An investigation into the relationship between ‘gel-effective’ and total numbers of crosslinks in irradiated LLDPE
✍ Scribed by Jones, Richard A.; Groves, David J.; Ward, Ian M.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 486 KB
- Volume
- 44
- Category
- Article
- ISSN
- 0959-8103
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✦ Synopsis
Rheological data for crosslinked LLDPE samples have been related to previous studies of similar materials. It has been found possible to attribute a range of time constants and characteristic moduli to the "gel-networkÏ (j 0i n ) ( G 0 i ) strength factor (S) of all these materials. Comparability established, the number of crosslinks estimated rheologically are compared with those computed by molecular modelling for equivalent gel fractions. Below about 0É4 gel fraction, all crosslinks are found to be e †ective in forming the gel. Beyond about 0É85 gel fraction, further increase in crosslinks produces only small changes in moduli ; this is observed at around Ðve crosslinks per pre-irradiated molecule. A simple power relationship is found between the rheological and "gel-e †ectiveÏ numbers of crosslinks. A previously postulated relationship between the gel fraction and numbers of "gel-e †ectiveÏ crosslinks appears to be universal for LLDPEs. "Gel-networksÏ arise at low gel fractions. Rheological data suggest that there is a dose-related progression of "gel-networkÏ, from initial viscoelastic polymer, through a medium containing a mobile distribution of "gel-networksÏ of increasing size, to a temporary "gel-networkÏ, still able to relax, and Ðnally a saturated permanent network.