ASTM D395 Compression Set Fixture UI-FT32

ASTM D395 Compression Set Fixture is to test rubber, elastomer, silicone rubber and others compression set after compressed for certain period under constant strain at given temperature. The compression set fixture measures how much squeeze a rubber keeps after it has been held compressed for a set time at a set temperature. A low compression set means the material springs back and keeps sealing, so this test is a core spec for O-rings, gaskets, seals, grommets and vibration mounts.

1. Unuo UI-FT32 ASTM D395 Compression Set Fixture Method B Features

The UI-FT32 holds specimens at a fixed deflection between flat stainless steel plates and steel spacer rings. It is built for ASTM D395 Method B — the method most seal and gasket specifications call for.

• Stainless steel: This compression set fixture is totally made of stainless steel, including the plates, spacer rings, nut; durable and rust-resistant, more reliable when the test runs under high temperature and humidity.
• Strong, rigid structure: the plates thickness 11.5mm, stay flat under clamping load, so the set deflection stays accurate throughout the test.
• Customizable steel spacer rings: 10%, 15%, 25% compression, or any thickness you specify.
• Holds both specimen sizes: Type 1 (29.0 × 12.5 mm) and Type 2 (13.0 × 6.0 mm).
• One fixture, multiple standards: ASTM D395 Method B, ASTM D1056, ISO 815, DIN 53517 and GB/T 7759 by changing the spacer rings.
• CNC machined, then precision ground: each compression plate is CNC machined and finished on a surface grinder, ensuring the surface roughness meets the standard requirement and the specimen can expand freely during the test.
• Calibration: Every single fixture meets ASTM D395 standards, and ISO 17025 CNAS calibration certificate can be provided on request.
• ASTM D395 method A compression set fixture under constant force in air available.

ASTM D395 Method B                                                                 Method A

Warm Tip: please pay attention to sample hardness. Choose the suitable compression set method and steel spacer for the compression set test fixture.

2. Compression Set of Rubber Standard

By using different thicknesses of spacer rings, this compression set test fixture can many test standards. Compression set of rubber standard includes ASTM D395 method B (ASTM D395B), ISO 815, DIN 53517, ASTM D1056 compression set and etc. Contact us today for Compression Set Fixture price & more details.

A typical Method B test: place the specimens between the plates, tighten the bolts until the plates contact the spacer rings, then put the fixture in an aging oven at the required temperature for 22 or 70 hours. Remove the specimens, let them recover 30 minutes at room temperature, then measure the thickness.

Compression Set Fixture test result would help you to know the properties of elastomers and can be a reference for your elastomer selection guide to choose low compression set rubber, elastomers. Know more about compression set test by this article.

3.  Comparison of ASTM D395 and ISO 815

4. Rubber Compression Calculation

C_B=[(t_o-t_i)/(t_o-t_n)]*100 (the test result would be expressed in %)

• C_B=compression set (ASTM D395 method B) expressed as % of the original deflection.
• T_o=original thickness of specimen
• T_i=final thickness of specimen
• T_n=thickness of the spacer bar used.

Warm tip: for your understanding compression set results, the lower % of the test result, the better your sample resists constant deflection.

The lower the %, the better your sample resists constant deflection. 0% means full recovery; 100% means the rubber took a permanent set at the spacer height.

5. Other needed equipment for compression set test

• Environment Chamber
• Aging Oven
• Thickness Gauge
• Hardness Tester/shore durometer

*Above lab testing machines are available from Unuo Instruments.

6. Unuo ASTM D395 Compression Set Fixture Specification

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