Halogen Free Flame Retardant  V0 Performance with Uncompromised Durability

1. Executive Summary

The global shift toward halogenfree flame retardant solutions has accelerated dramatically over the past decade, driven by increasingly stringent environmental regulations and growing awareness of the toxic byproducts associated with halogenated flame retardants during combustion. Yet for compounders and manufacturers of rubber and plastic components, the transition presents a persistent challenge: how to achieve V0 flame retardancy without compromising mechanical properties, processability, and longterm durability.

As a trusted Halogen Free Flame Retardant manufacturer China, Sanexin has developed GreenThinking® FR99RP – a highefficiency composite that delivers V0 performance while preserving tensile strength, enhancing heat aging resistance, and significantly improving compression set and resilience compared to conventional alternatives. This report presents a detailed technical comparison between FR99RP, FR98RP, and FR76RP, and explains the unique manufacturing foundation that enables these solutions. Working with a reliable Halogen free flame retardant supplier China ensures that your formulations are backed by realworld compounding expertise, not just laboratory data.

2. Product Portfolio Overview: FR99RP, FR98RP, and FR76RP

The GreenThinking® FR Series comprises three complementary flame retardant technologies, each engineered for specific performance priorities.

2.1 GreenThinking® FR99RP – The Flagship Balanced Performer

FR99RP is a highefficiency compounded flame retardant developed for applications requiring V0 certification, excellent physical properties, superior heat aging resistance, and low compression set. It operates through a multimodal mechanism: upon heating, it forms a dense, ceramiclike char layer that isolates oxygen and heat, while releasing water and carbon dioxide and scavenging combustionpropagating free radicals.

Key attributes of FR99RP:

• Achieves V0 reliably across EPDM, NBR, NR, SBR, CR, IIR, ACM, and silicone
• Maintains high tensile strength and elongation at break – truly a flame retardant that maintains tensile strength in rubber
• Delivers superior heat aging resistance (significantly lower property degradation after 100°C × 70h aging)
• Exhibits excellent compression set resistance at elevated temperatures (120°C × 24h)
• Forms a clean, stable ceramic char with minimal soot and smoke
• Halogenfree, REACH and RoHS compliant

2.2 GreenThinking® FR98RP – The HighLOI Option with TradeOffs

FR98RP is an earliergeneration composite flame retardant that achieves higher Limiting Oxygen Index (LOI) values compared to FR99RP. However, this fireperformance advantage comes with significant compromises in physical properties and longterm durability.

Key characteristics of FR98RP:

• Higher LOI (up to 42.3% in EPDM formulations)
• Strong intumescent behavior upon combustion (significant expansion)
• Produces substantial soot and ash during burning
• Reduces tensile strength and crosslink density (lower MHML)
• Prolongs curing time (higher TC90)
• Poor heat aging resistance (hardness increases sharply, tensile strength and elongation drop significantly)
• Inferior compression set and resilience compared to FR99RP

2.3 GreenThinking® FR76RP – The UltraFine, SurfaceModified Specialist

FR76RP is a highperformance composite flame retardant distinguished by its ultrafine particle size, surface modification, and superior dispersion characteristics. It is engineered for applications demanding smooth extrusion surfaces, high thermal stability, and antidrip performance during combustion. For manufacturers seeking Halogen free V0 level for rubber compound with exceptional surface quality, FR76RP is the ideal choice.

Key attributes of FR76RP:

• Ultrafine particle size (D(0.5) = 2.65 μm) with lamellar structure
• High specific surface area and purity
• Surfacetreated for excellent dispersion
• Produces smooth extruded surfaces – perfect as a flame retardant for smooth extrusion surfaces
• Superior hightemperature char formation with antidrip properties
• Low density and low moisture content
• Ideal for silicone (HCR), EPDM, NBR, and SBR compounds
• Recommended loading: 50–130 phr depending on hardness and flame retardancy requirements

---

3. HeadtoHead Comparison: FR99RP vs. FR98RP

To quantify the performance differences, a series of controlled tests were conducted in standard EPDM and NBR formulations.

