Synthesis of a caged bicyclic phosphates derived anhydride and its performance as a flame‐retardant curing agent for epoxy resins

A novel curing and flame‐retardant agent (PEPA‐TMAC) was successfully synthesized. The chemical structure was characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Use of PEPA‐TMAC as part of the curing agent in combination with another anhydride for a commercial epoxy resin (EP) was studied. Results of differential scanning calorimetry (DSC) indicated that PEPA‐TMAC was an effective curing agent for EP. The dynamic mechanical analysis (DMA) results showed that the glass transition temperature (T_g) and cross‐linking density (V_e) of EP composites exhibited an increase trend with the addition of PEPA‐TMAC. The limiting oxygen index (LOI) value of EP composites reached 26.9%, and the cone calorimeter results indicated that peak heat release rate (PHRR), total heat release (THR), smoke produce rate (SPR), and total smoke produce (TSP) remarkably decreased with increasing PEPA‐TMAC content. TGA data showed that the addition of PEPA‐TMAC greatly increased the amount of residual char during combustion. The morphology of the residual char was studied by SEM and showed that the addition of PEPA‐TMAC greatly increased the stability of EP composites. The thermogravimetric analysis (TGA), energy‐dispersive X‐ray spectroscopy (EDS), and FTIR results revealed the flame‐retardant mechanism that PEPA‐TMAC can promote the formation of charred layers with the phospho‐carbonaceous complexes in the condensed phase during burning of EP composites.     

Flame retardancy of epoxy resin nanocomposite with a novel polymeric nanoflame retardant

A wrapped nanoflame retardant, designated as polyhedral oligomeric silsesquioxane (POSS)‐poly(4‐bromostyrene) (PBS)‐carbon nanotubes (CNTs), was synthesized via π‐π stacking interactions between the walls of multiwalled carbon nanotubes and the silicon‐bromine containing hybrid copolymer (designated as POSS‐PBS) that was copolymerized by 4‐bromostyrene and acryloyloxyisobutyl polyhedral oligomeric silsesquioxane. The POSS‐PBS‐CNTs exhibited good dispersibility in epoxy resin (EP) without obvious aggregation. Furthermore, the fire behaviors of this flame‐retardant EP (FR‐EP) nanocomposites were examined via limited oxygen index (LOI) and cone calorimeter (CONE) tests. The FR‐EP had an ideal LOI value of 35.3% and its residual char yield obtained from CONE test was significantly enhanced from 5.9% to 15.3% with the incorporation of 4 wt% POSS‐PBS‐CNTs and 1.33 wt% Sb₂O₃ into EP matrix. Additionally, the addition of 4 wt% POSS‐PBS‐CNTs or POSS‐PBS can efficiently decrease the peak heat release rate (PHRR) of EP matrix by 41.0% or 45.6%, respectively.     

The polyoctahedral silsesquioxane (POSS) 1,3,5,7,9,11,13,15‐octaphenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (octaphenyl‐POSS)

Solvent‐free single crystals of 1,3,5,7,9,11,13,15‐octaphenylpentacyclo[9.5.1.1^3,9.1^5,15.1^7,13]octasiloxane (abbreviated as octaphenyl‐POSS), C₄₈H₄₀O₁₂Si₈, were obtained by dehydration/condensation of the tetrol Si₄O₄(Ph)₄(OH)₄. The powder pattern generated from the single‐crystal data matches well with the experimentally measured powder pattern of commercial octaphenyl‐POSS. The geometry of the centrosymmetric molecule in the crystal was compared with that in the gas phase, and had shorter Si—O bond lengths and a broader range of Si—O—Si bond angles. The average Si—O bond length [1.621 (3) Å], and Si—O—Si and O—Si—O bond angles [149 (5) and 109 (1)°, respectively] were within the same range measured previously for octaphenyl‐POSS solvates.     

