The minimum film-forming temperature refers to the minimum temperature at which polymers form a continuous film, expressed by MFT. If the cement hydration temperature is below this value, the energy supplied will not be enough to start film formation. At this time polymers will be present in the form of intermittent particles in the cement mortar. Only when the cement hydration temperature is higher than MFT of polymers can polymers form a uniform film structure and be distributed between cement hydration products, playing a bridging role when there is stress, effectively absorbing and transferring energy, thereby inhibiting the formation and development of cracks. Therefore, make sure that the MFT should be lower than the curing temperature of mortar in order to make redispersible polymer powders form a film in the hardened mortar.