Flame Retardancy and Weatherability: The NOR Halogen-Free Answer

Date: 2026-10-20

Topic 2Flame Retardancy and Weatherability: Can You Have Both?

A fibre that must pass a flame retardancy test and survive ten years of ultraviolet exposure presented a genuine conflict for decades. The NOR route resolves it by making the two functions the same chemistry rather than competing additives.

01Where the Conflict Comes From

A halogenated flame retardant and a hindered amine interact through a well-documented pathway:

1. Brominated retardant decomposes and releases HBr / Br− (strong acid)
2. HBr / Br− protonates the basic nitrogen of the N-H type HALS
3. The HALS is deactivated and can no longer trap free radicals
4. Net result: flame retardancy is met, but the fibre loses weathering resistance and embrittles early

Phosphorus-based retardants are milder, but their degradation products still consume hindered amines. Industry patent literature records this as a recognised technical conflict. The usual resolution is to specify a lower-basicity HALS, which helps yet leaves three problems unresolved:

  • The retardant remains a separately added component with its own logic, forcing repeated acid-base balancing during formulation development.
  • Lower basicity reduces consumption rather than eliminating it; measurable loss remains under strong acid load or elevated processing temperature.
  • The halogenated route stays under sustained compliance pressure. RoHS 2.0 restricts PBB and PBDE, HBCDD has been listed under POPs for elimination, and several organophosphorus retardants appear on the SVHC watch list.

02The NOR Route: One Chemistry, Three Functions

Within NOR chemistry, flame retardancy and light stability share one origin
Within NOR chemistry, flame retardancy and light stability share one origin
The distinguishing feature of an N-OR (nitroxide) system is that the flame retardant function comes from the hindered amine molecule itself. Char formation provides thermal insulation and suppresses combustible gas generation, without generating acidic degradation products. Since the molecule was already a light stabiliser, there is nothing to consume it.

Tiangang® FR-810A is a polymeric NOR halogen-free flame retardant based on hindered amine chemistry. It delivers genuine three-in-one performance:

  • Flame retardancy through condensed-phase char formation, which insulates the substrate and suppresses combustible gas generation.
  • Light stability through free-radical scavenging in a regenerative hindered amine cycle.
  • Long-term thermal stability from a polymeric high-molecular-weight backbone, which also widens the processing window.
Technical attributePerformance
True polymeric high-molecular-weight structureNot a small-molecule compound: low volatility, low migration, low extraction, long service life
Wider processing windowExcellent thermal stability, processing recommended ≤250°C; suitable for PE, PP, PA, POM, PET, PC
Excellent resin compatibilityUniform dispersion without blooming or exudation
Halogen-freeREACH / TSCA compliant; suitable for export and food-contact-adjacent scenarios
Proprietary technologyProprietary N-OR™ platform with international patent protection
Benchmark positioning: FR-810A is specified as a high-performance alternative to molecular NOR flame retardants. The differences that matter commercially are the polymeric structure’s thermal resistance, its tolerance of wider processing conditions, and its compliance profile. If you currently use a molecular NOR retardant and are constrained by supply or cost, this is a path worth evaluating.

03Compliance: The Practical Constraint

Regulation / standardCore requirementFormulation consequence
RoHS 2.0PBB and PBDE below 0.1% in homogeneous materialBrominated routes constrained; halogen-free becomes mainstream
REACHPBDE and HBCDD restricted or POP-listed; SVHC list continually extendedItem-by-item screening with retained supply-chain traceability
Four-element halogen screenBr ≤900 ppm, Cl ≤900 ppm, Br+Cl ≤1500 ppmA hard order-entry gate for European brands, frequently overlooked
GB 8624-2012Added smoke toxicity grading: CO ≤100 ppm, HCN ≤20 ppmMeeting the burning grade is not sufficient; smoke toxicity must also pass
EN 13501-1 / CPRReaction-to-fire requirements for construction productsPublic building applications need a complete compliance documentation chain

One point deserves emphasis: RoHS compliance is not halogen compliance. Halogens may enter through polymer pigments, inks, colour concentrates, fillers or cleaning agents. For European-bound product, build the four-element screen into incoming goods inspection rather than relying on a final RoHS report.

04Recommended Configurations

ObjectiveConfigurationRationale
Weathering only, no flame requirementHS-944 + UV-328 + AO-1010/AO-168Classical package, cost-effective
Flame retardancy plus weathering, export compliantFR-810A + HS-944 + AO-1010/AO-168NOR route removes the acid-base balancing problem
Flame retardancy plus long life, 10 years or moreFR-810A + XT-8 + AO-1010/AO-168Dual NOR protection with acid and sulfur resistance
Liquid dosing for ease of dispersionHS-112 liquid NOR + FR-810ALow molecular weight liquid, easy addition and uniform dispersion

Light Stabilizer for Plastics

Light Stabilizer for Coatings