Combustion and thermal properties of epoxy/phenyltrisilanol polyhedral oligomeric silsesquioxane nanocomposites

Organic–inorganic hybrid composites of epoxy and phenyltrisilanol polyhedral oligomeric silsesquioxane (Ph₇Si₇O₉(OH)₃, POSS-triol) were prepared via in situ polymerization of epoxy monomers. The nanocomposites of epoxy with POSS-triol can be prepared in the presence of metal complex latent catalyst, aluminum triacetylacetonate ([Al]) for the reaction between POSS-triol and diglycidyl ether of bisphenol A (DGEBA). The dispersion morphology of organic–inorganic hybrid was characterized by scanning electronic microscopy (SEM). The thermostability of composites was evaluated by thermal gravimetric (TG) analysis. The flammability was evaluated by cone calorimeter test. The presence of [Al] latent catalyst leads to a decrease in combustion rate with respect to epoxy and epoxy/POSS composites as well as reduction in smoke, CO and CO₂ production rate. The effect of [Al] is to reduce the size of spherical POSS particles from 3–5 μm in epoxy/POSS to 0.5 μm in epoxy/POSS[Al]. Furthermore, POSS with smaller size may form compact and continue char layer on the surface of composites more efficiently.     

Effect of Fe3O4‐doped sepiolite on the flammability and thermal degradation properties of epoxy composites

As‐received sepiolite/epoxy systems and Fe₃O₄‐doped sepiolite/epoxy systems were prepared, and the contents of sepiolite and Fe₃O₄‐doped sepiolite were kept as 2 and 4 wt%, respectively. Compared with sepiolite, the effect of Fe₃O₄‐doped sepiolite on the flame retardancy, combustion properties, thermal degradation, thermal degradation kinetics and thermomechanical properties of epoxy resin was investigated systematically by limiting oxygen index (LOI), cone calorimeter (Cone), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Some interesting results had been acquired. The addition of sepiolite decreased heat release rate, total smoke production and smoke production rate, and obviously improved LOI values of epoxy composites. Compared with sepiolite, the addition of Fe₃O₄‐doped sepiolite further reduced parameters mentioned above of epoxy composites, and further enhanced LOI values and char residues after cone test. There might be a synergistic effect between sepiolite and Fe₃O₄ on flame retardant epoxy composite. TGA results indicated that the addition of sepiolite had a slight effect on the thermal degradation of epoxy composites; however, the addition of Fe₃O₄‐doped sepiolite accelerated the thermal degradation of epoxy composites. DMA results showed that the addition of both sepiolite and Fe₃O₄‐doped sepiolite increased the glass transition temperature (T_g) of epoxy composite. The results obtained in this paper supplied an effective solution for developing excellent flame retardant properties of polymeric materials. Copyright © 2015 John Wiley & Sons, Ltd.     

Synergistic effect of bismuth oxide and mono‐component intumescent flame retardant on the flammability and smoke suppression properties of epoxy resins

A novel mono‐component intumescent flame retardant named pentaerythritol phosphate melamine salt (PPMS)‐hybrid bismuth oxide (PPMS‐Bi₂O₃) was synthesized and carefully characterized by FTIR, ¹H NMR, ³¹P NMR, SEM‐EDS, and TG analyses. Then, PPMS‐Bi₂O₃ was utilized as flame retardant for epoxy resins (EPs), and the thermal stability, flame retardancy, and smoke suppression properties of EP composites were investigated. TG results show that PPMS‐Bi₂O₃ is more conducive to enhance the thermal stability and char forming ability of EP composites compared with the same addition of PPMS or the mixture of PPMS and Bi₂O₃, and this positive effect is enhanced with the increasing Bi₂O₃ content. Cone calorimeter test reveals that the PPMS‐Bi₂O₃ can effectively reduce the heat release and smoke production in comparison with PPMS or the mixture of PPMS and Bi₂O₃ due to the formation of a more compact and intumescent char against fire, as judged by digital photographs and SEM images. EDS analysis indicates that the combination PPMS and Bi₂O₃ by hydrogen bonds promotes to generate more phosphorus‐rich and aromatization structures in the condensed phase that enhance the barrier effect and anti‐oxidation ability of the char, thus imparting higher flame retardant and smoke suppression efficiencies to EP composites.     

Microencapsulated ammonium polyphosphate with epoxy resin shell: preparation,characterization, and application in EP system

Microencapsulated ammonium polyphosphate with an epoxy resin (EP) shell (MCAPP) was prepared by in situ method, and was characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), and thermgravimetric analysis (TGA). Compared to ammonium polyphosphate (APP), MCAPP has smaller particle sizes and lower water solubility. The effect of MCAPP on the fire performance of EP was studied by using limiting oxygen index (LOI) and UL‐94 tests. When the same loading levels of APP or MCAPP were added into EP, the LOI and UL‐94 tests show similar results. Tensile, bending, and impact strengths of the EP/APP and EP/MCAPP composites were also evaluated, and the results indicate that MCAPP has much less negative influence on the mechanical properties than APP. Copyright © 2010 John Wiley & Sons, Ltd.     

