Unlimited Design Possibilities
- Tuesday, 14.09.2010
Special-Effect Masterbatches. A polypropylene film composite creates brilliant, streak-free color effects on every surface in an automobile interior. A special-effect Masterbatch developed specifically to provide a unique gloss and metallic look makes this possible. Potential applications for this concept can be found basically wherever an upscale design is the primary objective.
The increasingly demanding requirements of the automobile market for ever more specific and complex interior trim characteristics present makers of Masterbatches with significant challenges. From product development to full-scale production, producers of plastic products must react flexibly and quickly to the needs and demands of automakers. On the one hand, the material must save costs; on the other, it must satisfy the quality requirements of the OEM by providing attractive surfaces with a good feel and exceptional mechanical properties as well as low weight. Previously, creating and attractive surface with special effects posed problems for producers: These ranged from flow lines and material accumulations to other blemishes and weld lines in the finished product. Such plastic surfaces required finishing in several post-production operations until now.
Problems with Materials to Date
Thermoplastic parts in an automobile must satisfy the requirements of the OEM individually and in specific regards. Here, the Masterbatch supplier can have a decisive effect on the subsequent product quality. This applies to the surface as well as the color of the component to be manufactured. For instance, polypropylene (PP) has certain limits with regard to gloss as well as scratch and marking sensitivity. Engineering resins such as ABS and (PC+ABS) blends usually exhibit a high yet variable gloss. Painting the components is associated with large investments. In view of these problems, a well-known systems supplier has developed a film that takes into account a multitude of the requirements from various OEMs. The integrated decorating process of the film offers several benefits: Uniform surface quality, freedom regarding grain selection, high abrasion and chemical resistance, very good scratch and marking resistance, all within a moderate commercial framework. This development is based on use of a Masterbatch that provides gloss and a metallic look, since a high-grade interior plastic surface can also be achieved by creating stunning effects.
High-gloss effects in automobile interiors achieved in plastics through use of special-effect Masterbatches have opened up new design opportunities for GRAFE Advanced Polymers GmbH, Blankenhain, Germany. At the same time, cost savings result compared to component finishing processes used to date. When used in a polypropylene film composite, a newly developed special-effect Masterbatch for a gloss and metallic look creates such stunning, streak-free color effects on any grained surface. Simple yet highly variable control of the process yields significant economic benefits. That was previously possible only though use of painting, plating or other finishing technologies can now be achieved in the form of an injection molded PP-film composite. Thousands of possibilities for color variations and metallic effects result from combining transparent gloss-effect film with a colored substrate. Backlighting of a semi-transparent composite structure is also conceivable. This would provide a commercially attractive new framework for the trend toward ambient lighting in the vehicles interior though us of a PP material.
Demanding requirements for brilliance and optimal processability of the special-effect Masterbatch in the film process hat to be satisfied. In addition, development focused on compliance with automotive requirements. Using a multi-step development process, is was ultimately possible to develop a complex Masterbatch formulation. This formulation prevents, for instance, critical accumulation of metallic particles during extrusion of the film. Incorporating the special-effect pigments in such a way as the prevent disruption of the surface presented an additional challenge. These problems were resolved through processing and the formulation modifications. A suitable machine configuration was also selected for producing the combination Masterbatch: Especially gentle extrusion ensured some of the required properties such as brilliance and the metallic effect. This is achieved b< the balance between film quality, color brilliance and metallic look. This newly developed product is in line with current development trends in the plastics industry, namely, to find cost-effective material combinations for post-production finishing. At the same time, coloring a film during the production process presents material suppliers with demanding requirements – from the resin manufacturer to the additive supplier. Film-quality coloring – especially of very thin film – requires customer- specific formulations.
