Techtextil 2013: Strong adhesives for lamination of NFPP and PP in car interiors - Reliable bonding for highly difficult surfaces by using reactive hot melt adhesives

Detmold.- Jowat AG with headquarters in Detmold is one of the leading global suppliers of industrial adhesives. At this year's Techtextil in Frankfurt, Jowat AG is presenting the latest developments in adhesives for laminating substrates like NFPP and PP, materials used in vehicle interiors.

The challenge: Thermoplastic precoating

The process of thermoplastic precoating of decor materials - either pre-cut or on reels – with polyamide (PA) or polyester hot melt adhesives (PES) has been used in automotive interiors for quite some time. These substrates are joined in serial processes, for instance by using press lamination, to the respective base materials. The precoated hot melt adhesive is in these cases reactivated by heat and forms a very strong bond between decor material and substrate.

Lately, the automotive industry has started to use more and more newly developed substrates. One example for this consists of a mixture of natural fibres and polypropylene, abbreviated to NFPP. This material is increasingly used since it offers a number of advantages: By comparison to ABS substrates, NFPP has a much lower weight, thereby also reducing car weight and CO2 emissions. The natural fibre component consists of renewable raw materials like flax or sisal with a focus on the sustainability aspect. The base components can be formed at low cost with hot pressing methods, which makes the costly injection moulding obsolete. The challenge for the adhesive industry is now to ensure that these new NFPP substrates with their low surface tension can be laminated inexpensively and with absolute reliability.

The latest development from the product family of Jowat-Toptherm® allows precoating of decor materials for subsequent reliable bonding to NFPP components. Surface pretreatment of the NFPP prior to bonding is not necessary. The decor materials may be textiles or TPO foils - with or without foam backing. This polyolefin (PO) hot melt adhesive offers superior adhesion properties to low-energy surfaces like NFPP, while at the same time meeting the stringent requirements of the automotive industry concerning temperature resistance and bond strength.

The challenge: Lamination of components for vehicle interiors using reactive hot melt adhesives

In laminating processes for car interiors with reactive hot melt adhesives based on polyolefin (POR), the production efficiency can be substantially increased. This adhesive from the group of Jowatherm-Reaktant® entirely eliminates the step pretreatment of the polypropylene (PP) - surfaces before bonding.

One of the materials commonly used in vehicle interiors is polypropylene (PP). Components of this material exhibit a very low surface tension and so far represented a real challenge for laminating procedures which require full surface wetting with adhesive. In most cases a surface pretreatment used to be absolutely necessary.

The development of the new POR hot melt adhesive now allows to bond without pretreatment of the PP components with low surface tension, while still achieving complete surface wetting with adhesive. This system undergoes a chemical crosslinking reaction by exposure to moisture, in addition to the thermoplastic hardening. The result is an excellent adhesion to the substrates and a superior heat resistance of the bonded compound. The high initial strength in combination with a short open time facilitates the short processing intervals that are standard for the automotive industry - a major factor for components with complicated designs.

Both the Jowat-Toptherm®  adhesives and Jowatherm-Reaktant® based on polyolefin are already in serial production at well-known car companies.