Flame-Retardant Formulation Design Recommendations for Halogen-Free High-Impact Polystyrene (HIPS)
Customer Requirements: Flame-retardant HIPS for electrical appliance housings, impact strength ≥7 kJ/m², melt flow index (MFI) ≈6 g/10min, injection molding.
1. Phosphorus-Nitrogen Synergistic Flame-Retardant System
HIPS Flame-Retardant Formulation (Table 1)
|
Component |
Loading (phr) |
Remarks |
|
HIPS resin |
100 |
Base material |
|
Ammonium polyphosphate (APP) |
15-20 |
Phosphorus source |
|
Melamine cyanurate (MCA) |
5-10 |
Nitrogen source, synergizes with APP |
|
Expanded graphite (EG) |
3-5 |
Enhances char formation |
|
Anti-dripping agent (PTFE) |
0.3-0.5 |
Prevents molten droplets |
|
Compatibilizer (e.g., MAH-grafted HIPS) |
2-3 |
Improves dispersion |
Features:
- Achieves UL94 V-0 via intumescent char formation from APP/MCA synergy.
- Halogen-free and eco-friendly, but may reduce mechanical properties; optimization required.
2. Metal Hydroxide Flame-Retardant System
HIPS Formulation (Table 2)
|
Component |
Loading (phr) |
Remarks |
|
HIPS resin |
100 |
- |
|
Aluminum hydroxide (ATH) |
40-60 |
Primary flame retardant |
|
Magnesium hydroxide (MH) |
10-20 |
Synergizes with ATH |
|
Silane coupling agent (e.g., KH-550) |
1-2 |
Improves filler dispersion |
|
Toughener (e.g., SEBS) |
5-8 |
Compensates for impact strength loss |
Features:
- Requires >50% loading for UL94 V-0, but degrades impact strength and flow.
- Suitable for low-smoke/low-toxicity applications (e.g., rail transit).
3. Phosphorus-Nitrogen Synergistic System (Aluminum Hypophosphite + MCA)
Optimized HIPS Formulation
|
Component |
Loading (phr) |
Function/Notes |
|
HIPS (high-impact grade, e.g., PS-777) |
100 |
Base material (impact ≥5 kJ/m²) |
|
Aluminum hypophosphite (AHP) |
12-15 |
Phosphorus source, thermal stability |
|
Melamine cyanurate (MCA) |
6-8 |
Nitrogen source, synergizes with AHP |
|
SEBS/SBS |
8-10 |
Critical toughener for impact ≥7 kJ/m² |
|
Liquid paraffin/epoxidized soybean oil |
1-2 |
Lubricant, improves flow/dispersion |
|
PTFE |
0.3-0.5 |
Anti-dripping agent |
|
Antioxidant 1010 |
0.2 |
Prevents degradation |
Key Design Considerations:
- Resin Selection:
- Use high-impact HIPS grades (e.g., Chimei PH-888, Taifa PG-33) with inherent impact strength of 5–6 kJ/m². SEBS further enhances toughness.
- Flowability Control:
- AHP/MCA reduce MFI; compensate with lubricants (e.g., liquid paraffin) or plasticizers (e.g., epoxidized soybean oil).
- If MFI remains low, add 2–3 phr TPU to improve flow and toughness.
- Flame Retardancy Validation:
- AHP can be reduced to 12 phr if combined with 2–3 phr EG to maintain UL94 V-0.
- For UL94 V-2, reduce flame retardant loadings to prioritize impact/flow.
- Injection Molding Parameters:
- Temperature: 180–220°C (avoid AHP/HIPS degradation).
- Injection speed: Medium-high to prevent incomplete filling.
Expected Performance:
|
Property |
Target Value |
Test Standard |
|
Impact strength |
≥7 kJ/m² |
ISO 179/1eA |
|
MFI (200°C/5 kg) |
5–7 g/10min |
ASTM D1238 |
|
Flame retardancy |
UL94 V-0 (1.6 mm) |
UL94 |
|
Tensile strength |
≥25 MPa |
ISO 527 |
4. Alternative Solutions
- Cost-Sensitive Option: Replace AHP partially with microencapsulated red phosphorus (3–5 phr), but note color limitation (reddish-brown).
- Validation: Conduct small-scale trials to balance impact vs. flame retardancy before optimizing flow.
More info. , pls contact lucy@taifeng-fr.com
Post time: Aug-15-2025
