Composite flame retardant for polyester

Zhejiang Xusen Flame Retardants Incorporated Company has concentrated on halogen-free flame retardants since 1997, and composite flame retardant for polyester is one of the families where that focus shows most clearly. We supply phosphorus–nitrogen, nitrogen, inorganic and silicon composite systems that are let down into PBT, PET and PBT/PET blends, together with the masterbatch and functional additive grades that carry the same chemistry into fibre, film, coating and compounding lines. The range is built for projects where halogen-free compliance, thermal stability at polyester melt temperatures and repeatable dispersion all have to hold at the same time.

As a Composite flame retardant for polyester manufacturer, we run two production bases, a provincial-level research laboratory and a portfolio that stretches from single-substance raw materials through to finished composite packages. That vertical span is what allows us to tune a system to a specific polyester grade rather than offer a fixed catalogue item.

The Polyester Range: Systems, Substrates and Roles

Composite flame retardants combine two or more active mechanisms so that the flame-retardant package covers vapour-phase action, condensed-phase char formation and physical dilution at the same time. In polyester, that matters because the polymer melts and drips readily, and a single active rarely satisfies both the burning classification and the mechanical or electrical requirements of the finished part.

The Ammonium polyphosphate (APP) and melamine cyanurate platforms behind these composites are produced in-house, which is why we can adjust the ratio of acid source, char former and gas source instead of blending from a fixed external supply.

Application Fit Across Polyester Processes

PBT and PET engineering compounds

PBT and PET are processed well above 230 °C, so the flame-retardant system has to stay inert through the melting and metering zones and only decompose in the fire scenario. Phosphorus–nitrogen composites are the usual choice here because they act in both the vapour and condensed phase, which helps hold a classification in thin sections where a purely additive mechanism would need an impractical loading.

• Unfilled grades for connectors, switch housings and small mouldings
• Glass-filled grades where the filler already raises heat resistance and the FR package must not attack the fibre sizing
• Extruded profiles and sheet where melt strength and surface finish are visible acceptance criteria

Polyester fibre, film and textile coatings

In fibre and film the active has to survive high surface-area processing without degrading the polymer, blocking spinnerets or migrating to the surface. Nitrogen and silicon composites are frequently used where a soft hand, low discolouration and durable flame retardancy after washing are the real requirements rather than a rigid-plastic classification.

• Fine denier filament and staple fibre for apparel, upholstery and nonwoven
• Back-coatings for carpets and fabric where the FR sits in the coating rather than the fibre
• Biaxially oriented film where optical clarity and low haze are specified

Modified polyester, TPE and adhesive systems

Polyester chemistry also appears in TPE elastomers, PU insulation, epoxy and rubber compounds, cable materials, adhesives and coatings. These systems tolerate higher filler loading, so inorganic composites and hybrid packages can be used to reach smoke and heat-release targets that a pure phosphorus–nitrogen route would not meet economically.

Critical Specifications We Confirm Before Release

Every composite grade is characterised against the working point of the customer's process, not against a generic datasheet. The parameters below are the ones that decide whether a system performs in production.

• Active content: phosphorus and nitrogen content, and the ratio between acid source, char former and gas source
• Thermal onset: decomposition temperature relative to the polyester melt and metering temperature, so the additive stays stable in the barrel
• Particle size distribution: D50 and top cut, matched to the feeding system and to the wall thickness of the finished part
• Moisture and water solubility: controlled to limit hydrolysis during processing and to protect electrical properties in wet-service parts
• Bulk density and flow: consistent feed into gravimetric dosing and twin-screw compounding
• Surface treatment: coating chemistry selected for compatibility with the polyester matrix, reducing plate-out and black specks
• Colour and whiteness: relevant where natural, white or light-coloured compounds are produced
• Migration and extraction resistance: for textile, coating and long-service applications
• Electrical behaviour: tracking and insulation performance where the part carries current

Configuration Options and Let-Down Strategy

Composite flame retardants for polyester are supplied in forms that match the dosing equipment already installed on the line. We agree the physical form, the loading window and the carrier system with the customer before a trial batch is produced.

• Powder: standard grade for compounding lines with enclosed gravimetric feeding and dust extraction
• Surface-treated powder: coated for improved dispersion and lower plate-out in glass-filled compounds
• Masterbatch: composite active dispersed in a polyester-compatible carrier for fibre, film and lines that avoid powder handling
• Loading window: defined against the target classification, wall thickness and the mechanical or electrical property floor of the part
• Packaging: 25 kg inner-lined bags and jumbo bags, with palletised or bulk options agreed per order

Because the composite route lets us combine mechanisms, we can often reduce total additive loading compared with a single-substance approach, which protects tensile strength, impact and surface finish in the finished polyester part.

