抄録
Tensile creep tests of unplasticized polyvinyl chloride were carried out under constant load. Test pieces used in these tests were cut from the sheet of 1mm thickness.
We see that the following expression may be applicable in primary period of creep obtained from these tests,
ε=mtn
where ε is creep strain, t is time duration for loading, and m, n are constants. Both these constants vary their values subjecting to applied stresses and testing temperatures.
Next, creep in secondary period may be shown nearly as a straight line with tendency slightly concave upwards in the strain-time diagram as it may be regarded to be in the steady state.
Relation between minimum creep rate εmin, which is considered to be characteristics in secondary period, and conventional tensile stress σ at a constant temperatures is expressed by
εmin=c exp.(aσ),
where c and a are constants.
Minimum creep rates under constant stress at various absolute temperatures T are expressed by
εmin=A exp.(-B/RT),
where A and B are constants and R is gas constant.
The specimens kept at 60°C for 5 days show themselves to have smaller values of minimum creep rates than the normal, and become more brittle and considerably anisotropic.
