Tensile experiments were carried out at diverse test conditions using four types of MBS of different particle size for studying the factors controlling crazing
and shear yielding which are known to influence fracture behavior and the impact resistance.
The 90 wt% PS/10 wt% PVME blend [ILLUSTRATION FOR FIGURE 5A OMITTED] shows patch patterns separated by river patterns, which indicate multiple crazing
in the vicinity of fracture surface.
A description of the new static crazing
experiment is presented and is followed by some results.
Kramer, "Microscopic and Molecular Fundamentals of Crazing
," in Advances in Polymer Science, Vols.
The applied stress is believed to produce changes in the potential energy barrier in a way that decreases the height of the barrier in the direction of flow, enhancing reptation and conformational changes necessary for crazing
The first analysis was performed with a constant crazing
stress of 40 MPa and included experimental variables of relative craze density and strain rate.
Among processes of craze initiation to breakdown, craze tip advance and craze thickening are especially important since they are responsible for the major part of the energy dissipation during crazing
and thus directly influence polymer toughness.
Some limitations to this method are the ineffectiveness in measuring low amounts of crazing
and the necessity of the instrument to be in close contact with the surface being measured.
deformation and shear yield deformation are well known as the main mechanisms absorbing the destruction energy of a polymer alloy.
It has been shown that toughening in rubber-modified PP can be achieved via crazing
and shear yielding [9, 10, 12].
Despite multiple crazing
in PE1, the overall break separation remains lower than that for PE2 due to the lower value of [lambda] of the fibrils in any given craze of PE1.
Largely deformed rubber particles and crazing
were observed near the surface of the whitened fractured section nearest the notch (Fig.