Functionalizing stereolithography resins: effects of dispersed multi-walled carbon nanotubes on physical properties

Purpose - The present research investigates tailoring the physical properties of stereolithography (SL) epoxy-based resins by dispersing controlled small amounts of multi-walled carbon nanotubes (MWCNTs) directly in SL resins prior to layered manufacturing. Design/methodology/approach - A modified 3D Systems 250/50 SL multi-material machine was used where the machine was equipped with a solid-state (355 nm) laser, unique similar to 500 ml vat, overfill drain vat design that continuously flowed resin into the vat via a peristaltic pump, and 8.89 by 8.89 cm(2) platform. The vat did not include a recoating system. Pumping the composite resin assisted in maintaining the MWCNTs dispersed over long periods of time (with MWCNT settling times on the order of one week). The research approach required developing a method for dispersing the MWCNTs in SL resin, determining new SL build parameters for the modified resin and SL machine, and building and testing tensile specimens. Findings - Mechanical mixing and ultrasonic dispersion provided simple means for dispersing MWCNTs in the SL resin. However MWCNT agglomerates were observed in all the parts fabricated using the filled resins. Each concentration of MWCNTs resulted in a new resin requiring modifications to the SL build parameters, E(C) and D(P). Once characterized, the modified resins performed similar to traditional resins in the SL process. Small dispersions of MWCNTs resulted in improvements in the tensile strength (TS) (or ultimate tensile stress) and fracture stress (FS) of tensile specimens as 0.025 percent (w/v) MWCNTs in DSM Somos(R) WaterShed(TM) 11120 resin resulted in increases in TS and FS of 5.7 percent and 26 percent, respectively, when compared to unfilled resin. Increasing the concentration of MWCNTs to 0.10 percent (w/v) resulted in increases in TS and FS of 7.5 percent and 33 percent, respectively, over the unfilled resin. Transmission and scanning electron microscopy showed strong affinity between the epoxy resin and the MWCNTs. Research limitations/implications - Additional MWCNT type and concentrations in various SL resins should be investigated along with additional means for dispersion to provide sufficient information on developing new SL resins for unique functional applications. Practical implications - It is anticipated that the methods described here will provide a basis for further development of advanced nanocomposite SL resins for end-use applications. Originality/value - This research successfully illustrated the dispersion and use of MWCNTs as a reinforcement material in a commercially available SL resin.