I'm not sure how this heat shrink doesn't cover it.
https://multimedia.3m.com/mws/media/23074O/3mtm-heavy-wall-heat-shrink-tubing-itcsn.pdfAgency Approvals &
Self Certifications
UL Listed, UL 486D Standard, File E102356
CSA Certification, File LR86335
Voltage Rating 600 V
Direct burial and Submersible
For use with Listed, Crimp-type, Splice Connectors
All other product claims are made by 3M and not covered
by the UL Listing
Also, not that i believe you wouldn't be able to direct burial this splice but my thoughts on the application are in instances where you would use a compression butt splice, or maybe a junction block, all inside enclosures.Thanks for the point on the insulation though, I've only exothermic welded grounding and bonding conductors but i don't remember any kind of damage to the local insulation, definitely gonna look closer next time.
