Metal in engine compartment replaced

by innovative short-glass-fibre-reinforced PP

As a consequence of growing materials requirements, the modification of time-tested thermoplastics with special surface treatments or reinforcing materials has proven to be a particularly suitable application-specific solution. With this approach, reinforcing materials are distributed homogeneously throughout the plastic matrix and if necessary-as is the case with glass fibres, for example-these materials can be chemically coupled to the polypropylene (PP) matrix by means of special additives. Semi-crystalline PP is the base material used.

A supporting plate for an automobile seat design was initially produced by a leading plastics processor using a standard 30% glass‑fibre‑reinforced PP. When the finished parts were assembled, however, it became apparent that the material unfortunately lacked the necessary strength for the application, and the component ended up fracturing at the joints. After a thorough review of the component requirements in consultation with an application engineer from plastics distributor K.D. Feddersen, the component and design were optimised. When it came to selecting a suitable material, a grade of Hostacom-a PP homopolymer from LyondellBasell Industries-was chosen.

Thermoplastics generally exhibit a typical creep behaviour. Over time they deform under mechanical stress, even at room temperature. The specifically modified Hostacom G3 R05 used in this application-also reinforced with 30% glass fibres, but chemically coupled in addition-exhibits minimal creep under stress, even at elevated temperatures. Moreover, it features an extremely high heat ageing resistance.

Chemical coupling causes glass fibre to become more tightly bound to the matrix, resulting in improved tensile strength, flexural strength and notched impact strength as compared to conventional glass-fibre-reinforced materials. Thus most properties of chemically coupled glass fibre in conjunction with an optimised polymer matrix are comparable to those of a long-glass-fibre (LGF) material. Once the modifications had been made, the component was successfully manufactured and assembled using the new material in compliance with the ultimate buyer's specifications.

Glass-fibre-reinforced PP used in front-end component

Traditionally, metals or other engineered plastics have been the materials of choice in front-end components, and thus the use of short-glass-fibre PP to produce the front end in the new Volkswagen Tiguan represents yet another innovation.

High temperatures, impacts and vibrations-these are typical conditions in the engine compartment that place rigorous demands on components. Impact strength, dimensional stability, rigidity and heat resistance are essential properties of all materials used in this area. In addition to these material properties, a balanced benefit-cost ratio was of crucial importance for Volkswagen. By modifying the polymer matrix in Hostacom G3 R05, greater impact strength with unparalleled rigidity was achieved, plus a flexural modulus of over 7 000 MPa (on test plaques). Corresponding static and dynamic tests as well as fatigue tests were successfully carried out, and the material was consequently approved for the front-end application at Volkswagen.

Uniform fibre length and extremely even fibre distribution throughout the component are further characteristics of this new generation of glass-fibre-reinforced plastics. As a result components are less prone to warpage, and the material can also be used for injection-moulded parts with complex geometry.

Hostacom products from LyondellBasell Industries were developed specifically for use in vehicle interiors and engine compartments, as well as for electronics applications. In addition to non-reinforced products and products reinforced with mineral and glass-materials that affect rigidity, toughness, shrinkage behaviour, creep behaviour, mechanical strength, heat distortion temperature and processability, in particular-easy-flowing grades are also available. Above all, these grades enable improved cycle times, resulting in faster production times and ultimately, lower production costs. By using these easy-flowing grades, it is possible, for example, to reduce the wall thickness of moulded parts and produce low-deformation moulded parts.

Metal substitutes in the engine compartment

When replacing metals in the engine compartment, it is absolutely essential that the substitute material exhibits high heat resistance and resistance to chemicals, along with minimal creep.

Improved soundproofing and vibration damping compared to acrylonitrile butadiene styrene (ABS)-in the underbody trim, engine enclosure or housing of electronic parts, for example-are key product benefits for the end user. The material can be surface-treated with either a matte, scratchproof finish (for use in vehicle pillar trims) or a high-gloss finish for visible parts.

Special low-emissions and low-odour grades for use in vehicle interiors and HVAC unit housings round out the versatile, flexible properties of this product. For easier identification of the respective areas of use, LyondellBasell Industries PP grades for vehicle interior applications and engine compartments as well as electronics applications go by the trade name Hostacom, while products for vehicle exteriors are commercialised under the trade name Hifax. A new product family distinguished by extreme softness, flexibility and an exceptional feel is offered under the trade name Softell.

Front-end of VW Tiguan in short-glass-fibre-reinforced PP Hostacom G3 R05