Fiber-reinforced composites are a relatively small segment in the plastics industry in terms of unit sales or total production volume. Innovative and technically sophisticated solutions for the transport & vehicle manufacturing, construction industry, electrical and electronics industries, as well as sports & leisure testify to the special importance and extraordinary appeal.

The interplay of resin matrix, reinforcing material and processing offer a very wide spectrum to meet technical requirements and design solutions.

Composites / GRP

Fiber-reinforced plastics or composites form a subgroup of composite materials. This modern class of materials makes it possible to manufacture high-strength products with low specific weight.


Hand lay-up is the oldest, simplest and most widely used process for manufacturing glass fiber reinforced plastic components.

Advantages of the process:

  • Relatively low mold costs
  • Large-format and complex components can be produced
  • Particularly suitable for prototypes and small batches


  • Medium-sized and large-area parts
  • Machine covers
  • Boat hulls
  • Vehicle trailers
  • Facade cladding

In contrary to hand lay-up fiber spraying is a semi-automated process. Therefore, a mixing gun is used on which a cutter is mounted that cuts continuous fibers (rovings) into a desired length of between 20 and 60 mm, depending on the application. Together with a hardener, the resin is introduced into the mold via the fiber spray gun. As with the hand laminate, subsequent compaction and deaeration is carried out using a roller and brush.

Advantages of the process:

  • Manufacturing of large-area components
  • Fast and cost-effective production
  • Particularly suitable for higher volumes

The RTM process involves working under pressure, i.e., closed molds must be prepared in advance. A resin-hardener mixture is then injected into the closed mold via one or more resin injection ports, where it cures under heat and pressure. Additionally, to improve the resin flow, vacuum can be applied in the mold.

Advantages of the process:

  • Very good, paintable surfaces on both sides
  • Constant, high laminate quality
  • Precisely defined wall thicknesses
  • Sandwich constructions can be produced
  • Particularly suitable for reproducible series production

In this process, the single-shell mold is first lined with fiber materials. Subsequently, the mold is sealed airtight with a special vacuum film and a vacuum of around 0.8 to 0.6 bar is applied. The liquid resin is now sucked or into this mold or injected additionally.

Advantages of the process:

  • Low molding costs
  • High laminate quality
  • Particularly suitable for prototype production as well as for single piece production and small series campaigns

During the winding process reinforcing fibers are pulled through an impregnation bath with pre-accelerated resin and are then wound onto a positive core.

Advantages of the process:

  • Production of cylindrical, oval, conical, and spherical bodies
  • Partially automated process
  • Precisely adjustable wall thicknesses

As a rule, the casting process is carried out without reinforcing fiber. The activated resin is poured into the mold manually or by machine, where it cures. Fillers are often used in this process as well, which can reduce shrinkage, create optical or color effects, and reduce material costs.

The pultrusion process is used to produce profiles and hence, it is also called the profile drawing process. In this process, a defined number of rovings are soaked in an impregnating bath, then bundled and pulled through a heated die for shaping and curing. Precise temperature control is required to ensure complete curing of the material when leaving the mold.

Pultruded parts are characterized by a relatively high glass content and correspondingly high mechanical stiffnesses.

In this process, the reinforcing materials – mat blanks, fabrics or already preformed mats (preforms) – are inserted dry into the mold. Two-part molds are required.

A predetermined amount of the activated resin is poured over the reinforcing material and the mold is closed immediately. The usually high reactivity of the resin leads to a heating of the mold to 40–70 °C and therefore to a rapid hardening of the component.

Pressing compounds (semi-finished products) made of SMC or BMC are used particularly for the production of high volumes of FRP components for the automotive and electrical industries.

SMC – Sheet Molding Compound – processing of the molding compound by compression molding and curing at temperatures of approx. 150 °C.

BMC – Bulk Molding Compound – introduction of the compound into the mold by injection molding or injection compression molding.

Short cycle times and high levels of automation can be achieved with both processes.

In the centrifugal casting, the cut glass rovings and the activated resin are simultaneously introduced into a rotating cylindrical mold. Through centrifugal casting the rovings are impregnated and are being ideally compressed under the effect of centrifugal forces.

Advantages of the process:

  • Production of pipes, poles, rollers, and tanks
  • Partially automated process
  • Continuous processes possible
  • Good surface properties

Industries / Specialties

Fire protection systems

Fires can have devastating consequences, especially where escape routes are restricted. To meet the highest safety standards, Gremolith AG offers products for the manufacture of laminates, coatings and molding compounds that can be used for rail vehicles, shipbuilding, tunnel tubes, chemical plants, or offshore platforms.

