Photo-DSC method for liquid samples used in vat photopolymerization

Area of Science:

• Materials Science
• Polymer Chemistry
• Analytical Chemistry

Background:

• Photo differential scanning calorimetry (photo-DSC) is crucial for characterizing photopolymers in additive manufacturing (AM).
• Accurate photo-DSC analysis depends heavily on meticulous sample preparation, including sample shape, mass, and crucible selection.
• Surface effects like oxygen diffusion and evaporation can impact measurement reliability.

Purpose of the Study:

• To investigate optimal sample preparation techniques for photo-DSC analysis of photopolymers used in AM.
• To evaluate the influence of sample shape, mass, and preparation-to-measurement time on results.
• To develop a robust and time-efficient protocol for automated sample analysis.

Main Methods:

• Investigated two sample shapes (drop and spread) with different masses (1.0 mg and 2.8 mg).
• Tested varying preparation-to-measurement intervals (0, 4, and 7 hours) to assess surface effects.
• Evaluated different crucible covers and a shortened test protocol (24 min vs. 42 min) for automated sample changers (ASC).

Main Results:

• The 2.8 mg drop shape minimizes surface effects, while the 1.0 mg spread shape offers better comparability to high-resolution prints.
• A shortened 24-minute protocol maintained measurement accuracy.
• A combination of an 85 μL crucible covered by a 300 μL Al2O3 crucible (removed before measurement) minimized mass loss (<1% for 10 hours) for ASC compatibility.
• Photo-DSC successfully differentiated resin components, identified photoinitiators, and distinguished between methacrylate and acrylate systems.

Conclusions:

• Optimized sample preparation, including crucible selection and reduced measurement times, is essential for reliable photo-DSC characterization of photopolymers in AM.
• The developed protocol enhances the efficiency and accuracy of photo-DSC analysis, particularly for automated systems.
• Photo-DSC is a powerful tool for analyzing complex two-part resin systems used in Digital Light Synthesis (DLS).