Failing with PC, Tritan™ or PETG — a guide to moving up to sulfones
PC, Tritan™ and PETG are strong enough at room temperature, but their heat deflection temperatures are 125°C, 85°C and 64°C respectively (1.8 MPa), so cracking, warping and discolouration appear where hot water, dishwashing and steam sterilisation repeat. Sulfones sit at 175–205°C, above that band. Use PPSU for food and beverage contact; PSU or PESU for drinking-water, medical and industrial applications.
This page is written less for people who already know the materials than for people whose product has started failing. Not having identified the cause is fine — symptoms alone, such as cracking, whitening, warping or yellowing, are enough to narrow down the property limit involved and lead to the material that answers it.
Find it by symptom
You do not need to know the cause already. The symptoms visible on the floor are enough to narrow down which property limit has been reached. Select what you are seeing and we will show the mechanism and the material that answers it.
It cracks and splits after repeated use
What you see in the field
Cracks start where stress concentrates — handles, threaded areas, around the gate — and grow with each cycle until the part fails. Typically fine for the first few uses, then failing after tens or hundreds of cycles.
Why this happens
As service temperature approaches the material's heat deflection temperature, moulded-in residual stress relaxes and deformation accumulates. Add detergents or food constituents and environmental stress cracking (ESC) sets in, so parts that passed short-term testing break in repeated service. High room-temperature impact strength does not prevent this — it is a temperature and chemistry problem.
After repeated sterilisation or high-temperature exposure the part yellows and breaks under forces it used to survive. Once-clear parts take on a cloudy amber cast.
Why this happens
In hot water, steam and alkaline detergent environments, polycarbonate undergoes hydrolysis and its polymer chains are cut. Lower molecular weight means both discolouration and embrittlement. This is degradation of the material itself, not a surface effect, so polishing or coating cannot reverse it.
Relevant property limit
PC is vulnerable to hydrolysis under repeated steam sterilisation
Recommended material
PPSU where repeated steam sterilisation is required; PSU is also viable outside food contact.
After contact with detergents, coffee or fats, countless fine lines appear on the surface and clarity drops to a milky haze. This is the stage immediately before cracking.
Why this happens
Where residual stress remains at the surface, contact with certain chemicals triggers dense micro-cracking (crazing). These micro-cracks scatter light, which reads as whitening, and eventually link up into through-cracks. Both copolyesters and PC show this with detergents and alkalis.
Relevant property limit
Copolyesters and PC have limited chemical resistance to detergents and alkalis
Recommended material
PPSU for food contact. The higher the cleaning and sterilisation frequency, the greater the advantage of sulfones.
After hot water, a dishwasher cycle or a microwave, parts warp — assembly dimensions no longer fit, or seals begin to leak.
Why this happens
The simplest cause: service temperature has exceeded the material's heat deflection temperature. Dishwasher interiors exceed 70°C and rinse stages go higher, while PETG has an HDT of only 64°C (1.8 MPa) — immediately in the danger zone. Tritan™, at 85°C, has no margin against boiling water either.
Relevant property limit
PETG HDT 64°C · Tritan™ HDT 85°C (1.8 MPa)
Recommended material
Sulfones for constant hot-water or dishwasher exposure; PPSU for food contact.
Repeated 121°C or 134°C steam sterilisation produces cracks, colour change and loss of strength. Common in ultrasound probe housings, dental instruments and reusable medical devices.
Why this happens
Autoclaving applies high-temperature steam and pressure together. PC's HDT of 125°C leaves almost no margin against a 121°C cycle and is exceeded by a 134°C cycle. Hydrolysis proceeds in parallel in a steam environment. Tritan™ and PETG do not reach this temperature range at all.
Relevant property limit
PC HDT 125°C — no margin against 121/134°C steam cycles
Recommended material
PSU or PPSU. Both are candidates for medical devices, which are outside food-contact scope.
The properties are fine, but a customer or export specification will not accept a material made from BPA. This most often arises with food-contact products destined for Europe.
Why this happens
EU Regulation 2024/3190 bans the use of BPA and hazardous bisphenols in food-contact materials. The regulation text states that BPA is used in the manufacture of food-contact plastics made of polycarbonate and polysulfone. PC and PSU are therefore directly in scope, and PESU products — made from BPS — are also affected and require recertification.
Relevant property limit
PC and PSU are BPA-based; PESU is BPS-based
Recommended material
PPSU only for food contact — the one sulfone made without BPA or BPS.
Odour or taste transfers and the surface turns tacky
What you see in the field
Coffee, fats or detergent constituents soak in and leave an odour, or the surface loses gloss and feels tacky. Washing does not restore it.
Why this happens
When a material is not sufficiently rigid at service temperature, the surface softens slightly and constituents are absorbed and retained. The closer the service temperature is to the material's heat deflection temperature, the worse it gets. Sulfones have a far larger margin between service temperature and HDT, so this is much less common.
