A down-to-earth solution: combined use of differnt halogen-free flame retardants to achieve UL94 V0 at 1.6mm and below for halogen-free polycarbonate.
Normally, a single halogenated flame retardant is enough to achieve UL94 V0 thanks to its superior FR efficiency. By contrast, in formulation of a halogen-free flame retardant polycarbonate, achieving UL94 V0 for a thickness of 1.6 mm or below entails a combination of different commercial-grade halogen-free flame retardants, which include siloxanes, PTFE, phosphate esters, KSS and so on. This is because so far a single halogen-free flame retardant might not be so FR efficient. Hence a good synergy between different halogen-free flame retardants proves to work well, in many cases becoming a must for a halogen-free UL94 V0 grade PC.
How to create a halogen-free flame retardants combination?
In order to work out a proper combination of different halogen-free flame retardants, a formulator has to take into account several factors such as targeted flame-retarding efficiency, cost, mechanical strength, film thickness, HDT and color & appearance as well as quality & MI of PC resins, processing conditions and so on. For these considerations, lab work is often needed to evaluate and determine a FR combination so as to meet the requirements of customers.
A combination of some conventional halogen-free PC flame retardants among PTFE, phosphate ester, siloxanes and KSS is used to achieve UL94 V0 for a thickness of 1.6 mm or below. However, in certain situations, even such a combined use still could not meet the specific target for flame retarding in terms of efficiency, cost and consistency. Therefore other new types of halogen free flame retardants like LC-160 can help.
LC-160, which is based on organometallic coordination compounds, is a highly cost-efficient halogen-free PC flame retardant per se. In practical applications, LC-160 can be regarded as a much cheaper direct substitute for KSS. Most importantly, it exhibits strong synergy with conventional halogen-free PC flame retardants such as phosphate ester, siloxane, PTFE and KSS. Thanks to its relatively low price, a halogen-free FR combination containing LC-160 as a component can be a very cost-competitive solution to achieve UL94-V0 grade PC. Some examples for such a FR combination are given as follows.
- Black Pure PC (UL94 V0 1.6mm 10MFI): PC resin (10MFI) — 99.40%; LC-160 — 0.10~0.20%; PTFE — 0.40%; carbon black dispersion — 0.10%
- Transparent Pure PC (UL94 V0 1.6mm 10MFI): PC resin (10MFI) — 98.80%; LC-160 — 0.10~0.20%; Siloxane — 1.00%
- Modified PC (UL94 V0 1.6mm 20MFI): PC resin (20MFI) — 91.50%; ABS — 5.00%; BDP — 3.00%; LC-160 — 0.10~0.20%; PTFE — 0.30%
If interested, you can read about more examples and details here.