Warum ist die Verarbeitungstemperatur höher als die Gebrauchstemperatur?

Zum Formen muss das Polymer fließen – das erfordert deutlich mehr Wärme, als das fertige, feste Bauteil im Einsatz verträgt. Beide Werte beschreiben verschiedene Zustände: Schmelze beim Verarbeiten, Festkörper beim Gebrauch.

Woran erkenne ich, ob ein Kunststoff amorph oder teilkristallin ist?

Ein praktischer Indikator ist die Transparenz: Amorphe Typen sind oft glasklar (PC, PMMA, PSU), teilkristalline meist milchig-opak (PP, PE, PA, PEEK). Maßgeblich ist aber das Datenblatt, da Füllstoffe und Einfärbung die Optik verändern können.

Welcher Thermoplast hält die höchsten Temperaturen aus?

Unter den hier genannten sind PEEK und PTFE mit rund 250 °C Dauergebrauch führend. Definitionsgemäß zählen Thermoplaste mit einer Dauergebrauchstemperatur über 150 °C zu den Hochleistungs- bzw. Hochtemperaturkunststoffen.

Sind alle Thermoplaste recycelbar?

Grundsätzlich ja – die reversible Erweichung ist die physikalische Basis dafür. In der Praxis hängt es von Sortenreinheit, Additiven und Verunreinigung ab, und jedes Aufschmelzen kann das Material leicht thermisch schädigen.

Warum muss Polyamid (PA) vor der Verarbeitung getrocknet werden?

PA nimmt Feuchtigkeit aus der Luft auf. In der heißen Schmelze führt dieses Wasser zu Hydrolyse und Blasen – die Folge sind Festigkeitsverlust und Oberflächenfehler. Korrektes Vortrocknen ist daher Pflicht.

Thermoplastics: choice of materials & temperatures

01 — BasicsWhat makes thermoplastics special?

Thermoplastics are plastics that expand when heated reversible soften and solidify again when they cool - without changing their chemical structure. It is precisely this reversibility that distinguishes them from thermosets (which harden once and then remains solid) and makes them weldable, formable and recyclable.

In the molecular picture, thermoplastics are long, one below the other not chemically cross-linked polymer chains. Heat increases the mobility of these chains: the material becomes soft and flowable, can be shaped and “freezes” again when it cools down. In principle, this process can be repeated several times because no bonds are broken - the physical basis of recycling. In practice, however, aging, additives, contamination and thermal damage limit recycling.

Thermoplastics are processed by bringing them to the processing temperature with defined heat and using processes such as injection moulding, extrusion or 3D printing shapes. The precise temperature control is not a detail, but the crucial process parameter: too cold and the melt does not flow cleanly; too hot and the polymer begins to thermally decompose.

One exception confirms the rule: Not every thermoplastic can be processed using the traditional melting process. PTFE, for example, is thermoplastic, but has such a high melt viscosity that it can be pressed, sintered or processed from semi-finished products (more on this in the profile).

Note: When it comes to thermoplastics, it's not just the material that matters, but above all the temperature control. It determines whether a plastic is processed cleanly and whether the component will last in later use. The material properties provide the potential – the process decides whether it reaches the component.

02 — The crucial differenceAmorphous or semi-crystalline?

Most material overviews jump straight to profiles. In doing so, they skip a question that early determines the behaviour of a thermoplastic: How are its chains arranged? This results in trends in transparency, shrinkage, chemical resistance and - particularly important - behaviour under heat. It's not a panacea, but it's a strong first filter.

Amorphous

Disordered chains

Mostly transparent (e.g. PC, PMMA, PSU)
Height Dimensional stability, low shrinkage
Softening over one Area gone, no sharp melting point
Strength falls to the glass transition temperature (T_G) approximately linearly
Easy to stick, rather sensitive to stress cracks

Partially crystalline

Organized areas

Mostly opaque/milky (e.g. PP, PE, PA, PEEK)
Ordered zones have the effect of physical networking → high strength & chemical resistance
Have a clear one melting point (T_m)
Two levels: first T_G (amorphous parts soften), then T_m (Smelt Crystallites)
Stronger shrinkage, but good sliding and wear properties

Practice consequence: You need it Transparency and dimensional accuracy, you usually end up with an amorphous type. Do you need Chemical and wear resistance, with a partially crystalline. This one question does not replace a data sheet, but it narrows down the material list to a few candidates early on. The rest is then decided by factors such as fillers, glass fibre content, moisture absorption, flame retardancy, long-term load and component geometry.

