What is lycra fabric ? Why lycra fabric need to heat set?

Lycra is a brand name for spandex fiber, which is a synthetic polymer that is known for its exceptional elasticity. Lycra/spandex is commonly used in a variety of garments, including athletic wear, swimwear, and lingerie, as it allows the fabric to stretch and conform to the body.

Ly fabric heatset

Ly fabric heatset

The fabric is lightweight, smooth, and breathable, and it retains its shape even after multiple washes. Lycra is often blended with other fibers such as cotton, polyester, and nylon to enhance the properties of the fabric. Lycra fabric is a popular choice for clothing that requires a high degree of stretch and flexibility.

Why lycra fabric need to heat set

Lycra is a type of synthetic fabric made from spandex fibers that provide stretch and elasticity to the fabric. Heat setting is a process used to stabilize and set the stretch in the Lycra fabric.

During the heat setting process, the fabric is subjected to high temperatures, typically between 300-350°F (149-177°C), for a specified amount of time. This heat helps the fibers to bond together and set the fabric in its stretched position. This results in the fabric retaining its shape and elasticity even after multiple washings and wearing.

Heat setting is an essential step in the production of Lycra fabric because it helps to ensure the fabric’s durability and longevity. Without heat setting, the fabric would lose its elasticity over time and become less comfortable to wear.

Additionally, heat setting can also help to prevent the fabric from shrinking or distorting during subsequent washes or exposure to high temperatures. This is particularly important for Lycra fabric used in active wear, where the fabric is exposed to a lot of stress and strain.

Heat setting is a crucial step in the production of Lycra fabric, helping to ensure its quality, durability, and performance.

Different types of weft knit fabric used in garments industries
Different types of knit fabric faults

Why used lycra in knit fabric

Lycra is commonly used in knit fabrics for a variety of reasons, including:

Stretch and flexibility:

Lycra is a synthetic fiber known for its exceptional stretch and recovery properties. When blended with other fibers in knit fabrics, Lycra provides a high degree of stretch and flexibility, making the resulting fabric ideal for garments that need to move and stretch with the wearer’s body.

Shape retention:

Lycra’s stretch and recovery properties also help knit fabrics retain their shape over time. Garments made with Lycra can maintain their fit and shape, even after multiple washings and wearing’s.


Lycra is known for its soft and smooth texture, which makes it comfortable to wear against the skin. In knit fabrics, the combination of Lycra with other fibers can create a lightweight and breathable fabric that is comfortable for extended periods of wear.


Lycra is a durable fiber that can withstand repeated use and washing. When blended with other fibers in knit fabrics, Lycra can help increase the fabric’s overall durability and longevity.


Lycra can be blended with a variety of other fibers to create knit fabrics with different characteristics and properties. This versatility makes it a popular choice for a wide range of garments, including athletic wear, swimwear, lingerie, and more.

The combination of stretch, shape retention, comfort, durability, and versatility make Lycra a popular choice for knit fabrics in a variety of applications.

How to used lycra in knit fabric 

Knit fabric made with Lycra typically has a structure that is formed through the interlocking of spandex fibers with other fibers in a circular or warp-knit construction.

The specific structure of the knit fabric may vary depending on the particular knit pattern and composition of the fibers used, but some common characteristics include:

Interlocking loops:

Knit fabrics are made by interlocking loops of yarn, and in Lycra knits, spandex fibers are often used to create these loops. The spandex fibers are stretched during the knitting process, which helps to provide the fabric with its stretch and recovery properties.

Horizontal stretch:

Knit fabrics with Lycra typically have a significant amount of horizontal stretch due to the nature of the knit construction. The spandex fibers allow the fabric to stretch and recover in the width of the fabric, providing flexibility and ease of movement.

Smooth surface:

Knit fabrics with Lycra often have a smooth surface that is free of wrinkles or creases. This is due to the way the fibers are interlocked during the knitting process, which helps to create a flat, even surface.

Comfortable fit:

The combination of spandex and other fibers in knit fabrics with Lycra provides a comfortable and snug fit that moves with the body. This makes them ideal for use in athletic wear, swimwear, and other garments where a close, flexible fit is desired.

Knit fabrics made with Lycra are known for their stretch, comfort, and durability, making them a popular choice for a wide range of garments and applications.