PLA Nanocomposites Based on Various Other Nanoparticles

Chen et al. [63] synthesized PLA/CNT nanocomposites using a grafting to technique. To understand the effect of molecular weight on the properties of the final nanocomposites, they used PLA of three different molecular weights. They first oxidized MWCNTs by acid treatment. In a typical procedure, a 500 mL flask charged with 2.5 g of the crude MWCNTs and 200 mL of 60% HNO3 aqueous solution was sonicated in a bath (28 kHz) for 30 min. The mixture was then stirred for 12 h under reflux. After the solution was cooled to room temperature, it was diluted with 400 mL of deionized water and vacuum filtered through a 0.22 pm polycarbonate membrane. The solid was washed with deionized water until the pH of the filtrate reached approximately 7. The solid was then dried under vacuum for 12 h at 60°C to yield 1.5 g of the carboxylic acid-functionalized MWCNT (MWCNT-COOH). 

Hiroi et al. [15] prepared PLA/organically modified layered titanate (OHTO) nanocomposites by a melt extrusion method. For nanocomposite preparation, the OHTO (dried at 120°C for 8h) and PLA were first dry mixed by shaking them in a bag. The mixture was then melt extruded using a twin-screw extruder (KZW15-30TGN, Technovel Corp.) operated at 195°C (screw speed = 300 rpm, feed rate = 22 g/ min) to yield nanocomposite strands. XRD patterns and TEM observations showed the formation of intercalated structures. 

FIGURE 19.2 Temperature dependence of storage modulus (G ) of neat PLA and various PLACNs prepared with organically modified synthetic fluorine mica. The number indicates amount of organoclay loading [27]. Reproduced from Ref. 27 with permission of American Chemical Society, USA. 

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