Crosslinking methods

- Feb 27, 2019 -

Generally speaking, various crosslinking methods are used—Chemical crosslinking, silane crosslinking, peroxide crosslinking UV crosslinking, and irradiation crosslinking—All of which cover crosslinking via accelerating electron beams or gamma rays. For the production of technical components/parts foils, cable electric insulation, pipes, and houses, etc., electron beam irradiation leading to polymer crosslinking has many advantages in comparison to other methods.

First of all, the processing condition in the production of plastic parts (injection molding, extrusion etc.), is not influenced by crosslinking, since crosslinking itself is realized after processing. The crosslinking process is very rapid and can be realized in a simple way. Due to the possibility of changing the degree of crosslinking by means of the irradiation dose, it is also possible to modify/tailor polymers to customers’ needs. Electron beam crosslinking is considered to be the cleanest—And most environmentally-friendly—Crosslinking method since it does not involve other chemicals and uses only high energy electrons to perform. A possible disadvantage of irradiation crosslinking could be seen to lie in the need for significant investment and high requirements of operation safety zones.

Polymer behavior after irradiation depends on the polymer type. The effectiveness of irradiation depends on many factors that affect the structural changes of the irradiated polymers, and the resulting properties, both quantitatively and qualitatively. The main material and process factors—chemical structure, molecular weight and molecular weight distribution, polymer configuration, irradiation dose, irradiation source intensity, environmental parameters environmental temperature, as well as parameters, like the geometry of plastic products (thickness)—Can effectively be influenced by the addition of crosslinking agents: for example, TAC (triallyl cyanurate), TAIC (triallyl isocyanurate), and many others.

Two main processes occurred during the polymer irradiation crosslinking and degradation. Mainly, the chemical structure of the polymer effects the proportion of crosslinking and degradation. It is possible to differentiate polymers into two groups. Polymers from the first group (polyethylene, polystyrene, etc.)—Predominantly crosslink, their macromolecular chains, connected in 3D structures with high molecular weight, became lower.