PET, rPET, PP & PS Sheet for Thermoforming: Material Properties & Application Data

Overview #

Selecting the right plastic sheet for thermoforming is one of the most consequential decisions in rigid packaging development — it determines not just structural performance but print compatibility, food-contact compliance, recyclability claims, and total unit cost. This article covers the four materials we run most frequently on our thermoforming lines: PET, rPET, PP, and PS. Brand partners specifying clamshells, trays, blisters, and insert trays for cosmetics, food, electronics, and retail will find the most relevant data here. One thing we see consistently: brands underestimate how much material gauge variation — even ±0.05mm — affects draw depth consistency and trim quality at production speeds above 15 cycles per minute.

Material Properties: What the Numbers Actually Mean on the Production Floor #

When a brand partner sends us a thermoforming brief, the first thing we confirm is the substrate — not the print spec. The substrate drives everything downstream: mold temperature, draw ratio, trim tooling, and whether the finished pack will pass food-contact or recycling stream requirements.

Here are the core mechanical and thermal properties we work with across the four materials:

PET (Polyethylene Terephthalate) is our default recommendation for food-contact clamshells and retail blister packs. We run APET (amorphous PET) sheet at gauges between 0.25mm and 1.0mm. Forming temperature range is 80–100°C. Tensile strength typically runs 48–72 MPa depending on gauge and orientation. PET is fully compliant with FDA 21 CFR §177.1630 and EU Regulation 10/2011 for food contact, which matters for any brand selling into US or European retail.

rPET (Recycled PET) uses post-consumer or post-industrial PET content, typically 30–100% recycled content depending on the application. We source rPET sheet certified to ISO 15270 (plastics recycling guidelines). Mechanical properties are within 5–8% of virgin PET at equivalent gauge, which is acceptable for most non-structural applications. Forming temperature is slightly narrower — 85–100°C — because rPET has more variable IV (intrinsic viscosity), typically 0.72–0.80 dL/g versus 0.78–0.85 dL/g for virgin APET. Brands using rPET for sustainability claims should confirm the recycled content percentage is third-party verified; we can supply material with GRS (Global Recycled Standard) certification on request.

PP (Polypropylene) is our go-to for high-temperature applications and living-hinge trays. PP sheet runs at forming temperatures of 140–175°C — significantly higher than PET — and has a flexural modulus of 1,100–1,600 MPa, making it stiffer per unit weight than PS. We specify PP for microwave-safe food trays and pharmaceutical blister bases where moisture barrier is critical. PP’s WVTR (water vapor transmission rate) is 3–6 g/m²/day at 38°C/90% RH (ASTM E96), compared to PET at 8–15 g/m²/day under the same conditions — a meaningful difference for moisture-sensitive products.

PS (Polystyrene) — specifically HIPS (High Impact Polystyrene) — is the lowest-cost option and the easiest to thermoform, with forming temperatures of 130–160°C and excellent detail reproduction in shallow-draw applications. We use HIPS for cosmetic insert trays, point-of-sale display trays, and promotional packaging where structural depth is under 40mm. The limitation is environmental: PS is not accepted in most curbside recycling streams in the US and EU, and the EU PPWR (Packaging and Packaging Waste Regulation) trajectory is pushing brands away from PS for consumer-facing packaging. We advise brand partners to consider this before specifying PS for new product lines launching after 2025.

Thermoforming Process Parameters by Material #

The table below summarizes the key production parameters we use on our sheet-fed and roll-fed thermoforming lines. These are the values our process engineers set at job setup — not theoretical ranges from a resin datasheet.

Draw ratio is the parameter brands most frequently underestimate. When a structural designer sends us a tray with a 60mm draw depth on a 70mm cavity width — a ratio approaching 0.86:1 — we flag it immediately for PP and will not run it on HIPS without a redesign. Exceeding the draw ratio limit causes wall thinning below the minimum structural threshold, which on our line we set at 60% of nominal gauge. A 0.5mm HIPS sheet forming to a 30mm deep cavity should not thin below 0.30mm at the sidewall — if it does, the tray fails our drop test protocol based on ISTA 2A.

Print, Surface Finishing & Decoration Compatibility #

Thermoformed packaging is often decorated either before forming (in-mold or pre-printed sheet) or after forming (pad printing, screen printing, or label application). Each material responds differently.

PET and rPET accept UV offset and UV flexo printing on pre-formed sheet with good ink adhesion after corona treatment to a minimum surface energy of 42 dynes/cm (measured per ASTM D2578). We run corona treatment inline on our sheet-fed lines and verify surface energy on every reel change. Without adequate corona treatment, ink adhesion on PET fails the cross-hatch tape test per ISO 2409 at Grade 2 or worse.

PP requires more aggressive surface preparation — we target 44–48 dynes/cm for PP because its non-polar surface resists ink adhesion more than PET. Flame treatment is an alternative to corona for PP sheet above 0.8mm gauge where corona penetration depth is insufficient.

