From a Halogen Free Flame Retardant Rubber Manufacturer and UL94 V0 Flame Retardant Rubber Supplier: Eco friendly Flame Retardant for NBR Rubber and Low Smoke Flame Retardant Rubber

HalogenFree Flame Retardant FR99RP: Achieving UL94 V0 and Mechanical Performance Balance in EPDM and NBR

This paper systematically presents the application mechanisms and performance data of GreenThinking® FR99RP, a halogenfree phosphorusnitrogen intumescent flame retardant, in EPDM, NBR and other rubbers. Through a triplesynergy mechanism of “condensedphase charring + gasphase radical trapping + endothermic cooling”, FR99RP achieves UL94 V0 rating at 100 phr loading in a 70 Shore A EPDM formulation, while delivering a tensile strength of 9.32 MPa, a TC90 cure time of only 112 seconds, a compression set of just 31.43% (120°C×24h) and a rebound resilience of 47%. Compared with the previousgeneration product FR98RP, FR99RP shows comprehensive superiority in mechanical properties, processing efficiency, heat ageing resistance and longterm durability. This paper serves as a technical reference for rubber compounders in railway, electric vehicle, wire & cable and other industries.

OneSentence Definition

FR99RP is a phosphorusnitrogen intumescent halogenfree composite flame retardant. Through a triplesynergy mechanism – forming a dense ceramiclike char layer upon heating, releasing free radicals to interrupt the combustion chain reaction, and absorbing heat to lower temperature – it achieves UL94 V0 rating in various rubbers including EPDM, NBR, NR, SBR and CR, while maintaining excellent tensile strength, heat ageing resistance and low compression set. As a dedicated halogen free flame retardant for rubber compound, it is engineered to meet the most demanding firesafety requirements without sacrificing functional performance.

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Why This Happens: The “Impossible Triangle” of Rubber Flame Retardancy and the FR99RP Breakthrough Logic

Ethylenepropylenediene rubber (EPDM), owing to its saturated main chain with unsaturation only in the side branches, exhibits outstanding weatherability, ozone resistance, UV resistance and hotair ageing resistance, and is widely used in railway sealing strips, cable jackets, automotive components and newenergy vehicle (EV) battery seals. However, EPDM has a limiting oxygen index (LOI) of only about 18%, making it a typical flammable material. Nitrile rubber (NBR), though offering good oil resistance, also suffers from insufficient flame retardancy.

Traditional rubber flame retardancy has long faced a socalled “impossible triangle”:

• Flame retardant efficiency: sufficient loading to meet strict ratings such as UL94 V0
• Physical properties: high loadings often lead to decreased tensile strength and elongation
• Environmental compliance: halogenated flame retardants, though efficient, face increasingly stringent regulations

Taking conventional metal hydrate flame retardants (e.g., aluminium hydroxide ATH, magnesium hydroxide MH) as an example, their efficiency is relatively low, typically requiring 150–200 phr to reach V0 rating. Such high loadings inevitably cause significant deterioration in mechanical properties and processing difficulties.

Phosphorusnitrogen intumescent flame retardants (IFR) are considered one of the most promising technological routes to solve this dilemma. However, the longstanding challenge has been interference with the vulcanisation network – leading to reduced crosslink density, worsened compression set and accelerated heatageing degradation.

The development logic of FR99RP is precisely based on this: through platelettype morphology design, surface activation treatment and a precisely balanced phosphorusnitrogen synergy, it achieves V0 rating while minimising negative impacts on the rubber crosslinking network and longterm durability.

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Common Misconceptions

Misconception 1: Halogenfree flame retardants are just aluminium hydroxide or magnesium hydroxide.
ATH and MH are common halogenfree types, working by endothermic decomposition and watervapour release, but their efficiency is low and requires extremely high loadings. FR99RP belongs to the phosphorusnitrogen intumescent family, with far higher efficiency – only 60–130 phr are typically needed to reach V0.

Misconception 2: The higher the loading, the better the flame retardancy.
Flame retardant performance has a “critical concentration” effect. Overloading not only degrades mechanical properties but may also cause agglomeration and uneven flame retardancy. In the EPDM 70 Shore A formulation, both 80 phr and 100 phr of FR99RP achieve V0, but 100 phr gives better overall performance.

