Method for controlling surface concentration of a polymer additive
AssigneeCobe Cardiovascular Operating Co., Inc.
InventorsLloyd Forrestal, Marc Voorhees
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Abstract
The surface free energy of a polymer blend where a base polymer contains an additive having a different surface free energy than that of the base polymer can be controlled over a wide range of additive surface concentrations by appropriate choice of the mold surface free energy during fabrication. A high surface concentration of additive relative to a low bulk concentration can be achieved, leading to improved biocompatibility without loss of optical clarity.
Claims8
Method of controlling surface concentration of an LSL copolymer additive in a base polymer article comprising molding the article in a mold composed of a material having a given surface free energy whereby the lower the surface free energy of the mold material, the greater the surface concentration of polylactone-polydimethylsiloxane-polylactone in the resulting molded article.
Method of making a polymeric article, said article being composed of a polymer mix including a polycarbonate base polymer containing a polylacton-polydimethylsiloxane polylactone copolymer additive in an amount sufficient to retain normal transparency of polycarbonate, said amount being a maximum of 0.2% by weight bulk concentration of a polylactone-polydimethylsiloxane-polylactone copolymer additive, said bulk concentration corresponding to 0.08% to 0.1% by weight of polydimethylsiloxane in the polylactone-polydimethylsiloxane-polylactone copolymer, and having at least 20% by weight surface concentration of the polydimethylsiloxane component of said additive, comprising the steps of
- providing a mold having a low surface free energy mold surface;
- melt-molding said polymer mix in said mold having said low surface free energy mold surface and
- selecting said low surface free energy mold surface to provide at least 20% by weight surface concentration of the polydimethylsiloxane component of said additive.
A method for controlling surface concentration of a copolymer additive in a base polymer, comprising:
- predetermining a surface concentration range of the copolymer additive;
- preselecting a mold composed of a material having a predetermined surface free energy such that the lower the material's free energy, the higher the surface concentration of a low surface free energy copolymer and vice-versa;
- and
- molding the article in the preselected mold whereby the surface concentration of the copolymer additive is within a predetermined range.
Dependencies are inferred from the claim text.