Abstract
Recent experimental investigations have shown that large macromolecules can be fully stretched and fractured in an extensional flow. In this situation, the critical strain-rate for bond scission was found to depend on molecular weight as (M W) −2, in agreement with the theoretical predictions of the beadrod model. One of the conditions prerequisite to full chain extension is that the residence time at the appropriate strain-rate must be much larger than the terminal relaxation time of the macromolecule. If this requirement is not fulfilled, chain fracture could still occur at sufficiently high strain-rate, but in a partially uncoiled state. In the present studies we have measured the critical strain-rate for chain scission in transient extensional flow of extremely sharp PS fractions dissolved in dekalin at the θ-temperature. The molecular weight range investigated varied from 2.86 × 10 6 to 426,000. The critical strain-rate for chain scission was found experimentally to scale as (M W) −0.95 instead of (M W) −2 as predicted for stagnant extensional flow. Our results are in good accord with a recent theory for rupture of partly extended coils. Even in the partially uncoiled state, the degraded macromolecules showed a remarkable propensity for chain halving, indicating that midchain scission in flow is a general property that is not uniquely reserved to the fully extended chain.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
