This paper presents a thorough molecular characterization of ethyl acrylate (EA) and n-butyl acrylate (nBA) homopolymers made at high temperature (140−180 °C) to high conversions (50−90%) in xylene isomers without the use of added thermal initiator. Electrospray ionization/Fourier transform mass spectrometry (ESI/FTMS) analysis shows four dominant chain types formed during high-temperature polymerization. Chains initiated by β-scission radicals and by xylol radicals that grow and eventually terminate to form terminally saturated and unsaturated chains. These chain structures suggest the underlying secondary mechanisms in high-temperature acrylate polymerization include β-scission (disproportionation) of the carbon-centered tertiary radical that is most likely formed via intramolecular chain transfer. Additionally, chain transfer to solvent, xylene in this case, also plays an important mechanistic role. Results from 1D NMR using 13C, 1H, and distortionless enhancement polarization transfer (DEPT) corroborate the ESI/FTMS results and additionally predict (i) 2 branch points per chain on average for EA homopolymer with a number-average molecular weight of 4000 and (ii) 1.25 branch points per chain on average for nBA homopolymer with a number-average molecular weight of 3300. The presence of branch points indicates propagation of the midchain tertiary radical does occur to significant extent under the conditions of the experiments. Neither the ESI/FTMS nor NMR results suggest a mechanistic route by which the acrylates initiate polymerization without added thermal initiator.

Michigan Technological Unwersity Howhton, Michigan 49931 -1 295Increasing the thermal and electrical conductivity of typically insulating polymers, such as nylon 6.6, opens new markets. A thermally conductive resin can be used for heat sink applications. An electrically conductive resin can be used in static dissipative and Electromagnetic Interference/Radio Frequency Interference shielding applications. This research focused on adding various carbon based conductive fillers and a chopped glass fiber to nylon 6.6. These materials were extruded and injection molded into test specimens. Tensile tests as well as in-plane electrical resistivity, in-plane thermal conductivity, and through-plane thermal conductivity tests were conducted. One successful formulation consisted of 1Wh 3.2 mm chopped E-glass fiber/ 15Oh Thermocarb (high quality synthetic powdered graphite)/5Yo carbon black/70% nylon 6,6 (all Yo in wt%). For this formulation, the in-plane electrical resistivity was reduced from 1015 ohm-cm (neat nylon 6,6) to 15 ohm-cm. The through-plane thermal conductivity increased from 0.25 W/mK (neat nylon 6.6) to 0.7 W/mK. The tensile elongation at failure was 1.4%.

Increasing the thermal and electrical conductivity of typically insulating polymers, such as nylons, would open new markets. A thermally conductive resin could be used for heat sink applications. An electrically conductive resin could be used in static dissipative and Electromagnetic Interference/Radio Frequency Interference shielding applications. This research focused on adding conductive fillers (namely carbon black and Thermocarb, a high quality synthetic milled graphite) and a chopped glass fiber to high temperature nylon. These materials were extruded and injection molded into test specimens. Tensile tests as well as in-plane electrical resistivity, in-plane thermal conductivity, and through-plane thermal conductivity tests were conducted.