1. Simulation of crystallization in random ethylene/1-hexene copolymers. 2. Synthesis and computer simulation of polydimethylsiloxane networks. 3. Silicone seal compatibility with organic acid and conventional coolant formulations

Simulation of crystallization in random ethylene/1-hexene copolymers . Random ethylene/1-hexene copolymer chains were generated via Monte Carlo simulations. The comonomer distributions of the simulated chains and melting temperatures of real chains were used to compute the core crystallite thickness. Computed values of the core crystallite thickness matched values calculated from Raman Longitudinal Acoustic Mode (LAM) spectroscopy for some compositions; some computed and experimental values differed widely, presumably due to entanglements and high melt viscosity.; Synthesis and computer simulation of polydimethylsiloxane networks . Vinyl-terminated polydimethylsiloxysilane (PDMS) was endlinked with silanes having functionalities of 3, 4 and 40–50. SiH consumption was monitored before and after the gel point via Fourier-transform infrared spectroscopy (FTIR). Size exclusion chromatography (SEC) was used to determine the molecular weights of pre- and post-gel point sols. Gel samples were swollen in toluene so that cycle rank, the proportion of intramolecular bonds, could be estimated. Experimental values of sol molecular weight, gel mass fraction and cycle rank were compared to simulation results from MSI Polymer's network modeling software. The experimental and simulation results showed that the gel point extent of reaction and gel point sol molecular weight are inversely proportional to the crosslinker functionality. Computed and experimental values of sol molecular weight were close to one another up to the gel point; after the gel point, the simulation values were slightly lower because the software does not account for entanglements and viscosity. The software also underestimated the gel weight fraction. This discrepancy may be partly due to the software's inability to account for entanglement of cyclic compounds which are not covalently attached to the network.; Silicone seal compatibility with organic acid and conventional coolant formulations. Filled and unfilled silicone rubber samples were aged for 1000 hours or 2000 hours in generic or commercial coolant solutions at 280°F in order to simulate the aging of coolant seals in engines. The generic coolants varied with respect to the type of acid present. Swelling and extraction studies, Fourier-transform infrared analysis (FTIR) and gel permeation chromatography (GPC) were used to characterize the various materials.