Three-dimensional printing with binder agent

A three-dimensional printing kit, comprising:

• a polymer build material including from about 80 wt % to 100 wt % polymer build particles;
• and
• a binder agent including an aqueous liquid vehicle and polymer binder particles having an average particle size from about 5 nm to about 500 nm and a melting temperature that is lower than a melting temperature of the polymer build particles of the build material or a melting temperature reducible by a coalescing solvent to a melting temperature that is lower than a melting temperature of the polymer build particles of the build material;
• and
• wherein the three-dimensional printing kit does not require a fusing agent with a radiation absorber.

A system for three-dimensional printing, comprising;

• a polymer build material including from about 80 wt % to 100 wt % polymer build particles;
• a binder agent including an aqueous liquid vehicle and polymer binder particles having an average particle size from about 5 nm to about 500 nm and a melting temperature that is lower than a melting temperature of the polymer build particles of the build material or a melting temperature reducible by a coalescing solvent to a melting temperature that is lower than a melting temperature of the polymer build particles of the build material;
• and
• a radiant heat source positioned or positionable to expose a powder bed of the polymer build material to heat at a temperature less than a melting point of the polymer build particles but greater than a melting temperature of the polymer binder particles, wherein the heat causes the polymer binder particles to melt and adhere the polymer build particles together to form a three-dimensional object.