ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The five independent elastic moduli C11, C12, C13, C33, and C44 for uniaxially drawn polyoxymethylene with draw ratio λ = 1-16 have been measured from -60 to 120°C by an ultrasonic method at 10 MHz. Wide angle x-ray diffraction and birefringence measurements indicate that the chains in the crystalline regions are fully aligned at λ = 5 but the degree of amorphous orientation increases steadily up to the highest draw ratio. Below the major amorphous γ relaxation (∼0°C at 10 MHz), only the axial longitudinal and tensile modulus, C33 and E0, show large increases. At 120°C, however, all the moduli increase with λ, with E0, E90 (transverse tensile modulus), C44 (axial shear modulus) and C66 (transverse shear modulus) increasing 10, 2.5, 3, and 2.5 times, respectively, as λ rises from 1 to 16. This improvement in mechanical properties may be attributed largely to the effect of taut tie-molecules and crystalline bridges. Whereas the two-parameter model of Seferis seems to be valid only below the γ relaxation, the Halpin-Tsai equation can give a reasonable description of the mechanical behavior for the highly oriented samples (λ〉5) over the entire temperature range.
Additional Material:
21 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760231610
Permalink
