COMPRESSION STRESS RELAXATION

Gillen, K.T., M. Celina, and R. Bernstein, Validation of improved methods for predicting long-term elastomeric seal lifetimes from compression stress-relaxation and oxygen consumption techniques. Polymer Degradation and Stability, 82(1), 25-35, 2003. 

Closed-cell foams made from metallocene-based polyolefins (MPO) have potential for use in various applications because of their uniform composition and low toxicity. Compressive stress relaxation is used to investigate the behaviour of these foams. In particular, its behaviour is compared with open-cell PU foams, a material MPO foams could possibly replace. The effect of gamma radiation on MPO foam behaviour is also... 

Experience with compression stress relaxation measurement was not particularly widespread when the ISO standard was first formulated, a variety of apparatus was in use and reproducibility was not good. Birley et al ° studied a number of factors and made recommendations for change,... 

Compression stress relaxation is described in ISO 3. 84 (BS903, Part A42). The principal procedure uses Type A or Type B compression set test pieces compressed by 25% against lubricated surfaces, but ring test pieces are specified for tests conducted under fluids. 

The change in property measured up to, and past, equilibrium absorption is likely to show a marked change in the shape of the degradation curve. This is very noticeable in compression stress relaxation results on some rubbers in water at ambient temperature when a rise in modulus can be seen due to swelling at times greater than one year. Serebryakov ct al. [15] demonstrate a similar type of effect for the strength of polystyrene. 

Fig. 73. Compression stress relaxation for PMMA/bromobaizene gels at a deformation X — 0.85. Upper curves as received PMMA gds middle curves treated PMMA gels lower curves treated PMMA gels swollen to equilibrium. Reproduced from J Phys II France [Ref. 265] by the courtesy of the authors and of Les Editions dc Physique, Les Ulis, France...

Compression Stress Relaxation The definition of compression stress relaxation is that when a constant strain is applied to the gasket sample, the force necessary to maintain that strain is not constant but decreases with time this behavior is called stress relaxation. The test apparatus used for compression stress relaxation measiuements is the Wykeham Farrance device. It provides information for the prediction of the service life of materials by measuring the sealing force decay of a sealing gasket sample as a function of time, temperature, and environment. 

Compression stress relaxation ASTM D6147-97 Calculation of sealing force in the seal in various environments and temperatures Custom-designed jig... 

Pig. 4 Compression stress relaxation characteristics of different polymeric materials at 100°C and 100% relative humidity... 

When this material is used as a thermal insulator it is subjected to temperature gradients. In this paper we discuss the design and construction of unique test equipment to evaluate the compressive stress relaxation behavior of structural components when subjected to temperature gradients. Selected results are presented for temperature gradient stress relaxation tests of Min-K and an empirical model is presented to describe the gradient temperature stress relaxation behavior. 

Compressive stress relaxation, retained force, % Aged in SAE 5W30 Oil 168 h at 15(fC-change 43 68 66... 

Carboxyl ACM with much unproved compression set, compression stress relaxation resistance, and heat resistance while maintaining 30°C low-temperature flexibility, has been developed and named Nipol AR-12 by Zeon Corporation. A comparison of this grade with a standard ACM as well as a low swell AEM-G in Table 5.8 indicates that it will function very well as an improved replacement for AEM-G or standard ACMs [15]. 

Compressive stress relaxation in SF105 Oil at °C % force retained ... 

P.E. Manley and C.T. Smith, Improved Heat Compression Set Resistant Polyacrylate Elastomers—Part B Applications in Engine and Automatic Transmission Fluids Requiring Low Compressive Stress Relaxation, 158th Meeting, Rubber Division, ACS, October 17-20, 2000. 

Compressive stress relaxation percent retained force after ... 

Akron Polymer Laboratory. Compressive stress relaxation according to ISO 3384, Method B. Samples 12.7 mm (diameter) X 6.35 mm (nominal thickness)—Plied. 

Compression stress relaxation, percent retained force after 500 h — —... 

S. D. Waldman, and J. T. Bryant. Compressive stress relaxation behavior of irradiated ultra-high molecular weight polyethylene at 37 C. Journal of Applied Biomaterials 5 (4), 333-338 (1994). 

Fig. 10. Compression stress relaxation of polystyrene at 120°C. Mooney-Rivlin plot.

The compressive stress relaxation experiment followed immediately after compression measurements under 9 kg of a constant load. In the compressive stress relaxation, the behaviour was recorded as the decrease of the load from the initial 9 kg to about 1 kg. The results of measurements at 150 °C and 175 °C (Experiments 2, 3 and 5) are shown in Figure 3.11 with solid curves. 

Figure 3.11 Compressive stress relaxation, expressed as relaxation of load with time.

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