Low temperature foamable polycarbonate composition and articles thereof

1. A foamed polycarbonate composition comprising

5 to 95 wt % of a poly(siloxane) block copolymer comprising

a poly(carbonate-siloxane) comprising 90 to 99 wt % of bisphenol A carbonate units and 1 to 10 wt % of dimethylsiloxane units, each based on the weight of the poly(carbonate-siloxane),

a poly(ester-carbonate-siloxane) comprising bisphenol A carbonate units, isophthalate-terephthalate-bisphenol A ester units, and 5 to 200 dimethyl siloxane units,

or a combination thereof;

5 to 95 wt % of an auxiliary component comprising

a poly(alkylene ester),

a poly(aliphatic ester-carbonate) comprising bisphenol A carbonate units and aliphatic ester units derived from a C 8-12 aliphatic dicarboxylic acid and bisphenol A, wherein the poly(aliphatic ester-carbonate) has a weight average molecular weight from 15,000 to 45,000 grams/mole as measured via gel permeation chromatography using bisphenol A homopolycarbonate standards,

or a combination thereof, and

optionally, a homopolycarbonate;

optionally, up to 10 wt % of an additive composition comprising a flow modifier, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet light stabilizer, an ultraviolet absorbing additive, a lubricant, a mold release agent, an antistatic agent, an anti-fog agent, an antimicrobial agent, a colorant, a surface effect additive, a radiation stabilizer, a flame retardant, an anti-drip agent, or a combination thereof,

wherein the siloxane content of the foamed composition is 0.001 to 3 wt %,

wherein the composition has a glass transition temperature of 140° C. and below measured using differential scanning calorimetry, and wherein the poly(siloxane) block copolymer, the auxiliary component, and the optional additive composition total 100 wt %, and wherein the polycarbonate composition does not comprise an impact modifier, a filler, or a reinforcing agent.

2. The foamed polycarbonate composition of claim 1 , wherein the poly(carbonate-siloxane) copolymer comprises siloxane units of the formula

or a combination thereof,

wherein:

E has an average value of 2-200, 5-100, 5-50, 20-80, or 5-20, R 6 is a divalent C1_8 aliphatic group,

each instance of M in formula is independently halogen, cyano, nitro, C 1-8 alkylthio, C 1-8 alkyl, C 1-8 alkoxy, C 2-8 alkenyl, C 2-8 alkenyloxy, C 3-8 cycloalkyl, C 3-8 cycloalkoxy, C 6-10 aryl, C 6-10 aryloxy, C 7-12 aralkyl, C 7-12 aralkoxy, C 7-12 alkylaryl, or C 7-12 alkylaryloxy, and

n is independently 0, 1, 2, 3, or 4.

3. The foamed polycarbonate composition of claim 1 , wherein the poly(carbonate-siloxane) has a formula

wherein

x is 1 to 200;

y is 1 to 500, or 10 to 200, and

z is 1 to 1000, or 10 to 800.

4. The foamed polycarbonate composition of claim 1 , wherein the homopolycarbonate is present and comprises

a bisphenol A homopolycarbonate having a weight average molecular weight from 18,000-35,000 grams/mole; or

a bisphenol A homopolycarbonate having a weight average molecular weight from 25,000-35,000 grams/mole;

or a combination thereof,

each as measured via gel permeation chromatography using bisphenol A homopolycarbonate standards.

5. The foamed polycarbonate composition of claim 1 , wherein the poly(ester-carbonate) is a poly(aliphatic ester-carbonate) having

a poly(aliphatic ester-carbonate) having a weight average molecular weight from 18,000-30,000 grams/mole; or

a poly(aliphatic ester-carbonate) having a weight average molecular weight from 30,000-45,000 grams/mole;

or a combination thereof,

each as measured via gel permeation chromatography using bisphenol A homopolycarbonate standards.

6. The foamed polycarbonate composition of claim 1 , wherein the poly(alkylene ester) comprises a poly(cycloalkylene diester).

7. The foamed polycarbonate composition of claim 1 , wherein the additive composition is present.

8. The foamed polycarbonate composition of Claiml comprising

10 to 30 wt % of the poly(carbonate-siloxane) as the poly(siloxane) block copolymer; and

70 to 90 wt % of poly(aliphatic ester-carbonate) as the auxiliary component.

9. The foamed polycarbonate composition of claim 1 comprising

10 to 30 wt % of the poly(carbonate-siloxane) as the poly(siloxane) block copolymer; and

70 to 90 wt % of bisphenol homopolycarbonate and poly(cycloalkylene diester) as the auxiliary component.

10. An article made from the foamed polycarbonate composition of claim 1 .

11. A method for forming the article of claim 10 , comprising

immersing a mixture of the poly(siloxane) block copolymer, the auxiliary component, and the optional additive composition in a blowing agent to form a saturated foamed composition;

increasing the temperature of the saturated foamed polycarbonate composition to no greater than 130° C.

12. The method for forming the article of claim 11 , wherein foaming comprises a solid state foaming process, an extrusion foaming process, a bead foaming process, or a foam injection molding process.

13. The foamed composition of claim 1 , wherein the foamed composition has an average cell size of 10 nanometers to 20 micrometers.

14. The foamed composition of claim 13 , wherein the foamed composition has an average cell size of 10 to 1000 nanometers.

15. The foamed composition of claim 13 , wherein the foamed composition has an average cell size of 10 to 200 nanometers.

16. The foamed composition of claim 13 , wherein the foamed composition has an average cell size of 10 to 100 nanometers.