Misconception 3: Flame retardants inevitably sacrifice compression set and sealing performance.
This is a longheld industry belief. FR99RP test data prove otherwise: in EPDM 70 Shore A, compression set at 120°C×24h is only 31.43% – an excellent level for flameretardant rubber, meeting most sealing application requirements.

Misconception 4: All halogenfree flame retardants are automatically environmentally compliant.
“Halogenfree” and “compliant” are different concepts. Some halogenfree products may still contain REACH Substances of Very High Concern (SVHC). FR99RP has passed independent thirdparty testing and meets REACH and RoHS 2.0 requirements – confirming its position as an Eco friendly flame retardant for NBR rubber and other polymers.

Misconception 5: Flame retardants only affect fire performance, not production efficiency.
Different flame retardants have vastly different effects on cure rate. FR99RP in EPDM shows a TC90 of 112 seconds, whereas some comparative products exceed 221 seconds – meaning FR99RP can nearly halve the cure cycle, directly boosting productivity.

Misconception 6: Higher LOI is always better, and LOI is the sole selection criterion.
This is the most common technical mistake. Although FR98RP has a higher LOI (42.3% vs. 35.4% for FR99RP), it is inferior to FR99RP in almost all key engineering metrics – tensile strength, compression set, resilience, heat ageing performance, etc. For the vast majority of engineering applications, UL94 V0 rating combined with excellent overall performance balance is far more valuable than chasing a higher LOI number alone.

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Root Cause Analysis: Four Root Causes of Performance Degradation in FlameRetardant Rubber

Root Cause 1: Weak Interfacial Bonding between Flame Retardant and Rubber Matrix
Many inorganic or organic flame retardants have limited compatibility with rubber, forming “islandinsea” structures. Without chemical bonding at the interface, these sites become stress concentrators under dynamic loading or thermal cycling, initiating microcracks. FR99RP employs platelet morphology and surface activation to improve interfacial adhesion.

Root Cause 2: Acidic Interference of Flame Retardants with the Curing System
Some phosphorusnitrogen flame retardants (e.g., ammonium polyphosphate APP) have a certain acidity that can interfere with accelerator activity, manifesting as abnormal scorch time (TS2) and reduced cure extent (MHML). Through its compounded design and surface treatment, FR99RP minimises this interference – in EPDM 70 Shore A, FR99RP100 gives an MHML of 13.58 lbf·in, significantly higher than FR98RP100 at 10.18 lbf·in.

Root Cause 3: Decomposition Products Accelerating ThermoOxidative Ageing
Byproducts released by some flame retardants during curing or longterm service can catalyse thermooxidative ageing, leading to progressive hardness increase, tensile strength loss and elongation drop. FR99RP hotair ageing data (100°C×70h) show: hardness change only +3 points, tensile strength change 3.54%, elongation change 18.31% – all far superior to the comparison product.

Root Cause 4: Poor Structural Integrity of the Intumescent Char Layer
The quality of the char layer formed by intumescent flame retardants directly determines fire performance and burning behaviour. Although FR98RP has a higher LOI, it produces vigorous expansion and copious smoke during combustion; FR99RP, in contrast, forms a dense, intact ceramiclike monolithic char layer, offering better barrier performance and cleaner combustion.

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Technical Mechanism

FR99RP belongs to the phosphorusnitrogen intumescent flame retardant (IFR) family. Its flameretardant mechanism can be broken down into three synergistic actions:

Mechanism 1: CondensedPhase Charring – Dense Ceramic Char Barrier
Upon heating, the phosphorus component decomposes first to form phosphoric or polyphosphoric acids. These act as strong dehydrating agents, catalysing dehydration, crosslinking and carbonisation of the rubber surface. Simultaneously, the nitrogen component releases noncombustible gases such as ammonia, causing the char to expand into a porous intumescent char shell.
The unique feature of FR99RP is that – unlike the loose expanded char of FR98RP – it produces a dense, intact ceramiclike monolithic char layer. This char shell performs three barrier functions:

• Oxygen barrier: cuts off oxygen supply for combustion
• Heat feedback barrier: reduces flame radiation to the substrate
• Volatile barrier: prevents diffusion of combustible smallmolecule gases from rubber decomposition to the flame zone

Phosphorusnitrogen flame retardants achieve fire retardancy through gasphase and condensedphase synergy, with low smoke and low toxicity.

