Resin choice locks the sheet line, mold temperature, and whether you need a rim curling machine. Switching later means new drying, new molds, and often a new stacker recipe.
| PP | PS / HIPS | PET / APET | PLA | |
|---|---|---|---|---|
| Density (g/cm³) | 0.89–0.91 | 1.04–1.09 | 1.38–1.41 | ~1.24 |
| Use temperature (typical) | ~120°C, microwave-adjacent | ~70–80°C, cold drink | ~70°C, cold / lids | ~55°C |
| Clarity | Translucent (clarified grades exist) | Good / crisp print | Best (often cited ~90% light) | Clear |
| Drying | Low | Low | High — ~50 ppm at die | High — vendor <250 ppm |
| Sheet line | PP/PS/PE extruders | SC-PS-Single | PET/PLA | Biodegradable |
PP’s lower density means more cups per kilogram than PET — often cited around a 30% mass saving versus PET for the same geometry. PET needs energy for drying; PP needs higher forming heat and longer cool on deep draws. GABLER notes PET can cycle faster on some lids; PP yogurt cups often run slower because the wall must freeze.
Worked example — same 200 ml drinking cup
PP cup ~4.5 g vs PET ~6.2 g (illustrative walls). At 30 million cups/year that is tens of tonnes of resin. If the drink is hot tea, PP wins regardless of grams. If the buyer wants a crystal-clear cold cup and has a dryer, PET on SI/LSI plus an FS former is the path. Confirm local PS rules before you cut a 30-cavity PS mold for export.
What the resin change actually buys
Switching PP → PET is not a recipe on the HMI. You add a crystallizer/dryer, new roll temperatures, often a new mold because shrink and rim stiffness change, and you stop blending the two regrinds. Budget the dryer and a week of trials, not an afternoon.
Unsure? Send drink temperature, print/IML, and country of sale. We map resin → sheet → former on one turnkey drawing.
Fault map — what the line is telling you
| Symptom | Likely cause | First check |
|---|---|---|
| Clear cold cup goes oval with hot tea | PET or PS used above its use temperature | PP for ~120°C drinks; do not sell PET as hot-fill |
| Same mold, two resins, warped rims | Shrink and cooling recipe not swapped | Two molds or two written recipes — not a one-button HMI swap |
| Export buyer rejects PS after steel is cut | EU / some US channels restrict PS | Confirm country of sale before a 30-cavity PS tool |
| PET cups heavier than the PP quote promised | Density 1.38–1.41 vs 0.90 — not a forming error | Recalc tonnes/year; thin wall only if the mold allows |
| Rim cracks on PET after a weekend of open gaylords | Moisture, not the former | Dry again; 50 ppm at the die |
RFQ checklist — send this in one email
Fill what you know; blank is better than a guess. Attach it on Get a Quote with photos of resin or flake.
- Drink or fill temperature (cold / hot tea / yogurt)
- Country of sale and any PS or recycling rule you already know
- Clarity vs print/IML vs rim-curl requirement
- Annual tonnes or cups, and whether PP and PET must share one press
- Existing sheet line (PP/PS vs PET dryer already on the floor)
Frequently asked questions
Can I run PP and PET on the same cup machine?
Yes if heating zones and cooling are independent recipes. You still need two molds and usually two sheet specs. Do not treat it as a one-button swap.
Is PS banned everywhere?
No. Many domestic cold-cup markets still run PS. Export to the EU and some US buyers is the risk — confirm before tooling.
Does PP always need rim curl?
Drinking cups usually yes. Yogurt with a foil lid may not. Say which rim you need before we quote steel.
Why is PET heavier?
Higher density. You buy more kilograms for the same stack of cups unless you thin the wall — which the mold must allow.