Polymethyl methacrylate stress-relaxation

Rothwell, Martinson and Gorman have studied the formation of stress induced crazes in polymethyl methacrylate. The sample was initially stressed and held at a strain of 3.5 %. Upon relaxation, SAXS-patterns of 1.5 s were recorded using a linear photodiode detector array. A sequence of selected curves recorded in a plane parallel to the strain direction is shown in Fig. 49. The peak at h = 0.014 is probably due to an... 

The influence of molecular entanglements is illustrated by Figure 6.3, which shows the stress relaxation behaviour for two samples of polymethyl methacrylate. It is seen that the lower molecular mass sample does not show a rubbery plateau... 

Figure 6.3 Master stress-relaxation curves for low molecular mass (molecular mass 1.5 X 10 daltons, curve A) and high molecular mass (molecular mass 3.6 X 10 daltons, curve B) polymethyl methacrylate. (Reproduced with permission from McLoughlin and Toholsky, J. ColloidSci., 7, 555 (1952))...

---