Impact strength dynamic-mechanical property

Beckham and coworkers studied the dynamic mechanical properties of poly(urethane-crown ether rotaxane)s [138]. No difference was observed between the backbone and polyrotaxane, probably because of the low min value (0.02). However, 13C solid-state NMR detected die presence of the crown ether as a mobile structure at room temperature. The same observation was seen in polyrotaxanes with ether sulfone and ether ketone backbones (77-80) [114]. Although no detailed properties were reported, the detection of the liquid-like crown ether provided very important information in terms of mechanical properties, because these properties are the result of molecular response to external forces. For example, mobile crown ethers can play the role of plasticizers and thus improve impact strength. 

Another ultimate property which is difficult to interpret theoretically is the impact strength. For the relation between the impact strength and dynamic mechanical properties, the following equation was derived by Wada using the Maxwell model62) ... 

On the other hand, many studies on dynamic mechanical properties at temperatures lower than room temperatures have been reported 5,7 63,64). For example, a small (3 transition near —50 °C has also been observed in epoxy resins. Cuddihy 65,661 observed a (3 transition in resins cuted with different hardeners such as DETA, MPDA, HHPA, pyromellitic dianhydride (PMDA), and tris(dimethylaminomethyl)-phenol (DMP-30) (Fig. 19). The larger the size of the P transition, the higher the impact strength (Table 8). 

Figure 19.13 shows the dynamic mechanical properties of such a blend of sPS with a mixture of Kraton G 1651 (15 %) and microsuspension rubber particles (20%) consisting of 60% butyl acrylate (BA) core grafted with 40% styrene shell (S//BA). The glass transition temperatures of the Kraton (-60 °C) and the butyl acrylate (-45 °C) phases can be easily distinguished from one another. The TEM image of such a product after deformation is shown in Figure 19.14. The annealed specimen is shown since the two rubber types are better discernible than in the nonannealed sample. As expected, crazing and voiding in the rubber particles dominate. The product had the following notched impact strengths (ISO 179/eA) injection moulded (80 °C mould temperature) 6.3, injection moulded (140 °C) 4.0 and annealed 3.7kJ/m2.

The Izod notched impact strength (ASTH D-256) and the flexural modulus (ASTM D-790) of the obtained products were measured. For a number of specially selected samples, the dynamic mechanical properties were determined. 

Crystallinity of PLA has a strong impact on its mechanical properties. Suryanegara et al. have prepared PLA/MFC nanocomposites in both fully amorphous and crystallized states. The tensile modulus and strength of pristine PLA were improved with an increase of MFC content in both amorphous and crystallized states. Dynamic mechanical analysis (DMA) has been used to study the effect of MFC reinforcement on the thermomechanical properties of PLA in both states and the results are shown in Figure 9.5. In the amorphous state, the storage modulus of pristine PLA below Tg is almost constant at around 3 GPa. Above Tg, the modulus drops to 4 MPa at 80 °C, and then increases to 200 MPa at 100 °C owing to the cold... 

Plastics—Determination of Dynamic Mechanical Properties. Part 10 Complex Shear Viscosity Using a Parallel Plate Oscillatory Rheometer Plastics—Determination of Tensile-Impact Strength... 

Another research group led by Sukanya blended RR with waste polyethylene (WPE) collected from municipal solid waste (MSW) in different proportions composites were prepared with fly ash (FA) and characterized. Mechanical and dynamic mechanical properties of the blend and composites were studied in the presence as well as in the absence of a silane coupling agent (Si-69). It was found that the tensile strength, flexural strength, flexural modulus, impact strength and hardness properties of the FA composites improved in the presence of Si-69. 

The mechanical properties of rapidly polymerizing acrylic dispersions, in simulated bioconditions, were directly related to microstructural characteristics. The volume fraction of matrix, the crosslinker volume in the matrix, the particle size distribution of the dispersed phase, and polymeric additives in the matrix or dispersed phase were important microstructural factors. The mechanical properties were most sensitive to volume fraction of crosslinker. Ten percent (vol) of ethylene dimethacrylate produced a significant improvement in flexural strength and impact resistance. Qualitative dynamic impact studies provided some insight into the fracture mechanics of the system. A time scale for the elastic, plastic, and failure phenomena in Izod impact specimens was qualitatively established. The time scale and rate sensitivity of the phenomena were correlated with the fracture surface topography and fracture geometry in impact and flexural samples. 

Nelson investigated the relationship between density and physical properties, e.g., flexural modulus, Gardner impact, heat distortion, ten-sile/flexural strength, coefficient of linear thermal expansion, dynamic mechanical testing, and creep testing. The specific gravity of the SRIM obtained was changed from about 0.3 to 1.2. 

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