High reflectance polycarbonate
View Patent ↗In an embodiment, a reflector comprises a polycarbonate composition, the polycarbonate composition comprises: polycarbonate; 10 wt % to 20 wt % titanium dioxide, based upon a total weight of the polycarbonate composition; an optional flame retardant; and an optional UV stabilizer. A plaque formed from the polycarbonate composition has a reflectance of greater than or equal to 95%, as determined by reflectance measurements using a Gretag Macbeth Coloreye spectrophotometer (D65 light source, 10 degree observer, UV included) made at a wavelength of 680 nm. A molded article of the polycarbonate has transmission level greater than or equal to 90.0% at 2.5 mm thickness as measured by ASTM D1003-00 and a yellow index (YI) less than or equal to 1.5 as measured by ASTM D1925.
1. A reflector comprising a polycarbonate composition, wherein the polycarbonate composition comprises:
a polycarbonate, wherein the polycarbonate is interfacially polymerized from a bisphenol A having an organic purity of greater than 99.65 wt % and a sulfur level of less than 2 ppm; and wherein the polycarbonate has a free hydroxy level of less than 150 ppm;
10 wt % to 20 wt % titanium dioxide, based upon a total weight of the polycarbonate composition;
an optional flame retardant; and
an optional UV stabilizer;
wherein a plaque formed from the polycarbonate composition has a reflectance of greater than or equal to 95%, as determined by reflectance measurements using a Gretag Macbeth Coloreye spectrophotometer (D65 light source, 10 degree observer, UV included) made at a wavelength of 680 nm;
wherein a molded article of the polycarbonate has transmission level greater than or equal to 90.0% at 2.5 mm thickness as measured by ASTM D1003-00 and a yellow index (YI) less than or equal to 1.5 as measured by ASTM D1925.
2. The reflector of claim 1 , wherein the composition consisting essentially of the polycarbonate, the titanium dioxide, the optional flame retardant; and the optional UV stabilizer the reflectance is greater than or equal to 96%.
3. The reflector of claim 1 , wherein the composition has a melt volume rate as determined at 300° C. using a 1.2-kilogram weight, in accordance with ASTM D1238-04 of 5 to 50 grams per 10 minutes.
4. The reflector of claim 1 , wherein the titanium dioxide is present in an amount of 10 wt % to 15 wt %.
5. The reflector of claim 1 , wherein the titanium dioxide is present in an amount of 12.5 wt % to 15 wt %.
6. The reflector of claim 1 , wherein the titanium dioxide has an average particle size of 30 nm to 500 nm.
7. The reflector of claim 1 , wherein the titanium dioxide comprises coated titanium dioxide, where the titanium dioxide is coated with alumina and/or polysiloxane.
8. The reflector of claim 1 , wherein the titanium dioxide comprises rutile titanium dioxide.
9. The reflector of claim 1 , wherein when exposed to an LED light in a light box with 6 LED lights (GE-Tetra LED System 5 Amp max output 20 watts) for 2,000 hours, a 3.2 mm plaque formed from the composition has a color change of less than or equal to 0.5 DE.
10. The reflector of claim 1 , wherein the composition is able to achieve a UL94 V0 rating at 1.5 mm.
11. The reflector of claim 1 , wherein the composition further comprises potassium diphenylsulfone sulfonate and/or polytetrafluoroethylene encapsulated by the rigid copolymer of styrene-acrylonitrile copolymer.
12. The reflector of claim 1 , wherein the reflector is free of a metal coating.
13. The reflector of claim 1 , comprising a reflective surface having a reflectivity of greater than or equal to 95%, and wherein the reflective surface is free of metallization.
14. An illumination device, comprising:
a reflector of claim 1 ;
an LED; and
means for providing power to the LED.
15. A method of reflecting light comprising:
illuminating a reflective surface of a reflector of claim 1 with light from an LED.
16. A reflector comprising a polycarbonate composition, wherein the polycarbonate composition comprises:
a polycarbonate, wherein the polycarbonate is interfacially polymerized from a bisphenol A having an organic purity of greater than 99.65 wt % and a sulfur level of less than 2 ppm; wherein the polycarbonate has a free hydroxy level of less than 150 ppm;
10 to 20 wt % titanium dioxide;
a flame retardant; and
an optional UV stabilizer;
wherein the polycarbonate composition has a maximum reflectance of greater than or equal to 95% as determined by reflectance measurements using a Gretag Macbeth Coloreye spectrophotometer (D65 light source, 10 degree observer, UV included) made at a wavelength of 680 nm; and
wherein the melt volume rate of the composition as determined at 300° C. using a 1.2 kilogram weight, in accordance with ASTM D1238-04 is from 5 to 30 grams per 10 minutes, and
wherein, when in the form of a 1.5 mm plaque, the composition achieves a probability of first time pass of greater than or equal to 85%; and
wherein a molded article of the polycarbonate has transmission level greater than or equal to 90.0% at 2.5 mm thickness as measured by ASTM D1003-00 and a yellow index (YI) less than or equal to 1.5 as measured by ASTM D1925.
17. The reflector of claim 16 , wherein the polycarbonate composition consisting essentially of the polycarbonate, the titanium dioxide, the optional flame retardant; and the optional UV stabilizer has a reflectance of greater than or equal to 96%, as determined by reflectance measurements using a Gretag Macbeth Coloreye spectrophotometer (D65 light source, 10 degree observer, UV included) made at a wavelength of 680 nm.
18. The reflector of claim 1 , wherein the composition relies only on the reflective agent to provide the high reflectivity.
19. The reflector of claim 18 , wherein the reflectivity is greater than or equal to 96%.