It is usable, but pure 300,000 cSt dimethyl silicone oil is not recommended for conventional PC/ABS modification. It is only fit for specific applications such as high slip, hydrolysis resistance and low migration, with strict control over dosage and processing conditions.
1. Feasibility & Performance
Dimethyl silicone oil is partially compatible with PC/ABS. Compared with low-viscosity silicone oil, 300,000 cSt high-viscosity grade features slower migration, less bleeding and better thermal stability.
It can improve demoldability, surface slip, scratch resistance, water repellency and hydrolysis resistance, and also deliver flame retardant synergism and low smoke performance, with negligible impact on heat distortion temperature.
2. Potential Risks
- Poor dispersion & agglomeration: This high-viscosity silicone oil is nearly paste-like at room temperature. It is hard to shear and disperse during twin-screw compounding, easily forming agglomerates which lead to flow marks, fish eyes, uneven gloss and degraded mechanical properties.
- Reduced melt flow: It will increase the melt viscosity of PC/ABS obviously, lower the melt flow rate, and cause insufficient filling and high injection pressure for thin-wall injection molding.
- Deteriorated impact resistance: Weak interfacial adhesion between silicone oil and resin creates stress concentration points, resulting in decreased toughness, especially at low temperatures.
- Defective appearance: Refractive index difference and uneven dispersion may cause dull surface, spots and uneven luster.
3. Recommended Viscosity & Solutions
Conventional Modification (Preferred)
- Viscosity: 500 ~ 5,000 cSt
- Advantages: Easy dispersion, minor influence on fluidity, controllable bleeding
- Addition level: 0.5 ~ 2 wt%
Special Applications (High Slip / Hydrolysis Resistance)
If using 300,000 cSt dimethyl silicone oil:
- Maximum dosage: ≤ 1 wt%
-
Processing suggestion: Prepare silicone masterbatch first (5~10% silicone oil with ABS carrier) before blending with PC/ABS. Raise processing temperature by 10~20℃, enhance shearing and extend mixing secti
on.
- Formula combination: Blend 0.5% of 300,000 cSt silicone oil with 0.5% of 5,000 cSt silicone oil to balance dispersion and migration resistance.
Better Alternatives
- Reactive modified silicone oil (epoxy, hydroxyl or amino modified): Forms chemical bonds with PC/ABS, no migration and no loss of mechanical strength.
- Commercial silicone masterbatch for PC/ABS: Good dispersion; recommended addition: 1~3 wt%.
4. Reference Formulas
- For general slip & demolding: 97% PC/ABS + 1.5% 5,000 cSt dimethyl silicone oil + 0.5% antioxidant
- For high hydrolysis resistance & low migration: 98% PC/ABS + 0.8% 300,000 cSt dimethyl silicone oil + 1.2% silicone masterbatch
Conclusion
300,000 cSt dimethyl silicone oil can be used for PC/ABS modification only for special scenarios. Please prepare masterbatch in advance, limit the dosage below 1% and optimize processing parameters. For regular production, 500~5,000 cSt silicone oil or dedicated silicone masterbatch is more reliable.
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