PMMA, tensile behavior

Figure 25 shows that the tensile behavior of PMMA and PS, stretched some 10-30 °C below Tg, is very similar to that of PC. Like PC both PMMA and PS exhibit extensive stress-whitening at high extension ratios, k", where the peak or inflection of the stress-strain curve is observed. In Table 3, the value of k" measured for PMMA is compared to the maximum extension ratio, k , of chains between entanglement points. The fact that k" = k provides further evidence that the cavitation in PMMA must be attributed to the same deformation mechanism as discussed in Section 4.2 for PC. The value of k" = kikj" = 6.8 measured for pre-oriented PS is higher than the theoretical value of k = 4.1 included in Table 3. This result is not... 

Tensile behavior is of primary importance when considering the properties of a thermoplastic elastomer. The stress-strain dependencies for the 3-arm star PBA-PMMA block copolymers listed in Table 3 are shown in Figure 8. The data were recorded at room temperature and with drawing rate of 5 mm/min. 

Various composite models such as parallel model, series model, Halpin-Tsai equation, and Kerner s model can be used to predict and compare the mechanical properties of polymer blends [43-45]. For the theoretical prediction of the tensile behavior of PMMA/EMA blends, some of these models... 

Tensile and Tearing Behavior. As shown in Figure 4, the tensile and tear strengths increased with increasing PMMA content measurements of tear strength were not feasible at PMMA contents > 30%. In any case, the incorporation of PMMA at even relatively low levels greatly improves the rather low strengths of the unmodified PU. 

A series of four samples of different initial but prepared by analogous procedures, were subjected to near-ultraviolet degradation (Figure 7). The expected family of straight, parallel lines is obtained. Therefore, we could predict an ultimate tensile failure for PMMA when the molecular weight Mw had degraded beyond a certain threshold—ca. 70,000. This behavior was indeed observed (Figure 8). 

Velasco Santos et al. (27) measured both the dynamic mechanical behavior and tensile mechanical properties of MWCNT-PMMA composites. They observed 1135% increase in storage modulus at 90°C and increase in glass transition temperature by 40°C over neat PMMA with only 1 wt% functionalized nanotubes. The tensile... 

The plots clearly indicate the elastomeric behavior of the star copolymers. The films of all three materials exhibited similar high elongation at break, about 500%, independent of the copolymer composition. As expected, the increase of the PMMA content in the copolymers resulted in an increase of the E modulus of the films from 1.02 to 4.76 and 11.18 MPa for samples with 13%, 26% and 36% PMMA respectively, suggesting a simple approach for tuning the tensile properties by adjusting the copolymers composition. 

Confirmation of the general fatigue superiority of semicrystalline polymers is implicit in studies of a-N behavior at frequencies low enough to minimize temperature rises (169). While the ratios of the endurance limit to tensile strength for typical amorphous polymers (polystyrene, PMMA, and cellulose acetate) are approximately 0.2, values for nylon-6,6, acetal resin, and polyterafluoroethylene are 0.3, 0.5, and 0.5, respectively. At a low frequency, polyethylene (Mw > 50,000) exhibits no failure after 5 x 10 cycles, even at the relatively high alternating stress... 

Weathering behavior ofPMMA [680] a) degree of transmission of PMMA after weathering b) stiffness after weathering c) tensile strength after weathering... 

The effects of aging on the dynamic and tensile properties of EPEOE/PLLA pseudo-SIPNs have been studied by Inoue and coworkers [46, 47]. The dynamic behavior of FPEOF/PLLA pseudo-SIPNs differs from that of FPEOF/PMMA pseudo-SIPNs. For FPEOF/PLLA pseudo-SIPNs, the storage modulus of PLLA decreases upon the addition of FPEOF. In contrast, the storage modulus of PMMA increases upon the addition of FPEOF, as mentioned earUer. 

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