03 — The most common mix-upProcessing ≠ use temperature

One value, two completely different meanings - this is where the most expensive misunderstandings arise. Material tables often state a “temperature” without saying what is meant.

Processing temperature

The temperature to which the polymer is brought in the machine so that it flows and can be shaped. It is well above the operating temperature - for ABS around 220-260 °C, for PC 280-320 °C. It says nothing about what the finished component can withstand.

Continuous use temperature

The temperature at which the finished component is in use permanently withstands without impermissibly decreasing properties. It is often hundreds of degrees lower: LDPE, for example, only around 80 °C, PLA only around 60 °C - despite the higher processing temperature.

Rule of thumb: Processing tells how you make the part. Long-term use provides the first orientation as to whether a component is thermally suitable. The final approval depends on the load case (load, medium, component thickness, time, safety requirements) and on the data sheet of the specific type. If you choose the wrong number when designing, you will either produce scrap or a component that will fail in operation.

For amorphous types the T_G the practical upper limit because the strength breaks down there. Partially crystalline types retain above the T_G thanks to their crystallites still have strength - their limit is closer to T_m. This explains why semi-crystalline high-performance grades such as PEEK reach such high long-term service temperatures.

04 — Thermal mapWhere the materials are located

A classification according to Continuous use temperature – i.e. based on what the component can withstand in use. From cool (top) to hot (bottom):

~60°C

PLA

Bio-based, short-lived applications, 3D printing prototypes.

~80°C

PE (LDPE/HDPE), PS

Packaging, films, containers. Cheap, but thermally limited.

~100°C

PP

Food contact, mechanically resilient, good fatigue resistance.

~120°C

ABS, PMMA, PVC

Housing, visible parts, construction profiles. Medium temperature level.

~130°C

PC, PA

Impact-resistant, transparent or mechanically highly resilient technical parts.

~160°C

PSU

Sterilizable, chemically resistant – medical, aviation. Related types (PESU, PPSU) are higher.

~250°C

PTFE, PEEK

High performance: extreme chemical, temperature and wear requirements.

Guide values for unfilled standard types; Fillers, additives and specific load cases shift these values. The data sheet for the selected type is always binding.

05 — Material profilesThe most important thermoplastics in detail

Can be opened as required. Grouped into standard, technical and high-performance plastics - this classification roughly follows increasing temperature and performance capabilities (and increasing price).

About the numbers: The temperatures given are Guide values for unfilled standard types. Glass fibre, fillers, additives and the specific load case (duration, load, medium) sometimes shift them considerably. This is always binding Data sheet value of the selected type for your specific application.

Standard plastics

P.EPolyethylenepartially crystalline HDPE / LDPE▸

Processing: 160-280°CContinuous use: ~80°Cpartially crystalline

character: Flexible, light, very good chemical resistance. HDPE stiffer, LDPE softer.
When to vote?: HDPE for robust structural parts, LDPE for flexible films – whenever chemical resistance and low prices count.
Applications: HDPE: water pipes, canisters, playground equipment. LDPE: bags, films, packaging.

+ Very robust, chemically resistant, inexpensive

– Limited temperature resistance, UV sensitive

PPPolypropylenepartially crystalline▸

Processing: 200-280°CContinuous use: ~100°Cpartially crystalline

character: Lightweight, tough, high fatigue resistance (ideal for film hinges); many food grade types available.
When to vote?: When an inexpensive, permanently bending-resistant material with good chemical resistance is needed.
Applications: Food containers, bottle caps, bumpers, battery cases, carpet fibers.

+ Fatigue-resistant, food-grade types, inexpensive

– Low UV resistance without stabilizers

P.SPolystyreneamorphous · incl. EPS “Styrofoam”▸

Processing: 180-260°CContinuous use: ~80°Camorphous

character: Brittle, clear or opaque; as expanded EPS, a light insulating foam.
When to vote?: For very inexpensive disposable parts or insulation and packaging applications (EPS).
Applications: Disposable cups, food packaging, insulation boards, CD cases.

