The phenomenon of “blooming” is a common problem for polymeric materials. Incompatible materials added to polymers can migrate to the surface of the part, causing a “bloom” or “haze.” These defects have a negative effect on the cosmetic appearance of the material and sometimes can impact performance of the material. In polyester technology, blooming is a well researched phenomenon in poly(ethylene terephthalate) (PET) films and fibers. In the case of PET, the bloom is not an additive, but a thermodynamic by-product of step polymerizations, generally cyclic oligomers, which exist at equilibrium during the melt polymerization process. A similar phenomenon is known to exist in melt processed poly(trimethylene terephthalate) (PTT). Molded articles of PTT exhibit an oligomer bloom during elevated temperature aging tests. There is a need for a process to reduce the blooming effect on the surface of polymeric articles.
USPTO Backgrounds
USPTO Backgrounds