Abstract
The aim of this work is the investigation of the effect of ultrasound treatment on the structural characteristics of carbon nanotubes (CNTs) and the consequent influence that the shortening induced by sonication exerts on the morphology, rheological behaviour and thermo-oxidative resistance of ultra-high molecular weight polyethylene (UHMWPE)-based nanocomposites. First, CNTs have been subjected to sonication for different time intervals and the performed spectroscopic and morphological analyses reveal that a dramatic decrease of the CNT’s original length occurs with increased sonication time. The reduction of the initial length of CNTs strongly affects the nanocomposite rheological behaviour, which progressively changes from solid-like to liquid-like as the CNT sonication time increases. The study of the thermo-oxidative behaviour of the investigated nanocomposites reveals that the CNT sonication has a detrimental effect on the thermo-oxidative stability of nanocomposites, especially for long exposure times. The worsening of the thermo-oxidative resistance of sonicated CNT-containing nanocomposites could be attributed to the lower thermal conductivity of low-aspect-ratio CNTs, which causes the increase of the local temperature at the polymer/nanofillers interphase, with the consequent acceleration of the degradative phenomena.
Highlights
The outstanding electrical, magnetic and mechanical properties of carbon nanotubes (CNTs) have motivated a flurry of interest in exploiting their potential as nanofillers in polymer-based nanocomposites [1,2].several studies reported in the literature show that adding CNTs to a polymer matrix causes a reinforcement of mechanical properties [3] and an enhancement of thermal and electrical conductivity [4,5]
Several studies reported in the literature show that adding CNTs to a polymer matrix causes a reinforcement of mechanical properties [3] and an enhancement of thermal and electrical conductivity [4,5]
ultra-high molecular weight polyethylene (UHMWPE) is a commercial grade product purchased by Sigma-Aldrich (Saint Louis, MO, USA)
Summary
The outstanding electrical, magnetic and mechanical properties of CNTs have motivated a flurry of interest in exploiting their potential as nanofillers in polymer-based nanocomposites [1,2].several studies reported in the literature show that adding CNTs to a polymer matrix causes a reinforcement of mechanical properties [3] and an enhancement of thermal and electrical conductivity [4,5]. The final properties of CNT-containing nanocomposites strongly depend on the extent of the CNT dispersion within the polymeric matrix and on the quality of the polymer/nanofiller interfacial region. Due to their high surface-to-volume ratio, CNTs tend to interact through Van der Waals forces, forming agglomerates and aggregates that compromise the obtainment of a homogeneous distribution of CNTs thorough the host matrix and, a proper transfer of the CNT properties to the polymer [10]. The functionalization of CNT surfaces can be achieved by exploiting several methods, including covalent linkage [11] and physical absorption [12], and, besides ensuring improved dispersability of the CNTs in polymers, can provide them with new functionalities
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