Cyanate Ester/Polyhedral Oligomeric Silsesquioxane (POSS) Nanocomposites:  Synthesis and Characterization

Abstract

Cyanate ester (PT-15, Lonza Corp.) composites containing the blended polyhedral oligomeric silsesquioxane (POSS), TriSilanolPhenyl-POSS (C 42 H 38 O 12 Si 7 ), were prepared containing PT-15/POSS 99/1, 97/3, 95/5, 90/10, and 85/15 w/w ratios. The composites were characterized by FT-TR, X-ray diffraction (XRD), small-angle neutron scattering (SANS), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (X-EDS), transmission electron microscopy (TEM), dynamic mechanical thermal analysis (DMTA), and three-point bending flexural tests. TriSilanolPhenyl-POSS was throughly dispersed into uncured liquid PT-15 resin. After curing, XRD, SANS, and X-EDS measurements were consistent with partial molecular dispersion of a portion of the POSS units in the continuous matrix phase while the remainder forms POSS aggregates. Larger aggregates are formed at higher loadings. SANS, SEM, and TEM show that POSS-enriched nanoparticles are present in the PT-15/POSS composites. The storage bending moduli, E′, and the glass transition temperatures, T g , of PT-15/POSS 99/1, 97/3, and 95/5 composites are higher than those of the pure PT-15 over the temperature range from 35 to 350 °C. The E′ values for all these composites (except for the 15 wt % POSS sample) are significantly greater than that of the pure resin at T > T g . Therefore, small amounts (e5 wt %) of TriSilanolPhenyl-POSS incorporated into cyanate ester resin PT-15 can improve the storage modulus and the hightemperature properties of these cyanate ester composites versus the pure PT-15 resin. The flexural strength and flexural modulus are also raised by POSS incorporation.

Processability studies of silica‐thermoset polymer matrix nanocomposites

“…Nanocomposites with silica nanoparticles have been reported to display increased mechanical properties [8,9] such as modulus, tensile, flexural and impact strength up to a certain silica content (e.g. 2.5% [10]) and decreased mechanical properties thereafter, improved fracture toughness [11] and better thermal stability [12,13].…”

“…Dispersed silica nanoparticles have been used as a curing agent in an epoxy system in the presence of magnesium chloride, acting as a catalyst, to yield a silica-epoxy nanocomposite [20]. Incorporation of silica nanoparticles and silicates has been reported to raise the glass transition temperature, T g , of the resulting nanocomposite (cyanate ester composites [9], vinyl ester composites [1], epoxy composites [13,21]) but also to reduce Tg (clay-biobased epoxy nanocomposites [18]). …”

Preparation and properties of mesoporous silica/bismaleimide/diallylbisphenol composites with improved thermal stability, mechanical and dielectric properties

“…With regard to polyhedral oligomeric silsesquioxane (POSS)/ polymer composites, only several pieces of literature report the flexural properties. Liang's group prepared POSS/cyanate ester nanocomposites, and found that the flexural modulus of the nanocomposite with 3 wt% POSS is about 15% higher than that of neat cyanate ester resin, while the composite has the similar flexural strength as the resin does [26]. Li's group also reported similar results in the POSS/ epoxy nanocomposites [27].…”

Polymer nanocomposites for high-temperature composite repair

“…In Ash's same paper [43], which reported increases of the strain-to-failure for alumina nanoparticle/PMMA composites, the T g of the nanocomposites decreased by 25 °C compare to neat PMMA at certain nanoparticle loadings. Other researchers reported an increase in the T g of nanocomposites with increasing nanoparticle loading [45][46][47]. The effect of nanoparticles on the T g of nanocomposite is far more complex than the simple increase/decrease trend with particle loading.…”