The aim of the research project 3Dknit is to develop a new type of upholstered seat cover material based on 3D weft knitted fabrics that ensures permanent compressive elasticity, low wear and good physiological comfort properties. The objective is to produce an upholstered seat cover material (e.g. for public transport or furniture applications) made of only one material type for good recyclability. These three-dimensional textile structures should offer better climate physiological properties in terms of thermal conductivity, air permeability, moisture absorption and moisture dissipation compared to polyester and polyether foams.

Currently, pressure-elastic seat covers predominantly consist of foam-laminated products. These cost-effective polyurethanes (PUR) based structures are usually flame-laminated. The flame-lamination provides good processing qualities. But this technology is highly criticized for environmental reasons such as toxic emissions (i.e. hydrogen cyanide) during processing and the process-related CO₂ balance. Therefore, from an environmental point of view a material substitution by textile structures should be strived for. The focus will be on the development of 3D weft knitted constructions.

General goal is the development of a material which is characterised by an increasing performance, customer satisfaction, prolonged service life, easy cleaning and high recyclability. Expected results are enhanced comfort properties, ecologically laminated product which is cleanable and recyclable as well as a faster and customer-individual production.

In this project different types of 3D weft knitted fabrics in the application field of upholstered seat covers will be developed. Therefore, different production methods (flat knitting and circular knitting technologies) will be used. STFI will develop materials produced by the flat knitting machines and SINTEX a.s. will research on 3D fabrics formed by circular knitting machines. Both technologies will be compared according to economic and application-specific aspects.

In the research project the lamination and finishing of these pressure-elastic substrates while maintaining the specific shape and cushioning function is investigated. In this case an environmentally friendly alternative to the currently used flame lamination of PUR foam is examined. Therefore, the 3D knitted fabrics shall be laminated using hot melt adhesives. Main tasks of this project part are the lamination and finishing of these pressure-elastic substrates while maintaining the specific shape and cushioning function. The challenge here is to preserve the mechanical and climate physiological properties.

The project is positioned in the conflicted area between the substitution of ecologically questionable but industrially established products and the application of recyclable but more expensive textile structures. Here costs and benefits in terms of price, recyclability, achievable performance characteristics and usage behaviour must be compared and correlated. The 3D weft knitted fabrics are in direct competition to other 3D textiles or the commercially used laminates based on foams. For high-priced applications, warp knitted spacer fabrics and voluminous nonwovens are already established on the market. By using the 3D weft knitting technology shorter set-up times and lower mechanical effort are needed comparable to the warp knitting technology.

The 3D weft knitted fabrics offer a variety of pattern options due to the flexible individual needle selection, for example in flat knitting. Compared to 3D warp knitted fabrics 3D weft knitted structures allow a change of the pile thread material in the same fabric during the production run. Additionally, using weft knitting technology it can be worked directly from the creel and warp beams are not required.

Furthermore, the weft knitting is more efficient because the technology allows the production of large fabric widths already with one single spool. Another economic advantage of the flat knitting materials is in contrast to three-dimensional nonwoven fabrics (e.g., stitch-bonded nonwovens) is the feasibility of customized production with batch-size 1 or small series. With the flat knitting technology different designs and contoured structures can be realized.

2022

Handout Gültner, M.; Große, A.: „3Dknit – Neuartige Bezugsstoffe aus strukturierten, voluminösen 3D-Gestricken“, Sächsisches Textilforschungsinstitut e.V., Chemnitz, 2022