Many types of clothing and wearable products have cushioning materials that provide shock absorption and protection for the user. The newspaper Polymers considers weft or warp woven spacer textiles which have recently been used as a substitute for foam materials.
Wire path diagram of spacer fabric samples with inlaid tubes. Image credit: Yu, A., et al., Polymers
Spacer textiles have become a realistic choice due to their distinctive three-dimensional (3D) knitted construction, which allows for greater water and vapor permeability and improved breathability of the items. Shoes, sofas, car seats, rugs, beds, backpacks and other everyday items usually contain spacer textiles.
Padding fibers such as spacer fabrics can be reinforced by embedding substances in a connective layer of a material using a knitting procedure that improves the structure of the fabric. Compressive behavior is a crucial factor in evaluating whether a material can provide sufficient cushioning and “feel” for a variety of applications.
The compression characteristics of the polymeric foam can be altered by changing the composition and density to meet various applications. The spacer fabric is made up of two layers fused by the connecting layer of the spacer threads.
Any difference in the material properties of a spacer fabric and in the wearing comfort can have an impact. The thickness and compressive stiffness of the spacer fabric can be controlled by the width, composition, thickness, connection distance, pattern of the spacer threads and the angle of inclination.
Monofilament and multifilament yarns are often used as spacer yarns, and they can give the fabric completely different characteristics.
Numerous studies have been carried out on the compression characteristics of spacer textiles. One of the things that contributes to the compressive qualities is the elasticity and flexibility of the threads used in the top layer. It has been found that the amount of tucked-in stitches within the face layers has an impact on the compression characteristics of weft knitted spacer fabrics.
The compression characteristics of the spacer fabric, on the other hand, have been linked to the connection layer.
Composite materials with silicon-based components
Producing a thin fabric with high compressive strength and excellent energy absorption can be difficult when using a traditional spacer fabric structure. In order to improve the cushioning qualities of the spacer fabric, a composite construction containing additional silicone-based components was investigated.
Previously, a revolutionary sandwich construction with silicone tubes implanted into the connecting layer of the spacer fabric was produced. Silicone is a synthetic polymer with a silicon-oxygen primary strand. Silicone is flexible, fire resistant and chemically inert.
The setting of (a) tensile test and (b) compression test of tubular samples. Image credit: Yu, A., et al., Polymers
The silicone inlay tubes provide additional support towards the spacer structure, allowing the fabric to withstand the pre-stress of the skin without sacrificing its elasticity or energy absorbing qualities. Samples made using three types of silicone tubing materials were constructed and measured to further examine the influence of embedded materials on the qualities of the spacer fabric.
The displacement-force curves obtained from the compression test are represented by the force at 100% and 200% elongation of the tubes.
Silicone foam is in effect a porous viscous elastic polymer made up of foamed silicone rubbers. Silicone foam combines the qualities of silicone with those of foam, resulting in a lightweight product with high elasticity. The mechanical characteristics of the tube samples were evaluated, as well as the compression characteristics of the tissue samples and the connection between the two.
The implanted tubular materials significantly influence the compressive behavior of the spacer tissue. The inclusion of tubes embedded in the connective layer does not affect the compressive behavior of the spacer tissue, although at a starting compressive stress of 10%.
To reach the plateau stage, encrusted spacer fabrics require more force than standard spacer fabrics.
The compressive stress-strain curve of the material shows no noticeable plateau stage when an encrustation substance with higher tensile and compressive strength is used. Implanted spacer fabrics offer higher compressive strength and can collect more compressive energy than standard spacer fabrics.
The spacer fabric is effectively reinforced by the inlay of a ductile material such as silicone foam and silicone rods.
The compressive energy and toughness of the resulting textiles can be affected by various inlay materials with varying Young’s modulus and tensile behaviors. Since silicone foam also has lower tensile and compressive strength than silicone hollow tubes and silicone rods, the spacer tissue implanted with them can absorb more compressive energy.
The material samples exhibiting the ultimate compressive stiffness are the spacer tissues implanted with silicone rods, having high resistance to deformation and compression.
Relation between the Young’s modulus of the encrusted tube, (a) the compressive energy of the tissue samples, and (b) the deformation of the tissue at a stress of 60 kPa. Image credit: Yu, A., et al., Polymers
The results of this study may aid in the creation of synthetic fibers in the shape of a sandwich and in the improvement of wearable upholstery articles. Encrusted substances can be used as a new parameter to modify the compression and cushioning qualities of knitted spacer textiles, allowing the fabric to provide the energy absorption necessary for a variety of applications.
Yu, A., et al. (2021). Effect of silicone encrusted materials on enhancing the compressive strength of weft knitted spacer fabric for cushioning applications. Advanced textile-based polymer composites: synthesis, characterization and applications. October 22, 2021. https://www.mdpi.com/2073-4360/13/21/3645