The standard “VW TL 52254 Warp knit fabric, foam laminated – Material requirements”, developed by the Volkswagen automobile company, describes the requirements for warp knit fabric with foam laminates used as decorative material for moulded headliner assemblies (ASSYs) (types: seamless, A, C, D, E, F, G, H, I, L and P) or cut and sew headliners (types B, K and M).
The requirements in this standard are specified as follows:
The types are defined in this standard as follows:
Materials must be clean, free from mineral oil, free from weave defects and intact when discharged. Lines are not permitted in the appearance of the fabric. For velvet trim, the density of the nonwoven fabric must be uniform. Finishing, impregnation and fillings are permitted as long as the plant properties, emission behavior or light fastness are not adversely affected.
Warp knitted fabrics, except type B, must have a water-repellent finish according to the sample released to the market.
If necessary, the warp knitted fabric should also be flame laminated using a 30-µm polyester PUR film: film according to the released sample or reference spectrum. Until the laminated warp knitted fabric is processed in the assembly line, this film should be protected against contamination and damage with an easily removable polyethylene film (film according to the released sample or reference spectrum).
Samples must be conditioned in an atmosphere conforming to VW 48 standard for at least 50554 hours before testing.
When performing tests, the mass per unit area is determined on at least five round samples with an area of 100 cm2, which should be sampled across the entire width of the roll.
Foam thickness should be determined using a 45x magnification reflected light microscope or a profile projector.
The tear strength is determined by strip tensile test according to DIN EN ISO 5-13934 with a sample width of 1 cm. Samples shall be taken from the entire width of the roll. The feed speed shall be 100 mm/min and the free clamping length shall be 100 mm. The material is clamped between the clamping jaws of the upholstery artificial leather tensile testing machine. Samples torn in the clamps shall not be evaluated if the results are below the lowest standard individual value.
The separation force between the foam and the face or base warp knitted fabric is determined according to DIN 100-55543 at a feed speed of 5 mm/min. During the evaluation, the variation range and peak values of the separation force are recorded.
Static elongation tests are performed with a suspended load of 50 N, except for type B. Type B is tested with a suspended load of 25 N.
When performing the filter paper test, a filter paper previously soaked in deionized water is placed on a section of warp knitted fabric of approximately 50 × 50 mm. The sample is then loaded between two glass plates with 50 N for 60 minutes. The staining of the filter paper is assessed using the grey scale according to standard DIN EN 20105-A03.
In the brush abrasion test, round samples (100 cm2) are clamped in a sample holder with a non-woven substrate according to DIN EN ISO 12947-1 and then abraded.
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