Physical and Mechanical Properties Basics

Main property values are typically reported using the following format:

• Hardness, Shore D: ± 3 (ISO 868, 15 s)
• Hardness, Shore A: ± 3 (ISO 868, 15 s)
• Hardness, Shore OO: ± 3 (ASTM D2240, 15 s)
• Tensile strength: < MPa (ISO 527-1 / ISO 527-2)
• Young´s modulus E: < MPa (ISO 527-1 / ISO 527-2)
• Tensile elongation at break: < % (ISO 527-1 / ISO 527-2)
• Flexural strength: < MPa (ISO 178)
• Flexural modulus: < MPa (ISO 178)
• Flexural elongation at break: < % (ISO 178)
• Izod impact strength, unnotched: < kJ/m² (ISO 180)
• Heat deflection temperature (HDT): < °C @ 1.8 MPa (ISO 75)
• Glass transition temperature (Tg): °C (estimated from the contribution of the individual ingredients; internal calculation)
• Viscosity: < mPa·s at 23°C ± 2°C (ISO 3219)
• Density: ± 0.05 g/cm³ (ISO 2811-1)
• Surface tension: ± 1 mN/m 
• Refractive index nD20: ± 0.05 
• Water absorption: < % (24 h water immersion at 23°C) (ISO 62)
• Volumetric shrinkage:  < %
• Bio-based carbon content:  % (ISO 16620-2)

What the reported format means

• Threshold values with < indicate an upper reported benchmark value under defined internal reference conditions. The actual measured value for a given version, printer, color, viscosity grade or workflow is expected to remain below that reported threshold.
• Shore hardness is reported as a nominal Shore value with tolerance, for example Shore D80 ± 3, because hardness can vary slightly depending on formulation version, curing state, specimen preparation and processing conditions.
• LV and HV viscosity versions are reported separately where relevant because low-viscosity and high-viscosity variants may behave differently in process-specific workflows. HV viscosity versions have higher performance properties.

Why properties are reported this way

3Dresyns® materials are often supplied in multiple functional versions adapted to printer type, optical power, speed, viscosity target, color, functional additives and final application. Because of this, properties are not fixed as a single universal number for all configurations.

The reported format is intended to provide realistic and conservative technical guidance across different validated versions while avoiding misleading precision for properties that depend on the selected workflow.

Why properties vary

Physical and mechanical performance depends on multiple variables including formulation tuning, viscosity version, color, fine tuners, printer technology, optical intensity, exposure strategy, part geometry, cleaning conditions and post-curing conditions.

For this reason, two parts made from the same material family may show different final values if they are printed with different machine settings, resin versions or post-processing workflows.

Main mechanical and physical properties

The following properties are among the most relevant for interpreting the performance of photopolymer materials in additive manufacturing workflows.

Tensile strength

Tensile strength is the capacity of a material to resist tension.

Flexural strength

Flexural strength is the capacity of a material to resist deformation under a bending moment. It is sometimes called bending strength.

Tensile vs. flexural performance

Tensile and flexural strength both describe resistance to deformation under load, but the loading modes are different. Flexural strength is the maximum bending stress that can be applied before a material yields or deforms under a given load. It is also referred to as bending strength or modulus of rupture.

For materials that deform significantly without breaking, the flexural value is typically taken at the yield load and is often reported at 5% deformation of the outer surface, as flexural strength or flexural yield strength.

Flexural testing, also called a transverse beam test, evaluates bending behavior by placing a specimen on two supports and applying load using either one central loading point for 3-point bending or two loading points for 4-point bending. Maximum stress and strain are calculated as the applied load increases.

Young’s modulus

Young’s modulus describes the stiffness of a material in the elastic region. Higher values indicate a stiffer material that resists elastic deformation more strongly under load. In photopolymer systems, stiffness is highly informative, but it should always be interpreted together with impact resistance, elongation at break and real part geometry.

Elongation at break

Elongation at break describes how much a material can stretch before fracture. Low values often indicate rigid, low-deformation systems, while higher values are generally associated with more ductile, flexible or resilient behaviour.

Impact resistance

Impact resistance, Notched Izod describes the ability of a material to absorb energy under sudden impact, especially in the presence of a notch or stress concentrator. This property is highly relevant for real printed parts because many failures occur under local defects, sharp transitions or accidental overload rather than under ideal static loading.

Heat deflection temperature

Heat deflection temperature (HDT) indicates the temperature at which a standardized specimen deforms under a defined load. It is a useful comparative thermal property, but it should not be interpreted as an absolute service temperature because real part thickness, geometry and loading conditions may differ from the standardized test.

Viscosity

Viscosity indicates the resistance of the liquid material to flow and is highly relevant for recoating, vat renewal, jetting behaviour and process stability. In some product families, separate LV and HV versions are reported to reflect materials optimized for different processing conditions or printer architectures.

Water absorption

Water absorption describes the amount of water taken up by the material under defined immersion conditions. It is relevant for dimensional stability, long-term behaviour and application suitability in humid or aqueous environments.

Property reporting templates

The property-reporting framework can be understood as a common core template used across 3Dresyns® materials, with additional application-specific properties added for dental and medical families where relevant.

Common core template

The following property structure forms the transversal base used across many material families:

• Tensile strength: < MPa (ISO 527-1 / ISO 527-2)
• Flexural strength: < MPa (ISO 178)
• Young’s modulus: < MPa (ISO 527-1 / ISO 527-2)
• Elongation at break: < % (ISO 527-1 / ISO 527-2)
• Shore hardness: Shore [A / D / O] xx ± 3 (ISO 868)
• Impact resistance, Notched Izod: < J/m (ISO 180)
• Heat deflection temperature (HDT): < °C @ 0.45 MPa (ISO 75)
• Viscosity: < mPas at 23°C ± 2°C (ISO 3219)
• Viscosity of LV version: < mPas at 23°C ± 2°C (ISO 3219)
• Viscosity of HV version: < mPas at 23°C ± 2°C (ISO 3219)
• Water absorption: < % (24 h water immersion at 23°C) (ISO 62)

Dental-specific additions

Dental materials generally build on the common core template and may include additional application-specific properties relevant to oral and dental workflows:

• Water absorption: < µg/mm³ (relevant ISO 20795 reference framework, where applicable to the intended dental application)
• Water solubility: < µg/mm³ (relevant ISO 20795 reference framework, where applicable to the intended dental application)
• Biocompatibility assessment: to be evaluated according to the ISO 10993 risk-based framework, where applicable for the intended medical or dental use
• Residual reactive species / extractables: < % after validated curing and post-processing (internal validated chromatographic method; chemical characterization framework aligned with ISO 10993-18, and ISO 7405 where applicable for dental use)

Medical-specific additions

Medical materials also build on the common core template and may include additional application-specific properties relevant to regulated medical workflows:

• Biocompatibility assessment: to be evaluated according to the ISO 10993 risk-based framework, where applicable for the intended medical use
• Residual reactive species / extractables: < % after validated curing and post-processing (internal validated chromatographic method; chemical characterization framework aligned with ISO 10993-18)

Interpretation principle

The reported values should be read as practical technical guidance for material families and validated versions, not as absolute constants for every possible print condition. Final part performance depends on the complete manufacturing system: material version, printer, exposure conditions, geometry, cleaning and post-curing.

For this reason, the most robust reporting strategy is a shared core property template combined with additional application-specific layers for dental and medical families where required.