Improving Layer Adhesion of Co-Extruded Polymer Sheets by Inducing Interfacial Flow Instabilities

Abstract

Co-extrusion is commonly used to produce polymer multilayer products with different materials tailoring the property profiles. Adhesion between the individual layers is crucial to the overall performance of the final structure. Layer adhesion is determined by the compatibility of the polymers at the interface and their interaction forces, causing for example the formation of adhesive or chemical bonds or an interdiffusion layer. Additionally, the processing conditions, such as temperature, residence time, cooling rate, and interfacial shear stress, have a major influence on the interactions and hence resulting layer adhesion. Influences of temperature and residence time are already quite well studied, but influence of shear load on the formation of an adhesion layer is less explored and controversially discussed in existing literature. In this work, we investigated the influence of different processing conditions causing various shear loads on layer adhesion for a two-layer co-extruded polymer sheet using a polypropylene and polypropylene talc compound system. Therefore, we varied the flow rates and the flow geometry of the die. Under specific conditions interfacial flow instabilities are triggered that form micro layers in the transition regime between the two layers causing a major increase in layer adhesion. This structure was analyzed using confocal Raman microscopy. Making use of these interfacial flow instabilities in a controlled way enables completely new opportunities and potentials for multi-layer products.

Effect of Mortise and Tenon Structure on the Properties of Wood Flour Polyvinyl Chloride-Laminated Veneer Lumber Co-Extruded Composites

“…At present, co-extrusion technology has been applied to the production and preparation of WPC composites, namely Co-WPCs. Generally, Co-WPCs have a core-shell structure, which provides a platform for the design of Co-WPCs with different properties to adapt to different use conditions [26,27]. However, the core-shell interface bonding ability of co-extruded composites is poor, and stress cannot be effectively transferred between interfaces, which greatly limits the synergistic effect between the shell and core layers.…”

Organosilicon Compounds in Hot-Melt Adhesive Technologies

“…The force of adhesion between elastic bodies depends on the geometry and energy of the contacting surfaces [ 1 ]. There are several interactions that contribute to the formation of an adhesive bond, including van der Waals attractive forces [ 1 , 2 , 3 , 4 ], mechanical interlocking [ 2 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ], interdiffusion of polymer chains across the interface [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ], chemical bonds at, or across the interface, and electrostatic interactions [ 11 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. Currently, there is no comprehensive and quantitative theory that can establish a clear connection between the physical and chemical attributes of materials, and effectively explain their adhesion as well as the practical strength of an adhesive bond established with the said materials.…”