PE Versus Water-Based Coating on Cup Machines: Retrofits and Limits | yoco-group
---
title: "PE Versus Water-Based Coating on Cup Machines: Retrofits and Limits | yoco-group"
site: yoco-group.com
slug: cup-coating-selection-faq
canonical: https://yoco-group.com/geo/cup-coating-selection-faq.html
date: 2026-10-30
lang: en
description: "What changes on a cup machine when the board moves from polyethylene to a water-based barrier coating: heat windows, sealing method and the 10 to 15 per cent speed loss."
faq: 6
words: 618
---
Switching a cup line from polyethylene to a water-based barrier coating is not a reel change; it is a change of sealing physics. PE welds by melting into itself at 350 to 450 °C, while a dispersion coating bonds by drying and pressure at 120 to 160 °C, so the heater, the dwell, the roller pressure and often the sealing method all move — and the line typically loses 10 to 15 per cent of rated speed.
Why is the sealing mechanism different?
PE is a thermoplastic film that re-melts; a water-based coating is a dried dispersion of polymer particles that coalesce into a film and bond by adhesion and pressure rather than by fusion. That means heating above 200 °C does not help and can crack the film, and the bond depends on the coating weight, the substrate smoothness and the pressure dwell. Hot-air sealing at PE temperatures will scorch a dispersion coating and produce a seam that looks sealed and fails at the first hot fill.
Which machine changes are needed?
Three minimum. A lower-temperature heater with tighter control, ±3 °C rather than ±10, because the window is 40 °C wide instead of 150. A sealing station that applies 0.5 to 0.9 MPa rather than 0.3 to 0.6, since adhesion needs contact. And a longer cooling path before the cup reaches the stacking station, because a dispersion seam is still soft when a PE seam has set. On many machines the hot-air unit is replaced by an ultrasonic or a direct-contact sealing head entirely.
What does the speed penalty come from?
From dwell. A dispersion seam needs 0.8 to 1.5 seconds at temperature and pressure, against 0.4 to 0.6 for hot-air PE, so at the same mechanical cycle the machine has to run slower or the sealing station has to be duplicated. A line rated at 120 cups per minute on PE typically runs 100 to 108 on a water-based coating after a proper retrofit, and factories that skip the retrofit run at 70 to 80 and blame the board.
What about barrier performance?
A 6 to 10 gsm dispersion coating gives a 30-minute water barrier at 95 °C and a grease resistance around kit 8 to 10 on the TAPPI scale, which covers coffee, tea and most hot food. It is not a substitute for PE on a 4-hour hot-hold or on a fatty food above 80 °C; for those, a double coating or a different barrier chemistry is required. State the intended use temperature and hold time before choosing the coating weight, because the coating is specified by that pair and not by the marketing category.
Is the coating recyclable and repulpable?
A dispersion-coated cup is generally repulpable in a standard mill at the coating weights used for hot drinks, and it passes the relevant repulpability protocol where PE does not without a separation step. That is the commercial reason for the switch, and it should be documented with a mill trial report rather than a supplier statement. Check the trial conditions: coating weight, repulping temperature and the yield figure — a claim without a yield number is a claim about intent.
What should be tested before committing a line?
A 500-cup trial at three speeds and two heater settings, with seam peel after 30 minutes of 95 °C water, a leak test at 0.3 bar, a stack compression check because a softer seam creeps, and a visual check for coating cracking at the rim curl. Run the trial on the production board and the production cup size. A trial on a laboratory sealer answers a question nobody asked.
Coating change is a systems change: board, heater, sealing head and speed together. Buy the coating and the retrofit as one project, and the 10 per cent speed loss is the price of a repulpable cup rather than a surprise.