Technical terms from the original PLEXIGLAS®

Abrasion Resistance

is the resistance of the surface against the separation of small particles as a result of mechanical stress.

Acrylic Glass

Collective term for crystal-clear or transparent, translucent and opaque colored semifinished sheet products, primarily made of polymethyl methacrylate (PMMA). The crystal-clear thermoplastic or thermoelastic, which can be endowed with a great variety of colors, features both high light transmittance and extraordinary weather resistance. It was first developed by Dr. Otto Röhm, who registered it under the trademark PLEXIGLAS®.


Source: Evonik Industries AG

Break resistance

(see Impact Strength)


Recommendations for PLEXIGLAS®:

- Clear water and a damp cloth are all that are needed for normal daily cleaning.

- Water, grease and soap stains are easily removed by adding a little dishwashing liquid to warm water and wiping with a moist cloth.

- Diluted vinegar essence is the best cleaner for removing calcifications.

- Dirt that is harder to remove can be eliminated with acryl polish and a soft cloth.

Casting Process

The liquid, fully colored monomer is cast between two mirror glass sheets, where it is cured into acrylic glass. The use of textured panes of glass provides acrylic sheet with textured surfaces.

Chemical Resistance

In many plastics applications, the question of resistance when the plastic comes in contact with particular agents or materials is of concern. The simplest method of testing a plastic’s chemical resistance consists of bringing specimens into contact with the agents in question without adding any extra stress. This is accomplished by immersing the plastic into liquids or, in the case of solids, placing the solid on the surface of the plastic. The changes in appearance, weight and strength that may result after storage then serve as evaluation criteria.


In extrusion technology, the term “coextrusion” stands for the bringing together of identical or different plastic melts before extruding them through a single die. The multilayer composite sheets produced in this way can be classified as follows: 

Identical composites: e.g., acrylic glass with acrylic glass Different composites without adhesion promoters: e.g., ABS / acrylic glass
Different composites with adhesion promoters: e.g., ABS / polymer / acrylic glass

The multilayer composites sold in the sanitary market are different composites. The coextruded different composite sheets primarily consist of a plastic named acrylonitrile butadiene styrene – ABS – (90 to 95%) and have only a thin acrylic coating (only 5 - 10% of the total sheet thickness).


(see Lightfastness / yellowness index)


Adding and mixing colorants into plastics.

Easy to Clean

The surface of PLEXIGLAS® is perfectly smooth and shiny. Dirt can barely adhere. The surface repels water. These properties last for a lifetime. That’s it – without any extra coating.


Elasticity refers to the ability of a material to regain its shape after the removal of an externally applied mechanical stress (elastic modulus).

Elastic Modulus

The elastic modulus is the constant ratio of stress and deformation within the elastic limits of a material (elasticity). The following equation applies to the uniaxial tensile strain:

E = elastic modulus, σ = stress, ε = strain

The elastic modulus of cast and extruded sanitary acrylic equals 3,300 MPa.


PLEXIGLAS® grades made by Evonik meet the most stringent environmental requirements.

The PLEXIGLAS® grades contain no harmful heavy metals and no harmful plasticizers.

Extrusion process

In extrusion, the pure, fully colored acrylic granules are melted in an extruder and then smoothed on both sides between high-polish, hard-chromium-plated steel rollers and calibrated. Sheets manufactured in this manner feature an outstanding surface quality and thickness tolerance. The use of textured rolls provides sheets with textured surfaces.

Heat deflection temperature

The heat deflection temperature is a measure for the resistance of a material on exposure to heat and load. In practice, the maximum permanent service temperature is usually stated:



Impact Strength

Break resistance is measured by the impact test, which stresses test specimens, semifinished products, and molded parts by means of impact. The tests either determine the energy that is required to destroy the product or evaluate the extent of damage caused by a fixed amount of energy.

Source: Evonik Industries AG


Lightfastness refers only to the resistance against discoloration (yellowness index) under the action of light.Weathering tests lasting decades have documented that the material PLEXIGLAS® has no detrimental effect on the lightfastness and colorfastness of colorings. Its excellent colorlessness and outstanding weather resistance make PLEXIGLAS® an ideal “color carrier.”

Light Resistance

Resistance to discoloration and changes in physical properties under the action of light. Light resistance is a general term and refers to changes in properties under the action of light in general.

Light Transmittance


Light transmittance is a measure of how well a material transmits light that is perpendicularly incident to the surface. The spectral transmittance of colorless PLEXIGLAS® grades for perpendicular incidence in the visible range is a constant (92%). The peak value of 92% can be attributed solely to physically-caused reflection losses of 4% each at the light admission and light emission surfaces.

