View detail
If you work with PVC compounds and need to meet fire safety standards — whether for wire and cable, building profiles, flexible films, or wall panels — choosing the right flame retardant additive is one of the most consequential formulation decisions you will make. This guide covers everything: how PVC flame retardant additives work, the main chemical types, how to select the right one for your process, application-specific considerations, and what Joysun's PVC flame retardant product line offers.
PVC flame retardant additives are functional chemical compounds incorporated into PVC formulations to reduce ignitability, limit flame spread, and suppress smoke generation during combustion events. They work through one or more of three primary mechanisms: gas-phase radical quenching (interrupting the combustion chain reaction in the vapor phase), condensed-phase char formation (creating an insulating carbonaceous barrier on the polymer surface), and endothermic decomposition (absorbing heat energy and releasing non-combustible gases such as water vapor or CO₂ that dilute the oxygen-rich atmosphere around the flame).
Understanding which mechanism is active in a given additive system helps formulators predict synergies and avoid antagonisms when combining flame retardants with other additives.
PVC is inherently more flame-resistant than polyolefins such as polyethylene or polypropylene. The chlorine atoms in its molecular backbone participate in gas-phase quenching during combustion, which is why neat PVC has a relatively high Limiting Oxygen Index (LOI) of approximately 45 compared to PE at around 17. However, this inherent advantage diminishes substantially once plasticizers are added to produce flexible PVC. Common plasticizers such as DOP and DINP are essentially combustible oils; adding 40–60 PHR of plasticizer to PVC can reduce the LOI of the compound to 22–28, making fire retardant treatment necessary to meet building and electrical code requirements.
Even rigid PVC profiles and pipes, while more inherently flame-retardant than their flexible counterparts, frequently require additional flame retardant treatment to satisfy the elevated fire classifications demanded by construction regulations and procurement specifications — particularly for applications inside buildings, in enclosed transport, or in electrical infrastructure.
Three test standards dominate purchasing decisions in most global markets:
Limiting Oxygen Index (LOI, ISO 4589): measures the minimum oxygen concentration (expressed as a percentage) required to sustain combustion. A higher LOI indicates a material that is harder to ignite and keep burning. Most flame-retardant PVC building material requirements target LOI values of 28 or above, with demanding applications requiring 32+.
UL 94 (Underwriters Laboratories Standard for Safety of Flammability of Plastic Materials): a vertical and horizontal burn classification used widely in North American and global electrical/electronic markets. Ratings run from HB (lowest, horizontal burn) through V-2, V-1, and V-0 (highest, self-extinguishing within 10 seconds). Wire and cable insulation typically targets at least V-0.
EN 13501-1 (European fire classification for construction products): classifies products from A1 (non-combustible) through F. For PVC building materials including wall panels, door frames, and flooring, a Class B or Class C classification (which maps to Chinese standard GB Class B1 in most harmonized schemes) is a common minimum requirement in construction tenders. Joysun's ZR115 and ZR117 grades are both formulated to achieve Class B1(B) ratings in PVC building material compounds.
Smoke density and toxicity (ASTM E662, NF F16-101, EN 45545): increasingly scrutinized in rail, marine, and public building applications. Smoke suppression is evaluated separately from flame retardancy, and some flame retardants that perform well in UL 94 actually increase smoke density — a trade-off that must be managed.
Halogen-based systems rely on chlorine or bromine to quench combustion radicals in the gas phase. Because PVC already contains 56.7% chlorine by molecular weight, chlorinated paraffins are the most commonly used secondary flame retardants in flexible PVC — they contribute both plasticization and additional chlorine. Brominated compounds (such as decabromodiphenyl ethane or DBDPE) are used where extremely high flame retardancy is needed in a compact additive loading. The advantage of halogen-based systems is efficiency: relatively small loadings deliver large improvements in LOI and UL 94 rating. The disadvantage is regulatory pressure — the European REACH regulation restricts short-chain chlorinated paraffins (SCCPs), and certain brominated compounds face ongoing scrutiny under the Stockholm Convention. Formulators supplying European, Japanese, or premium export markets increasingly need halogen-free solutions.
Halogen-free flame retardants for PVC rely primarily on inorganic and phosphorus-based chemistries. Aluminum hydroxide (ATH) and magnesium hydroxide (MDH) are endothermic decomposers that release water vapor, cooling the flame and diluting combustible gases. Their limitation is that high loadings (often 100–180 PHR) are needed to achieve useful fire performance, which impairs mechanical properties and processing fluidity unless carefully balanced with coupling agents and lubricants. Inorganic phosphates and phosphonates are more efficient halogen-free options that function through both gas-phase and condensed-phase mechanisms, enabling lower additive loadings while achieving Class B1 ratings. Joysun's ZR115 is based on inorganic phosphorus chemistry, offering broad processing versatility and Class B1(B) classification in PVC flame-retardant building materials.
