Flex Fatigue Properties

Commercial polypropylene is isotactic since atactic polypropylene has poor mechanical properties and isotactic is difficult to synthesize. Polypropylene has similar structure and properties as HOPE, except that it has superior flex-fatigue properties and a higher melting point. Polypropylene is commonly used for nondegradable sutures. Like PE, polypropylene can be melt processed. ... 

POE/TPV materials have excellent flex fatigue properties, good impact resistance, and they are low in cost and easy to process. They can be formulated to provide a soft, silky feel, which lends itself to portable electronic applications, such as smartphones, headphones, and portable computers. They are also used for both interior and exterior automotive parts, building materials, appliance parts, and sporting goods. 

Compression Set. The compression set is an important property ki cushioning appHcations. It has been studied for polyurethane foams (185,186), and has been discussed ki reviews (32,60,156). Compression set has been described as flex fatigue and creep as weU. 

FZ elastomer offers a broad service temperature range, namely, from -65°C to 175°C (-85°F to 347°F) [110], excellent flex fatigue resistance, damping properties, and resistance to chemicals and fluids. 

Stretch void index (SVI). SVI provides an indication of the number voids in the part. It indicates how well the sintering and coalescence have eliminated small voids, which can be present because of the processing technique orthe properties ofthe resin. Voids directly affect the performance of a tube in the end-use. For example, a void free or low void content part will have a longer flex life and greater flex fatigue resistance than a part containing more voids. 

FIGURE 7.13 Vulcanizate properties —, 300% modulus (Mpa) —, DeMattia flex fatigue life (kHz X 10"-1) -0-0-0-, % retention of ultimate elongation after 2 days at 100°C. 

Specifications should include any specific properties required for the application, such as resilience, hysteresis, static or dynamic shear and compression modulus, flex fatigue and cracking, creep resistance to oils and chemicals, permeability, and brittle point, all in the temperature ranges to be encountered in service. 

The fabric substrate used for the filter media will need to provide certain characteristics, dependent on the application. The typical properties required include abrasion resistance, stretch resistance, dimensional stability, and resistance to flex fatigue. All these performance criteria can be assessed by using suitable test methods. The fabric will also be tested for correct warp and weft sett, air permeability, thickness, density, and fabric tensile properties. All the factors will affect the performance of the filter as they are directly related. If woven fabrics are considered, the porosity will be directly related to the sett and therefore air permeability. The combinations of the fibre types, fabric constructions, and coating substrate will provide the filter manufacturer with a range of properties for use in a range of appUcations. 

Since the structure contains very few weak links, it is oxidative and ozone resistant. The unique mechanical properties are low compression set, high modulus, excellent flex fatigue, and good abrasion resistance. Thus, it has been evaluated as an advanced sealant for aerospace applications. 

Heat buildup and compression fatigue D623 Rubber property—heat generation and flexing fatigue in compression 9.01... 

Like natural rubber, styrene butadiene rubber (SBR) can be blended in all proportions with bromobutyl rubber. However, SBR is less desirable for blending than natural rubber due to its low tack and green strength properties. In addition, heat, flex fatigue resistance, and weathering resistance are poorer with SBR blends than with natural rubber blends. Suggested cure systems are the same as those for bromobutyl/natural rubber blends. 

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