Synergistic flame‐retardant effect and mechanisms of boron/phosphorus compounds on epoxy resins

To explore the component synergistic effect of boron/phosphorus compounds in epoxy resin (EP), 3 typical boron compounds, zinc borate (ZB), boron phosphate (BPO₄), and boron oxide (B₂O₃), blended with phosphaphenanthrene compound TAD were incorporated into EP, respectively. All 3 boron/phosphorus compound systems inhibited heat release and increased residue yields and exerted smoke suppression effect. Among 3 boron/phosphorus compound systems, B₂O₃/TAD system brought best flame‐retardant effect to epoxy thermosets in improving the UL94 classification of EP composites and also reducing heat release most efficiently during combustion. B₂O₃ can interact with epoxy matrix and enhance the charring quantity and quality, resulting in obvious condensed‐phase flame‐retardant effect. The combination of condensed‐phase flame‐retardant effect from B₂O₃ and the gaseous‐phase flame‐retardant effect from TAD effectively optimized the action distribution between gaseous and condensed phases. Therefore, B₂O₃/TAD system generated component synergistic flame‐retardant effect in epoxy thermosets.     

Preparation,flame retardancy,and thermal degradation of epoxy thermosets modified with phosphorous/nitrogen‐containing glycidyl derivative

Phosphorus/nitrogen‐containing advanced epoxy resins were obtained by chain‐extension of the diglycidyl ether of bisphenol‐A epoxy (DGEBA) resin with phosphorus‐modified triglycidyl isocyanurate (TGICP). The structure of TGICP was characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Differential scanning calorimetry revealed that the EP/TGICP composites possessed higher glass transition temperatures than that of phosphorus free EP. The thermal stability and flame retardant properties of the epoxy resin/TGICP systems were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), and vertical burning test (UL‐94) test. When the TGICP content was 10 wt%, the LOI value of epoxy resin system was as high as 35.0% and it can obtain the V‐0 grade in UL‐94 protocol. From microscale combustion calorimetry (MCC) measurement, it was found that the addition of TGICP reduced the value of peak heat release rate and total heat release. The thermal degradation process of EP and EP/TGICP composite was monitored by real time FTIR. Moreover, scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS) were used to explore the morphology and chemical components of the char residues. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of DOPO‐based pyrazine derivative and its effect on flame retardancy and thermal stability of epoxy resin

A novel DOPO‐based pyrazine derivative 6‐((2‐hydroxyphenyl)(pyrazin‐2‐ylamino)methyl)dibenzo[c,e][1,2]oxaphosphinine 6‐oxide (DHBAP) was triumphantly synthesized by a two‐step addition reaction using 2‐aminopyrazine, 2‐hydroxybenzaldehyde and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) as reactants, and characterized by Fourier‐transform infrared (FTIR), ³¹P nuclear magnetic resonance (NMR) and ¹H NMR. Afterwards, the addition type flame retardant (DHBAP) was utilized to modify epoxy resin (EP) by blending method. When the content of DHBAP in neat EP was 8 wt%, it reached to the V‐0 rating and the limited oxygen index (LOI) value up to 34.0%. Furthermore, according to the cone calorimeter (CC) test results, the heat release rate (HRR), total heat release (THR), smoke produce rate (SPR) and total smoke production (TSP) of EP/8% DHBAP decreased by 26.3%, 21.3%, 37.0% and 60.9% when compared with neat EP, respectively, indicating that DHBAP had good inhibition on heat and smoke releases. Eventually, the flame‐retardant mechanism of DHBAP was further explored by X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS). The results showed that DHBAP had good flame‐retardant activity in the gasous‐condensed two phases.     

