starlim KeepCap
Keeping more than bottles covered.
Keep it sealed, keep pressure balanced, keep it touchable, keep it yours: four functions in a single silicone part. Discover what LSR injection molding can do.
KeepCap is a liquid silicone rubber (LSR) bottle closure that starlim developed as a technology demonstrator. It combines flexible sealing lips, a pressure relief valve, a haptic surface and laser personalization in one part that can be produced economically in series.
Keep It Sealed
One geometry. Multiple bottle standards.
Beer, wine, soft drinks, sparkling wine: every bottle has a slightly different neck. KeepCap keeps up. Flexible sealing lips adapt to different diameters and shape tolerances and seal the bottle tightly. A retention feature holds the closure securely on the bottle neck, and it is still easy to put on and take off.
This is made possible by the flexibility of liquid silicone rubber (LSR) and a sealing geometry that is produced as a single part by injection molding, with no additional components or assembly.
Demonstrates:
- Flexible sealing lips for tolerance compensation
- Reliable sealing across different bottle necks
- Snap-fit retention for sparkling wine/champagne bottles
- One part, no assembly
The cross-section shows how geometry and material behavior work together. Flexible sealing lips ensure reliable sealing and compensate for tolerances in the bottle neck. A snap-fit retention feature, designed for champagne and sparkling wine bottles, holds KeepCap securely in place. The integrated pressure relief valve releases pressure in a controlled way. Force-demolded undercuts show which complex geometries can be molded directly within a single LSR part, without slides or assembly.
Keep Pressure Balanced.
Smart pressure relief for carbonated beverages.
Carbonation builds up pressure, and it has to go somewhere. KeepCap solves this with an integrated pressure relief valve: if the pressure in the bottle rises too high, the valve releases it in a controlled way, while the closure stays tight during normal use. The valve is part of the silicone geometry and is molded directly during injection molding, as a thin-walled structure with no separate valve part and no assembly.
This is made possible by combining thin-wall LSR processing with a valve geometry that unites pressure relief and structural stability in a single part.
Demonstrates:
- Pressure relief valve integrated directly into the part
- Thin-wall LSR processing in series production
- Controlled pressure relief with a tight seal
- Multiple functions in one part, without assembly effort
Keep It Yours.
User-friendliness built right into the part.
Which bottle is mine? Anyone who hosts a party or shares drinks knows the question. KeepCap answers it right at the closure: integrated identification nubs make each bottle individually recognizable, with no accessories, labels or markings. The nubs are part of the silicone geometry and are formed in the same injection molding step as the entire closure.
KeepCap shows how customer-specific functions such as identification or operating aids can be integrated directly into the product geometry of an LSR part. This reduces complexity and improves the user experience.
Demonstrates:
- Identification built into the part, no extra components
- User-centered product development in a real example
- Precision toolmaking for fine details
- Fewer parts, less effort, more benefit
Keep It Touchable.
Surface engineering beyond appearance.
A closure is picked up every day, so it has to feel good and offer a secure grip. KeepCap combines different surface textures in a single part: grippy areas for turning and holding, finer textures for a pleasant feel. The structures are reproduced directly in the mold and formed in the same injection molding step as the closure.
KeepCap shows how precisely fine tool structures can be transferred to LSR silicone parts, and how surface design supports grip, usability and brand recognition.
Demonstrates:
- Multiple surface textures in one part
- Fine tool structures, precisely reproduced in silicone
- Haptics that support grip and brand impact
- Surface design directly in injection molding, without post-processing
Keep It Unique.
Laser personalization without ink or labels.
A name, a logo or a serial number: KeepCap can be individually marked after production, with no ink, labels or additional components. This is made possible by a laser-markable silicone material. During laser marking the surface changes color, creating a permanent, high-contrast mark directly in the material.
KeepCap shows how material development and downstream process steps can be combined: laser-markable LSR enables identification, traceability and individualization of series parts.
Demonstrates:
- Laser-markable silicone with color change
- Permanent marking without ink or labels
- Marking for traceability in series production
- Personalization without tooling changes
More than a Keepsake.
At first glance, KeepCap is a bottle closure. At second glance, it is an example of how much function fits into a single silicone part: flexible sealing lips, a pressure relief valve, identification nubs, haptic structures and laser personalization, all produced by injection molding and economically manufacturable in series.
For us, KeepCap represents what we do every day in customer projects: turning complex requirements into robust, manufacturable and scalable solutions.
Working on a challenging silicone application?
Complex geometry, integrated functions, specialized materials or high-volume series production: our engineering teams support you from the first idea to series production.
Let’s talk about your next silicone challenge.
Contact us to explore what’s possible.
Starlim Spritzguss GmbH
Mühlstraße 21
4614 Marchtrenk
Österreich
Telefon: +43(0) 7243 58596-0
Frequently asked questions
What is KeepCap and why was it developed?
KeepCap is a liquid silicone rubber (LSR) bottle closure that starlim developed as a technology demonstrator. It combines sealing, a pressure relief valve, identification, haptics and laser personalization in a single part, showing which functions can be integrated into silicone applications.
How can silicone seals be designed for reliable performance?
A reliable silicone seal results from the interplay of material, geometry and operating conditions. When designing seals, starlim takes into account tolerance ranges, compression set, environmental influences and long-term behavior, and develops the seal to fit the specific application.
KeepCap’s flexible sealing lips are an example: they compensate for the tolerances of different bottle necks and seal reliably even under changing conditions.
How can a pressure relief valve be integrated into a silicone part?
A pressure relief valve can be integrated into a silicone part as a thin-walled structure. It releases pressure in a controlled way without compromising the seal during normal use. starlim develops such functions together with customers and matches valve and seal to each other.
In KeepCap, the pressure relief valve is integrated into the LSR geometry and formed during injection molding, with no separate valve part.
How can customer-specific functions be integrated into a silicone part?
Silicone parts can do more than seal: positioning, operating aids, identification, guidance or assembly support can be integrated directly into the geometry. This saves additional parts and assembly steps.
In KeepCap, the integrated identification nubs show how such a function becomes part of the component itself.
How are tactile and touchable surfaces and textures created on silicone components?
Tactile surfaces result from the interplay of tool design, material selection and manufacturing: the structure is reproduced in the mold and transferred to the silicone part during injection molding. This allows touch, grip and brand perception to be designed deliberately.
KeepCap shows how a surface can be made to feel right: its textured grip area combines functional and tactile value, so the closure is not just seen but touched.
How can silicone parts be individualized and marked?
With laser-markable silicone materials: after injection molding, a laser creates a permanent, high-contrast mark directly in the material. This allows serial numbers, logos, product information or individual markings without ink or labels.
KeepCap’s laser-markable area shows how material development and downstream marking combine to support individualization, branding and traceability.
