Light-reflecting molded articles and methods of making the same

A light-reflecting enclosure for a light source, said enclosure having at least one aperture formed therein and being dimensioned and configured to receive a light source within the enclosure to transmit light through the aperture, said enclosure comprising:

• a matrix comprising a thermoplastic or thermosetting polymer and an organic flame retardant together having an effective refractive index of n1,
• the polymer matrix having dispersed therein particles of a reflective filler having a refractive index of n2, the particles of filler having a size range wherein at least about 60% by weight of the particles have a diameter of from about D to 4D, wherein D=λo/πn1δ in which λo is the mean free-space wavelength of the light range being reflected and δ=|n2−n1;
• the filler being present in enclosure;
• wherein the enclosure the has a reflectivity of at least about 93 percent for light in a wavelength range of from about 400 to 700 nanometers, measured as total reflectivity from a flat sample;
• and
• the flame retardant, comprising one or more compounds selected from the group consisting of decabromodiphenyloxide, octabromodiphenyloxide, tetrabromobisphenol A, brominated epoxy tetrabromobisphenol A-tetrabromobisphenol A diglycidylether, ethylenebistetrabromophthalamide, septabromotrimethylphenyl indane and octabromotrimethylphenol indane.

A light-reflecting article which comprises a composite of a thermoplastic or thermoset polymer matrix having dispersed therein a flame-retardant material, and dispersed particles of a reflective filler,

• the reflective filler comprising a dielectric material having a particle size and reflective properties which enhance total reflectivity of the composite, the filler further having an index of refraction which differs from the effective index of refraction of the other components of the composite;
• the flame-retardant material comprising one or more compounds selected from the group consisting of decabromodiphenyloxide, octabromodiphenyloxide, tetrabromobisphenol A, brominated epoxy tetrabromobisphenol A-tetrabromobisphenol A diglycidylether, ethylenebistetrabromophthalamide, septabromotrimethylphenol indane and octabromotrimethylphenol indane;
• and
• the filler and flame-retardant material being sufficiently dispersed and present in the article has an average total reflectivity as measured from a flat sample of at least about 93 percent over the range of visible light;
• wherein the filler is selected from the group consisting of titania, zinc sulfide and strontium titanate, and wherein when the filler comprises titania, at least about 60 percent by weight of the titania particles have a diameter of from about 0.12 to 0.44 microns;
• when the filler comprises zinc sulfide, at least about 60 percent by weight of the zinc sulfide particles have a diameter of from about 0.17 to 0.65 microns;
• and when the filler comprises strontium titanate, at least about 60 percent by weight of the strontium titanate particles have a diameter of from about 0.16 to 0.62 microns.

A light-reflecting enclosure for a light source, said enclosure having at least one aperture formed therein and being dimensioned and configured to receive a light source within the enclosure and to transmit light through the aperture, said enclosure comprising a composite of a thermoplastic or thermoset polymer matrix having dispersed therein a flame-retardant material, and dispersed particles of a reflective filler;

• wherein the flame-retardant material comprises (i) particles of a metal oxide synergist comprising antimony trioxide having a size range such that at least about 60 percent of the synergist particles have a diameter of from about 0.18 to about 0.72 microns, and (ii) a halogenated organic compound quenches and wherein the flame-retardant material reduces flammability of the enclosure relative to an otherwise identical enclosure lacking the flame-retardant material;
• the reflective filler comprising a dielectric material having a particle size and reflective properties which enhance total reflectivity of the composite, the filler further having an index of refraction which differs from the effective index of refraction of the other components of the composite;
• the filler and flame-retardant material being dispersed and present in the enclosure;
• wherein the enclosure has an average total reflectivity as measured from a flat sample of at least about 93 percent over the range of visible light;
• wherein the filler is selected from the group consisting of titania, zinc sulfide and strontium titanate, and wherein when the filler comprises titania, at least about 60 percent by weight of the titania particles have a diameter of from about 0.12 to 0.44 microns;
• when the filler comprises zinc sulfide, at least about 60 percent by weight of the zinc sulfide particles have a diameter of from about 0.17 to 0.65 microns;
• and when the filler comprises strontium titanate, at least about 60 percent by weight of the strontium titanate particles have a diameter of from about 0.16 to 0.62 microns.