Mechanical Properties of Composites Prepared by In Situ Polymerisation

4 Mechanical Properties of Composites Prepared by In Situ Polymerisation 

In situ polymerisation methods are expected to achieve large interfacial shear strength because they can provide strong, frequently covalent, polymer-nanotube interactions. 

In another study by Velasco-Santos et PMMA was polymerised in the presence of arc-MWNT. This is important as they have higher intrinsic strength or stiffness than CVD-MWNT or bundles of SWNT. Stiffness was increased from 1.5 to 2.5 GPa by 1 wt% MWNT, corresponding to dI7dFf 150 GPa. In addition, the strength increased from 30 to 50 MPa, with a proportional increase in toughness. 

Finally, Putz et al. in another study on PMMA and SWNT observed an increase in stiffness as measured by DMA from 0.3 to 0.38 GPa. However, this increase occurred at the extremely low volume fraetion of 8 x 10 . This corresponds to a reinforcement value of d YId V[ 960 GPa. This is close to the theoretical rule of mixtures maximum for long, well-aligned, well-graphitised nanotubes. However, it should be pointed out that this study was carried out at 100 rad s , which is a reasonably high frequency. Time-temperature equivalence of mechanical properties for visco-elastic materials suggests that this may be an over-estimate as compared with values obtained by pseudo-static measurements.  

Young s modulus values of 2.7 GPa. Plasma-enhanced chemical vapour deposition (PECVD) was successfully used to produce a PMMA conformal coating (using methyl methacrylate monomers) on MWNTs. This increased the Young s modulus to 2.85 GPa at 3 wt% which corresponds to dT/dFf of 28.4 GPa. The overall set of mechanical properties indicates that the polymer coating had a significant effect on the mechanical properties at a 1 wt% concentration of tubes, suggesting improved interfacial adhesion between the filler and the matrix material. 

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