Nanocomposites Clay-polyimide

There are numerous other possible packaging combinations. Materials such as PET, polyamides and polypropylene are coated with silicon or aluminium oxide to create barriers for oxygen and organics. Clay-polyimide nanocomposites have been evaluated as barrier materials for oxygen, carbon dioxide and water vapour. 

For his theoretical expressions, Nielsen [122] assumed that the sheets are placed perpendicular to the diffusive pathway. Therefore, the above expressions describe that the gas permeability of nanocomposite films depends primarily on three factors (1) the dimension of the dispersed layered silicate particles, (2) the dispersion of the layered silicate particles in the polymer matrix, and (3) the percentage of silicate particles loaded in the film. On the basis of Nielsen s model, Yano et al. [121] published several equations (Equations 12.23 and 12.24) where the diffusion process in nanocomposites (using polyimide-clay hybrids made by mixing 4,4 -diaminodiphenylether and pyromellitic dianhydride)... 

H.-L. Tyan, Y.-C. Liu, and K.-H. Wei, Thermally and mechanically enhanced clay/polyimide nanocomposite via reactive organoclay. Chemistry of Materials, 11... 

H.-L. Tyan, K.-H. Wei, and T.-E. Hsieh, Mechanical properties of clay-polyimide (BTDA-ODA) nanocomposites via ODA-modified organoclay. Journal of Polymer Science, Part B Polymer Physics, 38 (2000), 2873-8. 

TyanH. L., Liu Y. C. and Wei K. H. (1999), Thermally and Mechanically Enhanced Clay/ Polyimide Nanocomposite via Reactive Organoclay. Chem Mater, 11,1942-7. 

Permeability to oxygen as a function of the organoclay content in the polyimide nanocomposite. (A) Polyimide-dodecylamine-clay nanocomposites (from Khayankarn etal. ) (B) Polyimide (BATB-ODPA)-clay nanocomposite (from Yeh (C) Polyimide/dodecylamine-clay... 

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... 

In the case of the synthesis of polyimide, the polymerization solvent used for polyamic acid (a precursor of polyimide) is usually dimethyl acetoamide (DMAC). We found that clay ion-exchanged dodecyl ammonium ions could be homogeneously dispersed in DMAC. A solution of this organophilic clay and DMAC was added to a DMAC solution of polyamic acid. The film was cast from a homogeneous mixture of clay and polyamic acid, and was heated at 300 °C to achieve the desired polyimide clay nanocomposite film. Its permeability to water decreased to 50% upon addition of 2.0 wt% clay [13]. It was confirmed that its permeability to carbon dioxide also decreased by half [14]. 

Thermoset polymers like polyimide, crosslinked sulfonated poly(ether ether ketone) and polyacrylate can be used for membrane applications. The presence of nanoparticle nucleates the nanopore formation with the assistance of an agent. The nanopore is responsible for the solvent separation and transportation. Membranes such as solvent filters, filters for bacteria and virus, and membrane for gas separation can be developed using clay-polymer nanocomposites [118-119]. 

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]. 

This technique has found the following applications in addition to those discussed in Sections 10.1 (resin cure studies on phenol urethane compositions) [65], 12.2 (photopolymer studies [66-68]), and 13.3 (phase transitions in PE) [66], Chapter 15 (viscoelastic and rheological properties), and Section 16.4 (heat deflection temperatures) epoxy resin-amine system [67], cured acrylate-terminated unsaturated copolymers [68], PE and PP foam [69], ethylene-propylene-diene terpolymers [70], natural rubbers [71, 72], polyester-based clear coat resins [73], polyvinyl esters and unsaturated polyester resins [74], polyimide-clay nanocomposites [75], polyether sulfone-styrene-acrylonitrile, PS-polymethyl methacrylate (PMMA) blends and PS-polytetrafluoroethylene PMMA copolymers [76], cyanate ester resin-carbon fibre composites [77], polycyanate epoxy resins [78], and styrenic copolymers [79]. 

Racz et al. [85], in their studies of polyimide-montmorillonite clay nanocomposites, measured heat distortion temperature, tensile and compact strength, and deformation. 

The highest heat distortion temperature of 400°C flexural modulus (1.1 x 10 psi) and flexural strength (30,000 psi) of polyimide-montmorillonite clay nanocomposites made this polymer composite outstanding. 

On the other hand, clays modified with salts of aromatic amines, in which the N atom is directly linked to aromatic ring, exhibited higher thermal stability then those modified with alkylammonium compounds [117, 118]. The use of a combination of aromatic and aliphatic ammonium compounds was an effective strategy for synthesis of clays with sufficient thermal stability for thermoset polyimide resin (PI) [117]. In that case, the aromatic component of OLS provided higher thermal stability and the aliphatic component promoted intercalation. The benefits of combining aromatic and aliphatic surfactants to treat clay are also reported by other authors [ 119]. It was shown that clay treated with a 1 1 molar mixture of methylene dianihne (MDA) and dodecylamine resulted in an improvement in thermooxidative stability of Pl-based nanocomposites. 

Thermally stable polyimide/4,4 -bis(4-aminophenoxy)phenylsulfone-modified clay nanocomposites... 

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... 

T. Kurose, V. E. Yudin, J. U. Otaigbe, V. M. Svetlichnyi, Compatibilized polyimide (R-BAPS)/BAPS-modified clay nanocomposites with improved dispersion and properties. Polymer, 48 (2007), 7130-38. 

P. S. G. Krishnan, M. Joshi, P. Bhargava, S. Valiyaveettil, and C. He, Effect of heterocyclic based organoclays on the properties of polyimide-clay nanocomposites. Journal of Nanoscience Nanotechnology, 5 (2005), 1148-57. 

Srisuwan S, Thongyai S, Praserthdam P (2010) Synthesis and characterizatirai of low-dielectric photosensitive polyimide/silica hybrid materials. J Appl Polym Sci 117 2422-2427 Tagam N, Okada M, Hira N, Ohki Y, Tanaka T, finai T, Harada M, Ochi M (2008) Dielectric properties of epoxy/clay nanocomposites—effects of curing agent and clay dispersion method. IEEE Trans Diel Electr Insul 15 24—32... 

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