Challenges arising in formulation of UL94-V0 grade transparent PC
Potassium perfluorobutane sulfonate (KPFBS), such as FR-2025 from 3M or RM65 from Miteni, has long been regarded as a standard choice for a non-brominated & non-chlorinated flame retardant in transparent polycarbonate. But this is really a highly expensive flame retardant. Besides, for a thickness of 1.6 mm or below, KPFBS alone is still not sufficient in FR efficiency to achieve UL94 V0, and has to be combined with a siloxane, which is also a costly halogen free flame retardant. Because it is a highly hygroscopic substance, KPFBS is somewhat difficult to store and handle, especially when its original package has already been opened. Moreover, KPFBS has been included in the REACH-SVHC list.
A high-performance siloxane alone can also be used in formulating a transparent PC to meet UL94 V0 at 1.6 mm or below, but needs to be added at a relatively large amount, and this means relatively high raw material cost.
By contrast, the price of LC-160, a halogen-free flame retardant produced by Limax Chemical, is only a fraction of that of KPFBS and it can be used at a dosage similar to that of KPFBS. In transparent PC, LC-160 shows excellent synergy with either a siloxane, or a phosphate ester flame retardant, which is much cheaper than a siloxane. LC-160 is not a sulfonate type FR, it is strictly halogen-free and not in the REACH-SVHC list. Moreover, it is not hygroscopic at all, and thus it is easy to store and handle. Use of LC-160 in transparent PC is illustrated as follows.
- Transparent Pure PC (UL94 V0 3.2mm 10MFI): PC resin (10MFI) — 99.90%; LC-160 — 0.10%
- Transparent Pure PC (UL94 V0 1.6mm 10MFI) Example One: PC resin (10MFI) — 97.90%; LC-160 — 0.10%; Siloxane — 2.00%
- Transparent Pure PC (UL94 V0 1.6mm 10MFI) Example Two: PC resin (10MFI) — 96.90%; LC-160 — 0.10%; BDP (a phosphate ester FR) — 3.00%
- PC/ABS (75/25 UL94 V0 1.6mm): PC/ABS(75/25) — 93.80%; **RDP (a phosphate ester FR) — 6.00%; LC-160 — 0.20%
- PC/ABS (60/40 UL94 V0 1.6mm): PC/ABS(60/40) — 89.80%; **RDP (a phosphate ester FR) — 10.00%; LC-160 — 0.20%