epoxy resin and a 10 wt % POSS (polyhedral oligomeric silsesquioxane)‐filled epoxy nanocomposite have been measured using a thick‐walled tube method. It is found that just below the glass transition temperature the thermal pressure coefficient is ～ 20% smaller for the polymer composite containing 10% POSS than for the neat, unfilled resin. The thermal expansion coefficient and thermal pressure coefficient of the uncured POSS itself are also reported. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

POSS基聚合物的热性能和阻燃性

本文介绍了POSS单体和POSS基聚合物的结构、性能和制备方法。重点阐述了各类POSS基聚合物以及它们的热性能。同时简单介绍了POSS对聚合物阻燃性的影响,分析了POSS提高聚合物热性能和阻燃性的原因,并展望了POSS基聚合物的发展方向。     

Preparation and thermal properties of hybrid nanocomposites of poly(methyl methacrylate)/octavinyl polyhedral oligomeric silsesquioxane blends

A series of poly(methyl methacrylate) (PMMA)/octavinyl polyhedral oligomeric silsesquioxane (POSS) blends were prepared by the solution‐blending method and characterized with Fourier transform infrared, X‐ray diffraction, transmission electron microscopy, differential scanning calorimetry, and thermogravimetric analysis techniques. The glass‐transition temperature (T_g) of the PMMA–POSS blends showed a tendency of first increasing and then decreasing with an increase in the POSS content. The maximum T_g reached 137.2°C when 0.84 mol % POSS was blended into the hybrid system, which was 28.2°C higher than that of the mother PMMA. The X‐ray diffraction patterns, transmission electron microscopy micrographs, and Fourier transform infrared spectra were employed to investigate the structure–property relationship of these hybrid nanocomposites and the T_g enhancement mechanism. The results showed that at a relatively low POSS content, POSS as an inert diluent decreased the interaction between the dipolar carbonyl groups of the homopolymer molecular chains. However, a new stronger dipole–dipole interaction between the POSS and the carbonyl of PMMA species formed at the same time, and a hindrance effect of nanosize POSS on the motion of the PMMA molecular chain may have played the main role in the T_g increase of the hybrid nanocomposites. At relatively high POSS concentrations, the strong dipole–dipole interactions that formed between the POSS and carbonyl groups of the PMMA gradually decreased because of the strong aggregation of POSS. This may be the main reason for the resultant T_g decrease in these hybrid nanocomposites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of the Hierarchical Structure in Poly(propylene)/Clay Composites on their Thermal Stability: From Single‐ to Multi‐Step Degradation Processes

Composites with several hierarchical structures were prepared by using different clays, compatibilizers, and PPs. TGA showed that the thermal stability of the composites can be strongly improved, under either inert or thermo‐oxidative conditions, depending on the type of clay and its morphology. Drastic increases in the temperature of the maximum rate of weight loss (ΔT_peak ≈ 170 °C) under thermo‐oxidative conditions were observed depending on the clay dispersion. Furthermore, some composites had a complex multi‐step degradation behavior instead of a single‐step process related with different clay morphologies that can be present simultaneously. Finally, it was concluded that the TGA has a higher sensitivity toward the composite morphology than the mechanical properties.

     

The preparation and physical properties of UP/montmorillonite nanocomposite by UV radiation curing

This article describes the preparation and properties of unsaturated polyester (UP)/montmorillonite (MMT) nanocomposite by UV radiation. Benzildimethylketal and 1‐hydroxy cyclohexyl phenyl ketone (HCPK) as a photoinitiator in UP were photolyzed under nitrogen condition. Analysis of X‐ray diffraction patterns of the composites shows that the interlayer spacing of MMT is substantially increased. The type and amount of photoinitiator affects the level of improvement in mechanical properties, and our results suggest that HCPK is a more efficient photoinitiator of UP curing reaction. The interaction between photoinitiators and MMT should be considered to acquire the reinforcement effect of the dispersed MMT nanolayers. The properties of nanocomposite are dependent upon the amount of MMT. The effect of MMT concentration on thermal and dielectric properties is also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3609–3615, 2006     

Thermal and mechanical properties of polyhedral oligomeric silsesquioxane (POSS)/polycarbonate composites

