Nylon and polyester thread are both synthetic fibers, but they differ in strength, elasticity, and application. Nylon thread is more elastic and has greater flexibility, making it ideal for stretchy fabrics like swimwear, dancewear, and athletic clothing where the thread needs to move with the fabric. It's also stronger under tension and resists abrasion well. However, nylon can weaken when exposed to sunlight over extended periods and may degrade in humid conditions.
Polyester thread is less elastic but more stable overall, offering excellent resistance to shrinkage, moisture, and UV damage. It holds its strength better in outdoor applications and doesn't deteriorate as quickly in sunlight or damp environments. Polyester is generally preferred for general-purpose sewing, quilting, embroidery, and outdoor gear because of its durability and color retention. It also works well at higher temperatures without degrading.
In terms of cost, polyester is typically cheaper and more widely available. Nylon tends to be pricier but worth the investment for projects requiring stretch and flexibility. For appearance, polyester threads often have a wider color range and maintain their sheen better over time. Nylon may appear slightly duller or develop a matte finish after washing and wear. When threading a needle, nylon can be harder to work with because its elasticity makes it want to spring back, while polyester is more predictable. Choose nylon for garments needing movement and flexibility, polyester for durability and stability in most other sewing projects.