Controlling melt fracture in bimodal resin pipe

Abstract

A system for improving processing of polyethylene resins, comprising a processor; a memory; an output device; and an analysis component stored in the memory, that when executed on the processor, configures the processor to receive a shear stress as a function of shear rate for a plurality of multimodal metallocene-catalyzed polyethylene samples, wherein the determination of the shear stress as a function of the shear rate comprises using capillary rheometry; determine values for a magnitude of slip-stick, a stress for smooth to matte transition, and a shear rate for smooth to matte transition for each of the plurality of multimodal metallocene-catalyzed polyethylene samples based on the shear stress and the shear rate measured from capillary rheometry; identify individual multimodal metallocene-catalyzed polyethylene resins from the plurality of multimodal metallocene-catalyzed polyethylene samples having a reduced tendency to melt fracture characterized by a magnitude of slip-stick greater than about 300 psi, a stress for smooth to matte transition greater than about 90 kPa, and a shear rate for smooth to matte transition greater than about 10 s-1; and output an identification of the individual multimodal metallocene-catalyzed polyethylene resins to the output device.

Description

technical field [0001] The present disclosure relates to polyethylene compositions and pipes made therefrom, and more particularly to multimodal polyethylene compositions having improved processing characteristics. Background technique [0002] Polymeric tubing has replaced metal tubing in many applications such as high pressure fluid transportation. Polymeric tubing has several advantages over metal tubing, including relatively light weight, more corrosion resistance, less expensive, more thermal and electrical insulation, tougher, more durable, and easier to shape during fabrication. Such pipes are exposed during their service life to numerous stresses which can cause cracks or breaks which are very expensive to repair, especially if the pipes are buried in buildings or underground. Accordingly, polymeric pipes may need to meet industry-defined standards depending on their intended use. [0003] The polymeric materials used to make the tubes are often optimized to provid...

AI Technical Summary

Problems solved by technology

A challenge with using multimodal polymer compositions as polymeric materials for making pipe is that when these compositions are melted to form a polymer melt, they can exhibit poor processing characteristics, such as melt fracture, which is the result of extrusion at increased production speeds. Surface irregularities that arise during the process

Poor processing characteristics of these materials can cause reduced production speeds and / or products with undesired physical properties and / or appearance

Images