Polyurethane Foam Foaming Test Standards Summary

Testing Conditions:

1. Fast foaming is taken from the center of the foam, while molded foam samples are taken from the central part or for whole sample testing.

2. Newly made foam should be matured for 72 hours in its natural state before sampling. Samples should be placed in a constant temperature and humidity environment (as per GB/T2918: 23±2℃, relative humidity 50±5%).

Density: Density = Mass (kg) / Volume (m3)

Hardness: Indentation Load Deflection (ILD), Compression Load Deflection (CLD)

The main difference between these two test methods is the loading area of the foam plastic. In the ILD test, the sample is subjected to a compressed area of 323 cm2, while in CLD the entire sample is compressed. Here, we will only discuss the ILD test method.

In the ILD test, the sample size is 38*38*50mm, with a test head diameter of 200mm (with a round corner of R=10 on the bottom edge), and a support plate with 6mm holes spaced 20mm apart. The test head loading speed is (100±20) mm/min. Initially, a pressure of 5N is applied as the zero point, then the sample is compressed to 70% of its thickness at the zero point, and unloaded at the same speed. This loading and unloading is repeated three times as pre-loading, then immediately compressed at the same speed. The compression thicknesses are 25±1% and 65±1%. After reaching the deformation, hold for 30±1s and record the relative indentation value. The recorded value is the indentation hardness at that compression level.

Additionally, 65% ILD / 25% ILD = Compression Ratio, which is a measure of foam comfort.

Tensile Strength, Elongation at Break: Refers to the maximum tensile stress applied during the tensile test until fracture, and the percentage elongation of the sample at fracture.

Tensile Strength = Load at Fracture / Original Cross-sectional Area of Sample

Elongation at Break = (Fracture Distance - Original Distance) / Original Distance * 100%

Tear Strength: Measures the material's resistance to tearing by applying specified tearing force on a sample of defined shape.

Sample size: 150*25*25mm (GB/T 10808), with the sample thickness direction as the foam rise direction. A 40mm long incision is made along the thickness direction (foam rise direction) at the center of one end of the sample. Measure the thickness along the sample thickness direction, then open the sample and clamp it in the test machine fixture. Apply load at a speed of 50-20mm/min, using a blade to cut the sample, keeping the blade at the center position. Record the maximum value when the sample breaks or tears at 50mm.

Tear Strength = Maximum Force Value (N) / Average Thickness of Sample (cm)

Usually, three samples are tested, and the arithmetic mean is taken.

Resilience: Measures the foam's rebound performance by allowing a given diameter, weight steel ball to freely fall onto the surface of the foam plastic sample from a specified height. The ratio of the rebound height to the steel ball's drop height indicates the foam's resilience.

Test Requirements: Sample size 100*100*50mm, the ball drop direction should be consistent with the foam usage direction. The steel ball size is ∮164mm, weight 16.3g, and it drops from a height of 460mm.

Resilience Rate = Steel Ball Rebound Height / Steel Ball Drop Height * 100%

Note: Samples should be horizontal, steel ball should be fixed before dropping (static), each sample is tested three times with 20s intervals, and the maximum value is recorded.

Compression Permanent Deformation: In a constant environment, the foam material sample is maintained under constant deformation for a certain period, then allowed to recover for a period of time, observing the effect of the deformation on the sample's thickness. The ratio of the difference between the initial thickness and final thickness of the sample to the initial thickness represents the foam plastic's permanent compression deformation.

Compression Permanent Deformation = (Initial Thickness of Sample - Final Thickness of Sample) / Initial Thickness of Sample * 100

Fire Resistance

VOC (Volatile Organic Compounds)