Relevant standards:

DIN EN 13501-1:2019-05

  • Fire classification of construction products and building elements - Part 1: Classification using data from reaction to fire tests

DIN 4102-1:1998-05

  • Fire behaviour of building materials and building components - Part 1: Building materials; concepts, requirements and tests

DIN EN 45545-2:2020-10
(formerly: DIN 5510-2:2009-05)

  • Railway applications - Fire protection on railway vehicles - Part 2: Requirements for fire behavior of materials and components

Sewer rehabilitation

For many years, Gremolith AG has been the specialized supplier of polyester resin systems for the trenchless rehabilitation of sewers by means of "inliners". For this purpose, filled UP resins specifically formulated for this application are mixed with suitable hardener combinations so that they are optimally matched to the processing and curing conditions at the customers' site. Depending on the application, the flexible hoses are impregnated with special resin/hardener systems at the customers' site or on site and then inserted into the sewers, where they are cured with hot water or steam. For small sewers or house connections, Gremolith AG also supplies special systems for cold curing at different ambient temperatures.

This type of trenchless rehabilitation creates a new plastic pipe inside the old sewer that facilitates another 50 years of service life.


Hymer – Premium motorhome "Made in Germany"

HYMER has been the epitome of first-class motorhomes for almost 60 years, and it stands for tradition, service and quality "Made in Germany". Thanks to continuous pioneering work in terms of technology, safety, comfort as well as design, they have become the European market leader in the premium segment. The motorhomes are still manufactured in Bad Waldsee today.

HYMER uses GREMOPAL® polyester resin to produce garage tubs, storage boxes, and tubs for holding gas cylinders. The quality of the polyester resin takes is of highest importance and influences the entire manufacturing process. Only polyester resins from Gremolith AG meet the requirements in terms of processing, achieving the required component stability, and a long-lasting durability.

Vacuum injection method

"Besides the reliable product quality, HYMER appreciates the delivery reliability and services of Gremolith AG."

Hubert Schmid, Strategic Purchasing, HYMER GmbH & Co. KG

Thoma-Boote – Swiss Handmade Quality

The boat building company, founded in 1972 by Walter Thoma, produces between 20 and 30 boats per year. Each boat is comprehensively built in the company's own shipyard in Mühlehorn on Lake Walen and is a unique piece with individual finishing. Thoma boats can be found both on national and international waters and are particularly suitable for recreational pleasure and sport fishing. The hulls are hand-made from high quality polyester resins. Thanks to the double hull principle, most models are unsinkable. Carefully selected engines work economically and guarantee reliable operation according to modern environmental standards.


Gremopal® polyester resins from Gremolith AG are used as base building material for the entire shell of a boat.

Hand lay-up

Andreas Nötzli, with his company a customer of Gremolith for many years, particularly appreciates the very fast delivery speed, the flexibility in building material design (color, requirements), and the high quality of the polyester resin.

Bodus - sewer technology from practitioners for practitioners

Bodus' comprehensive product portfolio spans the entire spectrum of sewer technology and is presented under the slogan 'From Practitioner to Practitioner.' The range of services in technical equipment covers everything from sewer cleaning, canal and shaft inspection, sewer rehabilitation, and leak testing of pipelines to various products for sewer maintenance.


Bodus provides solutions for various challenges in the field of sewer management, ranging from canal cleaning, canal and shaft inspection, sewer rehabilitation, and leak testing of pipelines to various products for sewer maintenance. We offer tailored solutions for every problem, construction site, and task.

Sewer rehabilitation

Daniel Boller, who has been a partner with Gremolith for many years through his company, emphasizes the reliability in deliveries and services. Additionally, he values our profound industry expertise and the straightforward collaboration with our team. The prompt handling of inquiries and orders is also positively acknowledged. Particularly commendable is our willingness to address challenges that arise at short notice and provide suitable solutions.

CEM Composites - Composite Experts for Natural and Carbon Fiber

CEM Composites is an expert in the development and manufacture of fiber-reinforced plastics. High-quality designer furniture is produced, among other things, and it is proud to be a supplier for Vitra. In particular, the "La Chaise" chair, one of the flagships of design, uses Gremolith's resin.



The resins provided by Gremolith proved to be extremely reliable and of high quality. They meet high demands on the technical properties as well as the aesthetic quality of CEM Composites products. The processing of the resin is simple and efficient, which makes it possible to optimize manufacturing processes and achieve high production output.


The successful cooperation between CEM Composites GmbH and Gremolith as a resin supplier already exists for a number of years.

The reliable delivery and excellent customer service Gremolith offers is appreciated by CEM Composites. Our ability to respond to individual requirements and support the development of tailor-made solutions is also particularly appreciated.

It is gratifying for us to know that Gremolith is a reliable partner at our side. We would like to thank Gremolith very much for the good cooperation and expressly recommend Gremolith as a resin supplier.

Cem Koeylueer, Managing Director of CEM Composites GmbH

Müller Kunststofftechnik - Flexible and customized production of composite components

Quality, development and sustainability are represented by Müller Kunststofftechnik AG. The company's core competence lies in the individual development, custom-made manufacture and production of components and elements made of fibre-reinforced plastics. The exceptional flexibility of our products makes it possible to manufacture high-quality and highly specialized components for customers and to continuously improve them.


Composites have excellent properties: they are lightweight, retain their shape even under the highest loads, and resist corrosion, rust and oxidation.

