DSM Somos NanoForm™ 15120 Nanocomposite Resin for Stereolithography, UV Postcure is a filled photopolymer system in which nanoscale silica reinforcement is dispersed in a liquid epoxy-acrylate matrix. The material is intended for 355 nm vat photopolymerisation platforms and is supplied as an opaque tan liquid with a density of 1.25 g/cm³ under ASTM D792. Cured parts require a dedicated UV postcure step before mechanical testing or service loading. The principal physical distinction from unfilled stereolithography resins is a simultaneous increase in elastic modulus and a reduction in linear thermal expansion, accompanied by lower tensile elongation and lower notched impact energy. Typical cured-state property ranges reported in supplier technical literature include tensile modulus of 4,800–5,200 MPa under ASTM D638-14 and flexural modulus of 4,200–4,800 MPa under ASTM D790-17. Because the dispersed nanoscale phase raises optical scattering, process parameters developed for unfilled resins are not directly transferable without recalibration.

Wind-tunnel test models, composite tooling masters, and rigid checking fixtures are the application classes for which the product is most commonly evaluated. In these use cases, dimensional control after thermal excursions and resistance to moisture-driven expansion during storage are more critical than impact toughness. Published data for this specific configuration is limited when components are post-machined after UV cure, particularly where machined surfaces are left unsealed; verification coupons machined from the same build platform are recommended under ISO 10768 or equivalent internal methods.

Laser Exposure and Recoating Parameters on 355 nm Solid-State Systems

The filled resin has a lower practical cure depth per unit exposure than unfilled epoxy-acrylate systems because the nano-silica phase scatters the incident 355 nm beam. The manufacturing consequence is a narrower process window for hatched cross-sections: underexposed hatching produces weak interline fusion, while overexposure increases edge growth and loss of small negative features. On commercially available solid-state systems with beam power at the vat surface in the 100 mW to 400 mW range, a nominal layer thickness of 0.100 mm is used. Recoating is typically performed with a blade speed between 20 mm/s and 40 mm/s, but the selected speed should be reduced for large plan-view cross-sections exceeding 0.1 m² if resin fill behind the blade is incomplete. The supplier recommends periodic resin level checks because the filled formulation can develop a static yield stress in quiescent sump regions after extended idle periods.

On production arrays, the primary process conflict is particle settlement in the vat rather than bulk viscosity. Nano-silica dispersed in the liquid resin can stratify after idle periods exceeding 24 h; the upper layer becomes resin-lean in filler, and the lower layer becomes filler-rich. A vat stir sequence of at least 30 min before a build is advised, and some stereolithography platforms require a recirculation interval not exceeding 8 h during long builds to prevent concentration gradients at the build surface. Operators should monitor recoater blade wear because the nano-silica is mildly abrasive; replacement intervals for recoater blades may be shorter than those established for unfilled resins. Viscosity stratification is detected as a change in recoating uniformity or as progressive drift in layer thickness. If the resin is transferred from a storage container, gentle rolling or mechanical stirring under vacuum is preferred over high-shear mixing, which can entrain air bubbles that become scattering sites and cause local porosity in cured layers.

Liquid-phase rheology at 30 °C shows viscosity in the range of 1,000 mPa·s to 1,700 mPa·s under ISO 2555 or equivalent spindle viscometry. The filled system is shear-thinning at low shear rates and may exhibit a small yield stress after storage; therefore, spindle viscosity values recorded immediately after stirring are not representative of quiescent vat conditions. For recoating, the practical consequence is that levelling behaviour is governed by low-shear viscosity and surface tension, not by the high-shear viscosity used for transfer pumping. Transfer pumps should use low-shear seals and avoid dead-headed operation because the nano-silica can compact in stagnant lines.

Working curve measurements on a 355 nm system can be used to establish critical exposure and depth penetration. For this resin, the penetration depth of the filled formulation is lower than that of an unfilled epoxy/acrylate resin at the same wavelength. Process calibration is performed by exposing single-layer specimens with exposure energy from 10 mJ/cm² to 80 mJ/cm² and measuring cured layer thickness. A practical calibration target is a maximum layer thickness not exceeding 0.12 mm for cosmetic surfaces and 0.10 mm for dimensionally critical features. Thicker layers increase recoater stresses and reduce Z-axis accuracy.