Capacity, Consistency and Quality Control

Production runs from two bases, Jiashan in Zhejiang and Juancheng in Shandong, with a combined annual capacity of 12,000 tonnes that continues to expand. Both sites operate under the ISO 9001-2015 quality management system, with in-house production workshops, warehouses and complete production and inspection equipment.

Batch-to-batch consistency is the practical concern for anyone running a continuous polyester line, so we control raw material intake, synthesis, surface treatment and final screening as separate verified steps. Our Zhejiang provincial-level scientific research laboratory works alongside a joint laboratory established with the Shanghai Institute of Chemistry, and the light industry flame retardant engineering technology research centre set up with Beijing Technology and Business University, Shandong Haihuai Institute and Shandong Brothers supports the development work behind new composite formulations.

Compliance Evidence and Documentation

Halogen-free status is a starting condition for this product family, not a differentiator. Our products are formulated to comply with the WEEE, RoHS and EUP directives, and the MCA and APP platforms are REACH registered. Test documentation is available for the relevant product lines, including RoHS reports for APP, ATH, flame retardant for PA and flame retardant for polyolefin, plus halogen and RoHS 3.0 test reports for MCA.

• Technical data sheet with active content, thermal onset, particle size and moisture
• Safety data sheet in the required language and format
• RoHS and halogen test documentation for the supplied grade
• Batch certificate of analysis covering the agreed specification parameters
• Retained samples for traceability against the delivered lot

Information We Use to Configure Your Solution

A proposal is prepared from the working point, the material and the production target. The more precisely these are defined, the closer the first trial batch comes to the final specification.

• Substrate: PBT, PET, PBT/PET blend, modified polyester, TPE, PU, epoxy or coating system, with grade and intrinsic viscosity where relevant
• Filler system: glass fibre or mineral type and loading, plus any impact modifier or colourant already present
• Process: injection moulding, extrusion, fibre spinning, film or coating, with melt temperature, residence time and shear level
• Acceptance target: the classification or test method to be met, the specimen thickness, and whether glow-wire, cone calorimeter or smoke data are also required
• Property floor: minimum tensile, impact, elongation or electrical values that the finished part must retain
• Line equipment: dosing type, whether powder or masterbatch can be handled, and available let-down range
• Colour and appearance: natural, white or pigmented, with any surface-finish requirement
• Volume and packaging: trial quantity, expected annual tonnage and preferred bag or bulk format
• Documentation: the language, standard and format required for data sheets, certificates and compliance files

Frequently Asked Questions

Why use a composite flame retardant instead of a single substance in polyester?

Polyester melts and drips, so a single active usually has to be loaded heavily to reach the required classification, which costs mechanical properties and processability. A composite combines vapour-phase, condensed-phase and dilution mechanisms, so the same target can often be reached at a lower total loading with better retention of tensile strength, impact and surface quality.

Which polyester substrates does the range cover?

The composite range is used in PBT, PET and PBT/PET blends, in unfilled and glass- or mineral-filled grades, and in polyester fibre, film, coatings, adhesives, TPE elastomers and PU insulation systems. The XS-FR-1301/1310 series is the composite package we supply specifically for PBT and PET compounds.

Can you supply a masterbatch instead of powder?

Yes. Flame retardant masterbatch for polyester carries the composite active in a polyester-compatible carrier, which suits fibre, film and compounding lines that prefer dust-free metered let-down. The carrier and active loading are agreed against the customer's dosing equipment and target let-down ratio.

How is the loading level decided?

Loading is set from the acceptance target, the specimen thickness, the filler content and the property floor the part must retain. We confirm the working window on the customer's own resin and process conditions rather than quoting a fixed percentage, because glass content and wall thickness shift the required level considerably.

What compliance documentation accompanies a shipment?

Products are formulated to comply with the WEEE, RoHS and EUP directives, and the MCA and APP platforms are REACH registered. Shipments are accompanied by a batch certificate of analysis, and RoHS and halogen test documentation is available for the relevant grades on request.

What do you need from us to prepare a quotation?

Substrate and grade, filler system, process and melt temperature, the classification or test method to be met, the property floor, the dosing equipment on the line, colour requirements, expected annual volume and the documentation format you need. With those defined we can select the system, propose the physical form and loading window, and prepare a trial quantity for evaluation.