A comprehensive mathematical model is developed for the free-radical copolymerization of ethylene with various comonomers (e.g., vinyl acetate, methyl or ethyl acrylate, and acrylic or methacrylic acid) in high-pressure tubular reactors. Polar copolymers usually exhibit lower crystallinity and yield strength than low-density polyethylene grades and are used for applications requiring flexibility, toughness, stress-cracking resistance, and adhesion to coatings. In the present study, a detailed kinetic mechanism is proposed to describe the molecular and compositional developments in the free-radical copolymerization of ethylene with a comonomer. On the basis of the postulated kinetic mechanism, a system of differential mass balance equations are derived for the various molecular species, total mass, energy, and momentum in the polymerization system. The model equations are coupled with a set of algebraic equations for estimating the thermodynamic and transport properties of the reaction mixture. The number and weight molecular weight and copolymer composition averages, short-and long-chain branching frequencies, etc., are calculated in terms of the leading moments of the bivariate number chain-length distributions of "live" and "dead" copolymer chains. The predictive capabilities of the mathematical model are demonstrated by a direct comparison of the model predictions with industrial experimental data on the reactor temperature profile and pressure, the overall monomer conversion, and the final molecular and compositional properties of copolymers. Simulation and experimental results are presented for different copolymer grades including ethylene-ethyl acrylate, ethylene-methyl acrylate, and ethylene-vinyl acetate copolymers.

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The wettability of rubbers with silica nanoparticle modification was investigated with theory and experiment. A simple coating technology was applied to generate the superhydrophobic styrene–butadiene rubber (SBR). Silica nanoparticles were covalently bonded with γ-methacryloxy propyl trimethoxysilane (γ-MPTMS), which was employed to improve coating durability through the thiol–ene click reaction with the SBR matrix. The contact angles of water droplets on the net and modified surfaces were then measured. The application of a three-dimensional density functional theory approach to predict the wetting contact angles showed that the chemical composition, chain conformation, and micro/nanostructure have different contributions to the hydrophobic behaviors. The theoretically predicted contact angles were partly validated by their experimental counterparts.

Fluorinated polyhedral oligomeric silsesquioxane (F-POSS) nanoparticles have been widely used to enhance the hydrophobicity or oleophobicity of polymer films via constructing the specific micro/nanoscale roughness. In this work, we study the oleophobicity of pure and F-POSS-decorated poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) films using a dynamic density functional theory approach. The role of nanoparticle size and coverage and the chemical features of F-POSS and the polymer film in the wetting behavior of diiodomethane droplets has been integrated to the remaining ratio of surface potential to quantitatively characterize the corner effect. It is shown that, on the basis of universal force field parameters, the theoretically predicted contact angles are in general agreement with the available experimental data.