After build and before postcure, the green-state modulus is sufficient for careful support removal, but the resin is more brittle in the green state than unfilled resins. Aggressive support removal can initiate microcracks that propagate after UV postcure. Supports should be removed after a brief room-temperature rest period, or after a low-dose UV tacking exposure if large parts are handled. The use of high-speed rotary tools can generate local heating above the glass transition temperature of the green resin, causing smearing and loss of small features. Slow hand removal or machine removal with vacuum dust extraction is preferred.

How Does the Nano-Silica Reinforcement Shift Cured Properties Relative to Unfilled Epoxy/Acrylate Systems?

The inclusion of nanoscale silica raises the glassy-state elastic modulus through a hard-particle reinforcement mechanism, while the crosslinked epoxy-acrylate network remains the continuous phase. A direct consequence is reduced viscous creep at ambient temperature and a lower coefficient of linear thermal expansion. The trade-off is a reduction in strain to failure and notched Izod impact. The comparative table below shows typical ranges; the unfilled reference represents a general-purpose epoxy/acrylate stereolithography resin processed under identical conditions, not a specification value for any single commercial product.

The mechanical property shift is most relevant when a design is stiffness-limited rather than toughness-limited. The high modulus and lower thermal expansion improve the accuracy of thin-shell wind-tunnel models during resin shrinkage and postcure. However, low elongation values in the 1.3–1.8% range mean that snap-fit features, living hinges, or thin flexural elements require stress concentration testing before production release. The material is not a direct substitute for tough unfilled engineering resins such as ABS-like or polypropylene-like stereolithography grades when impact loading dominates.

In composite tooling, the resin is used for lay-up patterns and master models where autoclave cure temperatures are below the heat deflection temperature. The low coefficient of linear thermal expansion reduces spring-back after demoulding. Tooling blocks machined from NanoForm™ 15120 are evaluated on 3-axis CNC equipment with carbide tooling; shop-floor experience indicates that climb milling with chip load below 0.05 mm/tooth reduces edge chipping. Dust extraction is required because fine particulate generated during machining may contain silica and must be controlled under workplace exposure limits. Because the filled resin is brittle relative to unfilled grades, clamping pressure should be distributed with soft jaws, and tapped holes should use threaded inserts rather than direct tapping where repeated assembly is expected.

Compared with high-temperature unfilled stereolithography resins, NanoForm™ 15120 trades impact energy for lower thermal expansion and higher modulus. It differs from particulate-filled tooling boards and machined tooling board materials in that it is built additively, so internal lattice regions and conformal cooling channels can be incorporated before postcure. When compared with micro-scale ceramic-filled stereolithography resins, the nano-silica dispersion produces a smoother sidewall finish and lower abrasive wear on recoater blades. However, the cured resin remains a polymer; continuous service at temperatures approaching the heat deflection temperature under mechanical load is not recommended. Published data for this specific configuration is limited for long-term environmental ageing above 100 °C in air, and oxidative embrittlement may become the dominant failure mode.

Compared with micro-filled composite stereolithography resins, NanoForm™ 15120 provides lower sidewall roughness after recoating because the nano-silica particles do not protrude from the liquid surface in the same manner as larger fillers. The penalty is that the nano-silica can remain suspended for long periods, but also forms a stable concentration gradient if not agitated. The material is supplied as a one-component system and does not require metering of a separate filler. Its use with automated resin handling systems requires verification that level sensors are not fouled by the opaque liquid; optical sensors may require recalibration because the filled resin has lower optical transmittance than clear unfilled resins.