Glass fibre reinforced plastics, carbon components, sandwich components and composite materials with other materials (wood, metal, concrete, thermoplastics) are processed and designed by Müller Kunststofftechnik AG.

 Gremolith resins are used in the industrial sector, vehicle construction, medical technology and apparatus engineering.

Hand lamination

"I would like to emphasize that Gremolith is truly outstanding in terms of flexibility and reliability in delivery. Their ability to adapt to our changing needs has helped us a lot in many situations.

The quality of Gremolith's resinsis also remarkable.

The products you supply are always of high quality and meet our expectations in terms of durability and performance.

The professionalism of Gremolith AG customer services/support is exemplary.

Their staff are always courteous and competent, and they have always helped us quickly and efficiently in various concerns.

Overall, we are extremely satisfied with your company. The combination of flexibility and reliability in delivery, high-quality products and excellent customer service makes you a reliable business partner."

Ivo Lüthi, Owner and Managing Director of Müller Kunststofftechnik AG

Quality in every detail: Probst, the experts for sophisticated solutions

For 30 years, Probst has been processing various plastics and producing innovative products.

The entire team stands out as doers, with a keen sense for refined implementations and the perfect finish. At Probst, craftsmanship and design expertise is combined with in-depth knowledge of materials, tools and manufacturing processes.

Probst AG manufactures technical components, toys, and specialized sports equipment from fiberglass.

Their whitewater racing boats, made from carbon and Kevlar, are renowned worldwide and have won several world championships.

Probst AG is also active in container construction and coatings. Under the Greenbox label, they produce special plant boxes in all sizes.

Art objects and installations complete the fabrication range.

Everything from a single source: consultation, production of molds, components, manufacturing, and assembly.


Mr. Peter Probst states: We have and always had for many years a very good relationship with Gremolith . Technical information or problems are dealt with very quickly. The processing of orders and the dispatch of materials always run smoothly. Of course, exerting influence on the International Commodity Exchange is outside the sphere of influence of Gremolith AG. Nevertheless, the materials are always delivered on time. The quality of the products is high and remains constant, which is not insignificant nowadays.

On our 'scale', Gremolith AG achieves AAA.

Fiberglass Giant: Hugo Wolf AG - Excellence in Molding!

Hugo Wolf AG is a leading company in the processing of glass fiber reinforced plastics (GRP) throughout Switzerland. In addition to manufacturing a wide range of molded parts for the construction, transport and art sectors, Hugo Wolf AG is known throughout Europe for its Wolf cabins.


Hugo Wolf AG stands out with a wide array of core competencies, including cabin construction (for cash desks, restrooms, control rooms, technical rooms, etc.), prototype development, contract manufacturing (for small to medium-scale series), the production of high-quality plant containers under the brand, repairs of existing GRP parts, as well as carpentry and metalworking services.

Hand lamination, Fiberspraying

Through our long-standing partnership with Gremolith, we are pleased to have come to know an extremely reliable and committed company. Over the years, we have experienced Gremolith as a business partner that is always ready to respond to our individual wishes. Their ability to always complete orders on time and to our complete satisfaction is testament to their professionalism.

E. Plank - Fiber-Reinforced know-how since 1959

With over 50 years of experience, Ing. E. Plank GmbH is looking forward to new challenges with anticipation.

Since 1959, Ing. E. Plank GmbH has been recognized as a specialist in the processing of glass fiber reinforced plastics, particularly polyester (thermosets, GRP). Their extensive range includes, among other products, high-quality glass fiber reinforced plastic molded parts.

For glass fiber reinforced plastic molded parts, the highest quality is the standard. Each GRP molded part or thermoset component is individually configured according to specific needs.

Ing. E. Plank GmbH has played a significant role in equipping approximately 70% of all television towers in Europe with their high-quality panels for directional and broadband antennas. Moreover, the company is a leader in the manufacture of casings for electromagnetic linear acceleration motors, including stators and ventilation nozzles, which are used in the world's largest roller coasters. The production of protective covers for motorhomes and the large-scale manufacture of siren boxes for federal air protection services complete the versatile range of services offered by Ing. E. Plank GmbH.

Hand lamination, Vacuum process

At Ing. E. Plank GmbH, we would like to acknowledge the outstanding partnership with Gremolith AG and express our satisfaction with the quality of your resin products and the accompanying service offerings.

For 10 years now, we have been regularly procuring resin products from Gremolith AG, and we wish to emphasize that the quality of your resins has consistently met our expectations. The high purity, reliability, and consistency of your resin products have significantly contributed to ensuring the quality of our own plastic products.

We value the punctuality and efficiency with which your products reach our factory. This reliable supply chain helps optimize our production processes and avoid bottlenecks.

Furthermore, we would like to highlight the excellent support provided by your team. We have always been promptly and professionally assisted with any questions, concerns, or special requirements.

Overall, the collaboration with Gremolith AG leaves us greatly satisfied. We especially appreciate the outstanding quality of your products and the excellent customer care.

We look forward to continuing our successful partnership and are happy to recommend your resin products to others.