Flex modulus

Flexural modulus is the force required to deform a material in the elastic bending region. It is essentially a way to characterize stiffness. Urethane elastomers and rigid foams are usually tested in flexural mode via three-point bending and tite flexural (or flex ) modulus is obtained from the initial, linear portion of the resultant stress-strain curve. 

PESA can be blended with various thermoplastics to alter or enhance their basic characteristics. Depending on the nature of thermoplastic, whether it is compatible with the polyamide block or with the soft ether or ester segments, the product is hard, nontacky or sticky, soft, and flexible. A small amount of PESA can be blended to engineering thermoplastics, e.g., polyethylene terepthalate (PET), polybutylene terepthalate (PBT), polypropylene oxide (PPO), polyphenylene sulfide (PPS), or poly-ether amide (PEI) for impact modification of the thermoplastic, whereas small amount of thermoplastic, e.g., nylon or PBT, can increase the hardness and flex modulus of PESA or PEE A [247]. 

Other configurations are commercially available. PVDF has a use range from -40 to 302°F (150°C). PVDF has a high tensile strength, flex modulus, and heat deflection temperature. It is easily welded, resists permeation, and offers a high-purity smooth polymer surface. This is the polymer of choice for high-purity applications such as semiconductor, bioprocessing, and pharmaceutical industries. 

Figure 26.12 Relative flex modulus of ATH- and MgOH2-filled ES30. The solid line represents the Kerner model [Equation (1)] prediction...

Table VI compares the key properties of these two types of thermotropic polymers category by category. The samples compared had the same melting ranges, but were very different in reduced viscosities and solubility characteristics. The data compared were those processed under the most favorable conditions. Interestingly enough, the as-spun fibers from the polyester-carbonate can be heat-treated more efficiently than those fibers (of same tenacity) spun from the polyester. Both of them gave fiber properties far superior to those of nylons and polyethylene terephthalate. These two classes of polymers also had comparative properties (such as tensile strength, tensile modulus, flex modulus, notched Izod impact strength) as plastics and their properties were far superior to most plastics without any reinforcement.

Flexural Modulus. Figure 5 shows flex modulus values at 23 °C measured parallel and perpendicular to flow. The nonreinforced urethane polymer has a value of about 50,000 psi. Columns B and C show the results obtained with 8.5% and 20% loadings of milled glass fibers, respectively. Column D shows results obtained with 3.5% loadings of 1/8 chopped Integral strands. The flex modulus increased by about 20%. Column E shows data for 13.4% integral chopped strands the increase was more than 240% of the original... 

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