Thermally expandable microcapsules

Thermally expandable microcapsules (TEMs) are micro spheres of 10 0 pm in diameter, having thermoplastic shells filled with liquid hydrocarbon of low boiling points. As their temperature rise, the inner pressure increases and the shell is softened. That leads to huge expansion of the sphere up to 20M 0 times in volume, as shown in Fig. 40.6. The TEMs can be applied to dismantlable adhesives, thermally expandable adhesives, or sealants. 

Deformation mechanism of thermally expandable microcapsules fTEMs)... 

Dismantlable adhesive including thermally expandable microcapsules (TEMs)... 

Application of a dismantlable adhesive with thermally expandable microcapsules and blowing agents in the car industry, the ECODISM project (Papon et al. 2008)... 

Fig. 34.13 shows the thermal volume expansion of the microcapsules with the hydrostatic pressure as the parameter, obtained by using the bellows vessel and a heating rate of 3 K min . For confirmation of the heating rate, the same results were obtained when the PVT test was carried out using 2 K min as the heating rate. The microcapsules start to expand dramatically around 60 °C both... 

Fig. 34.15 shows the thermal expansion of the RT-cured adhesives under several pressures measured using the bellows vessel. The adhesives expanded greatly, even though they had been cured. The maximum volume expansion under atmospheric pressure was about four-fold at 90 °C. Above 100 °C, it seems that volume increased again. However, the volume expansion was caused by leaked gas it was confirmed that the gas leaked from the specimen by thermodilatometry with the glass syringe (Fig. 34.4). Since the microcapsules in the adhesive were expanded about eight-fold, only 1-2 MPa of hydrostatic pressure was apphed from the microcapsules to the matrix resin, as shown by the intersection in Fig. 34.14.

---