Since PLEXIGLAS® has no color of its own, it can be colored with extraordinary precision and into nearly any shade.


  • is our registered trademark for the first acrylic glass in the world

  • is a polymethyl methacrylate (PMMA)

  • was first produced in 1933

  • was invented by Dr. Otto Röhm


see Acrylic Glass


Polymerization is defined as the combining of a large number of separate molecules (monomers) into one larger molecule (polymer). During the cooling phase, the larger molecules solidify to form a solid. Amorphous substances can be considered as supercooled liquids. In the amorphous state (spatial felt structure), the macromolecules are completely unordered, like the molecules in a liquid.

Amorphous state (spatial felt structure)


The smooth PLEXIGLAS® surface makes it very easy to remove traces of use with polishing milk or polishing paste – even by hand. If a scratch should occur, it is easy to remove it from the smooth surface.It is also possible to have PLEXIGLAS® thoroughly repaired if necessary. The quality of the original surface can be reproduced on each point of the sanitary part by grinding followed by polishing.

Scratch Resistance

(Pencil Hardness / Scratch Hardness)

Cast and extruded acrylic glass features the highest surface hardness of all thermoplastics as well as outstanding scratch hardness. This is confirmed by the pencil hardness test. In this test, a pencil is clamped into a device at an angle of 45° to the test surface and then pushed over the surface of the specimen. The first pencil hardness (starting with the highest hardness) whose tip no longer leaves any perceptible scratches determines the characterizing physical variable.

Source: Evonik Industries AG

Solid State

This refers to the physical state in which the atoms or molecules of a substance (e.g., acrylic glass) are no longer able to move freely in relation to each other because their thermal motion has been frozen. This means that the molecules solidify to form a solid. This applies to all acrylic glasses.

Sound reduction Λ

(sound absorption) Sound reduction is a reduction in sound transmission in solid bodies, air and other gases. The greater the damping decrement of a material, the better its sound reduction.

Source: Evonik Industries AG

Speed of sound

The speed of sound indicates how fast the sound is transmitted in solid bodies, air and other gases. The lower the speed (c) of a material, the slower the sound transmission.

Source: Evonik Industries AG


PLEXIGLAS® GS is manufactured according to DIN EN ISO 7823-1 "Cast sheets" and PLEXIGLAS® XT to DIN EN ISO 7823-2 "Melt-calendered extruded sheets".

Surface hardness

Cast and extruded acrylic glass exhibits the highest surface hardness of all thermoplastics and has an outstanding scratch resistance.

Source: Evonik Industries AG

Ball indentation hardness is used to measure the hardness of materials whose hardness can no longer be measured by the Shore hardness method. Ball indentation hardness is determined by pressing a steel ball with a diameter of 5 mm onto a surface for a fixed time period. The hardness is then calculated as applied load (F) divided by the surface area of impression (A). Ball indentation hardness: H = F / A [N/mm²]. Ball indentation hardness proves that PMMA is a particularly hard material (see Figure).

Thermal Conductivity

Thermal conductivity is the ability of a solid, liquid or gas to transport thermal energy. The speed at which thermal energy is transmitted from one particle to the next when a material is heated determines its thermal conductivity.

Source: Evonik Industries AG

Thickness Tolerance

Tolerances are permitted deviations from the desired values. The size of the tolerance is affected by the raw material, the manufacturing process, and the processing variation. All technical properties are connected to the tolerance; i.e., the narrower and more constant the thickness tolerance, the more constant the technical properties, the processing parameters and the precise fit.

Tolerance for:

- Cast (GS) PLEXIGLAS®   Tolerance formula = +/- (0.4 + 0.1 x thickness)
  The tolerance for a 4-mm GS sheet is +/- 0.8 mm.
  This results in a sheet thickness of 3.2 to 4.8 mm.
- Extruded (XT) PLEXIGLAS®
  Tolerance: 5 % of the sheet thickness (≥ 3 mm thickness)
  The tolerance for a 4-mm XT sheet is +/- 0.2 mm.
  This results in a sheet thickness of 3.8 to 4.2 mm.


see Light transmittance

Weather Resistance

– also called weathering resistance –

Weather resistance is resistance to chemical change and change of physical behavior when exposed to weather. PLEXIGLAS® has been tested in all the world’s climates and exhibits better resistance to weather and UV light than any other thermoplastic material.

Source: Evonik Industries AG

PLEXIGLAS® does not require special anti-aging agents or stabilizers or a UV-absorber. PLEXIGLAS® exhibits no visible yellowing and nothing corrodes. There is virtually no significant drop in properties and no rotting (see Figure).