3.1 Comparative Data – EPDM 70 Shore A (80 phr and 100 phr Loadings)

Property	Unit	FR98RP80	FR99RP80	FR98RP100	FR99RP100
Cure Characteristics (180°C × 5 min)
MHML (Crosslink Density Indicator)	Ibfin	10.26	11.65	10.18	13.58
TC90 (Optimal Cure Time)	sec	207	96	221	112
Physical Properties (175°C × 6 min)
Hardness (Shore A)	–	74	74	78	76
Tensile Strength	MPa	7.63	9.26	6.35	9.32
Elongation at Break	%	406	421	417	497
M100 (Modulus at 100%)	MPa	2.64	2.77	2.59	2.69
Specific Gravity	g/cm³	1.22	1.238	1.241	1.242
Flame Retardancy
UL94 Rating	–	V0	V0	V0	V0
LOI	%	42.3	35.4	–	–
Combustion Behavior	–	Heavy intumescence, high soot	Clean ceramic char, low soot	Heavy intumescence, high soot	Clean ceramic char, low soot
Heat Aging (100°C × 70h)
Hardness Change	–	+5	+3	–	–
Tensile Strength Change	%	-7.56	-3.54	–	–
Elongation at Break Change	%	-34.05	-18.31	–	–
Compression Set (120°C × 24h)
Compression Set	%	–	–	52.94	31.43
Resilience	%	37	47	–	–

Source: Sanexin internal test data. Formulations available upon request.

3.2 Key Takeaways from the Comparison

FR99RP consistently outperforms FR98RP across nearly every nonfire metric:

• Higher crosslink density: MHML values are significantly higher with FR99RP, indicating a more fully cured network.
• Faster cure: TC90 is reduced by more than 50% (96–112 sec vs. 207–221 sec), directly improving production throughput.
• Superior mechanical strength: At 100 phr loading, FR99RP delivers +46% higher tensile strength (9.32 MPa vs. 6.35 MPa) and significantly higher elongation.
• Excellent heat aging resistance: FR99RP shows only 3.54% tensile strength loss and 18.31% elongation loss after aging, versus 7.56% and 34.05% for FR98RP.
• Outstanding compression set: FR99RP achieves 31.43% compression set vs. 52.94% for FR98RP at 120°C × 24h – a critical advantage for sealing applications.
• Better resilience: 47% vs. 37% – improved dynamic performance.

The only metric where FR98RP leads is LOI, but this comes at the cost of heavy intumescence, soot generation, and degraded physical properties. For most realworld applications – where longterm durability, heat resistance, and mechanical integrity are paramount – FR99RP is the clearly superior choice.

3.3 Performance in EPDM 50 Shore A

At 100 phr loading in a softer EPDM base:

Property	FR98RP100	FR99RP100
MHML (Ibfin)	8.4	9.31
TC90 (sec)	199	131
Tensile Strength (MPa)	8.03	9.31
Resilience (%)	44	51

FR99RP again delivers faster cure, higher tensile strength, and better resilience, with the same clean ceramic char formation versus the sooty intumescence of FR98RP.

3.4 Performance in NBR 70 Shore A

In polar NBR, widely used in oilresistant seals and hoses:

Property	FR98RP100	FR99RP100
MHML (Ibfin)	8.45	12.53
TC90 (sec)	79	94
Tensile Strength (MPa)	9.43	9.23
Elongation (%)	522	455
M100 (MPa)	2.55	2.94
Resilience (%)	24	33

FR98RP shows higher elongation but lower modulus and dramatically lower resilience (24% vs. 33%). FR99RP provides a valuable balance of tensile strength, modulus, and resilience – essential for dynamic sealing applications.

---

4. FR76RP: The Dispersion and SurfaceQuality Specialist

While FR99RP is the allaround flagship, FR76RP serves a specific niche where surface finish, ultrafine dispersion, and antidrip performance are critical. For applications such as automotive seals that require Halogen free V0 level for automotive sealing systems, FR76RP offers the perfect combination of flame retardancy and aesthetic quality.

