Polyamide–silica nanocomposites: mechanical, morphological and thermomechanical investigations

Abstract

BACKGROUND: The physical properties of polyamides can be enhanced through incorporation of inorganic micro-and nanofillers such as silica nanoparticles. Transparent sol-gel-derived organic-inorganic nanocomposites were successfully prepared by in situ incorporation of a silica network into poly(trimethylhexamethylene terephthalamide) using diethylamine as catalyst. Thin films containing various proportions of inorganic network obtained by evaporating the solvent were characterized using mechanical, dynamic mechanical thermal and morphological analyses. RESULTS:Tensile measurements indicate that modulus as well as stress at yield and at break point improved while elongation at break and toughness decreased for the hybrid materials. The maximum value of stress at yield point (72 MPa) was observed with 10 wt% silica while the maximum stress at break point increased up to 66 MPa with 20 wt% silica relative to that of pure polyamide (44 MPa). Tensile modulus was found to increase up to 2.59 GPa with 10 wt% silica in the matrix. The glass transition temperature and the storage moduli increased with increasing silica content. The maximum increase in the T g value (144 • C) was observed with 20 wt% silica. Scanning electron microscopy investigation gave the distribution of silica, with an average particle size ranging from 3 to 24 nm. CONCLUSION: These results demonstrate that nanocomposites with high mechanical strength can be prepared through a sol-gel process. The increase in the T g values suggests better cohesion between the two phases, and the morphological results describe a uniform dispersion of silica particles in the polymer matrix at the nanoscale.

Thermomechanical Properties of Nanocomposites

“…Recently, it has been shown that physical properties of polyamides can be improved by the addition of both inorganic micro -and nanofi llers to a poly(trimethylhexamethylene terephthalamide) matrix [2] . For this, the composite samples were prepared using a sol -gel technique, with the incorporation in situ of a silica precursor ( tetraethyl orthosilicate ; TEOS ), using diethylamine as the catalyst.…”

“…Yet, by using knowledge acquired with " old " composite materials, a great deal of success has been achieved in preparing nanocomposites with good miscibility and compatibility so as to guarantee the desired properties, based largely on the chemical modifi cation of the silicates that are used to introduce an organic character to a hydrophilic ceramic. To date, many reports have been produced on organic -inorganic composites that combine the desirable properties of a ceramic phase (heat resistance, retention of mechanical properties at elevated temperatures, low thermal expansion) with those of organic polymers (toughness, ductility, processability); the result has been the development of novel properties that are not demonstrated by regular composites [2] .…”

Synthesis and characterization of new heat resistance and organosoluble poly(ether-amide)

“…Aromatic polyamides are noted for high transparency, excellent mechanical properties, heat resistance, good char yield, low flammability, good barrier properties, and outstanding strengthto-weight ratios and solvent resistance [1][2][3][4]; however, they are difficult to process because of limited solubility and high glass transition (T g ) [5][6][7]. The processing of these polymers has been greatly hindered because they lack softening or melting property at usual processing temperature, and they tend to decompose at the softening temperature.…”

Synthesis and characterization of novel aliphatic–aromatic polyamide/Fe3O4 nanocomposites containing pendent 9H-xanthene groups

“…[14] Among the various polymers used for hybrid composites, polyamides have been particularly popular because they offer excellent physical and chemical properties, thermal and oxidative stability, flame resistance, and superior mechanical and dielectric properties. [15][16][17] However, they are difficult to process because of limited solubility and high glass transition (T g ). [15,18] The processing of these polymers has been greatly hindered because they lack softening or melting property at usual processing temperature, and they tend to decompose at the softening temperature.…”

“…[15][16][17] However, they are difficult to process because of limited solubility and high glass transition (T g ). [15,18] The processing of these polymers has been greatly hindered because they lack softening or melting property at usual processing temperature, and they tend to decompose at the softening temperature. Many efforts have been made to create structurally modified aromatic polymers having increased solubility and processability with retention of their high thermal stability.…”