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Abstract: In this paper, the effects of inclusion waviness and its distribution to the effective carbon nanotubes (CNTs)/shape memory polymer (SMP) composites stiffness is investigated. A micro mechanical model is developed to take into account the waviness effect of nanotubes, which are assumed as solid short fibers with a circular cross-section and exhibiting bow shape waviness. The mechanical properties of the composite are significantly increased by reinforcing with CNTs and the desired mechanical properties in addition to proper shape recovery behavior are obtained. The improvements in modulus are remarkably less than the micromechanical prediction assuming straight nanotubes. It is shown that the lack of fiber waviness distribution assumption was found to lead to inaccurate composite stiffness prediction. Since the effects of CNT waviness and aggregation in the composite frequently encountered in real engineering situation, in this study the effects of these defects on the overall properties of the CNT/SMP composite are simultaneously examined. The results indicate that both the waviness and aggregation can drastically reduce the stiffening effect of the CNTs and are two important factors influencing the reinforcing efficiency. [Copyright &y& Elsevier]

Abstract: This paper presents a study of polyamide 6/sepiolite clay nanocomposite, obtained by melt compounding in a mini twin-screw extruder, and characterised in terms of morphology (SEM and TEM analysis) and mechanical properties of the composite, along with their crystallinity and crystal structure of the semi-crystalline matrix. The tensile test results are interpreted in terms of two micromechanical models: the Halpin–Tsai model for stiffness and the Pukanszky equation for yield stress, and compared with the results on polyamide 6/smectite montmorillonite (MMT) clay nanocomposites from selected publications. This comparison between sepiolite (fibre-like shape, 1D) and smectite (platelet-like, 2D) clays offers an interesting model-study on the effect of nanofiller shape and orientation on final mechanical properties. It shows that 1D fillers are expected to provide better reinforcement in the case of oriented systems, whereas platelets should be more efficient in isotropic composites. It was demonstrated that sepiolite has a higher reinforcing efficiency (higher effective aspect ratio) than MMT in PA6 and a good filler-matrix interface, due to strong hydrogen bonds between silanol groups on the sepiolite surface and amide groups of PA6. [Copyright &y& Elsevier]

Abstract: Quaternized carboxymethyl chitosan (QCMC) was intercalated into the interlayer of rectorite (REC) to prepare QCMC/REC nanocomposite. XRD and TEM results revealed that REC was well dispersed in the polymer matrix and obtained the largest interlayer distance when the mass ratio of QCMC to REC was 2:1. FTIR, NMR and zeta-potential analyses showed that the intercalation of QCMC did not destroy the structure of REC layer, but there were hydrogen-bonding and electrostatic interactions between QCMC and REC. Quaternized chitosan (HTCC)/REC nanocomposite was prepared and studied in parallel. The comparative analysis of the two biopolymer/clay nanocomposites indicated that the free volume and positive charge density of biopolymers were important factors that affected the intercalation of biopolymer into clay. At last, thermal analysis indicated that QCMC/REC nanocomposites had obviously higher thermal stability in comparison with QCMC. This study shows that the combination with clay materials is a functional way to expand the possible application of QCMC as drug controlled-release carriers, antimicrobial agent and pulp-cap. [Copyright &y& Elsevier]