FR76RP is distinguished by:

• Lamellar (platelet) structure with surface treatment, providing excellent barrier properties
• Ultrafine particle size: D(0.5) = 2.65 μm, D(0.97) = 11.39 μm
• High brightness (95.9% at R457nm) and purity (active ingredient ≥98.5%)
• Very low moisture content (≤0.36%)
• Superior chemical stability, nontoxic, odorless

In flame retardant testing, FR76RP demonstrates:

• Reliable V0 achievement
• Excellent hightemperature char formation
• Antidrip properties during combustion – critical for thinwall or vertical components – making it an ideal Anti drip flame retardant for thinwall silicone parts
• Smooth extruded surfaces with consistent dimensional stability

When to choose FR76RP vs. FR99RP:

Criterion	FR76RP	FR99RP
Surface quality requirement	Very high (smooth extrusion)	High
Particle size requirement	Ultrafine	Fine
Antidrip need	Critical	Not primary
Overall physical property balance	Very good	Excellent
Heat aging resistance	Good	Superior
Compression set	Good	Superior
Primary application	Highgloss, thinwall, or aesthetic parts	Heavyduty, longlife, dynamic applications

---

5. Flame Retardant Mechanism: How FR99RP and FR76RP Work

Both FR99RP and FR76RP operate through the same fundamental multimodal mechanism, though FR76RP’s ultrafine lamellar structure enhances the barrier effect while FR99RP’s chemistry prioritizes ceramic char integrity.

Upon heating, the FR compound decomposes on the product surface, forming a viscous, charred crust and a porous insulating layer. This barrier physically isolates oxygen, heat, and volatile small molecules from the combustion zone.

Simultaneously, free radicals generated during decomposition react with H⁺ and OH⁻ radicals – the chain carriers that sustain combustion – thereby terminating the chain reaction.

In parallel, the decomposition releases water and carbon dioxide while absorbing a significant quantity of heat, suppressing flame propagation through cooling and dilution effects.

For FR99RP specifically, the ceramiclike char that forms is dense, stable, and nonexpanding – providing longlasting protection without the structural distortion and soot generation associated with intumescent systems like FR98RP.

For FR76RP specifically, the lamellar structure creates a highly efficient “tortuous path” (maze effect) that further slows oxygen and heat penetration, while the surface treatment ensures rapid and uniform dispersion in the compound. This makes FR76RP the preferred choice for flame retardant for EPDM compound and other elastomers where dispersion and surface quality are paramount.

---

6. Manufacturing Excellence: The Sanexin Advantage

6.1 Not Just a Chemical Supplier – A Compounding Powerhouse

Most flame retardant suppliers develop their products in isolation from realworld compounding challenges. Sanexin Polymer is fundamentally different. The company’s flame retardant portfolio is built upon decades of handson, productionscale compounding experience – experience that directly informs every aspect of FR product design, from particle size engineering to surface modification to loading recommendations. As a leading Halogen Free Flame Retardant factory China, we integrate production and compounding under one roof.

6.2 Three Integrated Manufacturing Pillars

Sanexin’s manufacturing platform rests on three interconnected capabilities:Pillar 1: Dedicated Flame Retardant Production
The GreenThinking® FR Series is manufactured in a purposebuilt facility utilizing superrefinement, surface activation, and controlled compounding processes. Each batch undergoes comprehensive physical, chemical, and flame retardancy testing to ensure consistent V0 performance and regulatory compliance.

Pillar 2: China’s First DustFree Colored Silicone Rubber Production Line
Sanexin operates China’s first dustfree colored silicone rubber manufacturing facility. This is not a side business – it is a testament to the company’s deep expertise in dispersion technology, pigment stabilization, and process control. Colorants are introduced in a fully enclosed, dustfree system, eliminating airborne contamination, protecting worker health, and ensuring batchtobatch color consistency. The dispersion and surfaceengineering knowledge developed for this facility has been directly transferred to the FR Series, enabling the ultrafine particle size and surface treatment that distinguish FR76RP and FR99RP.

