Expanded microspheres (also known as foamed microspheres) are high molecular polymers. Its outer shell is made of a high molecular polymer (acrylic eye copolymer) which is a hydrocarbon inside. In the case of heat (100-150 ° C), the outer shell softens and the hydrocarbons are vaporized by the liquid, thereby expanding the outer casing and changing the outer casing.
When the microspheres are heated to the glass transition temperature of the thermoplastic polymer material constituting the casing, the casing is softened and has plasticity. Since the low-boiling core material in the microsphere is heated to generate pressure, the expansion of the microsphere shell is caused. At the time of expansion, the pressure generated by the core material is balanced with the tension of the resin wall material due to stretching. In a certain temperature range, the higher the temperature, the greater the pressure generated by the core material, and the resin wall material will continue to stretch in order to balance the pressure, so that the microspheres continue to expand and maintain the balloon shape (stabilized foam) at a certain temperature. Even when the temperature is lowered, the microspheres can maintain their original state due to the hardening of the outer casing.
If heating continues, the casing continues to expand causing the shell wall to continue to thin. When the shell wall tension is insufficient to counteract the gas pressure, the gas diffuses through the shell wall to the outside of the casing, causing the internal pressure to rapidly decrease, thereby causing the microcapsules to retract.
Expandable microspheres are used as lightweight fillers and blowing agents to make the final product lighter, achieve different surface finishes, and reduce costs by reducing the need for raw materials. It is a very versatile product that offers advantages such as low density or better insulation, including in architectural and automotive applications.