The Application of Elastic Materials in Sanitary Products And Their Impact on Product Performance

The Development Direction of Sanitary Products

The primary development direction of sanitary products is to achieve optimal performance and the best fit. The baby diaper market is a prime example of this trend. Diaper products have been evolving towards this direction. Both baby diapers and adult incontinence products should allow wearers to move freely while ensuring comfort and maximum care. Initially, sanitary products were manufactured without elastic materials, resulting in a hard texture and poor fit. As consumer focus shifted from pure functionality to wearing comfort and user-friendliness, the technology of elastic materials has been continuously improving.

Requirements for Nonwoven Fabrics in Sanitary Products

The performance requirements for nonwoven fabrics used in sanitary products, especially their elongation, have a decisive impact on the elasticity of the finished product. The production of diaper tabs and their fixation on diapers also have specific requirements for elastic materials. From a technical perspective of various materials used in diapers, it is a very complex product that constantly presents new challenges and opportunities for nonwoven fabric manufacturers.

Elastic Bridge Materials and Elastic Side Closure Components

The application of elastic bridge materials in closures was the first step in using elastic materials. These elastic bridge materials consist of elastic films that ensure stretchability and strength, with both sides laminated to heat-bonded nonwoven fabrics that can be stretched horizontally. The nonwoven fabrics provide the elastic material with strength and a textile-like feel. Figure 1 illustrates the structure of elastic bridge materials in diaper closures.

Elastic bridge materials are often used in combination with other elastic materials, such as the elastic waistband at the back of diapers. Previously, these materials were mainly used in the leg cuff areas of diapers.

Evaluation of Elastic Material Performance

A specific tensile force is applied to stretch the material, and data from two cycles of the test are taken. The most commonly used tensile force is 10N, which is the typical force exerted on diapers during wearing. Theoretically, the tensile curve should be as flat as possible, indicating minimal contraction force during stretching. Additionally, the two final curves should be as consistent as possible. Consistent curve height indicates that repeated stretching does not damage the material, ensuring a good fit. It also shows that during the second and any subsequent stretching processes, the material achieves the same elongation at a certain tensile force. After each stretching cycle, the so-called permanent deformation is also measured. Permanent deformation indicates the extent to which the material returns to its original size. Elastic materials should theoretically have low permanent deformation. Figure 2 shows the hysteresis during the first and second stretching cycles of bridge materials and the permanent deformation.

Optimization of Diaper Tabs

To enhance the elastic effect of closures in adult and baby diapers, the so-called diaper tabs were invented. Previously, diaper closure systems used narrow elastic bridge materials fixed to the diaper body. Diaper tabs expand the elastic area, further improving fit and comfort. During the production of diaper tabs, the basic structure of elastic bridge materials remains unchanged, with elastic films laminated to nonwoven fabrics on both sides. Figure 3 shows the structure of diaper tabs.

In this composite material, a larger quantity of nonwoven fabric is used, and both the elastic film and nonwoven fabric are lighter. At the same time, higher requirements are placed on the materials. In diapers, the entire tab must withstand a greater tensile force of 25～30N. Therefore, very strong stretchable nonwoven fabrics are required. Generally, diaper manufacturers are responsible for attaching the tabs to the diaper body. Thus, the production process requirements are strict. The average speed of diaper production lines has reached about 1,000 pieces per minute. Therefore, in diaper production, tabs must be fixed and folded at high speeds. Additionally, high strength of the tabs is essential. To attach the tabs to the diaper body and fix the closure tape on the tabs, the side edges of the tabs must be non-stretchable and have high tensile strength, i.e., a zoned structure. Figure 4 is a stretchable composite material with adhesive strips.

Testing the Elastic Tensile Properties of Nonwoven Fabrics

The elastic tensile properties of nonwoven fabrics are tested by determining their stress-strain curves. The nonwoven fabric is clamped at both ends, stretched vigorously until broken, and then the elongation and tensile force required are measured. Theoretically, nonwoven elastic materials should have greater stretchability under smaller tensile forces.

Improved Elastic Materials: Higher Elasticity, Lower Activation Requirements

Further improved stretchable nonwoven fabrics for sanitary products use ultra-thin thermal-bonded materials with higher elastic stretchability, thus requiring lower activation. The tab structure containing elastic films has proven its effectiveness and has become the basis for elastic structures. Figure 5 shows the stress-strain curve of the improved thermal-bonded nonwoven fabric used as elastic material.

High-Elongation and High-Strength Spunlace Nonwoven Fabrics

A further development of elastic materials for sanitary products is the use of Spunlace nonwoven fabrics. Due to their unique production technology, Spunlace nonwoven fabrics have high elongation and tensile strength. A small tensile force can achieve high elongation, making diapers more convenient to use and more comfortable to wear.

Advantages of Spunlace Nonwoven Fabrics

Furthermore, due to the high tensile strength of Spunlace nonwoven fabrics, a lower basis weight of film can be used to provide stretching functions. This reduces raw material usage and correspondingly decreases post-use waste. Spunlace nonwoven fabrics also make diaper tabs fluffier and give them a more textile-like feel, providing manufacturers with more raw material options. In addition to commonly used polypropylene, polyester and polyester-polypropylene blends can also be used. Considering sustainable development, polylactic acid produced from lactic acid and renewable resources can also be promoted.

Spunlace-Meltblown Nonwoven Composite Materials — Enhancing Value at a Lower Cost

Using modern production technologies, meltblown nonwoven fabrics can be used as the core layer of elastic materials, with Spunlace nonwoven fabrics laminated on both sides.

Compared to composite materials containing elastic films, this elastic material with a textile-like feel is breathable and more comfortable to wear. Moreover, the materials are laminated without adhesives, integrating during the production process. Therefore, this nonwoven fabric is ideal for manufacturing adult incontinence products: its breathability allows wearers to forget they are using incontinence diapers.

Figure 7 shows a comparison of the hysteresis test results of the second stretching cycle of the stretchable Spunlace-meltblown-Spunlace nonwoven composite material with the standard hysteresis curve.

This composite material is currently under development and is being prepared for use in other elastic products. This further demonstrates that the product portfolio of elastic nonwoven fabrics is expanding. However, when used for baby diaper tabs, this composite material still exhibits significant permanent deformation. Figure 7 shows the gap between the permanent deformation of standard products and that of this nonwoven composite material.

Despite this, the composite material still has great potential. This further proves that the development of elastic materials in sanitary products has not reached its peak. In the rapidly developing and continuously innovating nonwoven industry, the next technological advancement may be just around the corner.