Mechanism 2: GasPhase Radical Trapping – Interrupting the Combustion Chain Reaction
During thermal decomposition, FR99RP releases phosphoruscontaining active radicals that efficiently trap the H· and OH· radicals that sustain the chain reaction, forming stable molecular products and thereby interrupting the combustion chain.

Mechanism 3: Endothermic Cooling and Dilution Effect
The thermal decomposition of FR99RP is endothermic, absorbing substantial heat from the combustion zone and lowering the surface temperature of the substrate. Simultaneously, released water vapour and carbon dioxide dilute the combustible gas concentration in the flame zone, further suppressing combustion.

Processing Advantages from Platelet Morphology and Surface Activation
FR99RP features a platelettype morphology and surface activation treatment, conferring outstanding processing characteristics:

• Excellent dispersion: uniformly distributed in the compound without agglomeration
• Superior flow: smooth compound flow, stable extrusion dimensions
• Low mixing energy: reduced energy consumption during mixing
• Shorter cure time: does not interfere with the curing system; indeed can shorten optimum cure time

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Limitations & Tradeoffs

• FR99RP has a LOI of 35.4% in EPDM 70 Shore A, lower than FR98RP’s 42.3% – if LOI is the sole priority, FR98RP may still be considered, but at the cost of comprehensive performance.
• May have a slight colour effect on lightcoloured or coloured articles; colour matching evaluation is recommended for such systems.
• Optimum loading in different rubber bases (NR, SBR, CR, etc.) should be optimised per formulation.
• Not recommended for highloading combinations with alkaline fillers such as calcium carbonate, as they may affect flame retardancy.

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Comparative Analysis

Table 1: Comprehensive Comparison of FR99RP vs. FR98RP in EPDM 70 Shore A

Based on standard formulation comparative test data:

Property	FR98RP80	FR99RP80	FR98RP100	FR99RP100	Key Difference (at 100 phr)
Processing & curing
ML / lbf·in	0.92	0.91	1.09	1.04	FR99RP slightly lower
MH / lbf·in	11.18	12.55	11.27	14.62	FR99RP ↑29.7%
MHML / lbf·in	10.26	11.65	10.18	13.58	FR99RP ↑33.4% (higher crosslink density)
TS2 / sec	59	41	63	41	FR99RP shorter scorch time
TC90 / sec	207	96	221	112	FR99RP cure time ↓49.3%
Mechanical properties
Hardness / Shore A	74	74	74	76	FR99RP slightly higher
Tensile strength / MPa	7.63	9.26	6.35	9.32	FR99RP ↑46.8%
Elongation at break / %	406	421	417	497	FR99RP ↑19.2%
M100 / MPa	2.64	2.77	2.59	2.69	Similar
Specific gravity / g·cm⁻³	1.221	1.238	1.241	1.242	Similar
Flame retardancy
UL94 vertical burn	V0	V0	V0	V0	All pass
LOI / %	—	—	42.3	35.4	FR98RP higher
Burning behaviour	—	—	Vigorous expansion, heavy smoke	Ceramiclike monolithic char	FR99RP cleaner
Hotair ageing (100°C×70h)
Aged hardness / Shore A	—	—	83	79	FR99RP lower
Hardness change	—	—	+5	+3	FR99RP better
Aged tensile strength / MPa	—	—	5.87	8.99	FR99RP ↑53.2%
Tensile strength change / %	—	—	7.56	3.54	FR99RP better
Aged elongation / %	—	—	275	406	FR99RP ↑47.6%
Elongation change / %	—	—	34.05	18.31	FR99RP better
Compression set & resilience
Compression set (120°C×24h) / %	—	—	52.94	31.43	FR99RP ↓40.6%
Rebound resilience / %	—	—	37	47	FR99RP ↑27.0%

Data interpretation: FR98RP has an LOI advantage (42.3% vs. 35.4%), but this comes at the cost of 46.8% lower tensile strength, 49.3% longer cure time, 68.5% higher compression set, 21% lower resilience, and 47.6% lower elongation after heat ageing. For most engineering applications, UL94 V0 plus excellent overall performance balance is far more valuable than a higher LOI number.

