Tensile yield in polypropylene

Abstract

Untaxial tension tests to the yield point were performed on polypropylene as a function of temperature from 22 to 143°C at a strain rate of 2 min−1. At 22, 42, and 71°C, measurements were also made at strain rates from 0.02 to 8 min−1. Yield energy was found to be a linear function of temperature extrapolating to zero at the melting point (164°C). The ratio of thermal to mechanical energy to produce yielding is about three times smaller than for glassy polymers. The ratio of yield stress to (initial) Young's modulus is about 0.024 at room temperature and increases to 0.043 at 143°C. Yield stress is a linear function of unstrained volume.

Cavitation and morphological changes in polypropylene deformed at elevated temperatures

“…Mechanical properties of PP were studied in tension at room and elevated temperatures (25,40,70, 100 o C) using an Instron tensile testing machine equipped with the environmental chamber. Samples before the test were conditioned at least 15 min at the drawing temperature.…”

“…It is known that the increase of drawing temperature influences the mechanical properties, among them a macroscopic yield 25 . The yield stress decreases with the increase of the temperature.…”

“…The yield stress decreases with the increase of the temperature. Hartmann et al 25 observed that the yield parameters: yield strain and a nonrecoverable permanent deformation both have a maximum at the temperature of deformation around 60-70 o C and also that the dependence of the yield stress on the temperature changes in this temperature range. They did not analyzed whether cavities were formed in their polymer during drawing or not.…”

Stretching temperature and direction dependency of uniaxial deformation mechanism in overstretched polyethylene

“…It is also generally accepted that stress‐induced fragmentation and recrystallization process would take place readily with increasing deformation temperature . Besides, the study of drawing behavior of polyethylene by Hartmann et al has shown that, the yield strain reaches a maximum value at the temperature of deformation around 60–70 °C and yield stress decreases with the increase of temperature.…”

Effects of simulated clinical fabrication heat treatment and artificial weathering on the tensile testing of prosthetics/orthotics polymers

“…Limitations of this standard and directions for its improvement include laboratory tests dealing with function, wear and tear, and environmental influences. Because there are no standards for such tests, appropriate procedures will need to be ~pecified.~ A number of aspects relevant to an understanding of tensile behavior under accelerated environmental conditions have been investigated (1) effect of polymer structure on the tensile behavioq6-13 (2) effect of processing on structural degradati~n;~~,''~'~ definitions and values of tensile strength for thermoplastic polymers with strain rates not always specified;7-8,10, [15][16][17][18][19][20][21][22] and (6) artificial eath he ring. ".^^-^^,^^ In addition, limited statistical a n a l y s e~'~J~-~~.~~ and rankings development19~20~22 have been published.…”