Pillar 3: One of China’s Top 5 Custom Compounding Facilities
Sanexin owns and operates one of the five largest custom compounding plants in China. This is not merely a production asset – it is the foundational technical engine behind the FR Series. Every flame retardant formulation is validated in this facility, using the same productionscale mixers, shear rates, temperatures, and cycle times that customers use. The compounding plant produces highvolume custom compounds for demanding applications across automotive, rail transit, electronics, and industrial sectors – providing a continuous stream of realworld formulation data that feeds back into flame retardant development.

6.3 The Virtuous Cycle: Formulation Expertise Drives Product Innovation

The integration of flame retardant development with highvolume compounding creates a unique closedloop innovation cycle:

1. R&D chemists develop new flame retardant concepts based on compounding insights
2. Pilot batches are compounded in productionscale mixers – not just lab mills
3. Performance data is generated using the same test methods applied to commercial compounds
4. Process feedback (dispersion behavior, cure response, extrusion characteristics) informs formulation refinement
5. Customer compounds incorporating FR Series products are validated in the same compounding facility before market release

This means that when a customer adopts FR99RP, FR98RP, or FR76RP, the formulation has already been productionvalidated under realworld conditions – not merely tested in an idealized laboratory setting.

6.4 Why This Matters for Customers

Sanexin’s compounding heritage provides three tangible customer benefits:

• Formulations that actually work on production equipment – not just labscale successes
• Technical support grounded in real manufacturing experience – the team understands your mixing constraints, cycle time pressures, and quality control challenges
• Accelerated development timelines – recommended formulations are already prevalidated, reducing your trialanderror cycle

---

7. Regulatory Compliance and Environmental Profile

7.1 HalogenFree Certification

The GreenThinking® FR Series is free from halogenbased flame retardants including polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PBDEs), chlorine, fluorine, and antimony trioxide. As Halogen free environmentally friendly flame retardant Suppliers China, we are committed to providing sustainable solutions that meet the highest environmental standards.

7.2 EU Directives Compliance

The entire FR Series complies with:

• EU REACH Regulation (EC 1907/2006)
• RoHS Directive 2011/65/EU (RoHS 2.0) and subsequent amendment (EU) 2015/863
• WEEE Directive 2002/96/EC

Thirdparty testing confirms compliance with all restricted substance limits. Therefore, we are a Reach compliant non halogen fire retardant supplier you can trust for global export.

7.3 Product Summary Table

Feature	FR99RP	FR98RP	FR76RP
UL94 Rating	V0	V0	V0
HalogenFree	Yes	Yes	Yes
REACH/RoHS	Compliant	Compliant	Compliant
Flame Mechanism	Ceramic char + radical scavenging	Intumescent + radical scavenging	Lamellar barrier + radical scavenging
LOI Level	Moderate (35–36%)	High (37–42%)	Moderate
Tensile Strength	Excellent	Moderate	Very good
Heat Aging Resistance	Superior	Poor	Good
Compression Set	Superior	Poor	Good
Resilience	Excellent	Moderate	Good
Soot/Smoke	Very low	High	Low
Surface Quality	Very good	Good	Excellent (ultrasmooth)
AntiDrip	–	–	Yes
Particle Size	Fine	Fine	Ultrafine (2.65 μm)

---

8. Application Scope

The GreenThinking® FR Series is widely used in flameretardant rubber and plastic components across multiple industries:

• Cables and wire insulation
• Rail transit components (seals, gaskets, vibration dampers)
• Electronic and electrical parts (connectors, housings, grommets)
• Automotive applications (underhood components, interior seals) – especially where Halogen free V0 level for automotive sealing systems is required
• Petroleum and coal mining equipment
• Construction materials (weather seals, expansion joints)
• Silicone rubber goods (hightemperature applications)

Compatible elastomers include EPDM, NBR, HCR (silicone), NR, SBR, CR, IIR, and ACM. For EPDMbased products, our FR99RP serves as an excellent flame retardant for EPDM compound, delivering both fire safety and mechanical robustness.

---

9. Technical FAQ

Q1: “Why should I choose FR99RP over FR98RP if FR98RP has a higher LOI?”

