Effect of weakly interacting nanofiller on the morphology and viscoelastic response of polyolefins

Abstract

Effect of silica nanofiller on the deformation response and morphology of low-and high-density polyethylene (HDPE, LDPE) and isotactic polypropylene (PP) modified with fumed silica was investigated. The dynamicmechanical thermal spectroscopy, differential scanning calorimetry, optical microscopy, and density measurements were carried out to determine the temperature dependence of storage and loss moduli as well as nanocomposite morphology. It was demonstrated that the degree of matrix reinforcement is considerably affected by the extent of matrix crystallinity, especially, in the temperature range from (T m -1308C) to T m . Based on experimental evidence and literature review, it is proposed that this phenomenon may be attributed to the alpha-mechanical relaxation process occurring above matrix T g . As a result of adding silica into the melted matrix, mobility of chains in contact with silica particles became reduced. This caused substantial changes in morphology of these semicrystalline nanocomposites.

Reinforcing Poly(ethylene) with Cellulose Nanocrystals

“…This network is established during formation of the organogel, and the percolation fit suggests that network is not broken up during the processing method. This conclusion is also supported by much the better reinforcement achieved in the present nanocomposites than similar systems using alternate fillers such as silica, modified clay, multi‐walled carbon nanotubes, where percolating network was not obtained due to filler dispersion issues. Gratifyingly, the diluted nanocomposites using melt‐processing also fit the theoretical model very well for the composition near to the percolation threshold, indicated the dispersion is maintained even though they have undergone significant shear.…”

Effects of SiO2 and Al2O3 nanofillers on polyethylene properties

“…I C values, presented in Table I, highlight a decrease of PE crystallinity with the increasing amount of nanosilica, but no important change of PE crystallinity for nano‐Al 2 O 3 composites. Some early studies have evidenced a similar behavior, that is, a decrease of the crystallinity of LDPE and other polyolefins when 2, 4, and 8 vol % nanosilica of 7‐nm diameter was added 43. A different behavior was signaled in the case of linear LDPE containing low concentration (under 4 wt %) of 16‐nm silica nanoparticles, treated with dimethyldichlorosilane, materialized in an increase of polyethylene crystallinity 44.…”

Dynamic mechanical analysis and thermal properties of LLDPE/EVA/modified silica nanocomposites

“…Why could not these particles affect the crystallization behavior? There are several mechanisms for reinforcement of the polymeric matrix by nanoparticles [22] which are briefly described as follows: 1-substitution of polymer matrix by hard nanoparticles which can increase the storage modulus. 2-chains mobility reduction above the glass transition temperature.…”