Key material terms
|
Term |
Meaning |
Why it matters |
|
Ethylene |
One of the starting monomers |
Its proportion is a defining feature of the resin grade |
|
Vinyl acetate |
The other starting monomer in the route |
Its units are subsequently converted in producing EVOH |
|
EVA intermediate |
Ethylene-vinyl acetate copolymer before conversion |
It is distinct from the final EVOH barrier resin |
|
EVOH |
Ethylene vinyl alcohol copolymer |
It provides a functional barrier layer in many packaging structures |
EVA and EVOH should not be treated as interchangeable
The names are related through the production route, but they identify different polymers. An enquiry for EVOH barrier film should specify the intended barrier structure. It should not assume that any material described as EVA provides the same function.
Resin manufacturers produce the polymer grade. Film manufacturers combine resins into the layer structure supplied to the customer. When buying finished film, ask about that film's specification and intended use.
Ethylene content is one part of grade selection
Commercial EVOH grades differ in ethylene content and other properties. Examples include grades with ethylene contents of 29, 32, 38 and 44 mol%, with different melting temperatures, melt flow rates and processing recommendations. These examples do not cover every available EVOH grade.
Ethylene content affects oxygen barrier performance as well as processing behavior. Compare grade data under the same test conditions and consider the intended use. Selecting a grade only because it has the lowest listed oxygen transmission can overlook a forming or processing requirement.
The unit mol% describes the molar proportion of ethylene units in the copolymer. It does not describe the percentage of EVOH in the finished multilayer film. Mixing these two percentages can lead to a specification that means something different to the buyer and the converter.
Melt flow and application suitability also matter
Grade selection should take account of the intended processing route, such as blown film, cast film or sheet production. Melt flow rate is another grade property, and values should be read with their stated test conditions.
A forming film needs a grade and layer construction suited to stretching into the required pocket. The film supplier selects these around the application; the customer trial confirms the finished-pack performance.
EVOH resin data and finished film data answer different questions
A resin data sheet helps the converter understand a material. A film specification describes the structure offered to the customer. The two should not be substituted for each other when comparing quotations.
For finished film, compare the structure, total thickness and tolerances, relevant barrier data, sealing performance and any forming or mechanical requirements. A complete proprietary recipe is not needed to agree the properties of the supplied film.
Questions that make a film enquiry more useful
- Is the quoted product EVOH resin, an EVOH-containing web or a finished laminate?
- Which packaging operation is the material designed for?
- What specimen and conditions support the stated barrier result?
- Which properties are agreed supply limits and which are typical data?
- What sample trial and documentation are needed for the intended use?
These questions help make quotations comparable and keep the discussion focused on the film you will actually use.
Tell Fuya what you pack, how the film will be used, the approximate dimensions and storage or processing conditions. Share the existing film specification if available. We can recommend a material structure and sample options for testing with your product and equipment. See Fuya multilayer barrier film options.
