Established halogenated FR systems still hold the dominant market share position, but Halogen-free Flame Retardants or HFFR systems are emerging rapidly and are making the most noise in the marketplace about their developments.
More stringent environmental and health regulation on the horizon is also driving FR development towards more sustainable alternatives. Let’s take a look at various traditional, circular, radical, synergistic, and recycling FR development routes.
Traditional FR Development Routes
Momentive’s Silicon-based FRs as Replacements for Halogenated-based FRs
Starting off, Momentive is promoting their low toxicity silicone-based additives as replacements for halogenated-based flame retardants (FR). The core silicone oxygen bond is very safe in use from environmental, health, and safety perspectives in light of expected regulation to phase out halogenated FRs. Silicone oxygen bonds also promote:
Very good mechanical property maintenance
UltraViolet (UV) stability
Flexibility range, and
Electrical insulation capability important in key low smoke, wire and cable applications.
Momentive’s specific silicone-based flame retarded grade is SFR320 that at low 1% by weight loading levels can deliver an Underwriters Lab UL94-V-0 highest flammability resistance rating, and is very compatible with many different plastics.
FR Testing (1.6mm)
Izod Impact Notched (-30°C)
Momentive’s SFR320 FR UL94 V-0 Grade (3rd Bottom Line) in Polycarbonate (PC) at 1% Loading
Huber’s FR Product Lines – Key Features and Applications
Next, Huber Engineered Materials is moving in multiple FR development directions with its Safire™ and Kemgard® product lines. Their new Safire™ 400 FR grade has:
Reduced flame spread
Low smoke suppression, and
High char formation
It is based on a zinc phosphate melamine formulation and is very effective in wire and cable sheathing applications. Safire™ 400 also blends well with aluminum hydroxide producing a halogen-free, low smoke additive system with a high char surface layer that prevents plastic cable resin dripping.
Huber’s molybdate-based Kemgard® FRs are more specifically targeted at crosslinked PolyVinyl Chloride (PVC) to deliver high surface char formation in cable applications without any sacrifice to extrusion processability.
Overall a 10% Safire™ 400 FR additive by weight loading, when added to a traditional Huber’s Hydral® 710 aluminum trihydrate clearly, demonstrates:
Improved char formation
Increased thermal insulation, and
Reduced thermal conductivity
It is ideal in low smoke, low dripping wire and cable applications.
Huber Heat Release (L) and Upper Surface/Under Surface Temperature Difference
Byk’s Silicate Clay-based FR Additives Targeted at Nylon and Related Thermoplastics
Continuing, Byk has commercialized BYK-MAX CT 4260 FR additive, specifically targeted at nylon and related thermoplastics. This silicate clay-based additive finds strong use in non-halogen compounds where it enhances not only FR properties but adds low material dripping under a flame and high surface char formation.
Also, BYK-MAX CT 4260 offers reduced filler content translating into lower finished part weight and ease of processability. Additionally, improved oxygen and water barriers in concert with increased melt viscosity yield excellent dimensional stability, for example, in profile extrusion. As a further rule, nylon compound mechanical and electrical properties remain unchanged.
Nylon Compound Flammability without Byk-Max CT 4260 (L) and with a 5% Addition (R)
Kraiburg’s Non-halogenated FR ThermoPlastic Elastomers for E&E Applications
Delving further, Kraiburg is marketing non-halogenated FR ThermoPlastic Elastomers (TPE) compounds based on a variety of commercially available FR additives that readily bond to nylon that allow for soft TPE, hard nylon combinations for demanding electrical and electronic applications such as connectors, and small housings/enclosures.
Kraiburg’s primary focus is on developing Underwriters Lab UL94 lower V-2 to highest V-0 TPE ratings with a unique attention to compound temperature sensitivity. Under existing normal processing conditions 240°C is required to obtain TPE/nylon adhesion, whereas with Kraiburg’s newly developed proprietary FR TPE compounds only 190°C is needed for adhesion, thereby adding a key benefit in more energy-efficient, lower cycle time processing.
