Polymeric mandrels: supersmooth finish by an infusion process

Extremely smooth surfaces (less than 1 mm maximum defect size) have been produced on acrylic polymer rods by an infusion process. The technique involves bathing the rod in a mixture of a solvent and a diluent, a nonsolvent for the polymer. This causes the rod to soften and permits limited flow and leveling of its surface. The solvent is then gradually displaced from the bath by additional diluent. As this occurs, the surface of the rod becomes rigid once more, but now with a defect-free finish. Acetone may be used as the solvent. The smoothest surfaces have been obtained using a mixture of 50% water and 50% polyethylene glycol with a molecular weight of about 4000 as the diluent