Novel phosphorus-modified polysulfone as a combined flame retardant and toughness modifier for epoxy resins

A novel phosphorus-modified polysulfone (P-PSu) was employed as a combined toughness modifier and a source of flame retardancy for a DGEBA/DDS thermosetting system. In comparison to the results of a commercially available polysulfone (PSu), commonly used as a toughness modifier, the chemorheological changes during curing measured by means of temperature-modulated DSC revealed an earlier occurrence of mobility restrictions in the P-PSu-modified epoxy. A higher viscosity and secondary epoxy-modifier reactions induced a sooner vitrification of the reacting mixture; effects that effectively prevented any phase separation and morphology development in the resulting material during cure. Thus, only about a 20% increase in fracture toughness was observed in the epoxy modified with 20 wt.% of P-PSu, cured under standard conditions at 180 °C for 2 h. Blends of the phosphorus-modified and the standard polysulfone (PSu) were also prepared in various mixing ratios and were used to modify the same thermosetting system. Again, no evidence for phase separation of the P-PSu was found in the epoxy modified with the P-PSu/PSu blends cured under the selected experimental conditions. The particular microstructures formed upon curing these novel materials are attributed to a separation of PSu from a miscible P-PSu-epoxy mixture. Nevertheless, the blends of P-PSu/PSu were found to be effective toughness/flame retardancy enhancers owing to the simultaneous microstructure development and polymer interpenetration.     

Preparation, characterization and mechanical properties of epoxidized soybean oil/clay nanocomposites

New epoxidized soybean oil (ESO)/clay nanocomposites have been prepared with triethylenetetramine (TETA) as a curing agent. The dispersion of the clay layers is investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD and TEM data reveal the intercalated structure of ESO/clay nanocomposites has been developed. The thermogravimetric analysis exhibits that the ESO/clay nanocomposites are thermally stable at temperatures lower than 180 °C, with the maximum weight loss rate after 325 °C. The glass transition temperature, T_g, about 7.5 °C measured by differential scanning calorimetry (DSC) and T_g about 20 °C measured by dynamic mechanical study have been obtained. The difference in the T_g between DSC and dynamic measurements may be caused by different heating rate. The nanocomposites with 5-10 wt% clay content possess storage modulus ranging from 2.0×10⁶ to 2.70×10⁶ Pa at 30 °C. The Young's modulus (E) of these materials varies from 1.20 to 3.64 MPa with clay content ranging from 0 to 10 wt%. The ratio of epoxy (ESO) to hydrogen (amino group of TETA) greatly affects dynamic and tensile mechanical properties. At higher amount of TETA, the nanocomposites exhibit stronger tensile and dynamic properties.     

Liquid-liquid phase separation and crystallization behavior of poly(ethylene terephthalate)/poly(ether imide) blend

The liquid-liquid (L-L) phase separation and crystallization behavior of poly(ethylene terephthalate) (PET)/poly(ether imide) (PEI) blend were investigated with optical microscopy, light scattering, and small angle X-ray scattering (SAXS). The thermal analysis showed that the concentration fluctuation between separated phases was controllable by changing the time spent for demixing before crystallization. The L-L phase-separated specimens at 130 °C for various time periods were subjected to a temperature-jump of 180 °C for the isothermal crystallization and then effects of L-L phase separation on crystallization were investigated. The crystal growth rate decreased with increasing L-L phase-separated time (t_s). The slow crystallization for a long t_s implied that the growth path of crystals was highly distorted by the rearrangement of the spinodal domains associated with coarsening. The characteristic morphological parameters at the lamellar level were determined by the correlation function analysis on the SAXS data. The blend had a larger amorphous layer thickness than the pure PET, indicating that PEI molecules in the PET-rich phase were incorporated into the interlamellar regions during crystallization.     

