1、 VDA Test Sheet April 2005 Automotive Leather Determination loose grain effect VDA 230-205 Continued on pages 2 to 4 VERBAND DER AUTOMOBILINDUSTRIE E. V. (VDA) Westendstrae 61 60325 Frankfurt Distribution: DOKUMENTATION KRAFTFAHRTWESEN E.V. (DKF) Ulrichstrae 14, D-74321 Bietigheim-Bissingen Foreword
2、 This standard method was prepared by the VDA leather working group in collaboration with the leather industry, the chemical industry and test laboratories. 1. Scope This test method is used to determine the loose grain effect of automotive leather. The method is applicable to non laminated leather
3、up to a thickness of 2,0 mm as well as laminated leather up to a total thickness of 5 mm. Additionally; a root cause analysis procedure is described for test samples showing grain varia-tions. Note: In the event of conflict between the German and English language, the German language shall take prec
4、edence. 2. Normative references ISO 2589 (2002-12): Leather Physical and mechanical tests Determination of thickness 3. Principle The leather under test is bent concave over a defined radius using a half pipe (Halpi). The result-ing wrinkling of the grain is compared with photographs of a standard l
5、eather under test condi-tions. A pentamerous rating scale is used for assessing the samples. page 2 VDA 230-205 April 2005 4. Terms and definitions Loose grain effect Visible wrinkling of the grain side of laminated leather during a concave bend is called loose grain effect. This wrinkling can be ca
6、used by the following: y The leather has a loose grain. y The leather has a loose fibre structure which is fixed by the lamination of the flesh side. This fixation results in vertical tension when concavely bent. The result is wrinkling of the grain layer. y When concavely bent the laminated materia
7、l is subjected to vertical tension. As a result rough wrinkles are visible. Loose grain A loose grain leather is characterised by a grain layer sitting loose on the lower leather layers due to insufficient binding. Under bending (concave to the flesh side) the grain layer of non-laminated leather pa
8、rtly or completely separates from the remaining leather hide thus causing wrinkles on the leather surface when bent. 5. Apparatus and materials 5.1 Standard metal half pipe (length 300 mm, inner diameter 36 mm, outer diameter 40 mm), the outer diameter is for reference only, dependent upon the metho
9、d of pipe manufacture, and two appending fixation rolls (length 71 mm, outer diameter 32 mm, mass 210 5 g) 5.2 Large metal half pipe (length 300 mm, inner diameter 74 mm, outer diameter 77 mm) ,the outer diameter is for reference only, dependent upon the method of pipe manufacture and two appending
10、fixation rolls (length 71 mm, outer diameter 64 mm). 5.3 Standard metal ring (inner diameter 36 mm, height 20 mm). 5.4 Large metal ring (inner diameter 74 mm, height 20 mm). 5.5 Single sided adhesive tape with the following properties: 50 mm width, carrier; transparent PVC, total thickness approxima
11、te 65 m, adhesive strength to steel approximately 3.0 to 3.5 N/cm, tearing force approximately 60 N/cm, elongation at break approximately 60 %. 5.6 Sharp scissors and razor blades. 5.7 Light microscope. 6. Sampling For procedure A described in 7.1, two (2) test samples (one longitudinal and one tran
12、sversal to the line of the back bone), of dimension 300 x 55 mm size are taken from the leather. The test samples shall be taken from the middle third, between neck and tail of the hide and shall be minimum 5 cm away from the line of the back bone. For outgoing or incoming inspection (non-destructiv
13、e testing) the test may be performed on com-plete hides. The adhesive tape shall be applied on the relevant position on the flesh side of the hide. For procedure B described in 7.2, two (2) test samples of dimension 300 x 100 mm are taken per-pendicularly to each other from the laminated leather. If
14、 the direction of the line of the back bone is unknown, test sample preparation is oriented on the part geometry. page 3 VDA 230-205 April 2005 7. Procedure 7.1 Determination of loose grain effect of non laminated leather Procedure A Place the test samples (section 6) with the grain side downwards o
15、n a smooth plane base. Then laminate one half of the test sample (150 mm) on the flesh side with the adhesive tape (section 5.5) starting from the middle of the test sample to outwards. To achieve a steady down force during this lamination one of the fixation rolls (section 5.1) is rolled over the a
