Shrink Sleeve Film Types Compared

Film Choice Drives Solvent Choice

The question is not “which solvent should I use?” but “what film am I seaming?” The polymer determines which solvents can dissolve or swell it, how quickly the chains interdiffuse, and how much dosing latitude you have. Pick the film first. The solvent class follows.

This matters because a solvent-welded seam is a polymer-level bond. The solvent must penetrate the film surface, mobilize polymer chains on both faces of the overlap, allow those chains to interdiffuse across the interface, and then evaporate cleanly. Different polymers resist that process in different ways — crystallinity, polarity, glass transition temperature — and those differences are what the five solvent classes address.

Film Comparison

Shrink ratios are typical industry ranges in the transverse direction (TD) and vary by grade and supplier.

Film-by-Film Summary

PETG is the dominant shrink sleeve substrate. Its amorphous structure — the CHDM comonomer eliminates crystallinity — makes it receptive to a broad range of solvents. Classes 1 through 3 all work. The risk is over-solvation rather than under-solvation. See PETG film details.

PET retains crystalline domains that block solvent penetration. Standard solvents used on PETG will wet the surface but fail to develop a structural bond. Class 4 solvents are formulated specifically for this substrate. The seaming window is narrower. See PET film details.

PVC was the original sleeve material and remains the easiest to seam. It responds predictably to Classes 1, 2, and 3, with the widest acceptable dosing window of any substrate. Environmental and regulatory pressure is steadily reducing its use. See PVC film details.

rPET requires the same Class 4 solvents as virgin PET, but recycled content introduces variability. Crystallinity levels and trace contaminants shift between batches, which can move the seaming window. More frequent seam testing is warranted. See rPET film details.

Polyolefin (PP and PE) cannot be solvent-welded by any conventional means. The polymers are non-polar and semicrystalline — there is no solvent that will dissolve them under seaming conditions. Class 5 products use a fundamentally different bond mechanism, and alternative methods such as adhesive-based or thermal sealing also exist. See polyolefin film details.

Film Thickness and Seaming

Most shrink sleeve films run 40–50 µm. At standard dosing — roughly 5 µm of liquid applied to the overlap — the solvent layer is about one-tenth the film thickness. Thicker films are more tolerant of dosing variation because the solvent has more polymer mass to diffuse into before it risks penetrating through to the print layer. Thinner films, conversely, punish over-dosing: the solvent reaches the ink faster, and blocking or print distortion follows.

When switching between film thicknesses on the same polymer, dosing is the first parameter to revisit. A setup validated on 50 µm PETG may over-dose on 40 µm PETG at the same flow rate.

The Sustainability Transition

The industry has been moving through a sequence of substrate transitions, each driven by environmental and recyclability concerns:

PVC to PETG. PVC contaminates PET recycling streams — even small amounts degrade recycled PET quality. Most brand owners have moved to PETG, which is compatible with PET recycling when sleeve removal is part of the process. For seaming, this transition was relatively smooth: PETG seams well with the same solvent classes, though it is more sensitive to over-dosing than PVC.

PETG to PET / rPET. PETG itself is increasingly scrutinized because the CHDM comonomer can affect recycled PET clarity. Virgin PET and rPET films are gaining share. For seaming, this is a harder transition: Class 4 solvents are required, the window is narrower, and rPET adds batch variability.

PET to polyolefin. For PE containers, a PE sleeve creates a mono-material package that can enter PE recycling streams without separation. This is the most disruptive transition for seaming operations — conventional solvent welding does not work, and equipment or process changes are needed.

Each transition narrows the seaming window and demands more from process control. The solvent class framework maps these substrate shifts to concrete changes in solvent selection and dosing.