Morphological self-control of a phase-separated polymer during photopolymerization in a liquid-crystalline medium

An acrylate monomer having a cyanobiphenyl mesogen (1) was photopolymerized in a liquid-crystalline (LC) ordering field of 4-hexyloxybenzoic acid (2). A blend of (1) and (2) (molar ratio: 1:4), containing a photoinitiator, an inhibitor and a crosslinker, was irradiated with UV light at 120 and 137 °C in order to investigate the effect of an LC phase on the resulting polymer. Here, both temperatures are in the nematic temperature range of the blend, however, the former is in the LC temperature range of the polymer, whereas the latter is in the isotropic temperature range. Scanning electron microscopy of the obtained polymers revealed that the polymer prepared at 120 °C consisted of oriented fine fibers, measuring ca. 400 nm in diameter, while that obtained at 137 °C had a fused bead-like morphology. In addition, we investigated the effect of crosslinking on the morphology by comparing the results from the blends with and without a crosslinker. We found that the LC phase of the phase-separated polymer is one of the necessary conditions for the formation of the fine fiber structures.     

Effect of an organoclay on the reaction‐induced phase‐separation kinetics and morphology of a poly(ether imide)/epoxy mixture

Organically modified layered silicates with a hydroxyl‐substituted quaternary ammonium surfactant as the modifier were incorporated into a mixture of poly (ether imide) and epoxy with 4,4′‐diaminodiphenyl sulfone as the hardener. The influence of the organically modified layered silicates on the reaction‐induced phase‐separation kinetics and morphology of the poly(ether imide)/epoxy mixture was investigated with time‐resolved small‐angle light scattering, phase‐contrast microscopy, and scanning electron microscopy. The phase‐separation kinetics were analyzed by means of the temporal evolution of scattering vector q _m and scattering intensity I_m at the scattering peak. The organically modified layered silicates obviously facilitated an earlier onset of phase separation but reduce the phase‐separation rate and greatly retarded the domain‐coarsening process in the late stage of spinodal decomposition. The temporal evolution of both q _m and I_m followed the power law q _m ～ (t ? t_os)^?α and I_m ～(t ? t_os)^?β, where t is the reaction time, t_os is the onset time of phase separation, and α and β are growth exponents. For the samples filled with organically modified layered silicates, α crossed over from 0 to about 1/3, following Binder–Stauffer cluster dynamics, and an interconnected phase structure was observed for cure temperatures ranging from 120 to 230°C. For the unfilled samples, the interconnected phase structure was observed only at cure temperatures below 140°C. At temperatures above 150°C, α crossed over from 0 to 1/3 < α ≤ 1 under the interfacial tension effect, following Siggia's theory, and the domain‐coarsening rate was very fast; this resulted in macroscopic epoxy‐rich domains. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1205–1214, 2007     

Fast isothermal calorimetry of modified polypropylene clay nanocomposites

Calorimetric experiments at cooling rates comparable to those during injection molding, as an example, are needed to study phase transitions under conditions relevant for processing. Ultra fast scanning calorimetry is a technique which provides a means to analyze the materials of interest under rapid cooling conditions and it is a promising technique by which the crystallization behavior of composite systems based on fast crystallizing polymers like isotactic polypropylene (iPP) can be studied. By combining conventional DSC and ultra fast chip calorimetry isothermal crystallization experiments were performed in the whole temperature range between glass transition and melting temperature of iPP. Because of the very small time constant of the calorimeter, isothermal crystallization processes with peak times down to 100 ms were investigated after cooling the sample from the melt at 2000 K/s. iPP grafted with maleic anhydride (PPgMA) - montmorillonite clay nanocomposites were studied. The influence of various clay loadings on the crystallization behavior of PPgMA at different temperatures was followed by ultra fast isothermal calorimetry. PPgMA clay nanocomposites showed a variation in crystallization peak times with different clay loadings at crystallization temperatures between 70 °C and 100 °C. No influence of clay loading was observed at lower crystallization temperatures. At these temperatures, where the mesophase is formed and homogeneous nucleation is expected, the contribution of the clay as a nucleating agent is negligible. For crystallization at about 80 °C, where the α-phase is formed, the nucleating effect of the clay is observed yielding complex crystallization kinetics. In the temperature range 75-85 °C in some nanocomposites a double peak during isothermal crystallization was observed corresponding to a fast and a slow crystallization processes occurring simultaneously. At higher temperatures, above 120 °C, the clay slightly retards the crystallization process.     