+ Very cheap, light

– Brittle, ecologically critical

PVCPolyvinyl chlorideamorphous hard & soft PVC▸

Processing: 160-210°CContinuous use: ~60-80°Camorphous

character: Cost-effective, durable, flame retardant. Hard PVC rigid, soft PVC (with plasticizer) flexible.
When to vote?: Hard PVC for profiles/pipes, soft PVC for flexible parts – when costs and longevity count.
Applications: Pipes, window frames, cable insulation (hard); Tubes, blood bags (soft).

+ Cheap, versatile, flame retardant

– Narrow processing windows, disposal issues

Technical plastics

ABSAcrylonitrile butadiene styreneamorphous▸

Processing: 220-260°CContinuous use: ~80-100°Camorphous

character: Tough, impact-resistant, good surface, easy to machine - balanced between rigidity and flexibility.
When to vote?: When impact resistance, good workability and a high-quality appearance are required. injection moulding classic.
Applications: Electronics housings, keyboards, car interior panels – and LEGO bricks.

+ Versatile, good mechanics & optics

– Not weatherproof without stabilization

P.APolyamide (nylon)partially crystalline▸

Processing: 240-290°CContinuous use: ~80-130°Cpartially crystalline

character: Tough, wear-resistant, highly mechanically resilient – often used as a metal replacement. However, absorbs moisture from the air; Residual moisture leads to bubbles, surface defects, loss of strength and hydrolytic degradation during processing. That is why PA is dried before processing.
When to vote?: With high mechanical load, wear and temperature – gears, bearings, structural parts.
Applications: Engine covers, intake pipes, plain bearings, bushings, fibers for textiles and ropes.

+ Wear-resistant, metal replacement possible

– moisture absorption; dry before processing

PCPolycarbonateamorphous▸

Processing: 280-320°CContinuous use: ~120-130°Camorphous

character: Transparent and extremely impact-resistant, good dimensional stability and temperature resistance.
When to vote?: When impact resistance must be combined with transparency and heat resistance.
Applications: Safety glazing, dome lights, headlight covers, housings.

+ Extremely impact-resistant, transparent, heat-resistant

– Sensitive to scratches, sensitive to solvents

PMMAAcrylic / Plexiglassamorphous▸

Processing: 220-260°CContinuous use: ~70-90°Camorphous

character: Highest optical clarity, weather and UV resistant, lighter than glass.
When to vote?: When transparency, aesthetics and weathering are in the foreground - as a glass replacement.
Applications: Windows, skylights, neon signs, optical lenses.

+ Excellent transparency, UV-resistant

– More brittle than PC, sensitive to scratches

High-performance plastics

PSUPolysulfoneamorphous▸

Processing: 340-400°CContinuous use: ~160°Camorphous

character: High thermal stability, chemically resistant, steam sterilizable, dimensionally stable. Related types of the polysulfone family (PESU, PPSU) achieve higher continuous use temperatures.
When to vote?: For demanding applications involving heat, chemicals and sterilization.
Applications: Sterilizable medical devices, surgical instruments, aviation components, isolators.

+ High temperature and chemical resistance

– Expensive, demanding workmanship

PTFETeflon / Polytetrafluoroethylenepartially crystalline · fluoroplastic▸

Processing: Sintering ~360-380°CContinuous use: ~250°Cpartially crystalline

character: Almost universally chemical resistant, very low friction (non-stick), wide temperature range - down to the low temperature range.
Special case: PTFE is thermoplastic, but can be melted due to its extremely high melt viscosity not classic injection moulding. Pressing, sintering, paste extrusion or machining of semi-finished products are common.
When to vote?: For extreme chemical resistance, non-stick or slip requirements, if the special processing effort is justifiable.
Applications: Non-stick coatings, seals, bearings, tubes, catheters, implants.

