According to the hole structure: open cell foam, semi-open cell (independent) foam, closed cell foam (independent foam), microcellular foam.
According to the material: silicone foam, PU foam, EPDM sound-absorbing cotton, EPE pearl cotton, PVC foam, PE foam, PPP foam, CCR foam, EVA foam, XPE foam, IXPE foam, acrylic foam and so on.
Categorized by material:
- Polyethylene foam: PE foam (chemical crosslinking, electronic crosslinking), EVA foam.
- Polyester foam: polyether foam (chemical foaming, physical foaming), polyurethane foam.
- Rubber foam: CR foam (neoprene), NR foam (nitrile rubber), SBR foam (styrene butadiene rubber), EPDM foam (EPDM).
Classified by foam structure:
- Open cell foam: soft texture, high water absorption, high compression rate, suitable for sound-absorbing sealing applications, such as compression sponge for headphones, air-conditioning sealing strips.
- Closed cell foam: independent foaming, low compression residual rate, low water absorption, good heat insulation and cushioning performance, good dustproof, suitable for electronic products sealing and dustproof, waterproof shock absorption.
Cell phone industry applications are more closed-cell foam, and the material is mostly selected polyethylene, polyurethane, the current market is mostly used in the following company's products:
Usually, we use the following parameters:
- Density is an important measure of microcellular polyurethane foam, in general, the lower the density of the foam resilience is smaller, compression ratio is larger. More suitable for today's cell phone screen is making more and more big trends.
- Resilience (also known as CFD) is the foam in compression of a certain percentage, and to achieve mechanical equilibrium, after the application of a response to the force. The same foam, if the greater the compression ratio, the greater the resilience. In the actual use of foam, the foam has been in a certain proportion of compression. The greater the compression ratio, the greater the resilience, the better the sealing and protection effect, but too much compression may have an impact on the LCD screen display effect and chassis fixing.
- Therefore, the structural design related to foam is to let the foam maintain a suitable compression state, the elasticity loss is a measure of the foam aging performance parameters.
- High-end microcellular polyurethane foam and low-end high-end microcellular polyurethane foam in the aging resistance, there is a very big difference. The compression ratio is the ratio of the compressed part of the foam to the original thickness. The maximum compression ratio is to ensure that under the premise of normal use, the foam can be compressed at maximum thickness and the original thickness of the ratio.
