Low viscous hydrophilic processing additives for extrusion of polyethylene at reduced temperatures

Abstract

Industry is using fluorinated polymer processing additives (PPA) to delay the onset of sharkskin to higher rates of extrusion of PE resins. Yet it is necessary to keep elevated temperatures during extrusion to reduce apparent melt viscosity. We propose to use low viscous PPA made from reacting mixtures of polyethylene glycol with organic polyacids, phosphoric acid, and polyesters of oxiacids of Phosphorus. Surprisingly, extrusion pressures and apparent viscosity with the novel PPA at reduced temperatures are less, than at elevated temperatures. In total, extrusion pressures can be reduced 2-5 times for concentrations of PPA from 0.1 to 0.5 wt%, while sharkskin melt fracture can be eliminated for concentrations of PPA above 0.02 wt%. Extrusion with the novel PPA at reduced temperatures potentially increases productivity, reduces production cost, and allows processing of PE resins of higher MW and highly filled polymer composites.The use of novel PPA is a challenging opportunity to simplify processing of PO resins. The use of low viscous PEG in the composition of PPA with existing machinery has to be combined with changes in the die design for film blowing, blow molding, and pipe extrusion to extract

Melt fracture and rheology of linear low density polyethylene - calcium carbonate composites

“…Melt flow instabilities of polyethylene, which is commonly used for extrusion, are well described in the literature. The influence of molecular weight distribution, die material and additives have also been studied . The sequence and origin of nascent melt flow instabilities during flow of linear low density polyethylene were extensively described in several papers .…”

“…), whose origin is connected with the polymer flow near the die entrance and with the macromolecular structure of the polymer. Many melt flow instability suppression and detection methods have been presented in the literature, e.g., incorporation of small amounts of boron nitride , application of polymer processing additives such as polyethylene glycol (PEG), esters of PEG or fluoropolymers , polymer blending , usage of induced temperature gradients , and application of signal processing methods allowing to control the extrusion process .…”