Materials for engineering, 3rd Edition - (Malestrom)

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Materials for engineering
30
4.5
25
Tensile strength (MPa)
20
15
10
3.0
1.5
Tensile strength (ksi)
5
0
0
0 10 20 30
Time in methanol (days)
5.11 Tensile strength of PUR aged in methanol at 60 °C as a function
of exposure time.
polyester-base polyurethane (PUR) as a function of exposure time in methanol.
The methanol is believed to swell the PUR and also causes molecular weight
reduction through chain breakage.
As an example of physical interaction when a plastic component is exposed
to an organic chemical, aggressive molecules may diffuse into the material
leading to plasticization. Swelling of the polymer results in high stresses
which can cause crazing or cracking. Fracture arising from physical effects
has been observed in many glassy plastics such as PMMA, PS and PC
because of anisotropic swelling.
5.7 Modelling of polymer structure and properties
Advances in computer technology have stimulated the construction of models
describing the microscopic structure of polymeric materials and the use of