Liquid Silicone Rubber (LSR) is widely used in medical, automotive, and electronic applications thanks to its excellent performance and fast curing. However, its low viscosity and rapid addition-curing reaction can also lead to molding defects if the process or materials are not properly controlled.
Here's a quick troubleshooting guide to the most common problems.
Problem: Internal voids or bubbles on the surface, reducing sealing performance and transparency.
Possible Causes
Injection speed is too high, trapping air inside the mold.
Poor mold venting or blocked vent grooves.
Air enters the A/B mixing system.
Moisture in fillers vaporizes during curing.
Solutions
Reduce injection speed and improve mold venting or vacuum assistance.
Check the sealing of the feeding system.
Dry fillers thoroughly.
Use low-volatility vinyl silicone fluid for better processing stability.
Problem: Ripple marks or uneven surface gloss.
Possible Causes
Mold temperature is too low.
Injection pressure is insufficient.
Silicone base has poor flow properties.
Vinyl and hydrogen silicone fluids are not properly matched.
Solutions
Increase mold temperature and injection pressure.
Choose vinyl silicone fluids with good flowability.
Optimize the Si-H to vinyl ratio for a more uniform curing network.
Problem: Yellow edges, burned parting lines, or excessive flash.
Possible Causes
Cure temperature is too high.
Clamping force is too low.
Platinum catalyst reacts too quickly.
Solutions
Lower curing temperature and adjust curing time.
Increase clamping force.
Select an LSR grade with a suitable pot life for your process.
Problem: Weak adhesion between LSR and substrates such as PC, PA, or metal.
Possible Causes
Poor substrate surface preparation.
Mold temperature is unstable.
Insufficient adhesion promoter or silicone resin.
Solutions
Clean or plasma-treat the substrate.
Keep mold temperature stable.
Add suitable silane coupling agents or modified silicone resins to improve bonding.
| Defect | Process Adjustment | Material Check |
|---|---|---|
| Air Bubbles | Reduce injection speed, improve venting | Check moisture and feeding system |
| Flow Marks | Increase mold temperature and pressure | Optimize vinyl silicone fluid and curing ratio |
| Flash/Burn Marks | Lower curing temperature | Check catalyst activity |
| Poor Bonding | Improve surface treatment | Verify adhesion promoter or silicone resin |
High-quality LSR parts depend on the right combination of materials, formulation, and processing conditions. Proper troubleshooting can significantly improve production efficiency and product reliability.
If you're looking for vinyl silicone fluids, hydrogen silicone fluids, modified silicone resins, or technical support for LSR formulations, we're here to help.
Website: www.siliconeoil.net
E-mail: zyf@siliconeoil.cn
