In vat photopolymerization cells operating at 355 nm, DSM Somos GP Plus 14122 is a low-viscosity, unfilled epoxide/acrylate liquid photopolymer that produces opaque white parts with a solid density of approximately 1.19 g/cm³ when tested to ASTM D792-20. The resin is processed on 3D Systems Viper Si2, SLA 3500, SLA 5000, and SLA 7000 platforms, and its liquid density is approximately 1.12 g/cm³ at 25 °C. The product is supplied as a UV-sensitive liquid and requires dark storage below 30 °C in sealed containers. After the supplier’s recommended post-cure, the Shore D hardness is 84 when measured per ASTM D2240-15.

For build shops running multiple resin types, the operational distinction is that GP Plus 14122 is an unfilled, low-viscosity grade rather than a ceramic-filled or fiber-reinforced stereolithography material. It drains readily from thin channels and can be cleaned with isopropanol, but it does not contain abrasive wear-resistant filler. Viscosity at 30 °C is reported in the range of 250 cP to 265 cP by Brookfield rotational viscometry. The low viscosity supports fine recoating, yet it also increases sensitivity to vat temperature drift below 24 °C, where recoat defects become more common on large cross-sections.

Why do XY and Z tensile values differ after post-cure?

The datasheet mechanical values are not green-state values; they are generated after UV and thermal post-cure. During laser scanning, conversion is intentionally incomplete in the green state to support layer adhesion and reduce shrinkage stress. After a full post-cure, the typical tensile strength is 47 MPa, tensile modulus is 2650 MPa, and elongation at break is 7 % when pulled in the XY orientation per ASTM D638-14. Flexural testing per ASTM D790-17 gives a flexural strength of 72 MPa and a flexural modulus of 2350 MPa. The notched Izod impact value is 32 J/m per ASTM D256-10. Z-oriented tensile specimens typically show lower elongation at break because interlayer conversion gradients create a weaker boundary between adjacent layers. Published data for the exact reduction across all post-cure profiles is limited; it should be measured on the intended build platform.

The heat deflection temperature under 0.46 MPa is 62 °C per ASTM D648-18. The equivalent ISO method, ISO 75-2:2013 Method B, may produce slightly different values because of specimen geometry and heating rate. In production, continuous service above approximately 50 °C is not recommended unless the part is supported and the applied load is low. Applications are therefore general-purpose prototypes, room-temperature vulcanizing mold master patterns, inspection fixtures, and parts that do not experience impact-dominated loading. The unfilled nature allows sanding and cyanoacrylate bonding with lower tool wear than filled grades, but the impact value is lower than that of toughened SLA resins such as Somos DMX-SL 100.

In photopolymerization, the working curve of critical exposure and penetration depth determines the maximum layer thickness. For GP Plus 14122 at 355 nm, the unfilled composition and low viscosity permit layer thicknesses typical of general-purpose stereolithography materials, with 0.100 mm used on many platforms. Larger layer thickness increases throughput but increases z-scallop and reduces tensile elongation in the Z axis. The supplier provides machine-specific build parameter sets rather than a single universal scanning recipe.

When this resin replaces a filled or high-temperature stereolithography grade

In an application where a ceramic-filled resin such as DSM Somos PerFORM or NanoTool is used for stiffness or thermal cycling above 120 °C, GP Plus 14122 is not a direct substitute. Its heat deflection temperature of 62 °C at 0.46 MPa means that a tool heated to 90 °C can soften the part if the fixture applies pressure. Conversely, when the process need is low viscosity, fine feature reproduction, or hand finishing rather than high-temperature stiffness, the GP Plus 14122 grade is selected over filled materials. The low filler content also reduces abrasive wear on recoater blades and pumps in production SLA equipment; filled grades can increase blade wear on machines without hardened recoater edges.

For snap-fit closures, the notched Izod impact of 32 J/m under ASTM D256-10 is lower than the values typical of impact-modified SLA materials. The resin is better suited to rigid housings and fixtures than to flexible or high-elongation components. Prototypes that require repeated insertion cycles should be tested on the actual injection-molding tool geometry using production-grade equipment such as an instrumented puncture tester or high-speed impact fixture; the datasheet value alone is not a substitute for multiaxial impact data.

Vat drift, gel-particle filtration, and batch release controls

The liquid resin can accumulate partially cured gel seeds over time. These particles may originate from thermal exposure, light leakage, or contamination with cationic catalysts. In production vats, gel seeds can damage recoater blades and create pits on part surfaces. Resin transfer should occur through a 100 µm to 150 µm mesh filter; finer filtration can be used with low-shear peristaltic pumps, but high-shear pumping may introduce air and increase the risk of skinning. Batch release testing should include viscosity at 30 °C by Brookfield rotational viscometer and density per ASTM D792-20. The supplier does not publish a universal maximum allowable viscosity drift; each user should establish a control limit based on incoming lot data and machine-specific process capability. If viscosity increases by more than 10 % relative to the incoming lot, the resin should be quarantined for mechanical testing per ASTM D638-14.

Post-cure shrinkage must be compensated in the build setup. XY scale factors are usually lower than Z scale factors because the part is constrained by the build platform and previous layers. Users should generate a calibration block with through-holes and boss pairs on each platform and adjust the scale factors until dimensional tolerance matches the intended use. Published data for a specific scale factor set is limited because the correct values depend on build style, recoater setting, and resin lot.

Exposure to concentrated amines, strong bases, or excess moisture can destabilize the uncured epoxide/acrylate system. The liquid resin must not be mixed with amine-functionalized mold releases or residues from amine-cured epoxy hardeners; contamination can initiate thickening or gel formation. In the cured state, water absorption after 24 h is approximately 0.35 % per ASTM D570-98. Parts stored in humid air should be dried before bonding or painting because surface moisture can reduce adhesive strength. Prolonged immersion in acetone or methylene chloride is not recommended; ketones and chlorinated solvents can swell and stress-crack the solidified network. Handling of the liquid resin requires nitrile gloves, local exhaust ventilation, and UV-protective enclosures as specified in the supplier’s Safety Data Sheet.

Within the DSM Somos portfolio, GP Plus 14122 differs from transparent WaterShed XC 11122 in opacity and in target inspection workflow; white opaque surfaces permit white-light scanning without talc coating or spray developer. It differs from ProtoTherm 12120 and PerFORM in heat deflection temperature and filler content, which places it in the general-purpose, unfilled category. Published comparative data under identical post-cure protocols is limited; users preparing a resin substitution should qualify the replacement on the specific production SLA platform using a build that includes both XY and Z-oriented ASTM D638-14 and ASTM D790-17 specimens, rather than relying only on datasheet comparisons.