What's the 5 Technical Parameters You Must Ask When Purchasing Vacuum Packaging Film ?

In the procurement of vacuum packaging films, focusing only on price is one of the most common mistakes made by many companies.

A price difference of just a few cents per unit may seem insignificant at first. However, once the film is running on production lines, issues such as high breakage rates, poor heat sealing, delamination, or ink adhesion failure can lead to machine downtime and scrap losses that are tens or even hundreds of times higher than the material cost difference.

So, beyond price, what are the key technical parameters you should clearly understand when purchasing vacuum packaging films?

1. Oxygen Transmission Rate (OTR) & Water Vapor Transmission Rate (WVTR): The “Lifeline” of Shelf Life

One of the core functions of vacuum packaging is to block oxygen and moisture, thereby extending product shelf life. Oxygen Transmission Rate (OTR) and Water Vapor Transmission Rate (WVTR) are two essential indicators that directly determine preservation performance.

Different food products have very different barrier requirements.

For example, for fresh meat and high-fat cooked foods, oxygen accelerates lipid oxidation and microbial growth. Therefore, extremely low oxygen permeability is required. Under standard testing conditions (23°C, 0% RH), seven-layer or nine-layer co-extruded films with an EVOH barrier layer can achieve an OTR as low as 3–5 cm³/m²·24h·atm, enabling a shelf life of 15–20 days.

For dried fruits and tea products, which are sensitive to both moisture and oxygen, both WVTR and OTR must be considered. In such cases, outer layers made of PE or PP (for moisture resistance), combined with barrier layers such as EVOH or PVDC, are preferred.

Reliable suppliers will provide data based on standards such as GB/T 1038 or ASTM D3985, rather than vague claims like “good barrier performance.”

2. Heat Seal Strength & Seal Initiation Temperature: Balancing Efficiency and Seal Reliability

Heat seal strength determines whether the seal is strong enough, while seal initiation temperature determines whether the film is suitable for high-speed automatic packaging machines. These two parameters are closely related.

On automated packaging lines, the heat sealing dwell time is often only 0.5–1 second. If the seal initiation temperature is too high, heat may not fully transfer to the inner layer in time, resulting in incomplete sealing and weak seals.

Lower seal initiation temperature generally means better compatibility with high-speed packaging. This is also why metallocene polyethylene (mLLDPE) is widely used in high-speed packaging applications.

At the same time, heat seal strength is the final safeguard of packaging integrity. According to QB/T 2358-1998, a properly sealed package should ideally fail by film tearing rather than seal opening, indicating that the seal strength exceeds the base film strength.

For heavy-duty packaging (e.g., 20 kg rice bags) or retort packaging, heat seal strength requirements are higher, typically ≥30 N/15 mm. Suppliers should provide standardized test data and confirm the failure mode.

3. Puncture Resistance: Critical Protection for Bone-In Meat and Seafood Packaging

Sharp bone fragments in meat products, hard shells in frozen seafood, and edges of frozen dumplings can all create continuous puncture stress during vacuum packaging and transportation.

If puncture resistance is insufficient, even adequately thick films may develop pinholes or direct puncture failure at stress points.

PA (polyamide / nylon) is the key material for improving puncture resistance. High-performance BOPA films can reach puncture strength values of 9–10 N (GB/T 10004 test basis).

Multi-layer co-extruded films further improve performance through multi-layer PA distribution design, significantly enhancing overall puncture resistance.

4. Tensile Strength & Elongation at Break: Mechanical Stability for Filling and Stacking

During filling, palletizing, and transportation, packaging films must withstand both impact forces from contents and static stacking pressure.

For heavy-duty applications reinforced with PA layers, the longitudinal tensile strength is typically required to be ≥35 MPa (GB/T 1040.3 test basis).

When sourcing, suppliers should provide standardized test reports, with special attention to differences between:

• MD (Machine Direction)
• TD (Transverse Direction)

These values are often different due to blown film processing.

It is also important to note: High tensile strength does not necessarily mean high elongation.

For packaging requiring drop impact resistance, elongation at break is equally important, typically requiring ≥300%.

Both directional tensile strength and elongation data should be requested during procurement.

5. Dyne Level (Surface Energy) & Lamination Strength: The Hidden Threshold for Printing and Lamination

If vacuum packaging films require printing or lamination (e.g., with aluminum foil), surface dyne level (surface tension) becomes a critical technical threshold.

Untreated PE or PP films typically have a surface tension of only about 31 dynes/cm, which is insufficient for ink adhesion, resulting in ink peeling or poor print durability.

For printable films, surface dyne levels should typically reach 38–42 dynes/cm or higher at delivery.

However, dyne levels naturally decay over time. After 3–6 months of storage, surface tension may decrease by 2–3 dynes/cm.

For laminated structures, lamination (peel) strength should also be verified to ensure strong interlayer bonding and long-term stability.

6. Frequently Asked Questions (FAQ)