Title: Structure and properties
of linear and crosslinked structural PVC foams
L. Aras, R.
Bailey, R. Brummer,
C. Bucknall, T.
Cervenka, D. Dijkstra,
J. He, F.
Steininger, and D.
To investigate the effect of crosslinking on the structure and properties
of rigid PVC foams. The establishment of the influence of thickness
and density on the structure and properties of rigid PVC foams.Important
properties which should be determined are the shear- and elastic-
modulus dependence upon temperature and frequency; fractural mechanical
behavior including fatigue crack growth depending on temperature
and load rate; compression behavior in air and water; thermal behaviour
by DSC. Morphological investigations should contribute to the understanding
of the micromechanical deformation behaviour.
Rigid foam cores are of high importance for structural applications,
such as bumpers, ship building, roof covering and crash belts. Important
properties are high strength and good stiffness to weight ratio,
Also, good thermal insulation, self-extinguishing, good fire behaviour
and very low water absorption without outgassing are important.Despite
the wide range of applications there is a need for a better understanding
of the influence of the morphological foam structure on the relevant
thermal and mechanical properties. To explore structure properties
relationships of polymer foams, two types of commercial PVC foams
with a crosslinked and linear matrix in a density range between
50 and 140 kg/m3 and a thickness range between 5 and 40 mm will
be investigated. The determination of DMA properties is well established
for compact materials. Hoewever, for foams, the method of load introduction
affects the results significantly. By comparing the results from
different equipment under tension, torsion and compression the differences
should be better understood and the influence of crosslinking, thickness
and density should be clarified. The reproducibility of the modulus
and the transition temperatures will be specifically investigated.Under
compression, yield strength, and the stiffness behaviour below and
above the yield point will be investigated as a function of the
loading rate and temperature. By making measurements in water the
effect of the air inclusions will be examined. The relationship
between modulus and density will be established and the modulus
of the compact material will be extrapolated from this.By fractural
mechanical investigations the KIC from CT-specimens as well as the
essential work of fracture will be determined. Finally the question
will be answered whether fractural mechanics is a suitable method
for the characterisation of polymer foams The investigation will
cover thermal- and mechanical properties as well as fracture mechanical
and fatigue properties in relationship of density and cell size.
First materials have been delivered in July 2000, more material
for additional contributions is available on request.