Sachet Film: Choosing Packaging Film for Sachet Machines

Leaking sachets waste the dose, while film drag and unreliable sealing stop the line. Choose a structure against the actual product, contamination and barrier requirements, then test seals and opening on filled packs. This page covers the machine side; sachet packaging covers the format.

Product inputs before choosing film

Record the actual formulation and storage conditions before comparing structures.

Where liquid or paste products carry fat or surfactant, the inner sealant can be attacked or the adhesive between layers can weaken. Ask for product compatibility testing on the real formulation, under agreed storage time and temperature conditions.

What sachet film does on the machine

A sachet machine pulls film from a reel, shapes it, seals the edges, fills the dose and seals the last edge. The film carries the print, protects the product and supplies the sealant surface. Sachets are small and run fast, so small variations in film behavior show up as leakers, skewed packs or stoppages.

Most sachet production runs on one of two machine types.

• 3-side seal: film is folded in half, either from a reel of single web or a pre-folded one. Two side seals and a top seal close the pack, and the fold forms the fourth edge. It is common for liquids, creams and powders.
• 4-side seal: two separate webs are sealed together on all four edges, so each side can use a different film, such as a clear side and a foil side. It is used for pharma powders, wipes and products that need a printed front and a barrier back.

Each can run as a single lane or as multi-lane, where a wide reel is slit and every lane makes its own sachets. On multi-lane machines, web flatness, even tension and slitting quality matter more, as covered for stick pack film.

Common sachet film structures

For material details see PET film, aluminum foil and BOPP film.

Seal integrity and seal-through-contamination

Sachets have small seal areas and the product is often right at the seal. A pack can look sealed and still leak if product sits in the seal.

These are the parameters to check:

• Seal temperature, dwell and pressure: too cool gives weak seals, too hot gives distortion or burn-through. See seal initiation temperature.
• Hot tack: liquid or powder dropped into a warm seal can open it. Hot tack is commonly measured per ASTM F1921.
• Seal strength: commonly tested per ASTM F88. Test seals that have product in them as well as clean ones.
• Sealant type: some PE-based sealants are formulated to seal through light contamination. Ask the supplier which grade suits your product and jaw pattern.
• Jaw pattern: compare the installed jaw pattern with the machine guidance and trial clean and contaminated seals separately.
• Seal width: use the agreed seal drawing and test its tolerance to actual contamination.

Leak testing of finished sachets is commonly done with dye, vacuum or bubble methods. ASTM F2096 covers gross leak detection by internal pressurization (bubble test); validate its applicability to the actual package. A seal-strength result does not substitute for leakage testing, and a leak test does not measure peel strength.

Tear notches and easy opening

A notch starts an opening; it does not establish the tear path of the whole laminate. Do not infer straight tearing from “PET” or “BOPP” alone. Record layer structure, orientation, thickness and notch/score position. A converter’s public laser-scoring guidance supports machine- and cross-direction scoring with settings chosen for different materials, not a universal tear direction.

Test filled packs in the intended opening direction after the agreed storage and temperature/humidity conditioning. Record whether the tear follows the intended path, opens the dose cleanly and leaves the product accessible. Confirm the scored pack still meets its barrier and integrity criteria.

COF, tracking and registration

Coefficient of friction controls how film runs over forming plates or collars and through the feed. Too high gives drag and wrinkles. Too low gives slipping on the rollers and variable pack length. ASTM D1894 is the usual test method; see coefficient of friction. Registration marks need good contrast against the background, and sensor settings must suit metallized or dark films.

Common sachet problems

Sachet specification and trial record

Copy this record for each material batch and trial condition; agree criteria before running a full-roll trial with the real product.

For the wider picture, read packaging film and machine compatibility.

Method and sources

The input and record tables are editorial suggestions. Public scopes checked 8 October 2026: ASTM F88/F88M-23, force to separate a seal specimen; F1921/F1921M-12(2023), instrumented hot seal strength; F2096-11(2019), gross leaks; D1894-24, starting/sliding friction under specified conditions. These scopes supply no project acceptance limits. A converter’s slitting and laser-scoring documentation describes directional scoring and material-dependent settings; it does not certify this page’s candidate structures.