Kraiburg FR TPE/Nylon Connector Bonding
Polymer Resources’ Creating FR Compound Developments with UL94 V0 Ratings
Finally, specialty compounder Polymer Resources has taken a very traditional FR compound development approach by creating a range of Underwriter Labs UL94 V-0 across high-end engineering plastic blends, such as:
Polycarbonate (PC)/PolyButylene Terephthalate (PBT) and
FR PC/PBT compounds are aimed at molded electrical and fiber optic sockets and plugs in medical electronic devices, and residential/outdoor uses. PC/ASA FR compounds are effective for medical/dental equipment molded electronic fixtures subjected to indoor UV light. Polymer Resources currently has seventy-five UL94 V-0 rated and approved compounds.
Polymer Resources Builds Out UL94 V-0 Connector Compound Choices
Circular FR Development Routes
Clariant’s Environmentally Friendly FR Versus Brominated FRs
First, let’s review Clariant’s environmentally friendly FR additive development approach. To this end, Clariant has internally developed a thirty-six standard Ecotain label keyed to emphasizing circular economy goals. For example, Clariant’s Exolit® OP 1400 FR additive for nylon use highlights sustainability in combination with a UL94 V-0 flame spread rating and a 600-volt comparative tracking index, ideal for use in the emerging electric vehicle market.
Similarly, Clariant’s Exolit® OP 1260 (TP) FR additive carries an Ecotain label for thermoplastic polyester like PolyButylene Terephthalate (PBT) use due to very good recycling capability in glass reinforced compounds averaging 30% regrind in a range of 10-50% regrind levels. Clariant’s Exolit® OP 1260 (TP):
Has the highest UL 94 V-0 flame resistance in thin 0.4-millimeter wall thicknesses
Maintains excellent color fastness
Has a 600-volt tracking index, and
Holds a good mechanical property balance targeted at demanding connector applications in electric vehicles, where it can replace traditional brominated flame retardants, or BFRs.
Clariant’s Exolit® OP 1260 FR (Orange) versus BFRs (Gray) Good Property Balance in 30% Regrind Glass Reinforced PBT Compound
George H. Luh’s Graphite-based FR for Nylon Compounds
Moving further, the George H. Luh company has developed a smoke-free, nonhalogenated, graphite-based FR additive for nylon compounds. Normally graphite has an upper 230°C temperature limit, rendering it useless in higher melting point nylons.
George H. Luh successfully introduced here their new expandable graphite GHL PX 95 HT 270 FR additive grade with its 270°C temperature capability that makes it useful in the 260°C nylon compound processing temperature range.
Work continues at George H. Luh on higher melting point expandable graphite grades. Temperature improvements center around blending different Magnesium DiHydroxide (MDH) and Ammonium PolyPhosphate (APP) combinations into expandable graphite to enhance its heat shield performance.
Flame Applied to George H. Luh’s Expandable Graphite Nylon Compound (L), Expandable Graphite Heat Expansion Before (Center L) and After (R) Ignition
NeoGraf Solutions’ Expandable Graphite Flake Additives for Aerospace and Automotive Paneling
Ending with NeoGraf Solutions’ synthetic graphite sheets and powders, here is another non-halogenated, low-smoke FR additive development approach. NeoGraf’s GrafGuard® 280-50N expandable graphite flake additive is aimed at plastic molded and thermoformed applications.
GrafGuard® 280-50N has a current market high 280°C temperature resistance. It is used in plastic compounds based on:
Acrylonitrile Butadiene Styrene (ABS)
PolyEthylene Terephthalate (PET), and
PolyAmide (PA, Nylon)
It can be blended with Magnesium Hydroxide (MgOH) for improved heat resistance and possesses a 300-micron particle size for ease of compound dispersion. It finds specialty application use in an extruded and thermoformed aerospace cabin and automotive FR heat shield paneling.