Case Study: Rugged Cover Molded from Crastin® PBT Protects Power Components
Molding productivity, excellent surface and long-term reliability make Crastin® PBT thermoplastic polyester resin a superior choice for large covers.
Application Description
Large covers for power network boxes for DaimlerChrysler minivans are injection molded from Crastin® PBT thermoplastic polyester resin. The cover measures approximately 10.5 in. long by 5 in. wide (267 by 127 mm) with an average wall thickness of about 0.080 in. (2 mm).
Materials Selected and Why
A special 15% glass-reinforced grade of DuPont™ Crastin® PBT resin with enhanced hydrolysis resistance, meets this application’s needs for:
- High flow to fill a large mold
- Excellent toughness and retention of toughness in the under-hood environment
- Superior surface appearance and weld line strength
Benefits Gained
- Reliability – The toughness of Crastin® helps prevent breakage of the cover’s snap latches. This Crastin® resin outperforms standard glass-reinforced PBTs in initial toughness and long-term retention of toughness in hot, humid under-hood environments.
- Molding productivity – Crastin® consistently fills the mold for this large part without resorting to excessive melt temperatures or pressure, which can reduce toughness and strength. Cycle time and yield meet targets for profitability.
- Excellent surface – Molten material enters the mold through edge gates at each end. With Crastin®, the two flow fronts merge to form a strong, scarcely visible weld. This is crucial because the weld is in an area where printed instructions are applied.
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