Modeling the Chain‐Length Differentiated Polymer Microstructure of α‐Olefins

Abstract

Summary: Due to a complex polymerization scheme, incorporating besides propagation, termination and transfer to monomer and chain transfer agents in addition intra-and inter-molecular transfer to polymer as well as b-scission, a-olefin (co)polymers feature a quite complex polymeric microstructure. It is demanding to design a kinetic model that describes these in a predictive manner in order to have a tool for computer-aided product design. The molecular weight distribution and branching indices together with the composition are the subjects of interest in this case. The latter quantities are often provided as being averaged over the molecular weight distribution. Modern coupled analytical techniques of size exclusion chromatography provide even more insight. The combination of size exclusion chromatography with fractionation techniques provide under adequate processing of the data branching indices and co-polymer composition differentiated with respect to chainlengths. This contribution will inspect how good a model for predicting the chain-length differentiated co-polymer composition in high-pressure hightemperature ethene -vinyl acetate-co-polymerizations will coincide with analytical results of technical products.

Computer Aided Modeling of Polymer Reaction Engineering—The Status of Predici, I‐Simulation

“…Then it is possible to balance additional chain‐length dependent properties and their variances, e.g., the average number of branches in chains of length s . This approach has been published in a series of papers 25, 29–31 and could successfully be compared to measurements. If an additional property is only of interest for small (rule of thumb: < 10) values, for each single value an independent polymer generation can be used, e.g., $R_s^k$ polymer of chain length s with k branches.…”

Characterization of Ethylene Copolymers with Liquid Chromatography and Melt Rheology Methods

“…Two different types of copolymers were selected for comparison: ethylene-vinyl acetate (EVA) and ethylene-methyl acrylate (EMA) resins. In the first case, close reactivity ratios [14] of the comonomers suggest that the chemical composition distribution of the EVA copolymers should be similar for autoclave and tubular products with the same average composition, so that any differences in rheological behavior are caused by molecular weight and/or branching distributions. In case of ethylene-methyl acrylate copolymers, a significant difference in reactivity ratios [14] allows for the possibility of a broad chemical composition distribution of the tubular products, which may produce an additional effect on the rheological properties.…”

From Fundamental Polymerization Kinetics to Process Application—A Realistic Vision?

“…The process is run on a 1 L high-pressure high-temperature reactor and the product of interest is at this point an ethene-vinyl acetatecopolymer. [38] The polymerization was run at 1700 bar pressure and a temperature of 220 8C. The copolymer contains 10 mol-% of vinyl acetate as comonomer.…”

“…It is a small scale commercial product from the class of low molecular weight copolymers. The process is run on a 1 L high‐pressure high‐temperature reactor and the product of interest is at this point an ethene‐vinyl acetate‐copolymer 38. The polymerization was run at 1700 bar pressure and a temperature of 220 °C.…”