Instructions for Use IFU for conductive resin systems

3Dresyns conductive 3D resins and additives contain micron, and/or submicron, and/or nanoparticles, and/or nanowires, and/or microfibers, which indendently on their shape need to be fully wetted, dispersed (fully uncoiled for nanowires and microfibers), stabilized in suspension, and fully homogenized to ensure maximum stability and conductivity readings for each conductive resin system.

Printing and postprocessing

Follow our general Instructions for Use "IFU" and our more specific IFU for different printing technologies, which can be requested by email to info@3Dresyns.com after ordering our 3Dresyns

Conductivity basics and requirements

• the conductivity results from the interconnection ensurance of individual particles, nanowires, or microfibers by creation of percolation or percolating networks. Conductivity is affected by their distribution in the 2D or 3D printed resin system. Unfortunately, nanowires and microfibers naturally tend to coil, creating webs, clusters, and clumps. Agglomeration of nano, micron, and submicron particles, nanowires, and microfibers in clumps or agglomerates also  occurs naturally due to electrostatic interaction, even in solid form. Gravitational separation and decantation tends to occur due to the high density of metallic materials (silver has a density of 10.49 g/cm³) in comparison to the much lower density of graphenes (and other carbon based non metallic conductive materials) and 3D resins since most resins have densities of 0.95-1.05 g/cm³
• full homogenization and homogeneous distribution of the active conductive material during printing, without settling issues is necessary for achieving conductivity of the prints

Difficulties and limitations of 2D & 3D printable conductive materials 

• unfortunately, ready to use conductive resins based on metallic nanomaterials, such as silver or copper, can gel during transportation since they are prone to polymerize at temperatures above 40-50ºC, reducing their shelflife significantly. Due to this limitation, they cannot be sent predispersed in the 3D resin because specially silver nanomaterials suffer from premature gelation, specially in summer due to exposure to excessive temperature during shipping. They are also prone to suffer from separation "settling" from the liquid medium, and gelation by "polymerization" and/or by foam formation, when exposed to too high shear and heat in the microscopic and macroscopic level, such as with too high speed mixing and too high sonication power, frequency and time

Key variables affecting conductivity

The provided conductivity values shown on each product information are achievable conductivities, not fixed values, since final conductivity readings depend on these key variables:

• the degree of deagglomeration, stabilization, and homogenization of the conductive material in the resin and the creation of percolation networks 
• the chosen resin and its potential contribution to conductivity
• the final suspension stability of the conductive additive in the chosen 3D resin, since each one has different viscosity, provide different wetting, and suspension stability
• dispersion equipment and specifications used since:
• too low dispersion speed settings cannot ensure full deagglomeration, stabilization, and homogenization of clumps or agglomerates
• too high dispersion speed settings can cause gelling of the resin, by excessive foam formation, or by polymerization, as well as breaking the conductive nano and micron materials. Specially sensitive to breakage are long and thin nanowires, which upon excessive mechanical shear can be broken reducing conductivity readings
• rotary mixers or stirrers are often too big for small mixing quantities, unless small Conn blades are used. Avoid excessive shear to prevent gelation, caused by foaming or by polymerization due to excessive heat generation or shear. Cowles blades are less prefered than Conn blades because they generate too much friction and breakage due to their sharp cutting edges
• vortex mixers are ideal for dispersing conductive resins at low concentrations and viscosities in test tubes since cross-contamination and excessive heat is prevented because direct contact with the conductive 3D resin system with sharp blades is prevented. Blades can cause excessive heat in the contact area of the blade with the resin inducing premature thermal polymerization. Vortex mixers tend to create excessive foam formation. Use vortex mixers gently. If too much foam is formed, warm it gently to promote foam elimination. Use sonication, or use vacuum to remove air bubbles
• magnetic stirrers are not recommended since they cannot fully disperse nanomaterials  at high concentrations or viscosities due to their low mixing yield 
• high-speed dispersers, also known as high-speed homogenizers, are capable of homogenizing efficiently conductive 3D resins. At too high speed they can cause gelation, due to excessive shear, and local heat generation, causing premature polymerization, excessive foaming, and breakage of delicate nanowires and microfibers, reducing their conductivity. On the other hand, high-speed homogenizers at low speeds can be used efficiently to mix viscous components. Avoid cross-contamination which may reduce the conductivity
• ultrasonic cleaning machines and ultrasonic probe sonicators (also known as ultrasonic liquid processors) are ideal for dispersion nano and submicron materials, but need to be used with caution to prevent chemical gelation (thermal polymerization) of the photo reactive conductive 3D resins. Excessive sonication by too high frequency and time, generate excessive heat, which can promote premature polymerization. Sonication can be used gently to eliminate foam
• instrumentation and specifications used for measuring conductivity
• multimeters with 2 point probes are less accurate and tend to give much lower readings for the same conductive material than 4 point probe conductomers as https://www.ossila.com/en-eu/products/four-point-probe-system
• For more information read: Two probe and four probe methods
• annealing of the prints by heating them to at least 80-140ºC for eg 30 min promote conductivity. The annealing temperature depends on each conductive material properties