16、dhesive tape without addi-tional pressure. No tension shall appear within the leather. adhesive tape fixation rollleather flesh side leather grain side Place the adhesive tape laminated leather with the grain side upwards into the standard half pipe (section 5.1). Install the leather in the intended
17、 position by placing the fixation rolls on top (flush-fitted with the ends of the half pipe). Evaluate the wrinkling of the leather surface in the area of the adhesive tape as well as in the non laminated area according to the photo standard scale (appendix A). In addition, note any irregulari-ties
18、which are not described in the rating scale. Evaluation of non laminated leather results in four rating values: lo - longitudinal direction, without lamination lm - longitudinal direction, with lamination qo - transversal direction, without lamination qm transversal direction, with lamination Commen
19、t: abbreviations have German origin 7.2 Determination of loose grain effect of laminated leather Procedure B Place both test samples with dimensions of 300 x 100 mm (section 6) into the large half pipe (sec-tion 5.2) without any additional lamination with adhesive tape. Install the leather in the in
20、tended position by placing the fixation rolls on top (flush-fitted with the ends of the half pipe). Evaluate the wrinkling of the leather surface according to the photo standard scale for laminated leather (ap-pendix B). Evaluation of laminated leather results in two rating values: lk - longitudinal
21、 direction qk - transversal direction Comment: abbreviations have German origin page 4 VDA 230-205 April 2005 8. Test report The test report shall contain the following: y Reference to this standard, including the method used (e.g. VDA 230-205 A) y Exact description of the test sample including all
22、relevant information y The resulting values using the abbreviations y All observations not defined in the rating scale y Deviations to this standard y If applicable, notes, which resulted from root cause analysis for problematic test pieces. 9. Remarks If test samples have a poor rating, the root ca
23、use shall be analysed. The cause of failure varies considerably (see definitions in section 4). The following procedures are used for the analysis: 9.1 Procedure for non-laminated leather Select the poorest of the two test sample (longitudinal or transversal). Cut two strips of 10 mm width from the
24、selected test sample (one from the area with the adhesive tape, one from the area without adhesive tape). Calculate the required strip length with the following equation: L = (inner diameter of metal ring 36 mm 2 x thickness of leather) * Cut the strips to the determined length. Ensure that one of t
25、he longitudinal edges of each strip is cut smoothly and accurately at right angle. Use the razor blade to achieve such a longitudinal edge. Place both strips into the standard metal ring. The grain side of the strips shall show to the centre of the ring. The smooth edge of the strips shall be flush-
26、fitted to the metal ring edge. This position ensures the same bending of the strips as the test sample during testing according to section 7.1. Areas in which wrinkling occurs are determined by a microscope. If the leather without adhesive tape is separated from the lower fibre structure then the le
27、ather has a loose grain layer. If the fibre structure on the flesh side of the leather with adhesive tape is vertically expanded, a loose fibre structure combined with fixation of the flesh side by the adhesive tape is responsible for the ob-served loose grain effect. 9.2 Procedure for laminated lea
28、ther For laminated leather the procedure is in general the same as in section 6.3.1, with the following deviations. The large metal ring (section 5.4) is used. The width of the test sample shall be 20 mm. The length is calculated as: L = (inner diameter of metal ring 74 mm 2 x total thickness) * If
29、a vertical tension of the laminate is visible in addition to the tension of the leather fibre structure under the microscope, the laminate material is not well tuned to the leather application. Appendix: Appendix A: Rating scale for non-laminated leather Appendix B: Rating scale for laminated leathe
30、r (The adhesive tape, Tesapack 4124, was used to fix the flesh side of the leather samples shown in the rating scale.) Determination of loose grain effect VDA 230-205 Annex A: For non laminated leather rating 5 rating 4 rating 3 rating 2 rating scale rating 1 Determination of loose grain effect VDA 230-205 Annex B: For laminated leather rating 5 rating 4 rating 3 rating 2 rating scale rating 1
