When sourcing PMI foam, the most critical factor is density, typically ranging from 30 to 200 kg/m³. You must ensure the compressive strength and shear modulus align with your structural requirements. For aerospace or automotive use, verify the heat distortion temperature (HDT), which should ideally exceed 180°C to 240°C to withstand autoclave processing. Additionally, check for cell size uniformity, as smaller, closed-cell structures provide better resin absorption resistance during sandwich panel infusion.