Asphalt and elastomeric polymer compositions crosslinked with mixed
polythiomorpholines or at least one alkyl polysulfide can give polymer
modified asphalts (PMAs) with improved properties and/or reduced H.sub.2S
evolution. When at least one alkyl polysulfide is used to completely or
partially replace conventional crosslinkers such as S or MBT,
mercaptobenzimidazole (MBI) may be optionally used as a co-crosslinker.
The use of mixed polythiomorpholines as crosslinkers provide PMAs with
better low temperature profiles (BBR m-values). The use of at least one
alkyl polysulfide crosslinker gives PMAs with improved PAV-aged DSR
results, and reduced H.sub.2S evolution. The use of at least one alkyl
polysulfide crosslinker together with MBI may give PMAs with improved PAV
DSR Fail Temperatures.