Polyimide nanocomposites thermal properties

Thompson, D.S., Thompson, D.W., and Southward, R.E. (2002) Oxo-metal-polyimide nanocomposites. 2 enhancement of thermal mechanical and chemical properties in soluble hexafluoroisopropyUdene-based poly-imides via the in situ formation of oxo-lanthanide(III)-polyimide nanocomposites. Chemistry of Materials, 14,... 

The incorporation of 5 % organically modified sepiolite, which is a microcrystalline-hydrated magnesium silicate, in a bisphenol A-based epoxy resin has no significant effect over the thermal stability of the epoxy resin, due to the poor dispersion of the clay and poor diffusion of the resin between fibres [69]. The effect of attapulgite (magnesium aluminium phyllosilicate) over the thermal properties of hyperbranched polyimides was studied. The presence of this silicate in the nanocomposites significantly improved the thermal stability of the neat polyimide [70]. 

H.-L. Tyan, C.-M. Liu, and K.-H. Wei, Effect of reactivity of organics-modified montmorillonite on the thermal and mechanical properties of montmorillonite/polyimide nanocomposites. Chemistry of Materials, 13 (2001), 222-6. 

Until 2003, Chen s [28], Qu s [29-31], and Hu s [32] groups independently reported nanocomposites with polymeric matrices for the first time the. In Hsueh and Chen s work, exfoUated polyimide/LDH was prepared by in situ polymerization of a mixture of aminobenzoate-modified Mg-Al LDH and polyamic acid (polyimide precursor) in N,N-dimethylactamide [28]. In other work, Chen and Qu successfully synthesized exfoliated polyethylene-g-maleic anhydride (PE-g-MA)/LDH nanocomposites by refluxing in a nonpolar xylene solution of PE-g-MA [29,30]. Then, Li et al. prepared polyfmethyl methacrylate) (PMMA)/MgAl LDH by exfoliation/adsorption with acetone as cosolvent [32]. Since then, polymer/LDH nanocomposites have attracted extensive interest. The wide variety of polymers used for nanocomposite preparation include polyethylene (PE) [29, 30, 33 9], polystyrene (PS) [48, 50-58], poly(propylene carbonate) [59], poly(3-hydroxybutyrate) [60-62], poly(vinyl chloride) [63], syndiotactic polystyrene [64], polyurethane [65], poly[(3-hydroxybutyrate)-co-(3-hydroxyvalerate)] [66], polypropylene (PP) [48, 67-70], nylon 6 [9,71,72], ethylene vinyl acetate copolymer (EVA) [73-77], poly(L-lactide) [78], poly(ethylene terephthalate) [79, 80], poly(caprolactone) [81], poly(p-dioxanone) [82], poly(vinyl alcohol) [83], PMMA [32,47, 48, 57, 84-93], poly(2-hydroxyethyl methacrylate) [94], poly(styrene-co-methyl methacrylate) [95], polyimide [28], and epoxy [96-98]. These nanocomposites often exhibit enhanced mechanical, thermal, optical, and electrical properties and flame retardancy. Among them, the thermal properties and flame retardancy are the most interesting and will be discussed in the following sections. 

PI nanocomposites have been prepared by various methods with different fillers. The nanocomposites might have many applications starting from barrier and thermal resistance to a compound with low coefficient of thermal expansion (CTE) [154-167]. These hybrid materials show very high thermal and flame retardation as well as barrier resistance and adhesion. Tyan et al. [158] have shown that depending on the structure of the polyimide the properties vary. Chang et al. [159] have also investigated the dependency of the properties on the clay modifiers. 

Polyimide-clay nanocomposites constitute another example of the synthesis of nanocomposite from polymer solution [70-76]. Polyimide-clay nanocomposite films were produced via polymerization of 4,4 -diaminodiphenyl ether and pyromellitic dianhydride in dimethylacetamide (DMAC) solvent, followed by mixing of the poly(amic acid) solution with organoclay dispersed in DMAC. Synthetic mica and MMT produced primarily exfoliated nanocomposites, while saponite and hectorite led to only monolayer intercalation in the clay galleries [71]. Dramatic improvements in barrier properties, thermal stability, and modulus were observed for these nanocomposites. Polyimide-clay nanocomposites containing only a small fraction of clay exhibited a several-fold reduction in the... 

H. Liu, Y. Li, T. Wang, and Q. Wang, In situ synthesis and thermal, tribological properties of thermosetting polyimide/graphene oxide nanocomposites. Journal of Materials Science, 47 (4), 1867-1874,2012. 

Polyimides (PI) are widely used in microelectronics and photonics because of their outstanding electrical properties, heat resistance, and chemical stability [10-12], Pl/clay nanocomposites have been reported to reduce the coefficient of thermal expansion, amount of moisture absorption, and dielectric constant for improved performance in these application areas already mentioned [13-22], For example, Yano et al. [13] prepared a PI (pyromellitic anhydride-4,4 -oxydianiline)/clay composite film [(PMDA-ODA)/clay] by solution-mixing of polyamic acid (PAA) and a dimethylacetamide (DMA) dispersion of clay. They used dodecylamine as the clay modifier, and the film showed reduced thermal... 

The preparation of polyimide-montmorillonite nanocomposites presents challenges that are unique compared with the constraints associated with the polymers discussed above. Polyimides are utilized in the aerospace industry because of their balance of mechanical properties and high thermal stability. Polyimides have found value in the electronic packaging and insulation industrial because of the additional quality of electrical insulation. 

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