Low flammability and smoke epoxy resins with a novel DOPO‐based imidazolone derivative

In this work, a DOPO‐based imidazolone derivative named DHI was synthesized using DOPO, 5‐amino‐2‐benzimidazolinone and 4‐hydroxybenzaldehyde as raw materials. The chemical structure of DHI was characterized by ¹H‐NMR, ³¹P‐NMR and Fourier transform infrared spectra (FTIR). Then, a series of different flame‐retardant epoxy resin (EP) thermosets were prepared by mixing flame retardant DHI. The thermal properties of the cured EPs was investigated by thermogravimetry analysis (TGA) and differential scanning calorimeter (DSC), and the results showed the thermal stability and glass transition temperature (T_g) of the cured EP modified with DHI declined slightly compared with that of neat EP. The limited oxygen index (LOI) and UL94 test results exhibited DHI imparted good flame retardancy to EP. The EP‐4 (phosphorus content of 1.25%) possessed a LOI value of 36.5% and achieved a V‐0 rating. Furthermore, the peak of heat release rate (PHRR) and total heat release rate (THR) of EP‐4 decreased by 38.7% and 24.5%, respectively. Excitedly, the total smoke production (TSP) of EP‐4 sample declined by 62.5%, which meant DHI also made EP obtain excellent smoke suppression property. Moreover, the flame‐retardant mechanism was studied by scanning electron microscopy (SEM) and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS). It was reasonable inferred that DHI could not only promote EP to form dense char layer in condensed phase, but also restrain combustion in gaseous phase through catching the free radicals sourced from the degradation of EP.     

Study of thermal properties of flame retardant epoxy resin treated with hexakis[p-(hydroxymethyl)phenoxy]cyclotriphosphazene

Hexakis[p-(hydroxymethyl)phenoxy]cyclotriphosphazene (HHPCP) is prepared and characterized by FTIR, ¹H-NMR, and ³¹P-NMR spectroscopy. Then an investigation of the flame retardancy, thermal decomposition behavior of epoxy resin (EP) containing HHPCP is carried out using limiting oxygen (LOI) test, horizontal flame test, smoke density rate (SDR) test, thermogravimetric analysis (TG), and thermal gravimetric analyzer-mass spectrometry (TG-MS). The decomposition process of HHPCP is studied by TG-MS and FTIR. The result shows that the LOI value of EP increase from 20.5 to 26.5 %, when 7.5 mass% HHPCP is added into EP. The addition of 1 mass% nano-montmorillonite (nMMT) into EP–7.5 mass% HHPCP sample as synergist can increase the LOI value of EP–7.5 mass% HHPCP–1 mass% nMMT sample from 26.5 to 27.5 %. The SDR test indicates that smoke suppression of HHPCP on EP is not significant. TG analysis reflects that the EP–7.5 mass% HHPCP sample and EP–7.5 mass% HHPCP–1 mass% nMMT show higher thermal stability properties with an increasing T _onset and T _max comparing with neat-EP. TG-MS result indicates that the main pyrolysis product of EP is H₂O, CO, CO₂, C₆H₆, C₆H₅OH, HOC₆H₄CH₃, and flammable hydrocarbon fragments C_xH_y. Compared with neat-EP sample, nonflammable water vapor of EP–7.5 mass% HHPCP sample increased, whereas CO₂ and the flammable hydrocarbon fragments C_xH_y and flammable gas CO decreased. TG-MS and FTIR result suggests that HHPCP decomposed first by inter-molecular dehydration, then P–N hexatomic ring of HHPCP decomposed during 470 and 560 °C, and a little no-flame gas containing nitrogen element volatilized into the gaseous phase.     

Co-flame retarding effect of ethanolamine modified titanium-containing polyhedral oligomeric silsesquioxanes in epoxy resin

A metal-doped organic and inorganic hybrid polyhedral oligomeric silsesquioxanes (POSS) with a titanium atom in the POSS cage and an ethanolamine substitute group in the corner, namely MEA-Ti-POSS, was synthesized through simple condensation reaction and substitute reaction. It was blended with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to form a kind of blending-type flame retardant system for the modification of epoxy resins. The thermal stability, flame retardancy and mechanical properties of cured epoxy resin composites were studied. Comparing with pure epoxy resin, the LOI value of EP/MEA-Ti-POSS/DOPO composites was raised from 25.2% to 32.7%, and the UL-94 grade reached V-0 level at a loading of the mixture of 5% MEA-Ti-POSS and 5% DOPO. In addition, the cone calorimetry results showed that the heat release rate, total heat release and total smoke production as well as smoke production rate were all reduced during the combustion of EP/MEA-Ti-POSS/DOPO composites. The residual char analysis revealed that carbon residues of EP/MEA-Ti-POSS/DOPO composite served as a physical protective layer to insulate the oxygen and combustible gases to reduce the ablation of the matrix. It was concluded that the mixture of MEA-Ti-POSS and DOPO not only effectively raised the thermal stability and flame retardancy of epoxy composited materials, but also improved their mechanical properties, which expanded a promising application of the metal-POSS derivatives as non-halogen additives in the flame retardant polymers.     