Morphology of heat-treated tunsgten doped monolithic carbon aerogels

The morphology of a tungsten-doped monolithic organic aerogel, prepared by the sol-gel method from the polymerisation of a resorcinol, formaldehyde and ammonium tungstate mixture, and of its carbonized derivatives at 500 and 1000 °C was studied by scanning and high-resolution electron microscopy. Tungsten influenced the surface morphology of the carbon aerogels. The tungsten-containing phase was homogeneously distributed in the organic aerogel and its heat treatment produced changes in the metal phase distribution throughout the pellets. Tungsten oxide particles of needle-like structure similar to hollow tubules were detected after heat treatments at different temperatures. In addition, particles of dendritic appearance, formed by tungsten carbide and an intermediate Magnelli phase, appeared when the heat treatment was carried out at 1000 °C.     

NMR investigation of the miscibility of new antiplasticizers in densely cross-linked epoxy-amine resins

The behaviour of antiplasticized epoxy-amine networks was investigated by variable-temperature determinations of ¹H NMR free induction decays. Up to 50 °C, all antiplasticized resins exhibited a solid-like behaviour. At higher temperatures, resins containing the less polar additives were shown to be phase-separated, in contrast to systems containing polar additives. The temperature dependence of the phase composition of the resins, as detected by NMR, supports the conclusions previously deduced from the dynamic mechanical analysis (DMA) study: non- or slightly-polar antiplasticizer molecules are sharply phase-separated in highly cross-linked epoxy-amine networks cured extensively. The resulting morphology mainly consists in nano-scale aggregates of additives entrapped within the polymer matrix.     

Copolymerization behavior and properties of dimethacrylate-styrene networks

Dimethacrylate oligomers diluted with styrene (commonly known as vinyl ester resins) are important matrix resins for fiber-reinforced composites used in construction, marine craft, and transportation vehicles. These comonomers react via free radical copolymerization to yield void-free thermosets. The inter-relationships among copolymerization kinetics, physical properties of the networks, and cure temperatures for a 700 g/mol dimethacrylate oligomer with systematically varied styrene concentrations were investigated. FTIR was used to monitor the reactions of the carbon-carbon double bonds of the methacrylate (943 cm⁻¹) and styrene (910 cm⁻¹). Reactivity ratios were determined via a non-linear method at four cure temperatures. The data were analyzed using the integrated form of the copolymerization equation and assuming a terminal reactivity model to predict copolymer compositions throughout the reactions. The results indicated that at early conversion more styrene was incorporated into the networks at lower cure temperatures. The experimental vinyl ester-styrene network compositions agreed well with those predicted by the integrated copolymer equation at early and intermediate conversion. Mechanical properties of dimethacrylate-styrene networks were determined for materials cured at room temperature and at 140 °C. Materials cured at room temperature were tougher and had lower rubbery moduli than those cured at 140 °C.     

Comparison of morphologies and mechanical properties of crosslinked epoxies modified by polystyrene and poly(methyl methacrylate)) or by the corresponding block copolymer polystyrene-b-poly(methyl methacrylate)

Polystyrene (PS, M_n=28,400, PI=1.07), poly(methyl methacrylate) (PMMA, M_n=88,600, PI=1.03), and PS (50,000)-b-PMMA (54,000) (PI=1.04), were used as modifiers of an epoxy formulation based on diglycidyl ether of bisphenol A (DGEBA) and m-xylylene diamine (MXDA). Both PS and PMMA were initially miscible in the stoichiometric mixture of DGEBA and MXDA at 80 °C, but were phase separated in the course of polymerization. Solutions containing 5 wt% of each one of both linear polymers exhibited a double phase separation. A PS-rich phase was segregated at a conversion close to 0.02 and a PMMA rich phase was phase separated at a conversion close to 0.2. Final morphologies, observed by scanning electron microscopy (SEM), consisted on a separate dispersion of PS and PMMA domains. A completely different morphology was observed when employing 10 wt% of PS-b-PMMA as modifier. PS blocks with M_n=50,000 were not soluble in the initial formulation. However, they were dispersed as micelles stabilized by the miscible PMMA blocks, leading to a transparent solution up to the conversion where PMMA blocks began to phase separate. A coalescence of the micellar structure into a continuous thermoplastic phase percolating the epoxy matrix was observed. The elastic modulus and yield stress of the cured blend modified by both PS and PMMA were 2.64 GPa and 97.2 MPa, respectively. For the blend modified by an equivalent amount of block copolymer these values were reduced to 2.14 GPa and 90.0 MPa. Therefore, using a block copolymer instead of the mixture of individual homopolymers and selecting an appropriate epoxy-amine formulation to provoke phase separation of the miscible block well before gelation, enables to transform a micellar structure into a bicontinuous thermoplastic/thermoset structure that exhibits the desired decrease in yield stress necessary for toughening purposes.     