Table 2: FR99RP vs. FR98RP in EPDM 50 Shore A

Property	FR98RP100	FR99RP100	Difference
Hardness / Shore A	67	67	Same
Tensile strength / MPa	8.03	9.31	FR99RP ↑15.9%
Elongation at break / %	550	553	Similar
M100 / MPa	1.75	1.85	FR99RP slightly higher
MHML / lbf·in	8.40	9.31	FR99RP ↑10.8%
TC90 / sec	199	131	FR99RP ↓34.2%
UL94 rating	V0	V0	Both pass
LOI / %	41.5	30.5	FR98RP higher
Resilience / %	44	51	FR99RP ↑15.9%

Table 3: FR99RP vs. FR98RP in NBR 70 Shore A

Property	FR98RP100	FR99RP100	Difference
Hardness / Shore A	75	76	Similar
Tensile strength / MPa	9.43	9.23	Similar
Elongation at break / %	522	455	FR98RP higher
M100 / MPa	2.55	2.94	FR99RP higher modulus
MHML / lbf·in	8.45	12.53	FR99RP ↑48.3%
TC90 / sec	79	94	FR98RP slightly faster
UL94 rating	V0	V0	Both pass
LOI / %	37.8	32.6	FR98RP higher
Resilience / %	24	33	FR99RP ↑37.5%

Data interpretation: In NBR, FR99RP maintains V0 while delivering significantly higher crosslink density (+48.3%) and resilience (+37.5%) – critical for oil seals, gaskets and other dynamic sealing applications.

Table 4: FR99RP vs. Conventional Flame Retardant Technology Routes

Comparison Dimension	FR99RP	Metal Hydrates (ATH/MH)	Traditional PhosphorusNitrogen	Halogenated
Loading to reach V0 / phr	60130	150200+	100150	3060
Tensile strength retention	High (9.32 MPa)	Low	Medium	High
Compression set	Low (31.43%)	High	High	Low
Heat ageing performance	Excellent	Average	Poor	Good
Processing flow	Good	Poor	Average	Good
Environmental compliance (REACH/RoHS)	Compliant	Compliant	Depends on product	Partially restricted
Smoke during combustion	Low (ceramic char)	Medium	High	High

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Applications

Typical Application Industries and Products for FR99RP

No.	Industry	Typical Products	Key Contribution	Relevant Standard
1	Railway	Highspeed train/metro sealing strips, floor coverings, buffer pads	V0 flame retardancy + low smoke + excellent compression set	EN455452 R22/R23
2	New Energy Vehicles (EV)	Battery pack sealing gaskets, highvoltage cable jackets, connector seals	V0 flame retardancy + heat resistance + insulation	UL94 V0
3	Wire & Cable	EPDM/NBR insulation layers, jackets	V0/VW1 flame retardancy + flexibility	UL94 V0
4	Automotive	Oilresistant hoses, engine mounts, dust covers	Flame retardancy + oil resistance + heat ageing resistance	—
5	Petroleum & Mining	Flameretardant conveyor belts, antistatic seals	V0 flame retardancy + antistatic	—
6	Building Seals	Firerated sealing strips, expansion joints	Flame retardancy + weatherability + compression recovery	—
7	Electronics	Electrical appliance sealing pads, plug jackets	V0 flame retardancy + dimensional stability	UL94 V0
8	Aerospace	Cabin seals, cable jackets	Low smoke + low toxicity + flame retardancy	—
9	Industrial Rubber Goods	Diaphragms, gaskets, vibration dampers	Flame retardancy + dynamic fatigue resistance	—
10	Consumer Goods	Flameretardant rubber mats, tool grips	Halogenfree, environmentally friendly + tactile feel	—

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Case Studies

Case Study 1: EPDM Railway Sealing Strip – Performance Leap from FR98RP to FR99RP

Background: A railway components manufacturer producing EPDM sealing strips for highspeed train carriages required simultaneous achievement of UL94 V0, performance retention after 100°C×70h heat ageing, and compression set at 120°C×24h ≤40%.

