Single step torsional stress relaxation experiments are performed on glassy cylinders made of poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) as a function of strain and temperature. In this type of experiment, it is required to apply not only a torque but also a compressive normal force to keep the length of the cylinder constant. The origin of the nonlinear effect of the normal force in glassy polymers is not well understood but there is evidence that it is related to the chemical structure of the polymer. In this work we test the hypothesis that the large normal force of PMMA is due to its prominent β-relaxation. Results show that the β-relaxation of the PMMA which is related to side chain motions, influences the normal force behavior. This is also confirmed by the fact that for specimens having weaker β-relaxation, i.e. poly(ethyl methacrylate) (PEMA), the difference between the normal force and torque relaxation behaviors is less.
|Number of pages||5|
|State||Published - 2005|
|Event||Society of Plastics Engineers Annual Technical Conference 2005, ANTEC 2005 - Boston, MA, United States|
Duration: May 1 2005 → May 5 2005
|Conference||Society of Plastics Engineers Annual Technical Conference 2005, ANTEC 2005|
|Period||05/1/05 → 05/5/05|