Relevant property limit
Occurs when service temperature approaches the material's HDT
As service temperature approaches a material’s heat deflection temperature, deformation and cracking begin. Below, real service conditions and each material’s heat deflection temperature are placed on the same axis.
60°C Hot water · coffee brewing70°C Dishwasher100°C Boiling water · steam121°C Autoclave 121°C134°C Autoclave 134°C
PETG
64°C
Tritan™
85°C
PC
125°C
PSU
175°C
PPSU
197°C
PESU
205°C
Based on heat deflection temperature (HDT/A, 1.8 MPa). PETG and Tritan™ are to ASTM D648, PC and the sulfones to ISO 75, so specimens and conditions differ and absolute comparison may be imprecise — read this as a family-level ranking. HDT is also a short-term deflection temperature under load, so continuous service temperature must be set lower.
Six materials compared
All figures are from the manufacturers’ published datasheets, with the test method stated alongside. Values measured to different standards are never merged into one cell.
PETG and Tritan™ figures are to ASTM, PC and BASF Ultrason® figures to ISO (PC to ISO 75-2). Specimen geometry and test conditions differ, so the columns cannot be compared one to one. The table is for judging whether materials sit in the same class; where precise comparison matters, request data measured to a common standard. Note also that Izod (ISO 180) and Charpy (ISO 179) are different tests — compare only like with like.
PETG — The TDS carries no optical data for injection-moulded parts. The transmittance above is for 250 µm film and cannot be compared directly with mouldings of a different thickness.
Tritan — Glass transition temperature is not stated in this TDS. Judge heat performance from the heat deflection temperature.
PC — This is an E&E/general-purpose grade, so the TDS has no optical section; transparent applications use dedicated optical grades. PC’s properties are sound — it is excluded from food contact by regulation, not by performance.
PSU — The lowest notched impact strength of the three sulfones (5.5 kJ/m²). If a part used PC for toughness, PSU is a step back rather than a replacement — look at PPSU instead.
PPSU — The only sulfone made without BPA or BPS, and therefore the family that answers EU food-contact regulation. Notched impact strength of 70 kJ/m² puts it on par with PC (75).
PESU — The highest heat resistance of the three sulfones. Being BPS-based, however, it requires recertification for food contact under EU Regulation 2024/3190. It remains valid for drinking-water and non-food applications.
Selection criteria by application
The three sulfones are not chosen on heat resistance alone. Two questions decide it — whether the part contacts food (feedstock bisphenol regulation), and whether it needs notched impact strength.
Under EU Regulation 2024/3190, BPA-based PSU and BPS-based PESU require recertification for food contact. PPSU is made without BPA or BPS.
Drinking-water contactWater purifier housings and flow parts, hot-water components
PSU · PESU valid
Regulation 2024/3190 covers food-contact materials and articles; drinking-water applications are out of scope. Judge against drinking-water standards such as NSF/ANSI 61.
Not food contact, so bisphenol regulation does not apply. The deciding factors are repeated autoclaving and the notched impact strength required — choose PPSU where toughness matters.
Non-food industrial · E&EInsulating parts, industrial housings, high-temperature structural parts
PSU · PESU both viable
PESU (HDT 205°C) where more thermal headroom is needed; PSU where cost and low water absorption come first. For glass-fibre reinforcement, PESU E 2010 G6.
These are the conversion reasons we actually receive. All three passed room-temperature testing and failed in service.
01
Baby bottles · water purifier parts · coffee equipment
Consumer goods · food & beverage
Tritan™→PPSU
Symptom
Cracking and discolouration after repeated use
Repeated exposure to hot water, the chemical constituents of coffee, cleaning agents and dishwasher cycles produced cracking and colour change. In every case the parts were fine at first and failed once the use count built up.
Cause
85°C heat deflection ceiling plus environmental stress cracking under repeated heat and detergent
Why
Food and beverage contact, so PPSU only. Its heat deflection temperature of 197°C leaves a wide margin over hot-water and dishwasher temperatures, and it is made without BPA or BPS.
02
Food and beverage containers
Food & beverage containers · export
PC→PPSU
Symptom
BPA migration concerns rule it out of food use; European export blocked
Not a performance problem but a feedstock one. Polycarbonate is made from BPA monomer, migration concerns have been raised, and it is therefore not used for food and beverage containers. European bisphenol regulation also closes off export.
Cause
BPA feedstock · EU Regulation 2024/3190 food-contact ban
Why
The only sulfone made without BPA or BPS. PSU is also BPA-based and therefore not an alternative.
03
Ultrasound probes · dental instruments
Medical · dental
PC→PSU or PPSU
Symptom
Cracking from autoclaving, detergents and repeated sterilisation
Repeated high-pressure steam sterilisation and detergent exposure cracked housings and instruments. These are not food-contact parts, so bisphenol regulation does not apply — this is purely durability under repeated sterilisation.