Phosphorus compounds — including ammonium polyphosphate (APP), triphenyl phosphate (TPP), resorcinol bis(diphenyl phosphate) (RDP), and various inorganic phosphate salts — are the backbone of most modern halogen-free flame retardant systems for PVC. They promote char formation through phosphoric acid generation, which dehydrates the polymer surface to form a stable carbonaceous layer that slows heat and mass transfer to the burning zone.
Antimony trioxide (Sb₂O₃) is not a flame retardant by itself; it is a synergist that amplifies the effectiveness of halogen-based systems. When halogen radicals (HCl or HBr) are released during combustion, they react with antimony trioxide to produce antimony trihalides and antimony oxyhalides, which are far more effective gas-phase radical scavengers than hydrogen halide alone. A typical loading ratio of antimony trioxide to halogen source is 1:3 by weight. However, antimony trioxide raises toxicological and regulatory concerns in certain markets, and its use adds to formulation cost. Joysun's ZR117, an inorganic salt-based grade, is explicitly antimony-free, providing a compliant alternative for markets where antimony compounds face restriction.
Flame inhibition and smoke suppression are related but distinct performance objectives. Zinc borate, molybdenum compounds, and certain metal oxides act as smoke suppressants in PVC systems, often working synergistically with halogen or phosphorus flame retardants. They promote more complete combustion of carbonaceous particles, reducing the optical density of smoke. When specifying a flame retardant package for applications where both fire rating and smoke density limits apply (transit vehicles, tunnels, hospitals), it is essential to test both parameters together rather than optimizing for UL 94 or LOI alone.
Flame retardant additives must integrate cleanly into the full PVC compound formulation without causing phase separation, plate-out on processing equipment, or migration to the product surface over time. This is especially critical in flexible PVC, where high plasticizer loadings (DOP, DINP, TOTM for high-temperature applications) can compete with or leach out incompatible flame retardants. Joysun's additives for flexible PVC products — including stabilizer grades CZ901 (for transparent sheets and crystal fabric) and CZ610 (for light box fabric) — are engineered for compatibility in plasticized systems, offering high transparency and excellent stability alongside the flame retardant package.
Equally important is compatibility with the thermal stabilizer. Ca-Zn stabilizers, which are the dominant heat stabilizer system in modern halogen-free and low-lead PVC processing, must be verified for interaction with phosphorus-based flame retardants. Certain phosphate esters can interfere with the zinc soap stabilization mechanism, accelerating early color development. Joysun's PVC Ca-Zn stabilizer product line is formulated to work in concert with Joysun's flame retardant offerings, enabling a coherent additive package tested as a system rather than individual components.
The extrusion or calendering temperatures used in PVC processing typically range from 160°C to 200°C depending on the product type, with rigid profile extrusion and pipe extrusion at the higher end. Any flame retardant that begins to decompose, volatilize, or release corrosive by-products within this window will cause plate-out, discoloration, die drool, and inconsistent product quality. For rigid profile and pipe applications, Joysun's additives for rigid profiles and pipes — stabilizer grades CZ2211L (for profiles and resin tiles) and CZ2303L (for extruded pipes) — are characterized by long thermal stability time and wide processing windows, supporting continuous production runs without degradation in compound quality.
Inorganic phosphorus-based flame retardants generally offer good thermal stability up to 220–250°C, making them suitable for most PVC processing conditions. Organic phosphate esters vary more widely — liquid grades used in flexible PVC must be checked for volatility at processing temperatures to avoid loss of flame retardant performance in the finished product.
RoHS (Restriction of Hazardous Substances Directive): applies to electrical and electronic equipment sold in the EU. It restricts heavy metals (lead, cadmium, hexavalent chromium, mercury) and certain brominated flame retardants (PBB and PBDE). Lead-based stabilizers are banned under RoHS, and any flame retardant package for wire and cable insulation or electronics enclosures must be checked for restricted substances. Joysun's Ca-Zn stabilizer line is inherently RoHS-compliant with respect to lead content.
REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals): the EU's comprehensive chemical regulation. Short-chain chlorinated paraffins (C10–C13, SCCP) are on the REACH SVHC (Substances of Very High Concern) list and are restricted in certain applications. Medium-chain chlorinated paraffins (MCCP) are under evaluation. Formulators exporting to Europe should verify the chain length profile of any chlorinated paraffin component. Antimony trioxide is also a REACH SVHC candidate. Joysun's antimony-free ZR117 and phosphorus-based ZR115 are positioned specifically for compliance-sensitive markets.
UL Certifications: for wire and cable products sold into North America and many Asian markets, UL 94 vertical burn testing is mandatory, and products may need to appear in UL's Yellow Card listing. The flame retardant system used must deliver consistent V-0 or V-1 performance within the specific compound formulation that is listed. Formulation changes — even to approved components — may require retesting and relisting. Joysun supports customers through this process with test reports and technical documentation.
This is one of the highest-stakes applications for PVC flame retardant additives. Low-voltage building wire, instrumentation cable, and data cable jacketing commonly use PVC due to its excellent electrical insulation properties and cost competitiveness. However, the plasticizer levels required for flexibility (typically 40–60 PHR) significantly reduce inherent flame resistance, making flame retardant treatment essential. Target performance is typically UL 94 V-0, with LOI values above 28, and increasingly, low-smoke and low-toxicity (LS-0H) requirements are layered on top. Joysun's flame retardant system for flexible PVC is engineered to meet these combined demands without compromising the electrical insulation properties or long-term plasticizer compatibility that wire and cable processors require.
PVC window profiles, curtain wall components, and pressure pipes present a different set of challenges. These are rigid compounds processed at higher temperatures with minimal or no plasticizer. The concern is not initial ignitability so much as fire spread in a building cavity or through a pipe installation. European building regulations (Construction Products Regulation, EN 13501) mandate that profiles used in buildings meet at least a Class C fire classification, with many specifications requiring Class B. Joysun's additives for rigid profiles and pipes include stabilizer packages specifically balanced for the high-calcium formulations common in profile extrusion, combined with flame retardant grades capable of achieving Class B1 in the finished article.
Flexible PVC products — transparent sheeting, decorative films, tarpaulins, light box fabrics, and crystal fabric — are used extensively in commercial interiors, advertising, transportation, and agriculture. Because many of these applications involve large surface areas in enclosed or semi-enclosed spaces, fire performance is increasingly regulated. Plasticizer selection dramatically affects which flame retardants can be used: DOP-based compounds behave differently from TOTM or citrate-based systems when flame retardant additives are introduced. For transparent applications in particular, the flame retardant must not cause haze, yellowing, or migration blooming. Joysun's CZ901 stabilizer, listed under additives for flexible PVC products, is formulated for transparent and crystal fabric applications where optical clarity must be preserved alongside flame retardant performance.
PVC wall panels, wood veneer boards, carbon crystal boards, anti-collision panels, and decorative door frame profiles represent a fast-growing segment of interior construction materials. In residential and commercial buildings, these surfaces must comply with national fire classification standards — in China, GB 8624 Class B1 is the typical requirement for interior finish materials, which aligns with EN 13501 Class B. Joysun supports this segment with a comprehensive family of stabilizers and foaming agents. The stabilizers for wall panels, wood veneer boards, anti-collision panels and carbon crystal boards and the foaming agents for wall panels are designed to be used alongside the ZR115 or ZR117 flame retardant grades, giving processors a complete, pre-validated additive system for Class B1 building materials.
For flooring, particularly SPC (Stone Plastic Composite) and WPC (Wood Plastic Composite) formats that dominate commercial and residential installation today, Joysun offers dedicated solutions: stabilizers for SPC, WPC, LSPC and ABA flooring and foaming agents for SPC, WPC, LSPC and ABA flooring, all capable of integration with the flame retardant system where fire classifications are required by specification.
For ventilation components, venetian blinds, and tool pegboards — applications that often require a combination of rigidity, dimensional stability, and fire resistance — Joysun's additives for ventilation windows, venetian blinds and tool pegboards provide the stabilizer and processing aid foundation into which the appropriate flame retardant grade can be integrated.
Similarly, for door panels and frame profiles that must meet both aesthetic and fire performance standards, the additives for door panels and door frame profiles from Joysun are available as a complementary system.
Joysun's PVC flame retardant product line currently includes two core commercial grades:
ZR115 — Inorganic phosphorus-based, powder form. Targets Class B1(B) in PVC flame-retardant building materials. Offers broad processing versatility, making it suitable across a range of rigid and semi-rigid PVC compound formulations. Recommended where phosphorus-based halogen-free performance is needed alongside good processing latitude.