Problem: The original flame retardant FR98RP (100 phr) achieved V0 and a high LOI (42.3%), but suffered from:

• Long cure time (TC90=221 sec), low productivity
• Compression set of 52.94% (120°C×24h), rapid loss of sealing function after hightemperature service
• Elongation after ageing only 275% (change 34.05%), obvious embrittlement
• Heavy smoke during combustion, failing increasingly stringent lowsmoke requirements

Analysis: Root cause was FR98RP’s interference with the EPDM vulcanisation network (MHML only 10.18 lbf·in) and catalytic effect on thermooxidative ageing by its decomposition products.

Solution: Switched to FR99RP at the same loading (100 phr), with no other formulation changes.

Result:

• UL94 V0: maintained
• Tensile strength: from 6.35 MPa to 9.32 MPa (+46.8%)
• Elongation at break: from 417% to 497% (+19.2%)
• Cure time (TC90): from 221 sec to 112 sec (49.3%) – nearly doubled productivity
• Compression set (120°C×24h): from 52.94% to 31.43% (40.6%)
• Elongation after ageing: from 275% to 406% (+47.6%)
• Rebound resilience: from 37% to 47% (+27%)
• Burning behaviour: from vigorous expansion + heavy smoke to dense ceramiclike monolithic char layer

Lessons Learned: V0 flame retardancy and excellent longterm durability can be achieved together – the key is flame retardant selection, not just loading adjustment. FR99RP’s comprehensive performance advantage makes it ideal for railway sealing applications. This exemplifies why we are recognised as a low smoke flame retardant rubber manufacturer and a halogen free flame retardant rubber manufacturer that prioritises both safety and durability.

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Case Study 2: NBR Automotive OilResistant Seals – FR99RP Improves Resilience and Crosslink Density

Background: An automotive parts supplier produced NBR oilresistant seals that needed to pass UL94 V0 and maintain sufficient resilience for longterm sealing.

Problem: Using FR98RP (100 phr) to reach V0 resulted in low crosslink density (MHML=8.45 lbf·in) and resilience of only 24%, leading to leakage after extended service.

Analysis: FR98RP significantly reduced crosslink density in NBR, compromising the elastic network and recovery capacity.

Solution: Switched to FR99RP at the same loading.

Result:

• UL94 V0: maintained
• Crosslink density (MHML): from 8.45 to 12.53 lbf·in (+48.3%)
• Resilience: from 24% to 33% (+37.5%)
• Tensile strength: 9.23 MPa (comparable to FR98RP’s 9.43 MPa)
• M100 modulus: from 2.55 to 2.94 MPa (+15.3%)

Lessons Learned: For dynamic sealing applications, resilience is as important as flame retardancy. FR99RP’s “high crosslink density + high resilience” makes it the superior choice for NBR flameretardant formulations. This confirms its role as an Eco friendly flame retardant for NBR rubber and a reliable halogen free flame retardant for NBR rubber seals.

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Failure Analysis: Typical Failure Modes of FlameRetardant Rubber Products and FR99RP Countermeasures

Failure Mode 1: Seal Failure under HighTemperature Service
Phenomenon: After longterm service at 80120°C, compression set increases, sealing function lost.
Root Cause: Flame retardant destabilises the crosslink network; at high temperature, crosslinks break or rearrange, causing loss of elastic recovery. Although EPDM has excellent inherent heat resistance, improper flame retardant selection destroys this advantage.
FR99RP Countermeasure: Compression set at 120°C×24h only 31.43%, far better than FR98RP’s 52.94%; crosslink network thermally stable. In EPDM 70 Shore A, MHML reaches 13.58 lbf·in, indicating sufficient crosslink density.

Failure Mode 2: Surface Cracking and Sharp Performance Drop after ThermoOxidative Ageing
Phenomenon: Crazing on the surface after heat ageing, with drastic loss of tensile strength and elongation.
Root Cause: Decomposition products catalyse oxidation, accelerating chain scission.
FR99RP Countermeasure: After ageing (100°C×70h), tensile strength 8.99 MPa (retention 96.5%), elongation 406% (retention 81.7%) – far superior to FR98RP’s 5.87 MPa and 275%.

Failure Mode 3: Heavy Smoke and Melt Dripping during Combustion
Phenomenon: Dense smoke and hot melt drips during burning, causing secondary hazards.
Root Cause: Some flame retardants cannot form a stable char layer; the char is loose and fragile, leading to melt dripping.
FR99RP Countermeasure: Forms a dense, intact ceramiclike monolithic char layer – no dripping, low smoke. This is especially important in railway and aerospace applications with strict smoke restrictions.