Liquid-liquid phase separation in a polyethylene blend monitored by crystallization kinetics and crystal-decorated phase morphologies

A series of polyethylene (PE) blends consisting of a linear high density polyethylene (HDPE) and a linear low density polyethylene (LLDPE) with an octane-chain branch density of 120/1000 carbon was prepared at different concentrations. The two components of this set of blends possessed isorefractive indices, thus, making it difficult to detect their liquid-liquid phase separation via scattering techniques. Above the experimentally observed melting temperature of HDPE, T_m = 133 °C, this series of blends can be considered to be in the liquid state. The LLDPE crystallization temperature was below 50 °C; therefore, above 80 °C and below the melting temperature of HDPE, a series of crystalline-amorphous PE blends could be created. A specifically designed two-step isothermal experimental procedure was utilized to monitor the liquid-liquid phase separation of this set of blends. The first step was to quench the system from temperatures of known miscibility and isothermally anneal them at a temperature higher than the equilibrium melting temperature of the HDPE for the purpose of allowing the phase morphology to develop from liquid-liquid phase separation. The second step was to quench the system to a temperature at which the HDPE could rapidly crystallize. The time for developing 50% of the total crystallinity (t_1/2) was used to monitor the crystallization kinetics. Because phase separation results in HDPE-rich domains where the crystallization rates are increased, this technique provided an experimental measure to identify the binodal curve of the liquid-liquid phase separation for the system indicated by faster t_1/2. The annealing temperature in the first step that exhibits an onset of the decrease in t_1/2 is the temperature of the binodal point for that blend composition. In addition, the HDPE-rich domains crystallized to form spherulites which decorate the phase-separated morphology. Therefore, the crystal dispersion indicates whether the phase separation followed a nucleation-and-growth process or a spinodal decomposition process. These crystal-decorated morphologies enabled the spinodal curve to be experimentally determined for the first time in this set of blends.     

Li NMR, ionic conductivity and self-diffusion coefficients of lithium ion and solvent of plasticized organic-inorganic hybrid electrolyte based on PPG-PEG-PPG diamine and alkoxysilanes

Organic-inorganic hybrid electrolytes based on poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether) (D2000) complexed with LiClO₄ via the co-condensation of an epoxy trialkoxysilane and tetraethoxysilane have been prepared and plasticized by a solution of ethylene carbonate (EC)/propylene carbonate (PC) mixture (1:1 by weight). The cross-linked hybrid network shows no solvent exudation and retains a large amount of plasticizer over 70 wt.% in stable state. The in situ built in silica network provides the hybrid electrolytes with good mechanical properties. The ionic conductivity of the dry hybrid electrolyte films was enhanced by two orders of magnitude via plasticization, reaching a maximum conductivity value of 4.0 × 10⁻³ S/cm at 30 °C. Variable temperature ⁷Li-{¹H} magic angle spinning (MAS) NMR demonstrated that the Li⁺ cations can be complexed by the polymer network as well as by the plasticizing solvents, but not with the incorporated silica network. Furthermore, the ⁷Li chemical shift change indicated a progressive change in the lithium coordination from lithium-polymer to lithium-solvent with increasing temperatures. The role of the solvents and the mobility of the lithium ions were investigated by pulsed gradient spin echo (PGSE) NMR measurements to elucidate the behavior of the ionic conductivity.     