Zeolitic imidazolate frameworks‐8 modified graphene as a green flame retardant for reducing the fire risk of epoxy resin

A novel hybrid material of ZIF‐8/RGO (zeolitic imidazolate frameworks‐8 loaded the surface of graphene) was synthesised by a simple method and characterized. Then, ZIF‐8/RGO was added into epoxy resin (EP), and the flame retardancy and smoke suppression of the EP composites were studied. Compared with pure EP, the peak heat release rate and the total heat release of the EP composites were reduced remarkably, and their LOI and UL94 vertical burning rating were also improved. In addition, their smoke production rate and total smoke production were decreased drastically. The improved flame retardancy and smoke suppression were mainly attributed to the physical barrier effect of graphene. Meanwhile, the metal oxide decomposed from ZIF‐8 could contribute to the production of char residue and enhance the compactness of the char layer.     

Effect of different ionic layered compounds decorated with zinc hydroxystannate on flame retardancy and smoke performance of epoxy resin

ZHS@ Mg‐Al‐LDH and ZHS@α‐ZrP hybrid materials were prepared by electrostatically loading zinc hydroxystannate (ZHS) on the layered compounds (Mg‐Al‐LDH and α‐ZrP) in this work. With the addition of 2 wt% of the two hybrid materials to epoxy resin (EP), respectively, the fire hazard of EP and its composites were investigated. The limiting oxygen index (LOI) of ZHS@ Mg‐Al‐LDH/EP composite increased by 19.0% compared with pure EP, while its peak heat release rate (PHRR), total heat release rate (THR), and peak smoke release rate (SPR) decreased by 48.2%, 20.8%, and 21.6%, respectively, evidenced by the results of the LOI test and cone calorimetry test (CCT). The LOI of ZHS@α‐ZrP/EP composite increased by 20.4%, and its PHRR, THR, and SPR decreased by 47.7%, 21.4%, and 27.1%, respectively. Both hybrid materials showed prominent flame retardant and smoke suppressing properties. In addition, through the analysis of the TG‐IR and Raman spectrum of residual char, the specific mechanism of flame retardance and smoke suppression was explored.     

The POSS side chain epoxy nanocomposite: Synthesis and thermal properties

The IPI‐POSS‐modified epoxy resin (IPEP) was prepared from isocyanato‐propyldinethylsilyl‐isobutyl‐POSS (IPI‐POSS) and diglycidyl ether of bisphenol A epoxy resin. The steric hindrance of the IPEP bulky POSS side chain improved the curing activation energies. The POSS particles sizes were about 2–3 nm and dispersed uniformly. At lower IPEP concentration (POSS < 12 wt %), the glass transition temperatures (T_gs) of the IPEP nanocomposites increased from 118 to 170 °C. The char yield increased from 15 to 20 wt %, and the LOI values increased from 22 to 28. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 643–652, 2010     

The influence of mesoporous silica modified with phosphorus and nitrogen‐containing hyperbranched molecules on thermal stability,combustion behavior,and toxic volatiles of epoxy resin

A hybrid material (HPPA‐SH‐mSiO₂) containing multiple flame‐retardant elements was synthesized and characterized using NMR, FTIR, and XPS techniques. This hybrid was synthesized by the “thiol–ene” click reaction of thiol‐functionalized mesoporous silica (SH‐mSiO₂) with ene‐terminated hyperbranched polyphosphate acrylate (HPPA).When 2 wt% HPPA‐SH‐mSiO₂ hybrid was added to an epoxy matrix, thermogravimetric analysis (TGA) showed that the incorporation of HPPA‐SH‐mSiO₂ increased the thermal stability of epoxy resin composites. Moreover, the combustion behavior of epoxy composites was investigated using a cone calorimeter, and the results show that the PHRR and THR of EP/HPPA‐SH‐mSiO₂ composites clearly decreased by 28.7% and 16%, respectively. Volatile toxic compounds such as aromatic compounds, CO, carbonyl compounds, and hydrocarbons were identified using TGA‐infrared spectroscopy coupling technique. The effect of HPPA‐SH‐mSiO₂ hybrids on the removal of toxic volatiles was also investigated. Functionalized mesoporous silica and polymer composites have potential applications.     