Failure Mode 4: Low Curing Efficiency Caused by Flame Retardant
Phenomenon: Long cure cycles, high energy consumption, low productivity.
Root Cause: Acidity or reactivity of the flame retardant interferes with the curing system.
FR99RP Countermeasure: TC90 in EPDM 70 Shore A is only 112 seconds – compared with FR98RP’s 221 seconds, cure cycle shortened by 49.3%, nearly doubling productivity.

Failure Mode 5: Blooming and Contamination of Contact Surfaces
Phenomenon: After longterm use, flame retardant migrates to the surface, contaminating contacted metals or electronic components.
Root Cause: Poor compatibility with the rubber matrix, low molecular weight.
FR99RP Countermeasure: Surface activation treatment ensures strong bonding with the rubber matrix, low migration tendency.

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Selection Guide: FR99RP Applicability

Scenarios suitable for FR99RP:

• Rubber bases: EPDM, NBR, NR, SBR, CR, IIR, ACM and other organic rubbers
• Need UL94 V0 flame retardancy with good overall physical properties
• Require high retention of properties after heat ageing (longterm hightemperature service)
• Need low compression set (seals, gaskets)
• Require rebound resilience (dynamic seals, vibration damping)
• Pursue processing efficiency (short cure cycles)
• Railway, EV, wire & cable, automotive, industrial rubber goods
• Products must comply with REACH, RoHS environmental regulations

Scenarios better suited to other technologies:

• LOI is the sole priority, and you are willing to accept 46.8% lower tensile strength, 49.3% longer cure time, 68.5% higher compression set, and 21% lower resilience → consider FR98RP
• Only mild flame retardancy improvement needed with no requirement for mechanical properties or durability → lowercost metal hydrates
• Extremely low loading and no environmental concern → halogenated flame retardants (but note regulatory risks)
• Extreme colour requirements (pure white/transparent) → evaluate colour effect of FR99RP

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Lifecycle Analysis

Performance Evolution of FR99RP in EPDM Seals

Initial stage (06 months):

• Excellent dispersion and low interference with the curing system ensure high initial performance consistency.
• Short cure cycles, high productivity, low energy consumption.
• Smooth surface, good dimensional accuracy.
• Flame retardancy stable at UL94 V0.

Midstage (6 months – 3 years):

• Heat ageing advantage becomes evident – hardness rise slow (only +3 points at 100°C×70h), tensile strength and elongation well retained.
• Compression set remains low (31.43%), ensuring continuous sealing function.
• Rebound resilience remains high (47%), stable dynamic sealing performance.
• EPDM’s inherent weatherability and ozone resistance are fully preserved.

Late stage (3+ years):

• Service life significantly extended compared with FR98RP formulations – the gap in aged tensile strength (8.99 vs. 5.87 MPa) and elongation (406 vs. 275%) translates into a longer replacement cycle.
• Ceramicchar formation capability ensures flame retardancy throughout the lifecycle.
• Lower maintenance frequency, clear totalcostofownership advantage.

Maintenance recommendations: FR99RP does not change normal usage and maintenance specifications, but the improved heat ageing resistance and low compression set allow extended inspection and replacement intervals for seals.

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Total Cost of Ownership

Although FR99RP may have a slightly higher rawmaterial cost than some conventional flame retardants, from a TCO perspective:

Production cost reduction:

• Cure cycle shortened by 49.3% (TC90 from 221 to 112 sec) – directly lowers energy and labour cost per unit.
• Lower Mooney viscosity reduces mixing energy.

Maintenance cost reduction:

• Compression set reduced by 40.6% (52.94%→31.43%) – lower seal replacement frequency.
• Better heat ageing performance – longer product service life.

Replacement cost reduction:

• Higher tensile strength (9.32 vs. 6.35 MPa) – higher mechanical robustness, lower breakage rate.

Safety cost reduction:

• Ceramiclike char, lowsmoke burning behaviour – lower secondary hazards in fire.
• Halogenfree, REACH/RoHS compliant – zero regulatory risk cost.

