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End-Use Case Study

  • High Gravity Compound Puts a Cap on Costs

Cap Insert

Cosmetics comprise just one element of that elusive quality known as style. In the marketplace, stylish packaging often influences initial cosmetics sales as much as the package’s content. As a leading supplier of caps and closures to cosmetics firms worldwide, Seidel GmbH and Co. of Marburg, Germany constantly monitors consumer preferences in an effort to top off their customers’ products with a distinctive style. From these efforts, Seidel has molded a global reputation for both technical innovation and marketing acumen, combining packaging of distinction with affordable quality.

At the end of 2000, Seidel was approached by the firm Dalli Werke, of Stolberg, Germany to jointly develop a new cap design for its Carlo Colucci brand perfume bottle. As the fragrance was planned for mass-market release, rapid product development and low production costs were essential. Requirements called for a matte gold metal cap with two different plastic inserts for Eau De Toilette and Splash versions of the containers. The caps needed to impart a solid, substantial feeling to give the impression of a high value product. This effect is usually achieved by attaching a steel weight inside the closure.

To imitate the weight of the piece of steel, while eliminating its time- and cost-intensive gluing and assembling steps, Seidel tried using a higher density thermoplastic compound. Additionally, the ideal material for these plastic inserts would need to be highly impact resistant, elastic enough to form a seal, and colorable. Dalli Werke and Seidel worked with RTP Company to achieve this effect. And, by the summer of 2001, the new caps with an insert molded from an RTP 100 Series high gravity compound were on display at cosmetic counters throughout Germany.

The chosen polypropylene compound features a specific gravity of 2.0—more than double the density of the unfilled base resin. With a relatively low flexural modulus of 430,000 psi (3300 MPa) and tensile elongation of over 10%, the compound exhibits the elasticity necessary to form a secure seal that is maintainable over time due to its inherent fatigue resistance. And, the polypropylene material was able to provide the high impact strength—unnotched Izod of 12 ft lb/in (25.2 J/m2)—necessary in a consumer product. The compound also features a natural light color, well suited to allowing design variations through coloring.

Seidel noted that the compound flows through the mold extremely well. The compound’s fillers produce a faster cooling rate than the previous unfilled resin so parts can be more quickly ejected from the mold. Thus, significantly lowered cycle times coupled with elimination of the bonding step have streamlined the production process and dramatically reduced costs. In most cases, plastics are introduced in metal applications for weight savings. Inverting the process demonstrates the expanded versatility of custom compounds and the results possible when a client teams with RTP Company and thinks outside the box, or in this instance, outside the bottle.

Seidel Gmbh & Co. manufactures for the worldwide cosmetics industry. They are located in Marburg, Germany. For more information visit their website at