+ Unsurpassed non-stick & chemical resistance

– Expensive, requires special processing

PEEKPolyetheretherketonepartially crystalline▸

Processing: 360-400°CContinuous use: ~250°Cpartially crystalline

character: Top values for strength, temperature and chemical resistance; T_G ~145 °C, hydrolysis resistant up to approx. 280 °C. Biocompatible.
When to vote?: When almost everything is required at the same time: load, heat, chemistry, lightweight construction - as a metal replacement in the high-end range.
Applications: Gear components, valves, implants, insulating bodies in electrical engineering.

+ All-rounder at a high performance level

– Very expensive, high processing temperatures

Bio-based / sustainable

PLAPolylactic acidpartially crystalline · biobased▸

Processing: 180-220°CContinuous use: ~60°Cbio-based

character: Bio-based and biodegradable, transparent and stiff - but clearly thermally limited.
When to vote?: For sustainable, short-lived applications and simple 3D printing.
Applications: Compostable bags, food packaging, 3D printing filament, absorbable stitching.

+ Biodegradable, easily printable

– Low heat resistance, brittle

APPROXCellulose acetateamorphous · biobased▸

Processing: 170-230°CContinuous use: ~70°Cbio-based

character: Bio-based, transparent, chewy and pleasant to the touch; more degradable than many standard plastics.
When to vote?: When looks, feel and a more sustainable profile count.
Applications: Glasses frames, handles, foils, blister packs.

+ Bio-based, aesthetic

– Less robust than technical types

06 — Decision pathIn six questions about the material

Instead of a long comparison table: work through the questions from top to bottom. Each answer eliminates candidates - in the end there are usually two or three types that you finally compare using the data sheet.

morphology

Transparency and moderation usually speak for themselves amorphous Materials such as PC, PMMA or PSU. Chemical and wear resistance are more likely to lead to partially crystalline Types like PP, PA or PEEK.

mechanics

Come for impact resistance ABS and PC in question. If there is high continuous load or wear P.A, PEEK and PSU closer.

temperature

Always up Continuous use temperature design, not processing. Very high temperatures speak for PEEK or PTFE, increased level for PSU.

media

Aggressive media and non-stick requirements often lead to PTFE. Sterilizable applications are more likely PSU or PEEK.

Cost

Are cheap PVC, P.E and P.S. Form the technical midfield ABS, P.A and PC; is premium PTFE, PEEK and PSU.

Bio-based

PLA and Cellulose acetate are options if temperature and long-term stress remain limited and the sustainability profile is technically relevant.

And always think: the best material is of little use without it clean temperature control in processing and use. This is exactly where repeatability and component quality are crucial.

From practicePrecise heat for plastic processing

Each of the processing temperatures mentioned must be precisely achieved and maintained in the machine - from standard types to high-performance materials such as PTFE and PEEK, which require particularly high and uniform nozzle temperatures. This is exactly why we produce the heating and control technology in-house: from the cylinder and nozzle heating to the control and temperature recording.

Heating bands & tool heatingCylinders, nozzles, tools up to 600 °C Control devicesConstant process management & monitoring Temperature sensorsThermocouples & resistance temperature sensors

FAQ

Frequently asked questions

Why is the processing temperature higher than the use temperature?

In order to form, the polymer has to flow - this requires significantly more heat than the finished, solid component can withstand in use. Both values describe different states: melt when processed, solid when used.

How do I know whether a plastic is amorphous or partially crystalline?

A practical indicator is transparency: Amorphous types are often crystal clear (PC, PMMA, PSU), semi-crystalline types are usually milky-opaque (PP, PE, PA, PEEK). However, the data sheet is decisive - fillers and coloring can change the appearance.

Which thermoplastic can withstand the highest temperatures?

Among those mentioned here, PEEK and PTFE are the leaders with continuous use at around 250 °C. By definition, thermoplastics with a continuous service temperature above 150 °C are high-performance or high-temperature plastics.

Are all thermoplastics recyclable?

Basically yes – reversible softening is the physical basis for it. In practice it depends on variety purity, additives and impurity. Each time it is melted, slight thermal damage can occur, which reduces quality.

Why does polyamide (PA) have to be dried before processing?

PA absorbs moisture from the air. In the hot melt, this water leads to hydrolysis and bubbles - the result is loss of strength and surface defects. Correct pre-drying is therefore mandatory.