K. Ramesh

Bio: K. Ramesh is an academic researcher from Texas Tech University. The author has contributed to research in topics: Sealant & Elastomer. The author has an hindex of 1, co-authored 1 publications receiving 5 citations.

Monolithic growth of partly cured polydimethylsiloxane thin film layers

Abstract: The demand for monolithic structures in many applications has increased to enable more reliable and optimized performances such as for dielectric electroactive polymers (DEAPs). For the layers of the elements to grow efficiently together, it is first of all required that the layers adhere together to enable interlayer crosslinking reactions either by application of an adhesion promoter or by ensuring that there are reactive, complementary sites available on the two surfaces. Polydimethylsiloxane (PDMS) is a widely used polymer for DEAPs. In this work, two-layered PDMS films are adhered together at different curing times. The monolithic films are investigated by rheology, scanning electron microscope, mechanical testing, dielectric relaxation spectroscopy, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The morphology, mechanical and dielectric properties, as well as thermal stabilities of the bilayer elastomer films are observed to change with the curing time of the monolayers before lamination. The objective of this work is to create adhesion of two layers without destroying the original viscoelastic properties of the PDMS films, and hence enable, for example, adhesion of two microstructured films which is currently a crucial step in the large-scale production of DEAPs. Monolithic polydimethylsiloxane (PDMS) thin film layers were prepared by adhering two partly cured films together at different curing times. For dielectric electroactive polymer (DEAP) uses the lamination performed slightly above the gelation threshold, namely at the time where the monolayer films had gained 30% of the final mechanical strength, was extremely favorable. The lamination process for DEAP bilayers can actually be used as a process to improve the overall performance of the DEAP, and hence enable the large-scale production of DEAP transducers.

Techniques for hot embossing microstructures on liquid silicone rubbers with fillers

Abstract: Embossing is an established process for the thermoplastic elastomers but not yet for the thermosetting elastomers. It has already been shown that hot embossing is a viable technology for imprinting microstructures in addition to curing thin silicone films at their gel point. It is one of the simplest, most cost-effective, and time-saving methods for replicating microstructures. In the present study, films made from liquid silicone rubber (LSR) formulations containing fillers are hot embossed under modified operating conditions. The use of such relatively hard silicone elastomers shows the versatility of this method that has been established for softer silicone elastomers. Also, as a proof of concept, a microstructured metal (nickel (Ni)) plate is used as an embosser for the films successfully. The ideal condition for hot embossing the LSR formulation (XLR 630 with titanium dioxide fillers) with a Ni embosser is 110°C preheating for 15–35 s, embossed with 2 bar pressure, and postheating for complete curing...