ZR117 — Inorganic salt-based, powder form. Antimony-free. Also targets Class B1(B). Specifically developed for markets and specifications where antimony compounds are restricted or undesirable. Noted for excellent processing performance in PVC building material compounds.
Both grades are detailed under the flame retardants product page with technical data available for download.
These flame retardant grades are designed to work within Joysun's broader additive ecosystem, which spans PVC Ca-Zn stabilizers, chemical foaming agents, SPC/WPC floor one-pack additives, CPVC one-pack additives, and PE WPC composite lubricants, enabling customers to source a complete, validated additive package from a single technical partner.
Zhejiang Joysun Advanced Material Co., Ltd. was established in 2005 and has operated a full-scale manufacturing facility in the Dushangang Chemical Industrial Park in Pinghu since 2016. The company holds a provincial-level postdoctoral research station (established 2024), a Zhejiang Provincial High-Tech Enterprise R&D Center designation, and multiple national invention patents. It has been recognized as a National High-Tech Enterprise and a Zhejiang Province "Hidden Champion" enterprise. Industry-academia partnerships with Zhejiang University, Zhejiang University of Technology, and Qingdao University of Science and Technology underpin the applied research pipeline.
Joysun's R&D team can develop custom flame retardant formulations for specific compound recipes, processing equipment configurations, or regulatory profiles. If your product requires a UL Yellow Card listing, an EN 13501 Class B certification, or compliance with a customer-specific procurement specification, Joysun's technical team can work through the development and validation process with you. Learn more about the company's technical capabilities on the R&D page.
Joysun operates under a certified quality management system (ISO 9001), environmental management system (ISO 14001), and occupational health and safety management system (ISO 45001). The company holds AEO (Authorized Economic Operator) Advanced Certification from Chinese Customs, enabling streamlined export documentation and faster customs clearance for international customers. With a production capacity of 70,000 metric tons per year across dual factory facilities and over 600 customers worldwide, Joysun has the scale to support both sample-stage development projects and large-scale commercial supply. Technical data sheets and test reports for the ZR115 and ZR117 grades are available through the product pages. For inquiries, visit the contact page.
What is the difference between a flame retardant and a fire retardant for PVC? The two terms are used interchangeably in most commercial contexts. Strictly, "flame retardant" refers to resistance to ignition and flame spread, while "fire retardant" is sometimes used more broadly to include resistance to structural damage from heat. In the context of PVC additive technology, they describe the same class of functional additives.
Can I use Joysun's ZR115 or ZR117 in flexible PVC compounds? Both grades are primarily positioned for rigid and semi-rigid PVC building material compounds where Class B1 classification is the target. For flexible PVC applications with high plasticizer loadings, the formulation interaction with the plasticizer system must be evaluated. Contact Joysun's technical team for compatibility data relevant to your specific flexible compound.
Does ZR117's antimony-free nature affect its flame retardant performance versus ZR115? ZR117 achieves Class B1(B) ratings through its inorganic salt chemistry without relying on antimony trioxide as a synergist. Performance is equivalent at target loading levels, with the additional benefit of antimony-free compliance for sensitive markets. Processing characteristics are also noted as excellent.
How does LOI relate to UL 94 rating in PVC compounds? The two tests measure related but distinct properties. LOI measures the minimum oxygen concentration to sustain combustion (a thermodynamic measure), while UL 94 measures the practical burning behavior of a fixed-dimension specimen under defined ignition conditions (a kinetic measure). A high LOI (≥28) generally correlates with a V-1 or V-0 rating in UL 94, but the correlation is not absolute — compound geometry, melt viscosity, and dripping behavior also influence UL 94 outcome. Both tests should be conducted on the actual compound and article dimensions.
What loading level of ZR115 or ZR117 is typically needed to achieve Class B1? Target loading depends on the base compound formulation, particularly the stabilizer and plasticizer levels. Joysun's technical data sheet provides recommended starting-point dosages. Custom trials are strongly recommended before finalizing the formulation for production.
Do these flame retardants affect the thermal stability of the PVC compound? When used within the recommended loading range alongside compatible Ca-Zn stabilizer systems, the ZR115 and ZR117 grades are designed to maintain thermal stability within standard PVC processing windows. For specific processing temperatures and residence times, consult with Joysun's technical team, particularly if your process involves prolonged residence in the die or compounder.
How can I request samples or technical data? Visit the contact page or reach the Joysun team directly at sale@joysunsh.com / 0086-21-39197569. Technical data sheets are also available for direct download from the flame retardants product page.
