Adhesion behavior of polymer networks with tailored mechanical properties using spherical and flat contacts

Four acrylate-based networks were developed such that they possessed similar glass transition temperature (~-37 °C) but varied in material stiffness at room temperature by an order of magnitude (2-12 MPa). Thermo-mechanical and adhesion testing were performed to investigate the effect of elastic modulus on adhesion profiles of the developed samples. Adhesion experiments with a spherical probe revealed no dependency of the pull-off force on material modulus as predicted by the Johnson, Kendall, and Roberts theory. Results obtained using a flat probe showed that the pull-off force increases linearly with an increase in the material modulus, which matches very well with Kendall's theory

Characterization of poly(para-phenylene)-MWCNT solvent-cast composites

Poly(para-phenylene) (PPP) is one of the strongest and stiffest thermoplastic polymers due to its aromatic backbone structure. However, because of this chemistry, this also means that typical processing techniques require high temperatures and pressures to allow for formability. This study demonstrates that, unlike similar aromatic thermoplastics, PPP has the unique ability to be solvent-cast using conventional solvents, which allows for facile fabrication of thin films and coatings under ambient conditions. The purpose of this research was to investigate the properties of solvent-cast PPP, which is not currently available in literature. In addition, through the solvent-casting technique, composite materials can be created by combining PPP with multi-walled carbon nanotubes (MWCNTs) in attempts to enhance structural properties and electrical conductivity. A method was developed for solvent-casting of PPP through chloroform evaporation and subsequent methanol soaking, resulting in homogenous average thicknesses of 0.10 ± 0.04 mm. Mechanical testing of solvent-cast PPP resulted in an elastic modulus of 4.2 ± 0.2 GPa with 13 ± 2.3% strain-to-failure. The addition of MWCNT reinforcement increased ultimate tensile strength at the expense of ductility. Composites maintained a yielding response up to 6 vol.% of MWCNTs, which also corresponded to the largest strength values observed. Ultimate tensile strength increased from 96 MPa from the matrix to a maximum of 121 MPa. Electrical conductivity of the composites increased from 4.5 × 10−6 to 1.02 × 10−3 S/cm from 3 to 20 vol.% MWCNTs, although values plateau at 5 vol.%

Adhesion behavior of polymer networks with tailored mechanical properties using spherical and flat contacts

Four acrylate-based networks were developed such that they possessed similar glass transition temperature (~-37 °C) but varied in material stiffness at room temperature by an order of magnitude (2-12 MPa). Thermo-mechanical and adhesion testing were performed to investigate the effect of elastic modulus on adhesion profiles of the developed samples. Adhesion experiments with a spherical probe revealed no dependency of the pull-off force on material modulus as predicted by the Johnson, Kendall, and Roberts theory. Results obtained using a flat probe showed that the pull-off force increases linearly with an increase in the material modulus, which matches very well with Kendall's theory