Methods for measuring properties in crosslinked polycarbonate

1. A method for determining the flame performance of a composition comprising a crosslinked polycarbonate and a fixed amount of a flame retardant and a fixed amount of a cyclic siloxane, comprising:

measuring the storage modulus (G′) versus temperature of the composition using dynamic mechanical analysis, the measurement including a rubber plateau of the composition;

extrapolating an average magnitude of the storage modulus over a temperature range within the rubber plateau; and

determining the flame performance of the composition based on the average magnitude of the storage modulus;

wherein the crosslinked polycarbonate is a bisphenol-A homopolymer having endcaps derived from 4-hydroxybenzophenone, a bisphenol-A copolymer having co-monomers derived from 4,4′-dihydroxybenzophenone, or a combination thereof.

2. The method of claim 1 , wherein the flame performance is determined by comparing the average magnitude of the storage modulus to a reference table.

3. The method of claim 1 , wherein the flame performance is determined by comparing the average magnitude of the storage modulus to a threshold value.

4. The method of claim 1 , wherein the temperature range over which the average magnitude is determined is at least 10° C.

5. The method of claim 1 , wherein the temperature range over which the average magnitude is determined is at least 30° C.

6. A method for selecting a crosslinkable polycarbonate that will achieve UL94 5VA performance at a thickness of 1.5 mm, comprising:

molding a part from a composition comprising a crosslinkable polycarbonate resin that contains an aromatic ketone-containing moiety derived from a dihydroxy compound or a monohydroxy compound, and a fixed amount of a flame retardant, and a fixed amount of a cyclic siloxane;

exposing the molded part to ultraviolet light to induce crosslinking; measuring the storage modulus (G′) versus temperature of the molded part using dynamic mechanical analysis, the measurement including a rubber plateau of the polycarbonate;

extrapolating an average magnitude of the storage modulus over a temperature range within the rubber plateau; and

selecting the polycarbonate resin if the G′ is 5 or greater;

wherein the crosslinked polycarbonate is a bisphenol-A homopolymer having endcaps derived from 4-hydroxybenzophenone, a bisphenol-A copolymer having co-monomers derived from 4,4′-dihydroxybenzophenone, or a combination thereof.

7. The method of claim 6 , wherein the temperature range over which the average magnitude is determined is at least 10° C.

8. The method of claim 7 , wherein the temperature range over which the average magnitude is determined is at least 30° C.

9. The method of claim 6 , wherein the temperature range over which the average magnitude is determined is at least 30° C.

10. A method for selecting a crosslinkable polycarbonate that will achieve UL94 V0 performance at a thickness of 1.2 mm, comprising:

molding a part from a composition comprising a crosslinkable polycarbonate resin that contains an aromatic ketone-containing moiety derived from a dihydroxy compound or a monohydroxy compound, and a fixed amount of a flame retardant additive, and a fixed amount of a cyclic siloxane;

exposing the molded part to ultraviolet light to induce crosslinking;

measuring the storage modulus (G′) versus temperature of the molded part using dynamic mechanical analysis, the measurement including a rubber plateau of the polycarbonate;

extrapolating an average magnitude of the storage modulus over a temperature range within the rubber plateau; and

selecting the polycarbonate resin if the G′ is 9 or greater;

wherein the crosslinked polycarbonate is a bisphenol-A homopolymer having endcaps derived from 4-hydroxybenzophenone, a bisphenol-A copolymer having co-monomers derived from 4,4′-dihydroxybenzophenone, or a combination thereof.

11. The method of claim 10 , wherein the temperature range over which the average magnitude is determined is at least 10° C.