HIPS is the most print-friendly of the four: it accepts solvent-based screen inks and UV inks without pre-treatment in most cases, and its matte surface texture (Ra 0.8–1.6 µm depending on tooling) gives good ink holdout for spot colors. For Pantone-matched cosmetic trays on HIPS, we achieve ΔE ≤ 1.5 against target under D50 illuminant, verified per ISO 13655.

Metallic finishes — vacuum metallization and hot stamping — are compatible with all four materials post-forming, but adhesion on rPET can vary with recycled content percentage. We run adhesion testing on every new rPET batch before approving metallization jobs.

Compliance, Sustainability & Certification Requirements #

Food-contact compliance is non-negotiable for any tray or clamshell that contacts product directly. Our standard material supply chain covers:

• PET and rPET: FDA 21 CFR §177.1630; EU Regulation 10/2011; for rPET specifically, EFSA (European Food Safety Authority) guidelines require a decontamination process validation — we source rPET sheet from suppliers with documented EFSA-approved recycling processes.
• PP: FDA 21 CFR §177.1520; EU 10/2011; suitable for microwave and retort applications up to 121°C.
• PS/HIPS: We do not recommend for direct food contact in new product development. Residual styrene monomer limits under EU 10/2011 are 0.6 mg/kg — achievable but requires careful supplier qualification.

For sustainability certifications, rPET with GRS certification is the most straightforward path for brands making recycled content claims. FSC certification does not apply to plastic substrates. REACH compliance (EU Regulation 1907/2006) applies to all materials we supply into the EU market — we maintain REACH declarations of conformity for all standard sheet grades.

The EU PPWR, which entered into force in 2024, sets mandatory recycled content targets for plastic packaging by 2030. Brands planning packaging refreshes now should factor in rPET or PP as the forward-compatible choices. We are already running rPET at 50% and 100% post-consumer content for several EU-market clients.

Specification Notes for Brand Partners #

When you brief us on a thermoforming project, we need the following to develop an accurate quote and sample: finished pack dimensions (L × W × D), draw depth, wall thickness requirement or product weight for structural sizing, material preference or sustainability target, food-contact requirement (yes/no and which regulation applies), and decoration method. The most common brief gap we see is missing draw depth — brands send us a 2D dieline without the Z-axis dimension, and we cannot confirm material gauge or draw ratio feasibility without it.

A mistake we see regularly: brands specify the thinnest possible gauge to reduce material cost, then find the formed tray fails drop or stack-load testing. We always recommend running a gauge optimization at sampling stage — the cost difference between 0.30mm and 0.40mm APET is minor per unit, but the structural difference is significant.

Our typical process: digital structural review in 2–3 working days, physical thermoformed sample in 10–15 working days, production lead time 20–28 working days after sample approval, depending on order volume and decoration complexity.

Frequently Asked Questions #

Q1: What is the minimum wall thickness we should specify for a PET clamshell that needs to survive retail handling?
A: On our line, we set a minimum post-forming wall thickness of 60% of nominal sheet gauge — so a 0.5mm APET sheet should not thin below 0.30mm at the deepest draw point. For retail clamshells subject to ISTA 2A drop testing, we typically recommend starting at 0.40–0.50mm gauge for draw depths up to 50mm.

Q2: What are your MOQs and lead times for thermoformed trays in rPET?
A: Our standard MOQ for thermoformed trays is 5,000 units for simple geometries, with physical samples available in 10–15 working days. Production lead time after sample approval runs 20–28 working days. rPET sheet availability can add 3–5 days to material procurement if we are sourcing a specific recycled content percentage outside our standard stock.

Q3: Does rPET meet FDA and EU food-contact requirements?
A: Yes, provided the rPET sheet is produced via an EFSA-approved decontamination process and the supplier holds the relevant documentation. We source rPET from qualified suppliers and can provide FDA 21 CFR §177.1630 and EU 10/2011 compliance letters with each production order. GRS-certified rPET is available for brands making verified recycled content claims.

Q4: Can we print Pantone colors directly onto thermoformed HIPS trays?
A: Yes — on HIPS we achieve ΔE ≤ 1.5 against Pantone target under D50 illuminant, verified per ISO 13655. HIPS accepts UV screen and pad printing without pre-treatment in most cases. For PET and PP, we run corona treatment to a minimum of 42–48 dynes/cm (ASTM D2578) before printing to ensure adhesion passes ISO 2409 cross-hatch testing.

Q5: We’ve had wall thinning failures with PP trays from another supplier — what causes this and how do you prevent it?
A: Wall thinning in PP thermoforming is almost always caused by forming temperature running too low (below 140°C) or draw ratio exceeding the material’s limit of approximately 0.8:1. PP has a narrower forming window than PET and requires precise temperature control across the sheet — we use zone-controlled infrared heating and verify sheet surface temperature with IR pyrometry before each forming cycle. If the draw ratio is the root cause, we will flag it at the structural review stage before cutting tooling.

Planning a thermoforming project? Contact our team to request a complimentary specification review and sample quote.