A novel halogen‐free co‐curing agent with linear multi‐aromatic rigid structure as flame‐retardant modifier in epoxy resin

A novel halogen‐free 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO)‐containing co‐curing agent, 6,6′‐(1,4‐phenylenebis(((4‐(phenylamino)phenyl)amino)methylene))bis(dibenzo[c,e][1,2]oxaphosphinine 6‐oxide) (DPN) was synthesized via a simple 1‐pot or 2‐step procedure with yield of 86.2% and 70.8%, respectively. The molecular structures of 4,4′‐((1,4‐phenylenebis(methanylylidene))bis(azanylylidene))bis(N‐phenylaniline) (DPN intermediate) and DPN are characterized by FTIR, NMR, and MS. TGA tests show that the char yield of DPN/EP composites raises to 30.9% when the molar ratio of DPN to 4,4‐diaminodiphenyl methane(DDM) is 20:80. T_g values of DPN/EP composites tested by DSC and DMA are similar to neat epoxy resin (EP), which is due to the secondary amine in DPN that participates in the cross‐linking reaction of epoxy resin. The storage modulus in the rubber stage (E′‐190 °C) of flame‐retardant epoxy resin is close to that of neat EP, while their tanδ's are lower, which indicates the similarity of samples' cross‐linking density due to the participation of DPN in the cross‐linking reaction. The results show that when the molar ratio of DPN and DDM is 5:95, the epoxy has a higher T_g value and better mechanical properties than other samples. The introduction of DPN efficiently improves the flame‐retardant properties of epoxy resin with V‐0 rating of UL‐94 vertical burning test, non‐dripping, 41% of limit oxygen index (LOI) value, low peak heat release rate (PHRR), and total heat release (THR).     

Composition optimization and UV‐annealing dependence on the electrical properties of Hf1−xSixO2/Si gate stacks

Hf_1?xSi_xO₂ gate dielectrics grown by UV‐photo‐induced chemical vapor deposition (UV‐CVD) using Hf(OBu^t)₂(mmp)₂ and tetraethoxysilane as precursors have been deposited on Si substrate. Composition dependence of the interfacial microstructure of the Hf_1?xSi_xO₂/Si gate stacks has been investigated via Fourier transform infrared spectroscopy (FTIR) systematically. It has been indicated that the physical properties of the Hf_1?xSi_xO₂ films can be effectively optimized by adjusting the silicon contents incorporated in the films. In order to evaluate its potential implementation as an alternative dielectric in future devices, detailed electrical characterization of Au/Hf_1?xSi_xO₂/Si capacitor has been performed as functions of the silicon contents and the UV‐annealing time. Copyright © 2010 John Wiley & Sons, Ltd.     

Preparation and properties of polycarbonate/polyhedral oligomeric silsesquioxanes (POSS) hybrid composites

Octaphenylsilsesquioxane (PH‐POSS) and octa(γ‐methacryloxypropyl)silsesquioxane (MA‐POSS) were successfully synthesized by hydrolytic condensation of phenyltrichlorosilane and γ‐methacryloxypropyltrimethoxysilane, and characterized by Fourier transform infrared (FT‐IR), ¹H and ²⁹Si nuclear magnetic resonance (NMR), and matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) mass spectrum. Morphology, degradation behavior, thermal, and mechanical properties of hybrid composites were studied by transmission electron microscopy (TEM), polarized optical microscopy (POM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), surface contact angle (SCA), tensile, and impact testing. Domains of PH‐POSS and MA‐POSS dispersed in the matrix with a wide size distribution in a range of 0.1–0.5 µm, while PH‐POSS exhibited a preferential dispersion. Because of the possible homopolymerization of MA‐POSS during the melt blending, the glass transition temperature of polycarbonate (PC)/MA‐POSS composites remained nearly unchanged with respect to PC/PH‐POSS composites that showed a depression of T_g due to the plasticization effect. It is interesting to note that the incorporation of POSS retarded the degradation rates of PC composites and thus significantly improved the thermal stabilities. Si? O fractions left during POSS degradations were a key factor governing the formation of a gel network layer on the exterior surface. This layer possessed more compact structures, higher thermal stabilities, and some thermal insulation. In addition, percentage residues at 700°C (C₇₀₀) significantly increased from 10.8% to 15.8–22.1% in air. Fracture stress of two composites showed a slight improvement, and the impact strength of them decreased monotonically with the increase of POSS loading. Copyright © 2011 John Wiley & Sons, Ltd.