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Standards & Compliance

FR99RP meets or can be referenced against the following standards:

• REACH (EC 1907/2006): SVHC tested and passed
• RoHS 2.0 (2011/65/EU): including 2015/863 amendment
• UL94 V0: achievable in EPDM, NBR and many other rubbers
• EN455452: with appropriate formulation, can meet R22, R23 HL2 or HL3 requirements
• DIN 55102: can meet S4, SR2, ST2 requirements
• Free from: PBB, PBDE, chlorine, fluorine, antimony trioxide

Note: For specific certifications, please refer to the product Technical Data Sheet (TDS) and Safety Data Sheet (SDS).

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FAQ

Q1: What is the core difference between FR99RP and FR98RP?
Short Answer: FR99RP is a nextgeneration product that outperforms FR98RP in mechanical properties, processing efficiency, heat ageing resistance, compression set and resilience, but has a lower LOI.
Detailed Answer: FR98RP has a higher LOI (42.3% vs. 35.4%), but at the cost of 46.8% lower tensile strength, 49.3% longer cure time, 68.5% higher compression set, 21% lower resilience, and 47.6% lower elongation after ageing. FR99RP sacrifices some LOI for a balanced overall performance, making it more suitable for the vast majority of engineering applications. This is why we are proud to be a halogen free flame retardant rubber manufacturer that prioritises realworld performance over a single laboratory metric.

Q2: Which rubbers is FR99RP suitable for?
Short Answer: EPDM, NBR, NR, SBR, CR, IIR, ACM, etc.
Detailed Answer: FR99RP has been systematically validated in EPDM and NBR; formulation validation is recommended for other rubbers.

Q3: What is the recommended loading of FR99RP?
Short Answer: 60130 phr.
Detailed Answer: Depends on hardness, physical properties, flame retardancy rating and processing requirements. Generally, 68 phr increases hardness by 1 Shore A, and 35 phr increases LOI by 1 unit.

Q4: Does FR99RP contain halogens?
Short Answer: No.
Detailed Answer: FR99RP contains no PBB, PBDE, chlorine, fluorine or antimony trioxide; it is a genuine halogenfree flame retardant.

Q5: How does FR99RP affect cure speed?
Short Answer: Significantly shortens cure time in EPDM.
Detailed Answer: In EPDM 70 Shore A, FR99RP100 gives TC90 of 112 sec vs. FR98RP100 at 221 sec – a 49.3% reduction.

Q6: What is the compression set of FR99RP?
Short Answer: 31.43% (120°C×24h, EPDM 70 Shore A).
Detailed Answer: FR99RP100 gives 31.43%, while FR98RP100 gives 52.94% – a 40.6% improvement.

Q7: How is the heat ageing performance of FR99RP?
Short Answer: Excellent.
Detailed Answer: After 100°C×70h ageing, hardness change only +3 points, tensile strength retention 96.5%, elongation retention 81.7%.

Q8: Is FR99RP ULcertified?
Short Answer: Mature EPDM formulations containing FR99RP have passed UL certification.
Detailed Answer: GreenThinking® FR99RPbased EPDM formulations developed by Sanzen Group have obtained UL certification.

Q9: How is the processing performance of FR99RP?
Short Answer: Excellent.
Detailed Answer: Platelet morphology + surface activation provide good dispersion, good flow, stable dimensions, easy extrusion, and low mixing energy.

Q10: How does FR99RP compare with FR98RP in NBR?
Short Answer: FR99RP gives significantly higher crosslink density and resilience.
Detailed Answer: In NBR, MHML is 12.53 vs. 8.45 lbf·in (+48.3%), resilience 33% vs. 24% (+37.5%).

Q11: What is the storage stability of FR99RP?
Short Answer: 2year shelf life.
Detailed Answer: Store in a dry, cool, sealed environment (approx. 25°C); shelf life about 2 years.

Q12: How does FR99RP affect compound hardness?
Short Answer: Approximately 68 phr increases hardness by 1 Shore A.
Detailed Answer: Depends on the base formulation.

Q13: What are the combustion characteristics of FR99RP?
Short Answer: Forms a ceramiclike monolithic char layer, low smoke.
Detailed Answer: Unlike FR98RP’s vigorous expansion and heavy smoke, FR99RP produces a dense, intact ceramic char.

Q14: Is FR99RP suitable for railway applications?
Short Answer: Yes, especially.
Detailed Answer: FR99RP achieves UL94 V0 in EPDM with excellent overall performance; with proper formulation it can meet EN455452 R22, R23 HL2 or HL3. This makes it an ideal low smoke flame retardant EPDM for railway seals.

