3-D jetting for enhanced functionality of thermoset elastomeric materials

2018-06-05T16:20:09Z (GMT) by Marija Lukic
The aim of this work was to assess the feasibility of 3-D inkjet printing of elastomers in latex form to create a novel material that would offer shielding against electromagnetic interference (EMI). To achieve this aim it was necessary to characterise and select suitable materials, carry out ink jetting trials, modify the materials accordingly to improve the printability and assess post jetting conditions including drying and curing behaviour. Particle size, surface tension, and viscosity measurements were made for a series of elastomer latex materials and carboxylated styrene butadiene rubber (XSBR) latex was identified as the most suitable. Latex ink optimisation included dilution with water and the addition of a humectant, triethylene glycol monomethyl ether (TGME), which delayed drying and reduced nozzle blocking. The surface energy was measured for arrange of potential substrates and PET was identified as the most suitable, due to its relatively high surface energy which allowed for an ideal level of wetting and spreading. Analysis of the cross-sectional profiles of the printed samples by white light interferometry showed that drying during printing was an important issue for the latex ink. Ink jetting of a composite material with control of filler distribution was shown to be feasible when ten layers of conductive carbon black ink were deposited alternately between ten layers of XSBR ink. Printing was successfully carried out with a latex combined with a resorcinol resin which was subsequently cured, indicating that it should be possible to 3D print a thermoset elastomer in this way. Conductive carbon black was printed in various patterns onto PET sheet and the dielectric properties measured. Results indicated that at very low carbon contents, the printed patterns could provide EMI shielding. The research has shown that it is feasible to create a cured 3D elastomeric object containing filler with a controlled distribution that is capable of providing EMI shielding.