Jeffrey M. Cogen

Semiempirical prediction of the thermochemistry of intermediates involved in the cyclic mechanism of hindered amine stabilizers

Abstract The suitability of the AM1 computational method for predicting the thermochemistry of amine derivatives related to the functioning of hindered amine light stabilizers (HALS) was established by comparing computed data with representative published experimental data for HALS-related intermediates. Thus, AM1 accurately predicts the relative energies of 2,2,6,6-tetramethyl-4-oxopiperidine, 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl and 1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidine. The AM1 method was then utilized to estimate key bond dissociation energies for which experimental values do not exist. For the 2,2,6,6-tetramethyl-4-oxopiperidine series the following bond strengths are predicted: NO • = 366 kJ/mol; NOH = 234 kJ/mol; NOH = 296 kJ/mol; NOCH 3 = 176 kJ/mol; NOCH 3 = 185 kJ/mol; NOCH 2 H = 359 kJ/mol; NOC 2 H 5 = 164 kJ/mol; NOC 2 H 5 = 172 kJ/mol; NOCH 2 HCH 3 = 344 kJ/mol; NOCH(CH 3 ) 2 = 143 kJ/mol; NOCH(CH 3 ) 2 = 154 kJ/mol; NOCH(CH 3 ) 2 = 333 kJ/mol. The data should be of general value for the thermodynamic evaluation of proposed HALS mechanisms.

Novel polymer crosslinking chemistries for cable insulation

Peroxide crosslinked polyethylene is the major insulation material used in todays electric cables carrying voltages above 5 kV. Peroxide-mediated crosslinking presents cable manufacturing challenges in that there is a propensity for premature crosslinking (scorch) in the extruder. Additionally, peroxide-mediated crosslinking generates byproducts that need to be removed from the cable before final cable construction. Novel organic peroxides and crosslinking coagent technologies have been designed to address these challenges. A novel peroxide, isopropenyl dicumyl peroxide, was found to greatly improve the resistance to scorch. In addition, the novel peroxide reduced the need for degassing, since a significant amount of the crosslinking byproducts became grafted to the polyethylene during crosslinking. A novel coagent, 2-methoxy-4-allylphenyl allyl ether, provided significantly higher scorch retardance at a given level of crosslinking when compared to compositions without coagent. Polyethylene insulation compounds crosslinked using these new additives demonstrated excellent dissipation factor and dielectric constant values, indicating promise for demanding high voltage insulation applications.