PLA nanocomposites

Polymer nanocomposites are a class of reinforced polymers produced by incorporating materials that have one or more dimensions on the nanometer scale ( 100nm), such as layered silicates, carbon nanotubes, nanofibers, whiskers, ultrafine layered titanate, or inorganic-organic hybrid systems. Layered silicates (mainly montmorillonite (MMT) and hectorite) are the most commonly used nanomaterials in the plastics industry today owing to their availability and low 

EpLA 1 T 4 ciay( clay/27)clay) The tortuosity factor (t) was defined as 

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) 

Intercalated. Where the insertion of the polymeric chains into the layered silicate structure occurs in a crystallographically regular fashion and at a constant spacing of a few nanometers. 

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This chapter first presents a brief discussion on the synthesis of PLA, then, it gives an overview of various processing techniques used to fabricate PLA nanocomposites, with a special focus on the microcellular technology. Lastly, the chapter discusses various viscoelastic, thermal, mechanical, thermal degradation, electrical... 

Moon et al. (61) showed from the mass loss curves for the degradation of PLLA and PLLA-MWCNT nanocomposites that PLLA degraded without forming any residue, but the nanocomposites left a residue of about 3-10% (Figure 9.14). Additionally, the decomposition temperature (Td), at 10% weight loss, was found to increase with the MWCNT loading by 10-20%. Rapid weight loss also took place at around 300 °C in both PLA and PLA nanocomposites. Similar results were also obtained by (64,73,75,76). 

In the second part of this chapter, an illustrative example of PARAFAC analysis for three-way data obtained in an actual laboratory experiment is presented to show how PARAFAC trilinear model can be constructed and analyzed to derive in-depth understanding of the system from the data. Thermal deformation of several types of poly lactic add (PLA) nanocomposites xmdergoing grass-to-rubber transition is probed by cross-polarization magic-angle (CP-MAS) NMR spectroscopy. Namely, sets of temperature-dependent NMR spectra are measured under varying clay content in the PLA nanocomposite samples. While temperature strongly affects molecular dynamics of PLA, the clay content in the samples also influences the molecular mobility. Thus, NMR spectra in this study become a three-way... 

A pertinent example for PARAFAC analysis based on NMR spectra of PLA nanocomposites is provided here to show how certain useful information can be effectively extracted from an actual laboratory experiment. 

PLA nanocomposite samples used in this study were prepared with PLA (Teramac , Unitika) and organically modified clay (S-BEN W , Hojun). The samples were put into a Labo-plastomill consisting of a 30C150 kneader and an RlOO mixer (Toyo Seiki Seisaku-sho, Ltd., Tokyo) to melt-blend at 190 °C and 50 rpm for about 10 minutes. Pellets thus obtained were pressed into 0.2 mm thick sheet sandwiched between two thick Teflon films by a hot press at 190 °C. 

Fig. 6. Temperature-dependent CP-MAS NMR spectra of neat PLA and PLA nanocomposite samples.

More importantly, careful comparison of the samples reveals that the main feature of the NMR spectra of the three samples looks somewhat different. For example, the temperature-dependent NMR spectra of the PLA nanocomposite including 15 wt% clay provides specific three peaks at 70.5, 69.5 and 68.4, indicating the presence of the crystalline structure in the sample (Tsuji et at, 2010 Kister et at, 1998). When the sample has no clay in the system. 

The basic background of PARAFAC and its practical example based on the temperature-dependent NMR spectra of the PLA nanocomposite samples are presented. The central concept of PARAFA decomposition of multi-way data lies in the fact that it can condense the essence of the information present in the multi-way data into a very compact matrix representation referred to as scores and loadings. Thus, while the score and loading matrices contain only a small number of factors, it effectively carries aU the necessary information about spectral features and leads to sorting out the convoluted information content of highly complex chemical systems. 

Generally, PLA nanocomposites exhibit moderate improvement in modulus, strength and thermal stability, decreased gas permeability, and rate of degradation. Lee et al. [128] reported that the modulus of the PLLA nanocomposites systematically increased with increasing montmorillonite [MMT] loading. They also claimed that the crystallinity and the Tg of PLLA nanocomposites were lower than neat PLLA. In the case of PLLA/multi-walled carbon nanotube (MWCNT) nanocomposites, it was observed... 

The manufacturing methods for PLA nanocomposites include intercalation of polymer from solution, polymer melt intercalation and intercalation of a suitable monomer and subsequent in situ polymerization. 

Abstract Biopolymers are expected to be an alternative for conventional plastics due to the limited resources and soaring petroleum price which will restrict the use of petroleum based plastics in the near future. PLA has attracted the attention of polymer scientist recently as a potential biopolymer to substitute the conventional petroleum based plastics. The chapter aims to highlight on the recent developments in preparation and characterization of PLA blends (biodegradable and non-biodegradable blends), PLA composites (natural fiber and mineral fillers) and PLA nanocomposites (PLA/montmorillonite, PLA/carbon nanotubes and PLA/cellulose nano whiskers). 

PLA nanocomposites hold the future in biopolymer nanocomposites as there is an urge for the development of green technology from sustainable and renewable... 

Nam et al. [44] studied the detailed crystallization behavior and morphology of pure PLA and one representative PLA/C18-MMT nanocomposites. They concluded that the overall crystallization rate of neat PLA increases after nanocomposite preparation with C18-MMT. These behaviors indicate dispersed MMT particles act as a nucleating agent for PLA crystallization in the nanocomposites. Lee and co-workers ([45]) who investigated the thermal and mechanical characteristics of PLA nanocomposite scaffold, reported that the recrystallization temperature (Tc) of quenched PLA and its nanocomposite systems decreased by the addition of MMT clay. The nanosized layered MMT platelets provide large surface area due to their small size and thus it is reasonable to consider that the MMT particles could act as effective nucleating sites of PLA crystallization. The increased nucleating sites are likely to facilitate the PLA crystallization process in the nanocomposite systems. 

Regardless of the improvements achieved in the development of PLA nanocomposites, PLA s brittleness had become more inherent, limiting its application for structural applications. Thus, the addition of plasticizers into PLA nanocomposites may provide a way to improve the elongation at break and toughness of the material. However, only several studies which had been contributed recently in the development of plasticized PLA nanocomposites [54—58] but the mechanical properties of these nanocomposites were yet to be studied in detail. 

Paul et al. [54] developed the plasticized PLA nancomposites by melt blending of PLA with 20 wt% of poly(ethyleneglycol) 1000 (PEG 1000) and different amounts of MMT to investigate the thermal and morphological properties of the plasticized PLA nanocomposites. X-ray diffraction (XRD) has pointed out that all the studied MMT led to intercalated nanostructures, even the unmodified MMT had produced an intercalated structure. The researchers stressed that the particular... 

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