Resilience test method

Before considering particular test methods, it is useful to survey the principles and terms used in dynamic testing. There are basically two classes of dynamic motion, free vibration in which the test piece is set into oscillation and the amplitude allowed to decay due to damping in the system, and forced vibration in which the oscillation is maintained by external means. These are illustrated in Figure 9.1 together with a subdivision of forced vibration in which the test piece is subjected to a series of half-cycles. The two classes could be sub-divided in a number of ways, for example forced vibration machines may operate at resonance or away from resonance. Wave propagation (e.g. ultrasonics) is a form of forced vibration method and rebound resilience is a simple unforced method consisting of one half-cycle. The most common type of free vibration apparatus is the torsion pendulum. 

The most straightforward way to measure the effect of low temperatures on recovery is by means of a compression set or tension set test. Tests in compression are favoured and a method has been standardised internationally. The procedure is essentially the same as set measurements at normal or elevated temperatures and has been discussed in Chapter 10, Section 3.1. As the recovery of the rubber becomes more sluggish with reduction of temperature the dynamic loss tangent becomes larger and the resilience lower (see Chapter 9), and these parameters are sensitive measures of the effects of low temperatures. Procedures have not been standardized, but rebound resilience tests are inherently simple and quite commonly carried out as a function of temperature. It is found that resilience becomes a minimum when the rubber is in its most leathery state and rises again as the rubber becomes hard and brittle. 

Saboo (1984) has generalized resilience test (32) to class 2 problems. However, his method is still limited to minimum unit HENs with no stream splits. 

The nonlinear resilience analysis methods of the previous few sections, although rigorous, are limited to rather specific situations (Saboo et al., 1987a,b) minimum unit HENs with piecewise constant heat capacities (but no stream splits or flow rate uncertainties), minimum unit HENs with stream splits (but constant heat capacities and no flow rate uncertainties), or minimum unit HENs with flow rate and temperature uncertainties (but constant heat capacities and no stream splits). Although it might be possible to combine these resilience analysis methods, the combined method would still be limited to HENs with a minimum number of units, and it would only be a sufficient test for resilience (at least for HENs with stream splits). 

ISO DIS 10580 Resilient, textile and laminate floor coverings. Test methods for emissions of volatile organic compounds... 

ASTM D1054 Standard test method for rubber property-resilience using a Goodyear-Healey rebound pendulum... 

ASTM D2632 (tailing weight) Standard test method for rubber property Resilience by vertical rebound... 

Annual Book of ASTM Standard, Road and Paving Materials Vehicle- Pavement system, Standard Test Method for Indirect Tension Test for Resilient Modulus of Bituminous Mixtures , D 4123-82, 2002. 

The most developed areas for imprinted polymers are for sequestration and separation. Several reported imprinted polymer sensors have in actuality been pretreatments by separation to allow a selective determination using a general detection method. The adaptation of this to an FIA system would be relatively simple. For example, Kriz et al. [31] report a sensor for morphine (see Chapter 18). The method of morphine detection involved two steps. The first step was to immobilise the morphine by loading it on the imprinted polymer. In the detection step, the morphine was released from the column by elution of an electro-inactive competitor (codeine) and the released morphine was detected by an amperometric method. The polymer was tested after exposure to extremes of heat and chemicals and proved resilient. This method would probably be suitable for automation as a flow injection technique. 

Representative test methods of flexible foam properties, as defined by the ASTM D-3574 are density, IFD (indentation force deflection), CFD (compression force deflection), sag factor, compression set, tensile and tear strengths, elongation, resilience, dry-heat aging and steam autoclave aging. 

ASTM D 1054-87 Standard Test Method for Rubber Property — Resilience Using a Rebound Pendulum, 6 pp (DOD Adopted) (FSC 9320) (MR) (Comm D-11)... 

