Short answer: A coil zipper, also called a nylon zipper, is built from a continuous plastic filament wound into a spiral and sewn onto a tape. The spiral forms the teeth. It is light, flexible, smooth to operate and inexpensive, which makes it the most common closure on sportswear, bags, bedding and light outerwear.
Coil zips dominate casual and performance clothing for good reasons. They bend around curves without kinking, they do not corrode, they accept dye well and they cost less than metal or moulded chains. The trade-off is strength: a coil chain is not designed for heavy lateral load, and it is sensitive to heat.
Detailed Explanation
The manufacturing process starts with a monofilament, usually nylon 6 or polyester, extruded to a precise diameter. The filament is wound into a helix and then either woven into the tape during weaving or sewn on afterwards. The pitch of the helix sets the tooth spacing, and the filament diameter sets the size. A #3 coil uses a finer filament than a #5, and the chain is correspondingly narrower and weaker.
Dyeing is a two-step affair. The tape is dyed as a woven product, and the filament is dyed before or after forming, depending on the process. Matching the tape and the coil is one of the harder parts of coil production, which is why colour consistency between lots is a standard quality requirement. A slight mismatch is visible on light colours and is a frequent cause of rejections.
The slider is matched to the coil profile. Coil sliders have a curved channel that gathers the spiral and interlocks it. An auto-lock slider adds a spring that pins the pull in place, which is why coil zips on jackets rarely creep open. A non-lock slider is used where the zip is opened often, such as on a bag pocket.
Flexibility is the coil's great advantage. It can follow a curved seam, it folds without permanent deformation and it is comfortable against the skin, which is why it is used on neck openings and cuffs. The weakness is heat: ironing directly on a coil will deform the filament, and tumble drying at high temperature can shorten the zip's life.
Colour flexibility is another reason coil dominates fashion. The filament takes dye readily, so a coil can be matched to almost any reference in the Pantone book, and the low tooling cost makes short runs viable. A metal or moulded chain would require a minimum order that many fast-fashion styles cannot support, which is why seasonal colour programmes almost always start with coil.
Comparison
| Property | Coil zip | Moulded plastic zip | Metal zip |
|---|---|---|---|
| Weight | Light | Medium | Heavy |
| Flexibility | Very high | Moderate | Low |
| Strength | Moderate | High | Very high |
| Corrosion | None | None | Possible on cheap plating |
| Heat resistance | Low | Medium | High |
| Relative cost | Lowest | Medium | Highest |
The comparison explains why coil is rarely used on denim flies or heavy luggage, and why metal is rarely used on leggings. Each family wins in a different part of the garment range.
How to Choose
Use coil for light and mid-weight fabrics, for curved seams, for garments that are washed frequently, and wherever comfort against the skin matters. Choose #3 for dresses, linings and pockets, #5 for jackets and bags, and #8 or #10 for heavy soft goods where a moulded chain is not required.
Consider a reverse coil where the face of the tape is visible and a clean look is needed. Consider a waterproof coated coil for light outdoor use. Avoid coil on garments that will be ironed directly over the zip or dried at high temperature.
Check the tape and coil colour match on a physical sample, not on a screen. Ask for the filament type, because nylon and polyester behave differently in dyeing and in heat. Donglong Zipper produces coil chains in matched tape and element colours and can supply the colour standard for approval.
Common Mistakes
Ironing over a coil is the most common cause of a deformed chain. The second is using a #3 coil on a bag that will be loaded heavily, where the chain spreads and the slider jams. The third is assuming that all coil zips are nylon; polyester coil is common and has different heat behaviour.
Buyers also forget the slider. A cheap slider on a good coil chain is the weakest link, and it is the part most likely to be copied. Specify the slider code, not just the chain size. Finally, check the tape width against the seam allowance, as with any zip.
FAQ Summary
- Continuous filament spiral: the defining feature of a coil zip.
- Light, flexible, smooth and low cost.
- Sizes from #2 to #10 in apparel, with #3 and #5 most common.
- Used on sportswear, bags, bedding and light outerwear.
- Avoid direct ironing and high-temperature drying.
Coil zips are the workhorse of the industry. They are not the strongest closure, but they are the most adaptable, and for the majority of garments the combination of flexibility, comfort and cost is hard to beat.