Summary
A combined experimental and computational approach is presented in order to study reactor fouling in high pressure LDPE tubular reactors. Indications are found that fouling is a process driven by low polymer diffusion speeds and higher friction in the region close to the reactor wall. These findings can explain the formation of polymer rich layers on the reactor wall which are responsible for the reduction of heat transfer and typical tailing observed in molecular weight distributions of LDPE.
Development of new or improved blown film products is an expensive and time-consuming exercise for converters. Often, many experiments and trial runs have to be performed, accompanied by evaluations of the resulting film samples. If no lab-scale blown film line is available, valuable production time is lost while seeking out optimum processing parameters. Utilization of model calculations relating polymer type and machine parameters to properties of films obviously is an interesting option to streamline the development process of films. The practical use of model calculations depends on reliability and versatility of the model used. In this paper, a Theological model is presented that was developed for low density polyethylene (LDPE), and relates rheological properties, processing conditions and die geometry to mechanical and optical properties of the films. Validation of the model on different blown film lines has proven its reliability for LDPE. Furthermore, the model has been extended to binary LDPE/LLDPE (linear low density polyethylene) blends, demonstrating its versatility for PE in general. An oversight is given of theoretical and experimental issues encountered during the development of the model, complemented with some instructive examples of practical usage.
In this paper, a model is presented that enables us to get a better understanding of the relationship between polymer type, machine parameters and blown film properties for PE. For the mechanical properties it appears that the key parameter is the stress at the freeze line. Validation of the model on different blown film lines has proven its reliability for LDPE. Furthermore, the model has been extended to binary LDPE/LLDPE blends, demonstrating its versatility for PE in general.
Polyethylene based ionomers are demonstrated to feature a thermo‐mechanical and dielectric property portfolio that is comparable to cross‐linked polyethylene (XLPE), which may enable the design of more sustainable high voltage direct‐current (HVDC) power cables, a crucial component of future electricity grids that seamlessly integrate renewable sources of energy. A new type of ionomer is obtained via high‐pressure/high‐temperature free radical copolymerization of ethylene in the presence of small amounts of ion‐pair comonomers comprising amine terminated methacrylates and methacrylic acid. The synthesized ionomers feature a crystallinity, melting temperature, rubber plateau modulus and thermal conductivity like XLPE but remain melt‐processable. Moreover, the preparation of the ionomers is free of byproducts, which readily yields a highly insulating material with a low dielectric loss tangent and a low direct‐current (DC) electrical conductivity of 1 to 6·10−14 S m−1 at 70 °C and an electric field of 30 kV mm−1. Evidently, the investigated ionomers represent a promising alternative to XLPE‐based high voltage insulation, which may permit to ease the production as well as end‐of‐use recycling of HVDC power cables by combining the advantages of thermoset and thermoplastic materials while avoiding the formation of byproducts.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.