In addition to the classic waste separation methods, which are based on the difference of the corresponding physical or physicochemical property between the various constituents of the waste stream, there have been also tested methods in the past, which are based on a combination of physical properties such as density, elasticity, and friction. These methods separate organic from inorganic materials, as well as heavy and resilient from light and inelastic. Ballistic, oscillating, and bounce and slide separators are some of the devices based on these principles. Because the necessary equipment is relatively simple, under certain materials characteristics, these separators could be used in relatively easy and low-cost waste recovery. 

Abrasion resistance is a difficult property to define as well as to measure. It is normally accepted that abrasion resistance depends on the polymer s hardness and resilience, frictional forces, load, and actual area of contact. ASTM D1044 evaluates the resistance of transparent plastics to one kind of surface abrasion by measuring its effects on the transmission of light. Another test method to evaluate abrasion, ASTM D1242, measures the volume lost using two different types of abrasion machines loose abrasion and bonded abrasion. 

It should be noted that the standard test methods for tensile stress- strain properties, tear strength, rebound resilience, and other dynamic properties provide for high-temperature measurements, preferably at the recommended temperatures of ISO 471. 

The resrilting foam is conditioned at 60% R.H. at 20 C for one week. Mechanical tests, i.e. compressive testing and resilience testing, are performed according to the method described by Tatarka and Cutuiingham. The foam density was calculated by sand replacernent volumetric measurement. The cell structure was analyzed by Scanning Electron Microscopy. 

Standard Test Method for Rubber Property-Resilience by Vertical Rebound. 

This test method is used for determining the resilient modulus by indirect tension test according to ASTM D 7369 (2011). The test is similar to but not exactly the same as the indirect tensile test specified in CEN EN 12697-26 (2012), Annex C. 

Figure 7.12 (a) LVDTs mounted on the specimen and (b) specimen during indirect testing. (Reprinted from ASTM D 7369, Standard Test Method for Determining the Resilient Modulus of Bituminous Mixtures by Indirect Tension Test, West Conshohocken, Pennsylvania, US ASTM International, 2011. With... 

Tanknoto, Y Saeki, H. Kimoto, S. Nishiwaki, T. Nishiyama,N. Evaluation of adhesive properties of three resilient denture liners by the modified peel test method. Acta. Biomater., 2009, 5(2), 764-769. 

It has been shown [56] that if we measure the areas under the approach and retract curves of the force-distance plot we can get quantitative values of the resilience. Resilience is closely related to the ability of the polymer chain to rotate freely, and thus will be affected by rate and extent of deformation, as well as temperature. Different materials will respond differently to changes in these variables [46] hence, changing the conditions of testing will result in a change in absolute values of resilience and may even result in a change in ranking of the materials. Compared to more traditional methods of resilience measurement such as the rebound resiliometer or a tensUe/compression tester. 

As the previous sections have shown, there are a large number of low temperature tests in existence. Even when ad hoc bending tests are disregarded, together with the use of the normal range of physical tests, such as tensile modulus and resilience, and the automation of a mechanical test by thermal analysis, there remain several types of specially developed low temperature tests. The various tests do not all have equal relevance to a given product. A test, or tests, should wherever possible, be chosen to provide the information most relevant to the particular application, but for many quality control purposes a test is used simply as a general indication of low temperature behaviour. Whatever the relative merits of the different methods in any situation, the question of correlation between the methods is frequently asked. 

The analysis techniques presented earlier in this chapter can be used to test the resilience of a synthesized network, and evolutionary changes can be made to the network, if necessary, to improve its resilience. However, this type of procedure may require many evolutionary synthesis-analysis iterations, and it may not be obvious which evolutionary changes are required to improve a network s resilience. Obviously, better methods are needed which incorporate resilience into the synthesis procedure itself. 

The resiliency quoted for an elastomer is normally a single expression of the result of a specified test. The results quoted will vary according to the method used. To compare results, elastomers must be tested by the same method. 

Resilience is one of the most common rebound tests. It is fundamentally a deformation of the material for half a cycle. The rebound resilience basically is the ratio of the indentor after to before impact expressed as a percentage. There are a large number of methods for this test, including the following. 

---