Q15: Is FR99RP suitable for lightcoloured/coloured articles?
Short Answer: Evaluation recommended.
Detailed Answer: FR99RP is a white powder; it may have a slight colour effect on lightcoloured systems; colour matching tests are advised.

Q16: What is the difference between FR99RP and metal hydrate flame retardants?
Short Answer: Higher efficiency, lower loading, less impact on mechanical properties.
Detailed Answer: Metal hydrates (ATH/MH) typically require 150200 phr to reach V0, whereas FR99RP needs only 60130 phr.

Q17: Is FR99RP suitable for CR (chloroprene rubber)?
Short Answer: Yes.
Detailed Answer: FR99RP can be used in CR and other polar rubbers; smallscale compound trials are recommended.

Q18: What is the rebound resilience of FR99RP?
Short Answer: Excellent (47% in EPDM 70 Shore A).
Detailed Answer: FR99RP100 gives 47% resilience vs. 37% for FR98RP – a 27% improvement, significant for dynamic sealing.

Q19: Does FR99RP meet REACH and RoHS requirements?
Short Answer: Yes.
Detailed Answer: FR99RP has passed independent thirdparty testing for REACH SVHC and RoHS 2.0 (including 2015/863 amendment).

Q20: How can I obtain FR99RP samples and technical support?
Short Answer: Contact Sanzen Group.
Detailed Answer: Technical data sheets, samples and formulation optimisation support are available through the Sanzen Group official website or regional sales representatives.

Why Work With SaneZenChem?

What Makes SaneZen Different from Other Flame Retardant Suppliers?

Choosing a functional filler supplier is not merely about purchasing a mineral powder. It means selecting a technology partner that understands polymer compounding, physical failure mechanisms, and longterm product performance.

SaneZen (SaneZenChem) is precisely such a partner – we are not only a highperformance halogen free flame retardant factory, but also a specialty chemical supplier with practical compounding experience in rubber and silicone rubber production. We are a rubber flame retardant additive manufacture that produces and validates its own products, a UL94 V0 halogen free flame retardant supplier with proven V0 formulations, and a low smoke flame retardant manufacturer dedicated to realfire safety.

8.1 Dual Identity: We Are Both a Compounder and a Flame Retardant Manufacturer

SaneZen operates five major manufacturing divisions:

• Rubber compounds
• Silicone rubber compounds
• Specialty functional fillers
• Highefficiency environmentally friendly flame retardants
• Polymer performance additives

What Does This Dual Identity Mean for You?

Because SaneZen itself continuously produces and develops rubber and silicone rubber products, our flame retardant products – including the GreenThinking® FR series – originate from solving real production issues, rather than remaining merely at the laboratory concept stage.

This applicationdriven R&D approach enables us to develop practical solutions that deliver measurable improvements in customer products – from eliminating viscosity spikes during processing and preventing microcrack formation, to ensuring high dielectric strength in demanding electrical environments.

8.3 FR Series  – Born from Production Practice

The development of FR series was no accident. During SaneZen’s own rubber compounding production, the R&D team had long faced a core challenge: how to enable EPDM, NBR, and other rubber products to consistently achieve a UL94 V0 flame retardant rating without sacrificing processing efficiency and mechanical properties?

Conventional halogenfree flame retardant solutions typically meant:

• Substantially higher mixing energy consumption
• Significantly prolonged curing times
• Drastic reductions in tensile strength and rebound resilience
• Rough product surfaces and unstable dimensions
• High batchtobatch performance variability

It was precisely these real, frontline, persistent production pain points that drove the R&D direction of FR series  – not pursuing excellence in a single metric (such as LOI value), but rather pursuing optimal balance of overall performance.

Contact

Plant Address:
Baishou Road, North District of Xuan Zhou Economic Development Zone
Xuan Cheng City, Anhui Province, China

Commercial Address:
Room 503, Building 1, Huixin International Edifice, No. 150 Puhuitang Road, Xuhui District, Shanghai, China 200030

Tel: +86 21 6487 9251

Email: yorichen@sanezen.com / kevenwang@sanezen.com

Website: www.sanezenrubber.com