Izod impact toughness

PPS is brittle and notch sensitive. A significant improvement in the notched Izod impact toughness can be obtained by the addition of a rubber modi-fier. ... 

Kes Oshinski, A. J., Keskkula, H., Paul, D. R. The role of matrix molecular weight in rubber toughened nylon 6 blends 2. Room temperature Izod impact toughness. Polymer Vol. 37 (1996) 22, 4909 918. 

Figure 3. Mineral loading level on room temperature notched Izod impact toughness... 

Table 7-17 Example of a simplified readout for TPs toughness or fracture behavior Izod impact test results...

The strong sub-rg relaxation in PCT also contributes to increased toughness of this polymer in the amorphous state. When measured on amorphous specimens, the notched Izod impact strength of PCT is greater than 1000 J/m, while that of PET is less than 100 J/m [22],... 

For a part to exhibit structural stiffness, flexural moduli should be above 2000 N/mm2 (290,000 psi). Notched Izod impact values should be determined at different thicknesses. Some plastics exhibit different notch sensitivities. For example, PC, 3.2 mm thick, has a notched Izod impact of 800 J/m (15 ftlbf/in.) which drops to 100 J/m (1.9 fflbf/in.) at 6.4-mm thickness. On the other hand, one bisphenol A phthalate-based polyarylate resin maintains a 250-J/m (4.7-ftibf/in.) notched Izod impact at both thicknesses. Toughness depends on the structure of the part under consideration as well as the plastic employed to make the part. Mechanical properties, like electrical properties, are also subject to thermal and water-content changes. 

FEP is closely related to PTFE but has a lower melt viscosity and may therefore be processed by conventional processes and possesses most of the PTFE properties. It is a tough, resilient material with an Izod impact value of 2.9 ft-lb/in. at -70F, no break at 73F, and 95,000 ft-lb/in. at 170F. FEP is noninflammable and melts at 545 to 563F. It has excellent chemical and solvent resistance and is largely used in such electrical applications as terminal blocks and valve and tube holders. FEP is also used for a variety of non-stick applications in food processing equipment. 

Impact Failure. Standard notched Izod impact measurements have been made over wide temperature ranges on specimens cut from compression molded %-inch thick sheets of BPA polycarbonate and two BPA carbonate-silicone block polymers (Figure 4) (see Table I for compositions and properties). In the homopolymer a ductile-brittle transition occurs at 0° to —15°C, as reported previously (4, 5). Introduction of 15 and 25% silicone lowers the transition to —45° and —110°C (block polymers A and B). As indicated in Table I, this increase in toughness at low temperature is accompanied by the reduction of modulus and yield stress. 

Most HIPS fail in the uniaxial loading of a cantilever impact (Izod) test only if the test specimens have been notched beforehand. In the notched impact test, the stress direction in injection molded specimens is the same as the preferred orientation direction. This increases the measured impact toughness and the flexural impact test and, therefore, serves primarily for comparing the toughness of different products. 

Izod impact strength increases with increasing injection speed and lower melt temperatures. Since the fracture plane is normal to the direction of orientation in the Izod sample, the increased toughness with slower injection speed can be explained by the reinforcing effect of the oriented polymer on the surface. This effect is less noticeable at very high melt temperatures, where the surface can actually be annealed by the temperature of the core and subsequent extended molding cycle time required by the hot melt temperature. 

From the table It appears that the Izod Impact strength Improves as the Interfacial adhesion increases. This Is also concluded In a recent publication about nylon 6.6 compounded with polyethylene-g-maleic anhydride polymer (15). Addition of more rubber In system 3 (30 %) affords hardly any addltonal Improvement In toughness, but the flexural modulus, which In ABA block copolymers Is already lower than In a dispersed rubber system, Is more than halved. 

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