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3.1.2 Sampling
The sampling area relevant to the material description of the PUR flexible foam has characteristics that are specific to the component and is therefore specified in the drawing. 3.2
Behavior with respect to upholstery cover material
Specimens with dimensions (70 x 70 x 30) mm, taken from any point on the PUR molded part, are covered as completely as possible with upholstery cover material. The covered specimen is positioned between two glass plates of 3 mm thickness and loaded with 100 g, including the upper glass plate.
This test setup is then aged for 300 h at elevated temperature of +90 °C in mechanically circulated air and for another 300 h in humid heat at +70 °C and (100 - 6)% relative humidity. After that, the specimen is evaluated. 3.3
Gross density (material density)
Determination acc. to DIN EN ISO 845. The preferable specimen dimensions are (70 x 70 x 30) mm.
Number of specimens: n = 5. 3.4
Compression set
Determination according to DIN EN ISO 1856, method A. Number of specimens: n = 5. Compression deformation: 50%. 3.5
Compression stress/compression stress change
Determination acc. to DIN EN ISO 3386-1; but compression by 60% performed 4 times. The preferable specimen dimensions are (70 x 70 x 30) mm. The 4th compression is recorded at 40% deformation of the PUR foam.
After humid aging at elevated temperature for 200 h at +90 °C and (100 - 6)% relative humidity, the st
1 compression can also be recorded at 40% deformation. Traverse speed: 100 mm/min, number of specimens: n = 5. 3.5.1
Calculation of the compression stress change
Fist, the compression stresses for the as-received condition and for the condition after aging at elevated temperature are determined in kPa.
Then, the stress change between the 4th compression after aging at elevated temperature and the 4th compression before aging at elevated temperature (as-received condition) is calculated using the following formula:
stress after−stress before [kPa]
×100 %
stress before [kPa]
Example:
5.36 [kPa]−6.48 [kPa]
×100 %=−17.28 %
6.48 [kPa]
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If the calculations result in a negative compression stress change, this means that the foam has become softer.A positive compression stress change means that the foam has become harder. 3.6
Tensile strength and elongation at break
Determination acc. to DIN EN ISO 1798, specimen A, but traverse speed 100 mm/min. A specimen with different dimensions in accordance with the shape of the components is permissible. 3.7
Deformation diagram (hysteresis) of the seat squab
A test machine according to DIN 51220 class 1 shall be used. The test is performed on a rigid, positively engaging backing.
The DIN 53579-1; representation see Appendix A.1
hysteresis characteristic values are recorded in the compression test according to A preliminary force. zero-point setting (displacement and load) is to be made after achieving the respective 3.7.1
Stamp XXI
Diameter 200 mm
Curvature radius 200 mm
Edge radius 5 mm
3.7.1.1 Procedure
Test direction perpendicular to the test point Test force acc. to drawing
Preliminary force Fv = 20 N where V = 100 mm/min Load force set cycle Fs = 600 N where V = 500 mm/min
Complete unloading of the foam (-15 mm from zero point) where V = 500 mm/min Preliminary force Fv = 20 N where V = 100 mm/min
Load force hysteresis Fh = 600 N where V = 100 mm/min
Unloading hysteresis where V = 100 mm/min
3.7.1.2 Evaluation of the hysteresis
Indentation depth EW [mm] Stress line, where Fb = 320 N
Damping characteristic value DKW [mm]
Difference of unloading line Fb = 320 N minus stress line Fb = 320 N
Spring travel (FW) [mm]
Difference of unloading line Fb = 480 N minus unloading line Fb = 320 N
3.7.1.3 Example of the indication of a foam hardness
EW XXI at 320 N: 46 mm according to PV 3410 Section 3.7 .
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3.8 Determination of the foam hardness on the finished part
A test machine according to DIN 51220 class 1 shall be used. The test is performed on a rigid, positively engaging backing.
Impression stamps according to DIN 53579-1 are used to record the measured values.
A zero-point setting (displacement and load) is to be made after achieving the respective preliminary force. 3.8.1
Stamp II for seat backrest
Diameter 112.8 mm Surface 100 cm2 Edge radius 1 mm
3.8.1.1 Procedure
Test direction perpendicular to the test point Test points according to drawing
Preliminary force Fv = 10 N where V = 100 mm/min Load force set cycle Fs = 150 N where V = 500 mm/min
Complete unloading of the foam (-15 mm from zero point) where V = 500 mm/min Preliminary force Fv = 10 N where V = 100 mm/min
Load force measuring cycle Fm = 120 N where V = 100 mm/min
3.8.1.2 Example of the indication of a foam hardness EW II at 120 N: 10 mm according to PV 3410 Section 3.8 . 3.8.2
Stamp XI for sides of seat and backrest
Hemisphere diameter 75 mm. 3.8.2.1 Procedure
Test direction perpendicular to the test point Test points according to drawing
Preliminary force Fv = 5 N where V = 100 mm/min Load force set cycle Fs = 80 N where V = 500 mm/min
Complete unloading of the foam (-15 mm from zero point) where V = 500 mm/min Preliminary force Fv = 5 N where V = 100 mm/min
Load force measuring cycle Fm = 50 N where V = 100 mm/min
3.8.2.2 Example of the indication of a foam hardness EW XI at 50 N: 18 mm according to PV 3410 Section 3.8 . 3.9
Static set
Determination based on PV 3410 Section 3.7 .
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3.9.1
Test sequence
3.9.1.1 Seat
Determination characteristics while at the same time recording the measured height hof the seat compression distance ESWo from the compression stress-strain force F set cycle.
0 under the preliminary v = 20 N in the 2nd
Static with pressure load with F = 320 N plus a preliminary force Fv = 20 N in moist heat +40 °C weights.
80% relative humidity for 16 h. The pressure load is realized by means of suitable
After reconditioning for 24 h in the DIN 50014-23/50-2 standard climate, the seat compression distance ESWsame time recording the measured height h1 is determined from the compression stress-strain characteristics, while at the set cycle.
1 under the preliminary force Fv = 20 N in the 2nd 3.10
Calculation formulas
Loss of height H = measured height ho minus measured height h1 [mm]
Shift compression distance ESWin characteristic curve ESW = seat compression distance ESW1 minus seat o [mm]
The static set is calculated by adding the loss in height H and the shift in characteristic curve ESW after static pressure load
S = H + ESW
[mm]
3.11
Tear propagation strength
Determination acc. to DIN 53356. Dimensions of the trouser specimen (100 x 30 x 10) mm. Length of the incision 40 mm. 4
Referenced standards*
DIN 50014 Climates and their Technical Application; Standard Atmospheres
DIN 51220 Materials Testing Machines; Generals for Requirements and for Verification and Calibration of Materials Testing Machines
DIN 53356 Testing of Artificial Leather and Similar Sheet Materials; Tear Growth Test DIN 53579-1 Testing Indentation Test on Shaped Parts
of Flexible Cellular Materials; Hardness Test on Finished Parts; DIN EN ISO 845 Cellular Plastics and Rubbers - Determination of Apparent (Bulk) Density DIN EN ISO 1798 Flexible and Elongation at Break
Cellular Polymeric Materials – Determination of Tensile Strength DIN EN ISO 1856 Flexible Cellular Polymeric Materials – Determination of Compression Set DIN EN ISO 3386-1
Polymeric Characteristic in Compression - Part 1: Low-Density Materials.
Materials, Cellular Flexible - Determination of Stress-Strain *
In this section terminological inconsistencies may occur as the original titles are used.
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Appendix A (informative) A.1
Deformation diagram