Cause
125°C heat deflection temperature — no margin against 121/134°C steam cycles — plus hydrolysis
Why
Not food contact, so both families are available. Choose PPSU (notched impact 70 kJ/m²) where drop or fastening stress is involved, otherwise PSU.
What to know before switching
Sulfones are not superior in every respect. The points below become obvious the moment you compare datasheets, so we state them upfront.
On room-temperature impact alone, Tritan™ is higher
Notched Izod impact strength (ISO 180, 23°C) is 93 kJ/m² for Tritan™ TX1001 against 58 kJ/m² for PPSU P 3010. For drop impact at room temperature, Tritan™ is the stronger material. The reason to change is not room-temperature toughness but the 85°C heat deflection ceiling and environmental stress cracking under repeated heat and detergent exposure. Select on room-temperature testing alone and the part will fail again in service.
PSU has far lower notched impact strength than PC
Notched Charpy impact strength (ISO 179, 23°C) is 75 kJ/m² for PC against 5.5 kJ/m² for PSU S 2010 — roughly one thirteenth. Replacing a PC part that was chosen for toughness with PSU raises heat resistance but gives up impact performance. Where PC-equivalent toughness is required, PPSU (70 kJ/m²) is the only answer.
Sulfones are transparent but not colourless
Light transmittance is 89% for PSU and 88% for PESU (DIN 5036-3, 2 mm) — numerically close to PC and Tritan™ — but sulfones carry a slight honey tint. BASF's own material comparison describes the optical character of PESU and PPSU as a slight honey tint. Where water-clear colourlessness is an absolute requirement, sulfones are not the answer.
Processing conditions are completely different
Tritan™ is processed at a melt temperature of 260–282°C and PETG at 249–271°C, whereas sulfones are typically processed above 340°C with much higher mould temperatures. They are also moisture-sensitive, so pre-drying is mandatory. Carrying over existing conditions produces short shots, splay and thermal degradation. Plan a processing-condition reset as part of the switch.
Cost goes up
Sulfones are super engineering plastics with a higher raw-material cost than PC or copolyesters. The right basis for comparison, however, is not price per kilogram but the cost of rejects, claims and remakes over the product's life. If cracking is already driving returns on a repeatedly used product, a total-cost view is the accurate one.
Frequently asked questions
Plastic parts used with hot water keep cracking. What should I change to?
Start with the heat deflection temperature of the current material: 64°C for PETG, 85°C for Tritan™, 125°C for PC (at 1.8 MPa). When service temperature approaches these, moulded-in residual stress relaxes and, together with detergents or food constituents, environmental stress cracking sets in. Where repeated hot water and washing are constant, move up to the sulfone family; for food and beverage contact the answer is PPSU, with a heat deflection temperature of 197°C.
Which has the highest heat resistance — PC, Tritan™ or PETG?
PC, with a heat deflection temperature of 125°C at 1.8 MPa against 85°C for Tritan™ and 64°C for PETG. However, PC is BPA-based and therefore banned from food-contact use under EU Regulation 2024/3190, and it also yellows and embrittles through hydrolysis under repeated steam sterilisation.
How do I choose between PSU, PESU and PPSU?
Two questions decide it. First, food contact means PPSU only — PSU is BPA-based and PESU is BPS-based, both in scope of the EU restriction. Second, if notched impact strength matters, choose PPSU: notched Charpy impact is 70 kJ/m² for PPSU against 5.5 kJ/m² for PSU. If you simply want maximum thermal headroom, PESU has a heat deflection temperature of 205°C.
Are sulfones transparent?
Transparent, but not colourless. Light transmittance is 89% for PSU and 88% for PESU (DIN 5036-3, 2 mm), numerically similar to PC and Tritan™, but sulfones carry a slight honey tint. They are not suitable where water-clear colourlessness is an absolute requirement.
Can I keep my existing tooling?
BASF states that existing injection moulds for PESU can continue to be used. Processing conditions differ substantially, though — copolyesters run around 250–280°C while sulfones are typically processed above 340°C with mandatory pre-drying. Shrinkage differences also need verification, so confirm with a trial shot.
How much does the cost increase?
Sulfones are super engineering plastics with a higher raw-material cost than PC or copolyesters. The basis for judgement, however, is total cost including reject rates, claims and remakes rather than price per kilogram. If cracking is already causing returns on a repeatedly used product, that is the accurate comparison. We quote specifically against your volume and grade.
We will work out which grade fits with you
Service temperature, cycle count, cleaning method and contact media — those four are enough to narrow the candidates. Evaluation samples are available.
Tritan™ and Eastar™ are trademarks of Eastman Chemical Company, INFINO® of Lotte Chemical, and Ultrason® of BASF SE. Competitor product names are used solely for factual identification and comparison, and do not imply affiliation or endorsement.
