Low melt fiber, also known as low melting point fiber or thermobonding fiber, is one of the most important specialty fibers in the global non-woven and hygiene products industry. Unlike conventional polyester staple fiber that melts at approximately 260 degrees Celsius, low melt fiber is engineered with a sheath layer that softens and activates at significantly lower temperatures — typically between 110 and 180 degrees Celsius. This unique property allows it to function as a thermal bonding agent, replacing chemical adhesives in a wide range of applications.

The demand for low melt fiber has grown substantially over the past decade, driven by three converging forces: the global expansion of the hygiene products market (baby diapers, feminine care, adult incontinence), the increasing adoption of thermal bonding in non-woven fabric production, and the tightening of environmental regulations that restrict the use of solvent-based adhesives. As a result, low melt fiber has moved from a niche specialty product to a mainstream raw material that every non-woven manufacturer and hygiene product brand must understand.

This article provides an in-depth exploration of low melt fiber technology, its classification, physical specifications, applications across non-woven and hygiene sectors, processing considerations, quality benchmarks, and sourcing guidance — with a particular focus on what buyers need to know when evaluating suppliers.

Low melt fiber belongs to the family of bicomponent fibers. A bicomponent fiber consists of two different polymer components arranged in a specific cross-sectional configuration. In low melt fiber, the two components are selected to have different melting points:

• The sheath (outer layer) is made from a copolymer polyester or polyethylene with a low melting point, typically in the range of 110 to 180 degrees Celsius.
• The core (inner layer) is made from standard polyester with a normal melting point of approximately 250 to 260 degrees Celsius.

When heat is applied during processing — whether through hot-air through-air bonding, calender roll bonding, or ultrasonic bonding — the sheath softens and flows while the core maintains its structural integrity. Upon cooling, the molten sheath resolidifies, creating strong, durable bonds at fiber crossover points throughout the web. This mechanism is what makes low melt fiber such an effective thermal bonding agent.

The key advantage of this technology is that it enables binder-free non-woven production. Chemical binders often introduce unwanted stiffness, reduce breathability, leave residual odors, and raise environmental and health concerns. Thermal bonding with low melt fiber eliminates these drawbacks while delivering consistent bond strength, soft hand feel, and excellent processability.

Low melt fibers are classified by their cross-sectional structure, sheath material, melting point range, and end-use application. The following table summarizes the main types:

The most widely used type in hygiene applications is the PE/PET ES fiber, where “ES" stands for the polyethylene sheath and polyester core combination. This type offers the lowest activation temperature, making it ideal for heat-sensitive applications such as diaper top sheets and feminine care products where substrate materials cannot withstand high processing temperatures.

Co-PET/PET fibers, sometimes called “low-melt polyester," use a copolymerized polyester sheath rather than polyethylene. Their higher melting point range makes them suitable for applications that require higher thermal resistance in the finished product, such as automotive interior padding, sound insulation, and mattress components.

Guangzhou Octopus Fiber Co., Ltd. manufactures both ES fiber for sanitary products and low-melt polyester fiber across a full range of specifications. The company offers ES fiber in deniers from 1.5D to 6D and lengths from 38 mm to 51 mm, as well as low-melt polyester fiber in deniers from 2D to 15D and lengths from 51 mm to 64 mm. All products are available in raw white, off-white, black, and customizable colors, and carry SGS, OEKO-TEX, ITS, and GRS certifications.

Understanding the detailed specifications of low melt fiber is essential for selecting the right product for your application. The following table provides a detailed specification comparison across the common variants:

Several specifications deserve special attention:

Sheath-to-Core Ratio: This ratio determines how much bonding material is available. A higher sheath ratio (40–50%) provides stronger bonds but may reduce fiber strength and increase cost. Most standard applications use a 30–40% sheath ratio.

Melting Point Selection: The sheath melting point must be compatible with your processing equipment and substrate materials. If your thermal bonding oven operates at 140–150°C, a PE/PET ES fiber with a 110–130°C sheath will activate fully. However, if the finished product will be exposed to high temperatures during use (such as automotive interiors), a Co-PET/PET fiber with a 160°C sheath may be more appropriate to prevent bond failure.

Denier and Cut Length: Finer deniers (1.5D–2D) produce softer, more flexible non-wovens suitable for hygiene product contact layers. Medium deniers (4D–6D) offer a balance of softness and strength for general-purpose non-wovens and interlinings. Coarser deniers (7D–15D) provide higher bulk and resilience for padding, sound insulation, and automotive applications.

Non-woven fabrics account for the largest share of low melt fiber consumption globally. The following sections examine the major non-woven application areas in detail.

Thermal bonding is the primary processing method for low melt fiber in non-woven production. In this process, a blend of low melt fiber and carrier fiber (typically regular polyester or polypropylene) is carded or air-laid into a web, then passed through a thermal bonding oven or between heated calender rolls. The low melt fiber sheath softens, flows to fiber crossover points, and upon cooling forms strong bonds that hold the web together.

The blending ratio of low melt fiber to carrier fiber is critical and varies by application:

Guangzhou Octopus Fiber Co., Ltd. provides a complete product range for non-woven applications. The company’s low-melt polyester fiber in 2D to 15D with 51 mm and 64 mm cut lengths is specifically designed for thermal bonding in non-woven production. Its 4D * 51 mm hydrophilic polyester staple fiber is engineered for hot-air non-woven fabrics used in clothing and industrial applications, featuring low crimp and non-siliconized finish for optimal thermal bonding performance.

Through-air bonding (also called hot-air bonding) is widely used for medium-to-high bulk non-wovens. In this method, heated air is forced through the fiber web in a conveyor oven. The low melt fiber sheath softens uniformly throughout the web thickness, creating three-dimensional bonding that preserves loft and bulk.

This method is particularly important for hygiene products because it produces soft, breathable fabrics with excellent drape and hand feel — critical qualities for diaper top sheets, feminine care cover stocks, and adult incontinence products.

Key processing parameters for through-air bonding with low melt fiber include:

Calender bonding uses heated rollers to compress and bond the fiber web. The low melt fiber sheath softens under the combined effect of heat and pressure, creating point bonds or area bonds depending on the roll pattern. Calender bonding produces thinner, denser fabrics compared to through-air bonding, making it suitable for interlinings, backsheet materials, and technical non-wovens where thickness control is critical.

In needle-punched and stitch-bonded non-wovens, low melt fiber is added as a supplementary binder to enhance dimensional stability and tensile strength. After mechanical entanglement, the web is passed through a thermal activation stage where the low melt component creates additional adhesive bonds at fiber crossover points. This combination of mechanical and thermal bonding produces fabrics with superior strength and durability, widely used in geotextiles, automotive trunk liners, carpet backing, and furniture backing.