A gasket looks like the simplest part of your pack and behaves like the most demanding. It has to squash, recover, resist your product chemically and survive whatever temperature your process puts through it.
The 4 Gasket Materials You Will Be Offered
| Material | What it survives | Where it lets you down |
|---|---|---|
| Silicone | Wide temperature range, hot fill, repeated compression. | Costs more, and can absorb strong aromas over a long shelf life. |
| EPDM | Steam, water, acids and alkalis at moderate temperature. | Swells in oils and fats, so it rules out oily fills. |
| Natural rubber | Ambient dry and wet goods, and it is inexpensive. | Takes a permanent set with heat, and ages in ultraviolet light. |
| Cured plastisol | Vacuum jars and twist-off lugs, flowed in and heat cured. | Needs a metal cap, so it is not an option on plastic closures. |
How Compression Set Decides Your Shelf Life
Every gasket compresses under the closure. What separates a good one is whether it springs back when you open the pack, and the measure for that is compression set.
A material with a high set stays flattened. Your first opening then leaves a gasket that no longer fills the sealing surface, so a reusable 750 ml (25 oz) swing-top loses its seal on the second use even though nothing looks damaged.
Where Your Glass Finish Comes In
The gasket seals against your finish, so the finish decides how hard that job is. A flat, round sealing surface with tight height tolerance lets a softer gasket work; an uneven one demands a thicker gasket and more clamping force.
SGSBOTTLE gauges sealing surfaces on all 14 lines in Shandong and Xuzhou, and the tolerance sits on the drawing your closure supplier uses. That drawing is what lets a gasket be specified once and repeated.
Clip-top and swing-top packs seal on a replaceable ring. SGSBOTTLE holds the finish across 14 lines in Shandong and Xuzhou.
Match the Gasket to Your Chemistry First
Match the compound to your product first and to cost second. Oils, essential oils and solvents are the usual killers, and they work slowly enough that a short trial misses the failure entirely.
Run an accelerated hold with your real fill at a raised temperature, then inspect the gasket rather than just the seal. Swelling, hardening and discoloration all tell you what will happen to a 330 ml (11 oz) bottle sitting in a warehouse through a summer.
What to Write on Your Specification
Name the material, the shore hardness, the cross-section, the food-contact declaration and the fill it was tested against. Add whether the pack is reusable, since that turns compression set from a detail into the main criterion.
What Goes on Your Enquiry
Your fill and its temperature, the format in ml and oz, the closure type, and whether your customer reuses the pack. SGSBOTTLE comes back with the finish drawing, its sealing-surface tolerance and samples for a gasket trial with your product.