A series of composite materials were produced incorporating polyhedral oligomeric silsesquioxane (POSS) derivatives into polycarbonate (PC), by melt blending. Significant differences in compatibility were observed depending on the nano-scale filler's specific structure: trisilanol POSS molecules generally provided better compatibility with PC than fully-saturated cage structures, and phenyl-substituted POSS grades were shown to be more compatible with PC than fillers with other functional groups. Trisilanolphenyl-POSS/PC composites possess the best overall performance among the POSS materials tested. The high compatibility between the trisilanolphenyl-POSS and polycarbonate matrix results in generation of transparent samples up to 5 wt% POSS content. Slightly enhanced mechanical properties including tensile and dynamic mechanical modulus are observed with the increase of trisilanolphenyl-POSS loading at the cost of decreasing ductility of the nanocomposites. Importantly, upon orientation of the PC/POSS nanocomposite, crystallization of POSS within the oriented material results—this observation is consistent with a growing number of observations which suggest that ‘bottom-up’ formation of structures incorporating multiple POSS cages result from orientation of these nanocomposites, and that the hybrid organic-inorganic inclusions may be at the heart of observed nano-scale reinforcement.     

Preparation,structural characterization,and properties of poly(methyl methacrylate)/montmorillonite nanocomposites by bulk polymerization

Poly(methyl methacrylate) (PMMA)/montmorillonite (MMT) nanocomposites were synthesized by a simple technique of a monomer casting method, bulk polymerization. The products were purified by hot acetone extraction and characterized by Fourier transform infrared spectroscopy, X‐ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), examination of their mechanical properties, and light transmittance testing. Although XRD data did not show any apparent order of the MMT layers in the nanocomposites, TEM revealed parallel MMT layers with interlamellar spacings of an average of 9.8 nm and the presence of remnant multiplets of nonexfoliated layers. Therefore, PMMA chains were intercalated in the galleries of MMT. DSC and TGA traces also corroborated the confinement of the polymer in the inorganic layer by exhibiting the increase of glass‐transition temperatures and mass loss temperatures in the thermogram. Both the thermal stability and the mechanical properties of the products appeared to be substantially enhanced, although the light transmittances were not lost. Also, the materials had excellent mechanical properties. Measurement of the tensile properties of the PMMA/MMT nanocomposites indicated that the tensile modulus increased up to 1013 MPa with the addition of 0.6 wt % MMT, which was about 39% higher than that of the corresponding PMMA; the tensile strength and Charpy notched impact strength increased to 88 MPa and 12.9 kJ/m², respectively. As shown by the aforementioned results, PMMA/MMT nanocomposites may offer new technology and business opportunities. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 348–357, 2005     

Epoxy/benzoxazinyl POSS nanocomposite resin with low dielectric constant and excellent thermal stability

Benzoxazinyl modified polyhedral oligomeric silsesquioxane (BZPOSS) is successfully synthesized and used to prepare nanocomposites with bisphenol A type epoxy resin (E51). The differential scanning calorimetry results showed the curing peak temperature of E51/BZPOSS blend decrease to 242°C, suggesting the high catalytic activity of BZPOSS to the polymerization of E51. The scanning electron microscope micrographs of poly(E51/BZPOSS)s and silicon element distribution maps given by EDS both demonstrated homogeneous dispersion of BZPOSS. Dielectric properties tests confirmed the dielectric constant can be reduced by the introduction of BZPOSS, which is attributed to the nano-pores from the cage structure of POSS. When 20 wt% BZPOSS was added, the dielectric constant decreased to 2.28 at 1 MHz. Meanwhile, DMA and TGA results indicated the thermal stability and heat resistance of poly(E51/BZPOSS)s at high temperature increased with the increase of BZPOSS, which is due to the increase of the crosslinking density and the change of crosslinking structure of copolymer.     

Thermal degradation and pyrolysis study of phosphorus‐containing polysulfones

This article deals with the thermal decomposition behavior of a polysulfone containing 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide versus the initial chloromethylated polysulfone under an inert atmosphere and in air. Thermogravimetric characteristics from thermogravimetry and differential thermogravimetry data revealed important differences related to the employed atmosphere, the types of substituted functional groups, or the degree of substitution. The introduction of the 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide pendent group into polysulfone enhanced the thermal stability of the initial chloromethylated polysulfone in both an inert atmosphere and air. Thermal degradation in nitrogen consisted of one degradation step, whereas thermooxidative degradation in air involved more steps. In air, the degradation mechanism was more complex. The volatile products and solid residues that resulted after pyrolysis in an inert atmosphere and in air were analyzed with Fourier transform infrared and mass spectrometry. Environmental scanning electron microscopy showed that the char residues had different morphologies, which suggested that a more compact structure led to better resistance to heat and oxygen. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 000: 000–000, 2011     

