Polyimide nanocomposites preparation

D. M. Delozier, R. A. Orwoll, J. F. Cahoon, J. S. Ladislaw, J. G. Smith Jr, and J. W. Connell. Polyimide nanocomposites prepared from high-temperature, reduced charge organoclays. Polymer, 44 (2003), 2231-2241. 

D. Chen, H. Zhu, T. Liu, In situ thermal preparation of polyimide nanocomposite films containing functionalized graphene sheets, ACSAppIMater Interfaces, vol. 2, pp. 3702-3708, 2010. 

Thompson CM, Herring HM, Gates TS, Connell JW (2003) Preparation and characterization of metal oxide/polyimide nanocomposites. Compos Sci Technol 63 1591-1598 Thurmann RB, Geiba CP (1988) Molecules mechanisms of viral inactivation by water disinfectants. Adv Appl Microbiol 33 75-105... 

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. 

Figure 6.6 shows a scheme of the CIELab system. Park and Chang [20] prepared some polyimide nanocomposites films with pristine clay and analyzed the transparency and color change. This is an important aspect since colorless polyimide films have in particular been widely used in electro-optical devices and semiconductor applications. The measurements were obtained for 80 pm thick films by a spectrophotometer and the color coordinates on CIELab system were determined. 

J. L. Hedrick, H.-J. Cha, R. D. Miller, D. Y. Yoon, H. R. Brown, S, Srinivasan, R. D. Pietro, R. F. Cook, J. P. Hummel, D. P. Klaus, E. G. Liniger, E. E, Slmonyi (1997) Polymeric organic-inorganic hybrid nanocomposites preparation of polyimide-modified poly(silsesqui-oxane) using functionalized poly(amic acid alkyl ester) precursor. Macromolecules 30, 8512. 

Chang J-H, Park D-K, Ihn K J, Polyimide nanocomposite with a hexadecylamine clay synthesis and characterization , J. Appl. Polym. Sci., 2002 84 2294—301. Chang J-H, Park K M, Cho D, Yang H S, Ihn K J, Preparation and characterization of polyimide nanocomposites with different oigano-montmorillonites , Polym. Eng. Sci., 2001 41(9) 1514-20. 

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. 

The kinetics of solid state imidization of PAA, synthesized from 4,4 -oxydianilinc and pylomellitic dianhydride, both without filler and with addition of 2 and 5 weight % Na+-montmorillonite [1], The nanofiller is processed by solution of P-phenylenediamine in HC1 and then washed with de-ionized water to ensure a complete removal of chloride ions. The conversion (imidization) degree Q was determined as a function of reaction duration t with the aim of Fourier transformation of IR-spectra bands 726 and 1014 cm 1. The samples for IR studies were prepared by spin-coating of mixture PAA/Na+-montmorillonite solution in N,N-dimethylacetamide on KBr disks. Then the KBr disks were dried in vacuum at 303 K for 48 h. It was shown, that the used in paper [1] method gives exfoliated nanocomposites. The other details of polyimide/Na+-montmorillonite nanocomposites synthesis and studies in paper [1] were cited. The solid state imidization process was made at four temperatures 7 423, 473, 503 and 523 K. 

Wise [2] prepared selected polyimides, (I), that formed dispersions of carbon nanotubes exhibiting long-term stability. Nanocomposites produced from these dispersions were useful in the fabrication of lightweight aerospace structures. 

Lee, T, Park, S.S., Jung, Y. et al. 2009. Preparation and characterization of polyimide/mesoporous silica hybrid nanocomposites based on water-soluble poly(amic acid) ammonium salt. Eur. Polytn. J. 45 19-29. 

Tang JC, Yang HC, Chen SY, Chen-Yang YW (2007) Preparation and properties of polyimide/silica hybrid nanocomposites. Polymer Compos 28(5) 575—581... 

Baneijee et al. [107] prepared polyimide-POSS (PI-POSS) nanocomposite membranes applying thermal imidization. At first, poly(amic acid)s were generated by the reaction of several diamine monomers, namely 4,4-( w[3 -trifluoromethyl-4 (4 -aminobenzo xy)benzyl]biphenyl l,4- w[3 -trifluoromethyl-4 (4 -aminobenzoxy)benzyl]benzene 2,6-te[3 -trifluorom ethyl-4 (4 -aminobenzoxy)benzyl]pyridine and 2,5 - w[3 -trifluoromethyl-4 (4 -aminobenzoxy)benzyl] thiophene with 6FDA as the dianhydride and 2 wt% POSS-NH2 as the nanofiller. The structure of poly(amic acid) intermediate, which was thermally imidized to form polyimide chain end tethered POSS, is shown in Scheme 6.25. 

Analogous nanocomposites were also prepared based on polyimide analogs, such as polyoxazolines, containing trietiioxysilane groups. ... 

For bulk materials, Jin et al fabricated poly (methylmethacrylate) (PMMA)/MWNT nanocomposites by melt mixing. MWNTs were well dispersed in the matrix [90]. Melt compounding is also widely used for the fabrication of composite fibers. Sandler et al mixed polyamide-12 pellets and CNTs in a twin-screw micro-extruder and then the extrudate was chopped and fed into a capillary rheometer with 1 mm die. The CNTs in the spun fibers were uniformly dispersed [91]. Not only can thermoplastic polymers be melt-compounded, polyimide, a thermoset plastic, can be also prepared by mixing the imide oligomer at 320 °C on a steel plate and then cured at 370°C. It was found that the dispersion of CNTs in... 

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