01 METALLIZED FILM COMPARISON
VMPET vs VMCPP: separate the barrier web from the sealing job
The silver appearance does not make VMPET and VMCPP interchangeable. Start with the polymer substrate, then define whether the metallized web is expected to provide barrier, stiffness, sealing or a combination of jobs.
02 DECISION FRAME
Substrate choice changes the structure around the metal layer
VMPET is commonly specified as a PET-based metallized barrier web and paired with a separate sealant. VMCPP is CPP-based and may combine a metallized barrier role with grade-dependent sealing. Actual performance depends on the substrate, deposited layer, coatings, treatment, conversion and finished laminate.
- A metallic laminate where the sealant layer is not yet assigned
- A cost or structure review that is comparing VMPET and VMCPP
- A barrier problem that needs more evidence than optical density alone
- That equal optical density means equal OTR, WVTR or metal adhesion
- That every VMCPP grade provides the required seal response
- That VMPET can replace VMCPP without changing the surrounding layers
03 COMPARISON MAP
Two substrates, two different starting architectures
Compare the complete laminate and the exact metallized grade. The acronym alone does not define barrier or sealing performance.
Swipe or scroll horizontally to review every evidence column.
| Decision | VMPET starting point | VMCPP starting point | Verify in the RFQ |
|---|---|---|---|
| Substrate | Metallized PET web | Metallized cast-polypropylene web | Exact substrate and grade designation |
| Typical layer job | Barrier, visual and dimensional web in a laminate | Barrier and flexible inner-web role; sealing may be included by grade | Layer position and every assigned function |
| Sealing | Usually planned with a separate sealant layer | May be supplied as a heat-sealable construction | Seal side, equipment, operating conditions and acceptance method |
| Metal side | Orientation affects lamination, coating and protection of the deposited layer | Orientation affects lamination, sealing and protection of the deposited layer | Metal side, treated side and unwind direction |
| Barrier evidence | Must be tied to the offered grade and test conditions | Must be tied to the offered grade and test conditions | OTR, WVTR, method, temperature, humidity and specimen structure |
| Conversion durability | Check metal adhesion, bond and flex after downstream conversion | Check metal adhesion, bond, flex and seal response after conversion | Trial steps and post-conversion acceptance criteria |
04 SELECTION SEQUENCE
Move from a broad comparison to an approvable decision.
Draw the complete laminate
Show the print, barrier, support and sealant layers. A comparison without the surrounding structure hides the real substitution work.
Protect and orient the metal side
State which side carries the deposited layer, which side is treated and which surface meets the adhesive, ink or seal interface.
Test after relevant conversion
Barrier, metal adhesion and bond should be judged on a clearly identified specimen and at the agreed stage of the converting process.
05 RFQ INPUTS
VMPET vs VMCPP RFQ checklist
Ask suppliers to quote against one structure, one orientation map and one acceptance plan.
Open the RFQ brief builder ↗- 01
Packed product, sensitivity, pack format, fill process and target shelf-life basis
- 02
Current and proposed laminate structures with each layer’s function
- 03
VMPET, VMCPP or open-to-recommendation status
- 04
Substrate thickness, total construction and dimensional tolerances
- 05
Metal side, treated side, print or lamination side and unwind direction
- 06
Optical-density target and measurement basis, if it is a controlled requirement
- 07
OTR and WVTR target, unit, method, temperature, humidity and specimen identity
- 08
Metal adhesion, laminate bond, flex and appearance acceptance methods
- 09
Seal conditions for VMCPP, roll format, sample plan, trial quantity and recurring volume
06 EVIDENCE BOUNDARY
A metallic appearance is not a barrier certificate
Optical density can describe one aspect of a deposited metal layer, but it does not replace grade-specific OTR, WVTR, adhesion and conversion evidence. Request results for the same specimen construction and agreed conditions used in the buying comparison.
07 BUYER QUESTIONS
Resolve the assumptions that make quotes diverge.
01What is the main sourcing difference between VMPET and VMCPP?+
VMPET starts from a PET substrate and is commonly treated as a metallized barrier web with a separate sealant. VMCPP starts from cast polypropylene and may include a grade-dependent sealing role. The full laminate decides which route fits.
02Can optical density be used as the only metallized-film specification?+
No. Include the measurement basis, but also request OTR and WVTR under stated conditions, metal adhesion, surface orientation, laminate bond, flex evaluation and the exact specimen construction.
03Why does the RFQ need the metal side and unwind direction?+
Those details determine which surface meets adhesive, ink, product or sealing equipment and how the web enters the converting line. An orientation mismatch can invalidate an otherwise suitable roll.
04Should barrier be tested before or after lamination?+
State the decision you need to make and agree the specimen stage with the supplier or laboratory. Base-film data and converted-laminate data answer different questions and should not be presented as interchangeable.