Thermal degradation of flax: The determination of kinetic parameters with thermogravimetric analysis

The thermal degradation of flax was investigated with thermogravimetric analysis. The flax used for these experiments underwent different stages of retting or, in one case, boiling. The most retted type of flax was also chemically treated to obtain elementary fibers. These samples were all tested in dynamic and isothermal runs after careful sample preparation. The resulting thermograms were analyzed and later used to calculate the kinetic parameters of cellulose degradation. These kinetic parameters included reaction constants and activation energies. A clear difference in the various tested types of flax was observed through a comparison of these values, and an explanation for these differences was suggested. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2634–2643, 2002     

Thermal,mechanical, and dielectric properties of aluminum silicate fiber reinforced aluminum phosphate–poly(ether sulfone) layered composites

In this study, a novel aluminum phosphate (AlPO₄) heat‐resistant layer reinforced with aluminum silicate fiber (ASF) was successfully compounded on a poly(ether sulfone) (PES) matrix via the preparation process of high‐temperature heat treatment and vacuum hot‐pressing sintering technique. The influence of the ASF content on the morphology, thermal, mechanical, and dielectric properties of the as‐fabricated aluminum silicate fiber reinforced aluminum phosphate–poly(ether sulfone) (ASF/AlPO₄–PES) layered composite was investigated. The results reveal that the incorporation of aluminum silicate fiber/aluminum phosphate (ASF/AlPO₄) heat‐resistant layer can significantly improve the thermal stability and mechanical performances of the PES matrix composites. Compared with the pristine PES, the ASF/AlPO₄–PES layered composite containing 8.0 wt % ASF exhibited better high‐temperature resistance properties (300 °C) and a lower thermal conductivity (0.16 W m^?1 K^?1). Furthermore, the dielectric constant and dielectric loss tangent of this PES matrix composite decreased to 2.16 and 0.007, respectively. Meanwhile, the frequency stability of the dielectric properties for the ASF/AlPO₄–PES layered composites was remarkably enhanced with increasing ASF addition at frequencies ranging from 10² Hz to 5 MHz. This was attributed to the existence of microscopic pores within the ASF/AlPO₄ layer and the strong interfacial bonding between the ASF/AlPO₄ layer and the PES matrix. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45542.     

Thermal degradation kinetics of poly(N‐adamantyl‐exo‐nadimide) synthesized by addition polymerization

The thermal decomposition behavior and degradation kinetics of poly(N‐adamantyl‐exo‐nadimide) were investigated with thermogravimetric analysis under dynamic conditions at five different heating rates: 10, 15, 20, 25, and 30°C/min. The derivative thermogravimetry curves of poly(N‐adamantyl‐exo‐nadimide) showed that its thermal degradation process had one weight‐loss step. The apparent activation energy of poly(N‐adamantyl‐exo‐nadimide) was estimated to be about 214.4 kJ/mol with the Ozawa–Flynn–Wall method. The most likely decomposition process was an F1 deceleration type in terms of the Coats–Redfern and Phadnis–Deshpande results. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3003–3009, 2007     

Phenolic resin-trisilanolphenyl polyhedral oligomeric silsesquioxane (POSS) hybrid nanocomposites: Structure and properties

The structure and properties of organic-inorganic hybrid nanocomposites prepared from a resole phenolic resin and a POSS mixture containing >95 wt% trisilanolphenyl POSS was investigated by POM (polarized optical microscopy), SEM, TEM, WAXD, FT-IR, DSC, and TGA techniques. Composites with 1.0-10.4 wt% of POSS were prepared by dissolving the POSS and the phenolic resin into THF, followed by solvent removal and curing. Both nano- and micro-sized POSS filler aggregates and particles were shown to be heterogeneously dispersed in the cured matrix by POM, TEM, SEM, and X-EDS. POSS was found everywhere, including in both dispersed phase domains and in the matrix. The nanocomposite morphology appears to form by a multi-step POSS aggregation during the process of phase separation. Both the matrix and dispersed ‘particulate’ phase domains are mixtures of phenolic resin and POSS. POSS micro-crystals act as the core of the dispersed phase. The bigger dispersed domains consist of smaller particles or aggregates of POSS molecules that exhibit some order but regions of matrix resin are interspersed. A WAXD peak at 2θ∼7.3° indicates crystalline order in the POSS aggregates. This characteristic peak's intensity increases with an increase in POSS loading, suggesting that more POSS molecules have aggregated or crystallized. FT-IR spectra confirm that hydrogen bonding exists between the phenolic resin and POSS Si-OH groups. This increases their mutual compatibility, but H-bonding does not prevent POSS aggregation and phase separation during curing. TGA measurements in air confirmed the temperature for 5% mass loss in increases with increase of POSS loading and at T>550° the thermal stability increases more sharply with POSS loading. The nanocomposite glass transition temperatures (T_g) are only slightly be affected by the POSS filler.     

