Melt blending of ethylene‐vinyl alcohol copolymer/clay nanocomposites: Effect of the clay type and processing conditions

Abstract

Ethylene-vinyl alcohol copolymer (EVOH)/clay nanocomposites were prepared via dynamic melt blending. The effect of the processing parameters on blends containing two clay types in different amounts was examined. The blends were characterized with a Brabender plastograph and capillary rheometer, differential scanning calorimetry, dynamic mechanical thermal analysis (DMTA), X-ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). XRD showed advanced EVOH intercalation within the galleries, whereas TEM images indicated exfoliation, thereby complementing the XRD data. A dilution process with EVOH and clay treatment in an ultrasonic bath before melt blending did not add to the intercalation level. Different trends were observed for the EVOHs containing two different clay treatments, one claimed to be treated for EVOH and the other for amine-cured epoxy. They reflected the differences in the amounts of the strongly interacting polymer for the two nanocomposites. Thermal analysis showed that the melting temperature, crystallization temperature, and heat of fusion of the EVOH matrix sharply decreased with both increasing clay content and processing times. Significantly higher viscosity levels were obtained for the blends in comparison with those of the neat polymer. The DMTA spectra showed higher glass-transition temperatures for the nanocomposites in comparison with those of the neat EVOH. However, at high clay loadings, the glass-transition temperature remained constant, presumably because of an adverse plasticizing effect of the low moleculared mass onium ions treating the clays. The storage modulus improved when clay treated for EVOH was used, and it deteriorated when amine-cured epoxy clay was incorporated, except for the sonicated clay. TGA results showed significant improvements in the blends' thermal stability in comparison with that of the neat EVOH, which, according to TEM, was greater for the intercalated structures rather than for exfoliated ones.

Preparation and characterization of tapioca starch‐poly(lactic acid)‐Cloisite NA+ nanocomposite foams

“…[25] Additionally, the silicate acted as a nucleating agent, causing the viscosity of the matrix to drop, decreasing the T m . [33] Artzi et al [19] observed the same occurrence of decreased T m with increasing clay content. The influence of nanoclay on the reduction of crystallization and melting behavior of PLA became distinct when the concentration of clay was around 3 wt % due to the intercalated nanostructure.…”

“…[17] The intercalated and exfoliated nanocomposites currently are of primary interest because their properties are significantly improved, even at low clay concentrations. However, the formation of intercalated or exfoliated nanocomposites depends on the type of organoclay, [9] [18] the clay content, [19] [20] and the processing conditions. [21] The objective of this study was to prepare tapioca starch (TS)/PLA/Cloisite NA + nanocomposite foams of different clay contents via melt-intercalation and to investigate the influence of clay content on selected structural, morphological, thermal, physical, and mechanical properties of the foams.…”

Thermoplastic Nanocomposites and Their Processing Techniques

“…In thermoplastics the long chain molecules are held together by weak vander waal forces where as in thermosetting, the long chain molecules are held together by strong bonds. Some of the common thermoplastic polymers are; acrylonitrile butadiene styrene (ABS) [Zheng et al, 2004), Acrylic (PMMA) (Khaled et al ., 2007), Ethylene vinyl alcohol (EVOH) (Artz et al, (2002), Polyacrylonitrile (PAN) (Zhang et al, 2009), Polyamide-imide (PAI) (Ma et al, 2010),Polyamide (PA or Nylon) (Bourbigot et al, 2002), Polyethersulfone (PES) (Wang et al 2011), Polypropylene (PP) Polystyrene (PS) (Meincke et al,2003) Polytrimethylene terephthalate (PTT) (Hu et al, 2004) and Polyvinyl chloride (PVC) (Awad et al, 2009), etc. As mentioned above the weak www.intechopen.com vander waal force can be overcome at high temperatures, resulting in a homogenized viscous liquid, which can be further moulded into various shapes.…”

Characterization of Polymer Layered Silicate Nanocomposites by Rheology and Permeability Methods: Impact of the Interface Quality

“…Therefore, many publications focused on the compatibility improvement between the filler and the matrix. The influence of the type of cations surrounding the platelets together with the cationic exchange rate has been widely documented [16][17][18][19][20][21][22][23][24][25][26][27][28][29]. For certain polymers, the introduction of a compatibilizer was found to be the successful way to separate the clay platelets in the matrix.…”