Our latest machine delivery for polyurethane production and processing in Weitra.
3 main components, 4 colors, 3 additives and state-of-the-art control technology on this machine allow us to produce challenging and very high quality demanding polyurethane products for worldwide use. In terms of quality, we make no compromises.
Let’s take a look at the wonderful products we make: https://asmapur.polyurethane.at/products/
HOW DOES THE COATING AND MOULDING OF PU PRODUCTS WORK?
Polyurethane products are mainly cast products; other methods like spraying, vacuum casting, or injection moulding (only for thermoplastic polyurethanes (TPU)) can also be applied.
In the low pressure casting process, chemically reactive polyurethane formulations, consisting of the main components polyol, isocyanate and cross-linkers, are blended by hand or using machinery after pre-treatment and then poured into open moulds. In these heated moulds, the material reacts and changes into a solid state. The product is then removed from the mould and stored in tempered post-curing ovens overnight.
Advantages:
Use of light-weight and cheap moulds (due to low or no pressure)
High flexibility in processing (wide range of different material components can be combined in many different ways)
Customized product properties
Production of both low quantities or series
Disadvantages:
Labour and energy intensive production (difficult to automatize)
Limits in the design (undercuts, shrinking)
Some interesting variations are rotational casting (the highly reactive liquid is poured directly onto the rotating roll core), centrifugal casting (casting into rotating drums or moulds), and vacuum casting. The vacuum casting process is similar to the low pressure casting process; the only difference is that all steps are carried out under vacuum. This method combines the advantage of low pressure casting with the possibility to produce high-precision products, complex geometries and thin walls without trapped air bubbles and pin holes.
Advantages:
Use of simple moulds (no pressure applied)
High flexibility in processing
Customized material properties
Production of difficult designs and geometries (undercuts, thin walls)
Compact material quality
Disadvantages:
Limit of formulations that can be processed under vacuum
Highly complex technical process (even more complex than low pressure casting)
Suitable only for small quantities or very special, complex parts
Injection moulding is used for thermoplastic polyurethanes (TPU), where granulated material is melted under high temperature and injected into special moulds under high pressure.
Advantages:
High level of automation (unmanned operation)
Precision finish and high surface quality (even undercut, complex designs)
High precision and repeatability
Disadvantages:
Complex and expensive moulds and machines (to withstand the high processing pressures), Reduced flexibility in terms of material variety
Problems with adhesion to metal
In spray coating no moulds are used. A highly reactive type of polyurethane is sprayed directly onto the (metal) surface to be coated. Within a few seconds, the polyurethane coating turns into a solid, compact and wear-resistant plastic coating.
Advantages:
Quick and simple method to produce wear-resistant coatings on big surfaces, especially in the construction and steel industry.
Disadvantages:
Unappealing surface (suitable only for technical/functional applications)
Inferior properties in comparison with polyurethanes made in casting procedures
Only suitable for a few purposes
In mechanical processing steps such as cutting, milling, turning, grinding, etc., semi-finished goods (e.g. rods, plates and tubes) are produced using special tools and machinery to produce high-precision parts.
Advantages:
High precision
Low or limited investment in moulds or equipment
Disadvantages:
Limited application as not all polyurethanes, especially soft materials, are fit for machining