Polyurethane soft foam products include high-resilience foam, block sponge, slow-recovery foam, self-skinning foam (SF), and semi-rigid energy-absorbing foam. The cellular structure of polyurethane soft foam is predominantly open-celled, exhibiting characteristics such as low density, excellent elasticity, sound absorption, breathability, and insulation properties. These foams are primarily used in furniture padding, various soft cushioning layers in laminated composite materials, and also find applications in industries and households as filtering materials, sound insulation, shock absorption, decorative materials, packaging materials, and thermal insulation.
Polyurethane soft foam, often open-celled, typically possesses features like low density, breathability, sound absorption, insulation, and good resilience. High-resilience polyurethane foam is commonly employed in vehicle seats, furniture padding, various laminated cushioning layers, as well as for sound insulation, filtering, decoration, shock absorption, packaging, and thermal insulation. Self-skinning polyurethane foam plastic products are mainly used in automotive steering wheels, headrests, armrests, motorcycle seats, bicycle seats, recliner armrests and headrests, door handles, spoiler boards, and bumpers.
With the increasing market demand for polyurethane soft foam, common issues in the production process are gaining attention from manufacturers. Accidents and problems encountered in actual foaming production are diverse, and the causes of each incident are often attributed to different factors. Below, we summarize some common problems and their corresponding solutions encountered in the production process of soft foam, specifically in a flat foam production line.
Common Issues and Solutions in Soft Foam Production (Flat Foam Production Line):
1. Issue: Large bubbles appear on the surface and burst into a boiling state.
Possible Causes:
Degraded or insufficient silicone oil.
Degraded or insufficient tin catalyst.
Solutions:
Replace silicone oil and verify the accuracy of the silicone oil metering pump.
Replace tin catalyst from a different batch and verify the accuracy of the metering pump.
2.Issue: Foam collapses after reaching a certain height during expansion.
Possible Causes:
Degraded or insufficient silicone oil.
Insufficient tin or excessive amine, or both.
Contamination in the foaming system.
Solutions:
Check the quality of silicone oil and the metering pump.
Adjust the ratio of tin and amine and check for degradation.
Inspect the foaming system for contamination.
3.Issue: Shortening of the clearing area, with the milky line moving towards the mixing head.
Possible Causes:
Conveyor belt speed is too slow.
Foam expansion speed is too fast.
Solutions:
Increase conveyor belt speed and angle.
Appropriately reduce amine catalyst dosage.
4.Issue: Smoke or white smoke emanates from the foam surface.
Possible Cause:
Excessive TDI evaporates on the surface.
Solution:
Check the accuracy of various component measurements, with a focus on water, TDI, and PPG flow rates.
5.Issue: Cracks appear above and below the foam surface.
Possible Causes:
Imbalance in gelation and post-foaming reaction rates.
Solutions:
Check the accuracy of amine and tin measurements.
Adjust the ratio of amine and tin.
Check the quality of silicone oil.
6.Issue: Foam collapses and sinks after reaching maximum height during curing, and foam rebound is slow.
Possible Causes:
Insufficient silicone oil.
Curing reaction speed is too slow.
Solutions:
Check the accuracy of silicone oil metering.
Increase silicone oil amount appropriately.
Check the accuracy of tin and amine measurements.
Increase tin or decrease amine usage.
7.Issue: Slow rebound during curing, and foam shrinks with slow fingertip recovery.
Possible Cause:
Mainly, foam undergoes closed-cell formation.
Solutions:
Reduce tin usage.
Reduce silicone oil usage.
Increase gas injection.
Increase mixing head speed and decrease mixing head pressure.
8.Issue: Coarse foam pores.
Possible Causes:
Insufficient nucleation centers in foam formation, insufficient input energy.
Solutions:
Appropriately increase silicone oil usage.
Increase mixing head speed and decrease mixing head pressure.
Increase gas injection.
