Radiation crosslinking gives inexpensive commodity plastics and technical plastics the mechanical, thermal and chemical properties of high-performance plastics. This “upgrading” enables these plastics to be used under conditions which they would not withstand otherwise. The energy-rich beta or gamma rays trigger chemical reactions in the plastic parts and thus result in a crosslinking of molecules – comparable to the vulcanization of rubbers that has been used for a long time.
Since the finished plastic product is modified in this way, it is even possible to vary the level of crosslinking and/or the crosslinking process within the component by protecting parts of the product from radiation. Thus, BGS helps you to optimize the material properties of plastics and opens up new areas of application.
The process takes place at room temperature and under normal pressure.
Irradiation takes place after the moulding process. In this way, the processing advantages of thermoplastics are combined with the properties of thermosetting plastics.
Parameters can be flexibly adapted to individual requirements in each case.
The use of relatively inexpensive commodity and/or engineering plastics leads to substantial cost savings. Generally, this makes the acquisition of new injection moulding tools no longer necessary.
The admixture of crosslinking chemicals such as peroxides is no longer necessary. This provides advantages with regard to material costs, reproducibility and processing. For example, without the in-line crosslinking, higher extrusion speeds for PE pipes can be achieved that are three to four times faster.
Crosslinking is carried out after production as an outsourced processing step at BGS. This enables the manufacturing of your product at an optimal speed. Another advantage is that plastic production waste (for example, injection moulding residues) can simply be returned to the production process.
Radiation crosslinking is also suitable for material combinations – even metal parts are able to be irradiated in combination with polymer materials.
Many polymer materials are suitable for radiation crosslinking. In general, all plastics which are capable of being crosslinked with radical initiators such as peroxides can be optimized through radiation crosslinking. However, unlike chemical crosslinking methods, radiation crosslinking takes place at low temperatures. The plastics most often processed are those with the broadest range of applications: Polyethylene (PE) and its co-polymers, polyamide (PA), polyesters such as PBT and polyvinylchloride (PVC). For some materials with low reactivity, a special crosslinking accelerator is required. These additives may either be added directly before the moulding process, together with the raw granulate as a masterbatch, or used directly as a finished compound.
When polyamides are radiation crosslinked, they are able to withstand considerably higher temperatures of up to 350 °C and show a significantly improved wear behaviour. The dimensional stability under thermal stress is also improved. Radiation crosslinked polyamide can often replace thermosetting plastics and/or more expensive high-performance plastics such as PPS, PEI, LCP, etc. Applications proven over many years include radiation crosslinked parts for the electrical and automobile industry – e.g. switching components or components for the engine compartment - as well as parts for mechanical engineering. Currently preferred types comprize PA 6, PA 6.6, PA 11 and PA 12. Polyamides must contain a special additive (crosslinking enhancer) to be capable for crosslinking.
Crosslinking of polyethylene (PE) extends the application range of this plastic material for the use at higher temperatures or for high mechanical and chemical requirements. All types of polyethylene (PE-HD, PE-LD, PE-UHMW, etc.) and its copolymers (EPDM, EVA) can be radiation crosslinked. As a semi-crystalline material, PE is mainly crosslinked in amorphous areas – the degree of crystallization and the density remain almost unchanged. Radiation crosslinked PE-Xc is a well-tried and proven material for pipes and tubes, e.g. for use in underfloor heating as well as gas and water utilities. But also other application areas, such as transport boxes and rotating components, benefit from the significantly improved mechanical properties of irradiated PE.
The advantage of PBT radiation crosslinking is a considerably higher heat resistance: This enables short-term exposure to temperatures of up to 400 °C. An important application area is for example the electrical industry. By means of radiation crosslinking, thermosetting plastics are replaced by thermoplastics and therefore provide significant processing advantages.
The crosslinking of thermoplastic elastomers (TPO, TPC and TPA) is becoming increasingly important. Advantages are improved compression sets and hot set values. In this combination, the advantage of easy processing of a TPE with the properties of an elastomer presents itself.
In principle, the crosslinking of polypropylene is also possible, although with this material, degradation reactions tend to predominate. Successful radiation depends on the selection of a suitable (co-)polymer type in combination with a crosslinking accelerator. Our experts will be happy to advise you in this regard.
Due to the chemical composition, standard PU types cannot be crosslinked by radiation. However, modified types are available, which are easily capable of being radiation crosslinked. Please contact your raw material supplier.
In recent years, many new materials and co-polymers came onto the market. It is not possible to list all materials that are suitable for crosslinking. In general, radiation crosslinking is always able to be carried out, if chemical crosslinking with free radical initiators (such as peroxides) is possible. Please contact our experts!