Crosslinking Agents

are additives for the crosslinking of thermoplastics, especially for polyolefins. In the macromolecular chemistry crosslinking reactions are the linkage of linear or branched macromolecules of the same or different chemical identiy to a three-dimensional polymeric network. Covalent bonds are initiated by a controlled radical degradation in polyolefins. The built-up macroradicals react in form of a polymeric self-crosslinking, which is controlled conforming to suitable reaction conditions and/or additional bi- and polyfunctional reagents of low molecular weight (crosslinking agents). The higher the degree of crosslinking (crosslink density, number of crosslinking points in a given polymer quantity), the harder the polymer. Various materials arise from the length of the crosslink bridges: close-mesh crosslinked polymers behave like thermoset materials, wide-mesh crosslinked polymers like elastomeric materials, physically over domains crosslinked like thermoplastic elastomers. However, there are also crosslinking reactions during the normal production and ageing process of polymers.

Compatibilizer

Adhesive agents improve the adhesion strength or blending ability of materials with a different polarity by creating bipolar systems on the interfaces of the materials within the melt or on extrudates.

Extrusion Aids

Polymeric materials have a macromolecular structure with melts of high viscosities. The processing of these melts in injection molding machines and extruders is only possible under pressure. In the machines and tools maximum temperature and mechanical forces are built up due to shearing and friction which exceed the chemical stability of the macromolecules. The processing aids improve the rheology of the melt by reducing the internal (molecule/molecule) and external (polymer/metal) dissipations. Especially for the extrusion of highly viscose polyolefins with a high shear rate processing aids are necessary in order to avoid malfunctions on the extrudate surface and to prevent melt fracture.

Melt modifiers

Melt Modifiers change the rheology of the polymer melt by reducing the apparent or real viscosity of the melt. Regarding these additives there are reactive and non-reactive substances. The non-reactive substances reduce the frictional resistance inside and outside of the polymer, so that the polymer chains can better slip along each other or that there is less sticking of the polymer chains at the hot surfaces of the production machine. The reactive scissors divide the polymer chains in smaller units, so that the mechanical properties are changed apart from the improved flow properties. Many reactive modifiers contain peroxides, which do not completely react during processing and thus can still influence the mechanical properties of the final products later. Substances without peroxide are stable in this reaction window.