Storage modulus, adhesion

The incorporation of SWCNTs induces a remarkable increase in the storage modulus of the matrix at temperatures below the glass transition, which becomes worthless at higher temperatures. The increase in E is more pronounced for the compatibilized samples, attributed to their improved CNT dispersion and interfacial adhesion between the filler and matrix interfaces. 

While this paper reports only preliminary findings. It does Illustrate the usefulness of photocalorimetry to define optimum cure conditions for UV curable adhesives. In addition, once the mechanical spectrum of fully cured adhesive has been mapped, mechanical spectroscopy can be used to monitor cure efficiency. In this paper we have not explored the molecular weight Implications of Incomplete polymerization. Preliminary evaluation of loss and storage modulus data would suggest that time-temperature superposition may be necessary to evaluate molecular welght/degree of cure relationships and terminal, plateau, and transition zones (4). 

Figure 26 Shear storage modulus (thin lines) and damping (thick lines) for an uncured (a) and cured phenolic adhesive (b).

Figure 27 Shear storage modulus, G, and damping, G", as a function of temperature for a carbon fiber-reinforced epoxy adhesive cured at 120°C. 

Figure 10. Comparison of the storage modulus curves obtained for four epoxy adhesives before immersion (C20), after emersion (C20 -I- W), and after emersion and drying at 20°C and 65% RH for one month (C20 + W -I- D) [20],...

Tensile measurements were taken in most cases to determine the mechanical properties of NR/CNT nanocomposites. Initial modulus, determined from stress-strain curves, was observed to remarkably increase with the filler content. At 1 wt%, the increase was 25.9%, compared to pure NR, ° at 3, 5, 7 and 10 wt% the increase % was 142, 306, 680 and 850, respectively.It was commented that the modulus increase is due to the hydrodynamic effect, further increased by the filler anisotropy, and by the presence of occluded rub-ber.i° For composites with 37 wt% of CNT, the storage modulus was about three orders of magnitude higher than that of the pure rubber. CNT modification with resorcinol caused an increase in modulus at all CNT loadings, indicating improved filler-matrix adhesion. 

Joseph et had also prepared the oil palm microfibril-reinforced NR composites by conventional mechanical blending. The used microfibrils were separated from the oil palm fibres by using the steam explosion method, and were subsequently subjected to treatments such as mercerization, benzoylation, and silane treatment. They found that the storage modulus value of untreated and treated microfibril-reinforced NR composites was higher than that of macrofibre-reinforced composites. The Tg values of microfibril-reinforced composites were slightly higher than that of macrofibre-reinforced composites. The treated microfibril-reinforced NR composites displayed better adhesion between fibre and NR matrix. 

The effect of AAPP treatment on the properties of namral fibre reinforced cellulose acetate butyrate (CAB) composites was then further studied [66]. At a fibre loading fraction of 30 wt%, the storage modulus of the short fibre composites improved by as much as 370% (Fig. 6.4). This is due to the enhanced interfacial adhesion between the fibres and the matrix as a result of AAPP treatment (as measured by single fibre pull-out test) [79], In addition to this, the increment in the mechanical glass transition temperature and a reduction in the height of tan 5 showed better fibre-matrix bonding and fibre-in-matrix distribution. It is evident that AAPP treatment is able to improve the fibre-matrix interface, resulting in composites with improved mechanical properties. 

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