Mechanical properties and thermal stability of poly(L‐lactide)/calcium carbonate composites

Poly(L ‐lactide) (PLA) was melt‐mixed with micrometer‐sized and nanosized calcium carbonate (CaCO₃) particles before and after modification with calcium stearate. Adhesion between the CaCO₃ particles and the PLA matrix was assessed qualitatively by scanning electron microscopy observation of the fractured surface morphology of the composites. The effect of the incorporation of the CaCO₃ particles on the thermal stability of the PLA‐based composites was quantified by the temperatures corresponding to 5 and 50% of weight loss and the activation energy determined through thermogravimetric analyses of the composites. The tensile strength and modulus values of the composite were improved greatly without a significant loss in the elongation at break when the nanosized CaCO₃ was incorporated up to 30 wt %. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal degradation of LC epoxy thermosets

A novel liquid crystalline (LC) epoxy monomer was cured with different types of hardeners. The thermal‐degradation properties of cured thermosets were evaluated by thermogravimetric (TG) analysis. Several widely used kinetic models were reviewed and used to fit the TG data. The experimental results showed that the methods from one constant heating rate are insensitive to the magnitude of reaction order n. The Kissinger and Osawa methods from multiple processes would give more confident kinetic parameters in these observed systems. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1514–1521, 2000     

Selective preparation of oligomeric naphthylene ether and its applications to epoxy resin for silicon carbide power semiconductor device materials

In this study, a novel method for selective synthesis of naphthylene ether trimers by self‐condensation of 2,7‐dihydroxynaphthalene in the presence of catalytic amount of potassium hydroxide was reported. An epoxy resin from the trimers was prepared and properties of the cured epoxy resin were examined. The cured resin showed not only good physical thermal stability, such as high glass transition temperature and low thermal expansion coefficient, but also good chemical thermal stability like high thermal decomposition temperature. Additionally, low moisture absorption of the cured resin was confirmed. From these results, the newly prepared epoxy resin with naphthylene ether skeletons was considered to be suitable for advanced applications such as silicon carbide power semiconductor device. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43339.     

Thermal degradation kinetics of polyimide nanocomposites from different carbon nanofillers: Applicability of different theoretical models

In this study, the nanocomposites of polyimide (PI) with the nanofillers multiwalled carbon nanotube (MWCNT) and carbon nanofiber (CNF) were prepared by in situ polymerization technique. The thermal stability of the nanocomposites were investigated and discussed with respect to nanofillers type, concentration, and their functionality within the PI matrix. It is observed that there are 16 and 18 °C increment in thermal degradation temperature with the addition of 3 wt % MWCNT and CNF within the PI matrix, respectively. The thermal degradation kinetics of the nanocomposites were studied by Kissinger–Akahira–Sunose method, Flynn–Wall–Ozawa method, and Kim–Park method. The results show that these models are well fitted with the experimental data. It is found that the calculated activation energy increases with the increase in nanofillers loading and PI/CNF nanocomposites exhibit higher activation energy compared to PI/MWCNT composites at their similar loading. Moreover, the effect of nanofillers type and loading on the glass transition temperature of nanocomposites were also investigated in details. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45862.     

Thermal degradation kinetics of epoxy/organically modified montmorillonite nanocomposites

Nanocomposites based on a commercial epoxy resin and organically modified montmorillonites (OMMTs), containing 5 and 10 phr OMMT, were prepared and characterized. Poly(oxypropylene) diamine (Jeffamine D400) and octadecylamine were used as organic modifiers. Another poly(oxypropylene) diamine (Jeffamine D230) was used as a curing agent. The thermal degradation kinetics of the neat resin system and nanocomposites were investigated by thermogravimetric analysis. The dispersion of silicate layers within the crosslinked epoxy matrix was verified by transmission electron microscopy. The activation energy of degradation for the investigated systems was determined by the isoconversional Kissinger–Akahira–Sunose method. The thermal behavior of the neat resin systems and nanocomposites was modeled with an empirical kinetic model. The influence of organic modifiers and the OMMT loading on the thermal stability of the nanocomposites was discussed. © 2007 Wiley Periodicals, Inc. JAppl Polym Sci, 2008