Thermal decomposition of 2-methylpyridine N-oxide: Effect of temperature and influence of phosphotungstic acid as the catalyst

The thermal decomposition of 2-methylpyridine N-oxide was studied at temperatures between 190 °C and 220 °C using an Automatic Pressure Tracking Adiabatic Calorimeter. The effect of the catalyst on the decomposition was evaluated using different amounts of phosphotungstic acid. It was determined that 2-methylpyridine N-oxide decomposes faster with low amounts of catalyst and temperatures above 200 °C. Below 200 °C, the decomposition is very slow. For the cases presented here, the decomposition reaction was accompanied by substantial production of non-condensable gasses, and 2-methylpyridine and pyridine were identified as the main decomposition products.     

Fracture behaviours of in situ silica nanoparticle-filled epoxy at different temperatures

Fracture behaviours of nanosilica filled bisphenol-F epoxy resin were systematically investigated at ambient and higher temperatures (23 °C and 80 °C). Formed by a special sol-gel technique, the silica nanoparticles dispersed almost homogenously in the epoxy resin up to 15 vol.%. Stiffness, strength and toughness of epoxy are improved simultaneously. Moreover, enhancement on fracture toughness was much remarkable than that of stiffness. The fracture surfaces taken from different test conditions were observed for exploring the fracture mechanisms. A strong particle-matrix adhesion was found by fractography analysis. The radius of the local plastic deformation zone calculated by Irwin model was relative to the increment in fracture energy at both test temperatures. This result suggested that the local plastic deformation likely played a key role in toughening of epoxy.     

Synthesis of novel bisphenol containing phthalazinone and azomethine moieties and thermal properties of cured diamine/bisphenol/DGEBA polymers

A novel bisphenol(1,2-dihydro-2-(4-((4-hydroxy)phenyliminomethylidene)phenyl)-4-(4-((4-(4-hydroxy)phenyliminomethylidene)phenoxy)phenyl)(2H)phthalazin-1-one, DPP) and a diamine(1,2-dihydro-2-(4-aminophenyl)-4-(4-(4-aminophenoxy)phenyl)(2H)phthalazin-1-one, DAP) were synthesized and characterized. The novel epoxy polymers containing phthalazinone and/or azomethine moieties were prepared by binary polymerization of DAP (or DPP) with diglycidyl ether of biphenyl A (DGEBA) and ternary polymerization of hybrid curing agents, DAP/DPP (DAP and DPP under different molar ratios) with DGEBA. The cure behaviors of these new epoxy systems were studied by dynamic differential scanning calorimeter (DSC) and Infrared (IR) scans. Especially, the activation energy of DAP/DGEBA calculated by Kissinger and Ozawa methods were 73.8 and 77.4 kJ/mol, respectively. For ternary epoxy system, it was found that hybrid curing agents of DAP/DPP exhibited significant associated effect on their reactivity towards the oxirane group. Glass transition temperatures (T_g's) of these new epoxy polymers were all above 150 °C from the results of DSC, and the initial thermal decomposition temperatures (T_d,5%'s) and integral procedure decomposition temperatures (IPDT's) of these new epoxy polymers are above 350 and 850 °C, respectively from results of thermogravimetric analyses (TGA). These results show that new epoxy polymers containing phthalazinone and/or azomethine moieties exhibited excellent thermal properties. Especially, thermal properties of the ternary epoxy polymers could be modified by changing the content of DAP and DPP. The linear relationships between char yield (Y_c,wt%) and the structural compositions of these new polymers (weight percentage of phthalazinone, azomethine and nitrogen, C/H weight ratio) were built.     