The polyolefin film is colored though use of a specially developed Masterbatch and has a wall thicknes of < 400μm. Since the film and component substrate are both made of polypropylene, optimal bonding during the injection molding process is ensured without the need for pretreatment. Compared the classic materials such as ABS and PMMA, this PP-based process offers a special benefit with regard the warpage of the finished product and saves costs as well. The real challenge is incorporating the metallic particles, the size of which is relatively large in relation to the film thickness, making them difficult to process. By using a specifically formulated for the film process, the processor can color molded components without knit or flow lines. The product can also be combined. This means that the substrate and overlying film can be transparent or translucent. In this case, the overlying film is produced with the desired transparent metallic effect. In the combination mentioned, the composites can be illuminated, thus offering a multitude of design possibilities. Possible examples in this regard include backlighting and sensitive ambient lighting. This makes tit possible to play with several colors and an elegant appearance of vehicles interior components. There is also the opportunity to extend the appearance of the exterior paint finish to plastic components in the interior through use of the special-effect Masterbatch. Freedom regarding grain selection offers additional design opportunities. Though use of gloss and metallic effects in the PP-film composite, various grains can be replicated on a component. A simple change of the decoration or film during the process increases the processors flexibility even further. Full expression of the grain in radii and identical component colors from different production equipment are assured. Even complex textures on the back can be incorporated. The cost savings from not having to color the substrate – a PP material – are a welcome side effect. The PP component bonds to the PP film without an adhesion promoter.
The Process Sequence
As already mentioned, the PP film is produced with a thickness of < 400 μm and the PP substrate material is backmolded onto it. No pretreatment of the bonding surfaces with additional adhesion promoters is needed for bonding to occur. The production process is called thin-film backmolding. The process proceeds as described in the following sequence: For deep components, the PP film is formed prior to backmolding; this is not necessary with shallow components. The preform or film is placed into the injection mold, which then closes. The PP substrate material is then injected into the mold, where is bonds to the grained film. The edges of the molded component are then laser-trimmed. This multi-step process creates a certain system complexity.
The objective of automakers is the have competitive products at competitive prices while providing maximum use to the customer. This process meets these requirements by satisfying the following criteria: Cost savings: The principle of a PP-film composite is a cost-effective alternative to the previously painted plastic surfaces in the vehicles interior. Cost savings of 30 % and more are possible. The component is produced using expensive resin combinations such as PE or PP while achieving an upscale appearance. This reduces overall costs. In this way, engineering resins such as PET and PMMA can be replaced. The system as a whole provides weight savings in the vehicle as well. Feel: the pleasant fell is an additional benefit over freshly molded plastic surfaces. In this regard the great freedom with regard to grain selection should not be overlooked. Use of the gloss and metallic effect in the PP-film composite makes it possible to achieve various grains on a molded part, and replicate them fully even in radii. Substitution: Not only expensive and heavier resins (PET, PMMA) are replaced in the automobiles interior by more favourably priced polyolefin such as PE or PP. Even materials such as wood, aluminium and other metals can be imitated. The PP-film composite gives the component the high quality appearance of an upscale material. Environmental compatibility: The purely PP composite – PP film and PP substrate – means that the final product can be recycled without any contamination. This environmental aspect permits re-use of the final product, since the material is fed back into the production cycle.
The Possible Applications
The special-effect Masterbatch for gloss and metallic look can be used where ever a design calls for an upscale appearance. In addition to automotive interior components, such applications include household appliances, furniture and design fascia. The high- quality appearance imparted by the film as well as the streak-free color effect makes it possible to substitute lower-cost materials for a metallic design. Brushed metal fascia can be imitated and replaced without difficulty. Thanks to this new process, it is now possible to replace costly engineering resins such as PMMA and PET. Other possible applications for the Masterbatch include ambient lighting through semi- transparent film. With different lighting option – backlighting among them – there are no limits to product design.
First publication: Kunststoffe March 2010
Publication: September 2010
Apart from color and additive master batches, the product spectrum of GRAFE Advanced Polymers GmbH includes a wide range of functional plastic compounds. One of the industry’s largest R&D departments is focusing its efforts on the latest technologies that can equip plastic with intelligent functions. Founded in 1991, the company is now operating as GRAFE Group with its three divisions: Color Batch, Additive Batch and Polymer Technik. The employees develop new products and produce in the highly modern facility at Blankenhain (Thuringia) in heart of Germany for the national and international market. The Group is certified pursuant to DIN EN ISO TS 16949 and DIN EN ISO 9001/2000. Further information under: www.grafe.com
GRAFE Advanced Polymers GmbH
Sarah Weber-Liel Phone: 036459-45-216
Waldecker Straße 21 Fax: 036459-45-123