About conductivity

• final conductivity readings depend on the creation of percolation networks, which depend on the already mentioned variables, which are beyond 3Dresyns direct control. Additionally, conductivity values and dosages are generic or typical as highlighted on each product information, since for example, nanowires, due to their relative high length and low thickness tend to coil in webs and clumps, and are prone to suffer breakage with excessive shear. Nanowires length and integrity need to be preserved during processing. They need to be fully deagglomerated, uncoiled, stabilized, and homogenized before and during printing to avoid any decrease of conductivity. Similar requirements are needed for conductive materials with particle morphology, since despite not suffering coiling, their agglomerates need to be wetted, deagglomerated, stabilized, and homogenized, and its re-agglomeration and sedimentation prevented, to ensure the creation of a percolating network and conductivity

Recommended additives for 3D printable conductive resins 

The following 3Dresyns additives are recommended for custom design of conductive resin systems:

• 3D-ADD Disper-All3 WS, ultra effective dispersant for water and solvent soluble systems has high polarity to wet and disperse nanomaterials without decreasing significantly their conductivity

• 3D-ADD ASC1, anti sedimentation additive (HHP version) is a polar antisettling additive for stabilizing in suspersion nano and micron powders, nanowires, and fibers. Its usage is required for keeping in suspènsion nano, submicron, and micron materials and prevent their coiling (for wires, and fibers), sedimentation and formation of agglomerates, clusters, or clumps. It provides excellent flow but relatively high yield value at zero shear to promote superior suspension stability. Dosages depend on the original viscosity of the used resin system

Conductive additive processing

• if conductivity values are lower than the achievable reported ones mentioned on each product information, the whole dispersion, stabilization and homogenization process may need optimisation
• excessive foaming can reduce conductivity readings since entrapped air act as conductivity insulator. Use a sonicator to eliminate foam
• a decrease or increase of the conductive additive dosage is recommended since conductivity values are approximate, depend on the dosage, specific resin to which the conductive additive is added, and on the overall processing conditions used
• excessive dosage may promote the formation of clusters, or clumps (sea-island or nodular structures) and asymptotic behavior of the percolation network
• too low dosage below the percolation threshold will yield poor conductivity
• if needed increase or decrease the dosage of conductive additive as much as needed, and ensure formation of a percolating network, by its full dispersion, deagglomeration, stabilization, and homogenization before printing
• if clumps are created by excessive concentration decrease the dosage of conductive additive as much as needed, to prevent clump formation, ensuring its full dispersion, deagglomeration, stabilization, and homogenization before printing
• without the optimum deagglomeration of agglomerates / clumps, and formation of a percolation network conductivity will be significantly reduced. The conductivity depends not only on the degree of dispersion and deagglomeration of the conductive additive but also on its dosage, its suspension and percolation network stability, and the potential contribution to conductivity of the chosen 3D resin

Contact us for consultation before placing your orders at: info@3Dresyns.com