PP V2 Flame Retardant Masterbatch Reference Formulation
For achieving UL94 V2 flame retardancy in PP (polypropylene) masterbatches, a synergistic combination of flame retardants is required while maintaining processing performance and mechanical properties. Below is an optimized formulation recommendation with explanations:
I. Base Formulation Recommendation
Flame Retardant Formulation:
|
Component |
Loading (wt%) |
Function Description |
|
PP Resin |
50-60% |
Carrier resin (recommend high melt flow index grade, e.g., MFI 20-30 g/10min) |
|
Aluminum Hypophosphite |
15-20% |
Acid source, promotes char formation, good thermal stability for PP processing |
|
Zinc Borate |
5-8% |
Synergistic flame retardant, suppresses smoke and enhances gas-phase flame retardancy |
|
Surface-Modified Aluminum Hydroxide |
10-15% |
Endothermic decomposition, lowers combustion temperature (surface treatment, e.g., silane coupling agent, recommended) |
|
Dipentaerythritol (Di-PE) |
5-8% |
Carbon source, synergizes with acid source to form intumescent char |
|
Melamine Polyphosphate (MPP) |
3-5% |
Gas source (recommended supplement), releases inert gases to enhance intumescence |
|
Anti-Dripping Agent (PTFE) |
0.3-0.5% |
Reduces melt dripping (optional for V2, as dripping is permitted) |
|
Antioxidant (1010/168) |
0.3-0.5% |
Prevents thermal oxidative degradation during processing |
|
Lubricant (Zinc Stearate) |
0.5-1% |
Improves processing flowability and dispersion |
|
Color Carrier & Pigment |
As needed |
Select high-temperature-resistant pigments to avoid reactions with flame retardants |
II. Key Optimization Points
- Synergistic Flame Retardant System
- Intumescent Flame Retardant (IFR): Aluminum hypophosphite (acid source) + Di-PE (carbon source) + MPP (gas source) forms an IFR system, creating an insulating char layer to block heat and oxygen.
- Zinc Borate Synergy: Reacts with aluminum hypophosphite to form a glassy protective layer, enhancing gas-phase flame retardancy.
- Modified Aluminum Hydroxide: Surface treatment reduces moisture release during processing while providing endothermic decomposition to lower combustion temperature.
- Processing & Performance Balance
- Total flame retardant loading should be controlled at 35-45% to avoid significant mechanical property loss.
- Use high-MFI PP resin (e.g., PPH-Y40) to improve masterbatch dispersion and reduce viscosity.
- Testing & Validation Recommendations
- UL94 Vertical Burning Test: Ensure flames self-extinguish within 60 seconds after two ignitions.
- Mechanical Testing: Focus on tensile strength (≥20 MPa) and impact strength (≥4 kJ/m²).
- Thermal Stability (TGA): Verify flame retardant decomposition temperatures match PP processing range (180–220°C).
III. Optional Adjustments
- For Higher Flame Retardancy (e.g., V0):
- Increase aluminum hypophosphite to 25%, add 2% silicone (smoke suppression), and raise PTFE to 0.8%.
- Cost-Sensitive Applications:
- Reduce MPP content and moderately increase aluminum hydroxide (ensure processing stability).
IV. Key Considerations
- Masterbatch Production: Pre-mix flame retardants with carrier resin; twin-screw extrusion (180–210°C) is recommended.
- Aluminum Hydroxide Drying: Dry at 110°C for 4 hours to prevent bubbles during processing.
- Di-PE/Aluminum Hypophosphite Ratio: Maintain 1:2 to 1:3 for optimal char formation efficiency.
With this optimized formulation and processing approach, UL94 V2 flame retardancy can be consistently achieved while preserving processing performance and color stability. Small-scale trials are recommended for fine-tuning based on test results.
More info., pls contact lucy@taifeng-fr.com
Post time: Jul-08-2025
