If not placed in a completely sealed aluminum foil bag, PMI will absorb moisture in the air. After the foam absorbs moisture, it will reduce the compression creep performance, so that under certain temperatures and pressures, such as in autoclave, RTM or molded During the process, the dimensional stability of the material will be affected. Therefore, it must be dried before use to remove water vapor during processing and improve its resistance to compression creep.
Generally, if the humidity of the storage place or use site is below 70%, it should be used within 1 month; if the period is exceeded or the humidity of the use site is above 70% for more than 24 hours, it should be dried before use. Heating at a speed of no more than 2.5°C/min, drying in an air circulation oven at a temperature of 130°C for a minimum of 3 hours. During this process, the plates are spaced at least 35mm from each other, and the requirements for plate placement and temperature control must be strictly implemented. When the thickness of the board is greater than 25.4mm, the insulation section needs to be extended to more than 4 hours.
Because high-temperature heat treatment at 190°C will damage the material surface, and the material will undergo changes in dimensional accuracy during the drying process, machining of shaped core materials should be performed after high-temperature heat treatment.