LOI is an indicator of oxygen concentration required to sustain combustion, but it does not correlate directly with realworld fire performance in standard UL94 testing – both products achieve V0. The practical question is: what do you give up for that higher LOI? With FR98RP, the tradeoffs include significantly lower tensile strength, dramatically worse heat aging resistance (34% loss in elongation vs. 18% for FR99RP), nearly double the compression set, and heavy soot generation. FR99RP delivers the same V0 rating while preserving the longterm mechanical integrity that determines actual service life. LOI is a laboratory number; durability is field performance. Our FR99RP is truly a flame retardant that maintains tensile strength in rubber – a claim backed by concrete data.

Q2: “When is FR76RP the better choice over FR99RP?”

Choose FR76RP when your application demands exceptional surface finish, ultrafine particle dispersion, and antidrip properties during combustion – typically thinwall components, highgloss extrusions, or parts with strict aesthetic requirements. FR76RP’s surface treatment and lamellar structure provide unmatched dispersion and smooth extruded surfaces, making it the ideal flame retardant for smooth extrusion surfaces. However, if your priorities are maximum heat aging resistance, lowest compression set, and highest resilience for dynamic or sealing applications, FR99RP remains the superior choice.

Q3: “Can I use these flame retardants in silicone (HCR) compounds?”

Yes. FR76RP and FR99RP are both compatible with HCR (highconsistency silicone rubber). FR76RP, with its ultrafine particle size and surface treatment, is particularly wellsuited for silicone applications where dispersion and surface quality are critical. Sanexin’s own silicone compounding facility – China’s first dustfree colored silicone production line – regularly validates FR Series performance in silicone formulations, ensuring that the products are not merely theoretically compatible but productionproven.

Q4: “How do these products perform in NBR gaskets regarding compression set?”

For NBR gaskets, compression set is a key performance indicator. FR99RP offers excellent compression set resistance (31.43% at 120°C × 24h in EPDM, and similar benefits in NBR), making it the preferred low compression set flame retardant for NBR gaskets. This ensures longterm sealing effectiveness under elevated temperatures and continuous pressure.

---

10. Conclusion: The CompoundingValidated Path to HalogenFree Compliance

The transition to halogenfree flame retardants is no longer optional – it is a regulatory and market imperative. But not all halogenfree solutions are equal. FR98RP delivers high LOI at the expense of physical properties, heat resistance, and longterm durability. FR76RP offers exceptional dispersion and surface quality for aesthetic and precision applications. FR99RP, however, stands alone as the balanced flagship – delivering reliable V0 performance while preserving tensile strength, resilience, and heat aging resistance. Whether you are seeking a Halogen free environmentally friendly flame retardant Manufacturers or a dependable partner for custom formulations, Sanexin offers the expertise and production scale to meet your needs.

The data in this report demonstrates that compounding expertise matters. Sanexin’s unique position as both a flame retardant developer and one of China’s Top 5 custom compounders ensures that every FR Series product is designed for realworld production, not just laboratory success. By choosing us, you are partnering with a Halogen Free Flame Retardant manufacturer China that understands both the chemistry and the compounding.

For engineers and manufacturers evaluating halogenfree solutions, the recommendation is clear: validate performance in your actual compound, on your actual equipment. And work with a supplier who understands both the chemistry and the compounding.

---

11. Resources and Contact

Technical Documentation

• Product Technical Data Sheets (TDS) for FR76RP, FR98RP, FR99RP, and other FR Series products
• REACH and RoHS compliance certificates
• Custom formulation development reports
• Productionscale trial documentation
• Formulation recommendations for specific elastomer systems

Facility Visits and Sample Testing

Sanexin welcomes technical visitors to its manufacturing and compounding facilities. Onsite visits provide an opportunity to:

• Observe flame retardant production processes
• Review quality control and testing protocols
• Tour China’s first dustfree colored silicone rubber production line
• Visit the Top 5 custom compounding facility and witness productionscale mixing
• Discuss custom formulation requirements with technical staff
• Review realtime production data and batch consistency records

Sample requests for laboratory evaluation and production trials are available upon request. Sanexin offers technical support during customer scaleup and formulation optimization.

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

Website: www.sanezenrubber.com

Email: yorichen@sanezen.com (General Inquiries)