Phase separation and mechanical responses of polyurethane nanocomposites

Nanocomposites of a diamine-cured polyurethane with nanofillers of different kinds, sizes, and surfaces were studied. Atomic force microscopy, scanning electron microscopy, X-ray diffraction, tensile tests, and dynamic mechanical thermal analysis were employed in the experiments. Experimental results suggest that mechanical properties are strongly correlated to polymer phase separation, which depends on the nature of the interface between the polymer and the nanoparticles. Two stages of phase separation were observed: the first stage involves the self-assembly of the hard segments into small hard phases of about 10 nm in width; the second stage involves the assembly of the 10 nm wide hard phases into larger domains of about 40-100 nm in width. In the case of polyurethane/ZnO nanocomposites with 5 wt% (less than 1 vol%) 33 nm ZnO nanoparticles, the covalent bonds that were formed between the polymer and ZnO surface hydroxyl groups constrain both stages of phase separation in polyurethane, resulting in approximately 40% decrease in the Young's modulus, 80% decrease in the strain at fracture, and 11 °C increase in the glass transition temperature of the soft segments. In the case of polyurethane/Al₂O₃ nanocomposites with 5 wt% 15 nm Al₂O₃ nanoparticles, hydrogen bonds between the particles and the polymer mainly constrain the second step of the phase separation, resulting in about 30% decrease in the Young's modulus and 12 °C increase in the glass transition temperature, but only a moderate decrease in the strain at fracture. The most striking results come from polyurethane/clay composites, where only van der Waals type interactions exist between polyurethane and the organically modified clay (Cloisite 20A). With the addition of 5 wt% surface modified clay (Cloisite 20A), both the Young's modulus and the strain at fracture decrease more than 80%, but the glass transition temperature increases by about 13 °C. Adding 10 wt% Cloisite 20A into polyurethane almost totally disrupts the phase separation, resulting in a very soft composite that resembles a “viscous liquid” rather than a solid.     

Sintering characteristics of kaolin in the presence of phosphoric acid binder

The kaolin-phosphoric acid mixtures with various percentages of phosphoric acid (5 wt%; 10 wt% and 15 wt%) have been investigated at room temperature. During the maturation and the sintering processes, acid reacts with aluminium of kaolin to give a new phase of aluminophosphate. This new phase's appearance has been confirmed by the thermal analysis, infrared spectroscopy, X-ray diffraction and scanning electron microscopy measurements before and after the sintering processes at different temperatures (800 °C, 1100 °C and 1250 °C). The rupture strength of the body-shaped samples made with the kaolin-phosphoric acid mixtures is higher than that of those made with only kaolin. The porosity decreases with both the sintering temperature rise and the addition of phosphoric acid in the mixture. The addition of 10 wt% of phosphoric acid to the kaolin decreases its calcined temperature by 200 °C.     

Influence of nano-aluminum filler on the microstructure of SiOC ceramics

Ceramic SiC-mullite-Al₂O₃ based nanocomposites were successfully obtained at temperatures below 1500 °C after pyrolysis and annealing of green compacts prepared by cross-linking and shaping in a warm press step of commercial poly(methylsilsesquioxane) MK polymer mechanically mixed with aluminum filler having nanoparticle size. The heat treatment takes place under the exclusion of oxygen (inert argon atmosphere) and temperatures as low as 800 °C initiate the crystallization of a silicon carbide phase. The influence of the nano-aluminum filler and of the pyrolysis temperature on the crystallization behavior of the materials has been investigated. It was confirmed that an appropriate amount of nano-aluminum filler leads to a cristobalite free bulk SiOC ceramic. In consequence, the received ceramic samples have to be considered as a nano/micro-ceramic composite consisting of crystals of mullite (average dimension in the range of 200 nm), silicon carbide (20 nm) and α-alumina (50 nm).     

Influence of deposition parameters and annealing treatment on the properties of GZO films grown using rf magnetron sputtering

In this study, transparent conductive films of gallium-doped zinc oxide (GZO) are deposited on soda-lime glass substrates, under varied coating conditions (rf power, sputtering pressure, substrate-to-target distance and deposition time), using radio frequency (rf) magnetron sputtering, at room temperature. The effect of the coating parameters on the structural, morphological, electrical and optical properties of GZO films was studied. This study uses a grey-based Taguchi method, to determine the parameters of the coating process for GZO films, by considering multiple performance characteristics. In the confirmation runs, with grey relational analysis, improvements of 14.1% in the deposition rate, 39.81% in electrical resistivity and 1.38% in visible range transmittance were noted. The influence of annealing treatment, in a vacuum, oxygen, and nitrogen gas atmospheres, at temperatures ranging from 130 to 190 °C, for a period of 1 h, was also investigated. GZO films annealed at 190 °C, in a vacuum, showed the lowest electrical resistivity, at 1.07 × 10⁻³ Ω-cm, with about 85% optical transmittance, in the visible region. It is likely that films grown at lower temperatures (190 °C) could be coated onto polymeric substrates, to produce flexible optoelectronic devices.     

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.