THE DEFINITIVE EXPLANATION OF THE WORLD’S ORIGINAL PMI STRUCTURAL FOAM**

ROHACELL® is the original PMI (polymethacrylimide) structural foam, created in Germany more than fifty years ago and still regarded globally as the benchmark for high-performance composite core materials. It combines exceptionally low density with high stiffness, excellent thermal stability, and predictable long-term mechanical behaviour. Because of its proven engineering performance, ROHACELL® is used in aerospace, Formula One, defence systems, UAVs, medical technology, robotics, marine structures and high-tech industrial manufacturing.

ROHACELL® is not simply another lightweight foam. It is a precision-engineered, chemically advanced, fully traceable composite core material with a data set spanning five decades. This makes it the most trusted PMI foam in the world and the reference point against which all competing or copycat PMI foams are compared.

PMI FOAM EXPLAINED: THE CHEMISTRY BEHIND ROHACELL®

PMI foam (polymethacrylimide) is a rigid, closed-cell structural foam produced from methacrylate-based precursor polymers. Through a controlled thermal expansion and imidisation process, the polymer forms a highly crosslinked, thermally stable molecular structure. This chemical network gives PMI foam its unique combination of stiffness, heat resistance and dimensional stability.

Most foams—PVC, PET, PU and other thermoplastic cores—soften, shrink or distort during high-temperature composite curing. PMI does not. The imide structure provides a thermoset-like stability that allows ROHACELL® to survive aerospace prepreg cycles without losing shape or strength.

The core advantages of PMI chemistry include:

• high specific modulus and strength
• excellent shear stiffness
• very low resin uptake
• closed-cell structure for predictable laminate performance
• dimensional stability under static or cyclic load
• reliable creep resistance
• consistent machining behaviour
• stable dielectric properties

ROHACELL® is the most advanced and most thoroughly tested PMI formulation of this family.

HOW ROHACELL® IS MANUFACTURED: CONTROLLED GERMAN ENGINEERING

ROHACELL® is produced exclusively in Germany using a sequence of controlled processes refined over more than fifty years. Each stage influences final mechanical properties, which is why the consistency of the German manufacturing process is essential.

The manufacturing process involves:

1. Synthesis of the PMI Precursor Polymer

The base polymer is produced from methacrylate monomers using carefully tuned chain-length distributions. Small variations here significantly alter stiffness and creep behaviour.

2. Controlled Foam Expansion

The precursor undergoes a precisely engineered thermal cycle. Pressure, temperature and expansion rate determine cell size, density uniformity and microstructure integrity.

3. Stabilisation through Heat Treatment

Post-expansion heat treatment locks the molecular structure into place and ensures long-term stability across temperature cycles.

4. Precision CNC Slicing and Shaping

Blocks are sliced into panels with extremely tight tolerances. ROHACELL® offers some of the most accurate thickness tolerances of any structural foam, essential in aerospace and motorsport laminates.

5. Multi-Point Quality Control and Certification

Every batch is subject to mechanical testing—compressive strength, shear modulus, heat ageing, creep resistance—and is fully traceable through production records.

This rigorous, highly specialised process is why genuine ROHACELL® continues to outperform all imitation PMI foams.

WHY ROHACELL® IS STILL THE LEADING PMI FOAM

Thermal Stability up to 180°C

ROHACELL® maintains its shape and mechanical integrity during the high temperatures of autoclave and out-of-autoclave prepreg curing, where competing foams typically collapse or distort.

High Specific Stiffness

The rigid PMI matrix provides exceptional stiffness at minimal weight, allowing composite skins to carry bending loads more efficiently.

Exceptional Creep Resistance

Long-term creep and fatigue data exist for ROHACELL® spanning multiple decades. This makes it suitable for structural components that must remain stable for many years.

Outstanding Machinability

ROHACELL® machines cleanly using CNC routers, 5-axis machining, laser cutting, waterjet cutting and knife trimming without tearing, shattering or excessive powdering.

Minimal Resin Uptake

The closed-cell structure keeps the final part lighter, more consistent and more predictable.

RF Transparency and Dielectric Stability

ROHACELL® is widely used in radomes, antenna housings and RF-sensitive equipment because of its stable dielectric behaviour.

ROHACELL® PRODUCT GRADES

ROHACELL® is offered in multiple specialised grades, each refined for specific composite applications.

ROHACELL® IG

The original all-purpose PMI foam used in aerospace and high-performance industries.

ROHACELL® IG-F

A fine-cell version of IG engineered for thin composite skins, improved surface quality and reduced resin absorption.

ROHACELL® WF

An ultra-lightweight grade ideal for UAV structures, thin aerodynamic parts and motorsport components requiring very low density and fine cell structure.

ROHACELL® HERO

A grade optimised for extreme temperature cycles and demanding thermal environments.

ROHACELL® HT

The high-temperature flagship grade for components that must endure elevated heat for long durations with minimal creep.

ROHACRYL®

The next evolution of PMI foam offering ultra-fine microstructure, superb surface finish and enhanced process control.

Each grade is supported by mechanical data, dimensional tolerances and full certification.

INDUSTRIES THAT RELY ON ROHACELL®

Aerospace

ROHACELL® is used in interior panels, secondary structures, flight control surfaces, radomes, satellite components and any composite part requiring stiffness, stability and low mass.

Formula One and Motorsport

Teams depend on ROHACELL® for monocoque structures, aerodynamic surfaces, energy-absorbing components and ultra-thin carbon laminates where consistency is critical.

UAVs and Defence Systems

ROHACELL® provides lightweight stiffness and RF transparency ideal for drones, surveillance platforms and communication housings.

Medical Devices

Used in orthotics, prosthetics, imaging systems and diagnostic equipment where dimensional stability is essential.

Industrial and Robotics Components

ROHACELL® is selected for machine housings, automation components and composite panels requiring strength without adding weight.

ROHACELL® VS COPYCAT PMI FOAMS

The global market has seen a rise in imitation PMI foams—particularly from manufacturers seeking to replicate the appearance of ROHACELL® without the controlled chemistry or decades of testing.

Copycat PMI foams typically suffer from:

• inconsistent density across the sheet
• irregular or oversized cell structures
• poor thermal ageing (warping, shrinkage, brittleness)
• unpredictable creep and fatigue behaviour
• lack of long-term mechanical data
• absence of verified certification
• no traceability through production batches
• weaker shear strength and unreliable compressive performance

In critical structures, these issues can lead to premature failure, dimensional inaccuracy and long-term reliability problems.

Only genuine ROHACELL® is supported by fifty years of validations, aerospace approvals and data integrity.

EMKAY PLASTICS: THE UK’S OFFICIAL ROHACELL® DISTRIBUTOR

Emkay Plastics Ltd is the exclusive authorised UK distributor of ROHACELL® and ROHACRYL® and also supplies these materials across 17 additional international territories. Emkay offers:

• guaranteed authentic German-manufactured ROHACELL®
• complete traceability for every batch and block
• aerospace-level storage, handling and cutting
• technical support from PMI specialists
• zero risk of counterfeit material entering your supply chain

Emkay’s position as the UK’s only approved distributor ensures customers receive the original product with full documentation, full certification and long-term reliability.

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