If a UV-Only Postcure Is Selected Without a Follow-On Thermal Cycle

The product designation includes UV postcure, and the standard workflow specifies an enclosed ultraviolet chamber with high-intensity UVA fluorescent lamps. A postcure chamber with nominal peak irradiance of 5 mW/cm² to 20 mW/cm² at 365 nm is used in some production lines for thin-section parts, with cumulative radiant exposure controlled by total time rather than a single pass. Published data for this specific configuration is limited for thick cross-sections exceeding 25 mm; thick monolithic builds may retain residual unconverted monomer in internal regions because UV penetration is attenuated by the filled resin. In such cases, stepwise postcure with intermittent cooling is advised to limit exotherm and prevent surface cracking. The material does not require thermal-only postcure; however, optional low-temperature conditioning at 40 °C to 60 °C for dimensional stabilisation is used in some tooling applications. The absence of a thermal step after UV cure may leave slightly lower heat deflection temperature and greater sensitivity to humid absorption relative to a combined UV-thermal cycle.

The UV postcure chamber should be fitted with reflective side walls and a rotating platform to achieve a uniformity ratio better than 0.80 across the build envelope. Irradiance is measured with a calibrated radiometer at 365 nm; if the measured irradiance falls below 5 mW/cm², the postcure cycle should be extended or lamps replaced. Chamber temperature should be monitored at the part surface because exothermic cure of thick sections can exceed 65 °C; if surface temperature exceeds 70 °C, thermal cracking may initiate in sections with sharp internal corners. A cycle of 30 min on and 10 min off for thick parts reduces the risk of thermal runaway in large cross-sections.

Postcure conditions should be established with the part mounted on a non-reflective support to prevent shadowing; rotating tables and reflectorised interiors can improve uniformity. If UV energy is delivered in a low-power fluorescent cabinet without controlled temperature rise, residual stress relaxation may occur and small features may warp. The filled resin scatters UV more than unfilled systems, so postcure penetration is lower; the practical consequence is that wall thicknesses above 3 mm require verification of through-thickness cure by hardness or glass transition measurement. The supplier’s instructions recommend that uncured material be removed from deep channels before postcure because polymerised surface skins can seal liquid and cause later cracking.

The liquid resin is sensitive to moisture uptake during storage and should be kept in sealed containers at 20 °C to 30 °C unless otherwise stated on the safety data sheet. Avoid combining the resin with amine-based additives or reactive thinners not approved by the supplier, as premature crosslinking or phase separation of the nano-silica can occur. Parts should not be exposed to ketone, chlorinated, or aromatic solvents for extended periods before full postcure because solvent absorption can reduce modulus and promote microcracking. When machining cured parts, compressed air cooling is preferred over water-based coolant unless the coolant is immediately removed and the part is dried at 25 °C to 30 °C for at least 24 h before dimensional inspection.

Storage at relative humidity above 60% without sealed containers can increase water content in the liquid resin; water uptake affects the UV curing response and can produce surface haze after postcure. Pre-drying of parts before UV postcure is not required if handling is brief, but conditioning at 23 °C and 50% RH for at least 24 h before dimensional inspection is standard because the filled resin absorbs moisture at a lower rate than unfilled grades. The lower water absorption values in the table do not mean that moisture exposure has no effect; dimensional changes are smaller but not zero.

The operational boundaries for the material include a maximum continuous service temperature below the heat deflection temperature under load, especially when parts are subjected to bending loads. Because the resin has low elongation, stress concentrations at holes, notches, and abrupt changes in cross-section must be assessed under the intended service load. Sharp notches should be radiused where possible, and threaded inserts are recommended for assembled parts. Paint and adhesive compatibility should be tested before production because the nano-silica surface and residual monomer may affect adhesion. The material should not be used for potable water contact, food-contact surfaces, or medical implant applications unless specific regulatory approvals are obtained under the applicable jurisdiction.

For users transitioning from unfilled stereolithography resins, the main process adjustments are exposure recalibration, vat agitation after idle periods, and postcure cycle validation on printed process specimens. Build orientation should place critical surfaces away from the recoater side if possible, because the filled resin can show slightly higher haze and line-to-line variation on the recoater-facing side. Published data for this specific configuration is limited for build sizes larger than 500 mm, and preliminary builds with process coupons are recommended before production tooling is committed.