PVDC (polyvinylidene chloride) is widely used as a barrier coating because of its dense molecular structure. When applied as a thin layer on one side of a PET film, it helps restrict water vapor transmission while the PET substrate provides mechanical strength, dimensional stability, and transparency.
This article explains how the coating works, how moisture barrier performance is measured, and where single-sided PVDC-coated PET film is commonly used. It is a general technical overview; final performance should always be confirmed against a grade-specific TDS and the finished laminate.
How PVDC creates a moisture barrier
The chlorine atoms in the PVDC chain are highly polar and promote strong intermolecular attraction. This helps form a dense polymer structure that resists the passage of water molecules.
When PVDC is coated evenly on one side of a PET substrate, the result combines two functions:
- PET substrate: mechanical strength, dimensional stability, and transparency
- PVDC coating: moisture barrier and additional surface protection
The coating is typically very thin, so the film retains most of the handling and printing characteristics of the PET base while gaining a substantially lower water vapor transmission rate than uncoated PET under the same test conditions.
Measuring moisture barrier performance
Moisture barrier performance is usually expressed as Water Vapor Transmission Rate (WVTR): the amount of water vapor passing through a given area of film per unit of time under specified temperature and humidity conditions. Lower WVTR indicates a better moisture barrier.
WVTR should be measured on the finished structure—not only on the base film—because adhesive, sealant, coating weight, and converting quality all affect the final result.
Advantages of single-sided PVDC-coated PET film
Extended shelf life
For moisture-sensitive foods and pharmaceuticals, water vapor ingress can raise internal humidity and contribute to mold, spoilage, caking, or loss of efficacy. A PVDC coating can help limit moisture pickup and support the shelf life defined for the product.
Preserved product quality
Moisture-sensitive foods such as biscuits and candies can lose crispness or become sticky when they absorb water. In pharmaceutical formats, humidity fluctuations may affect stability. A moisture barrier helps reduce these risks, but it does not replace proper formulation, sealing, and stability testing.
Potential packaging cost reduction
In some applications, a reliable moisture barrier may reduce reliance on desiccants or dehumidification. The mechanical properties and transparency of PET can also support downgauging, provided that seal strength, stiffness, and line performance remain acceptable. Any thickness reduction should be validated on the actual packaging line.
Practical applications
Food packaging
Single-sided PVDC-coated PET film is used in laminates for moisture-sensitive products such as biscuits, candies, cakes, meat products, and dairy. The coating helps keep the product dry and supports shelf life. Where the complete structure also provides an oxygen barrier, it can further help protect flavor and quality—but the oxygen barrier should be evaluated for the specific laminate.
Pharmaceutical packaging
For tablets, capsules, and powders that require protection from humidity, PVDC-coated PET can serve as a moisture barrier layer. PVDC is chemically stable and has a long history of use in packaging, but compatibility between the packaging material and the drug product must be confirmed through appropriate testing and documentation for the destination market.
Other applications
The same moisture barrier principle is used in packaging for electronic components, seeds, agricultural products, and other moisture-sensitive goods. Requirements for ESD protection, chemical resistance, and regulatory compliance vary by product and market.
What to validate before specifying
Before commercial approval, confirm:
- WVTR and OTR on the finished laminate, using the agreed test method and conditions
- Adhesion and coating integrity before and after lamination
- Seal strength and package integrity at production line speed
- Compatibility with the product, adhesive, and sealant
- Food-contact or pharmaceutical compliance for the destination market
- End-of-life requirements — PVDC is chlorine-based, and recycling and disposal regulations vary by market, so environmental claims should be supported by market-specific evidence
Outlook
Demand for longer shelf life, product safety, and reduced packaging waste continues to shape film development. For PVDC-coated PET, current work focuses on coating uniformity, thinner barrier layers, compatibility with different laminate structures, and market-specific compliance. Any environmental or recyclability claim should be verified against local requirements before it is used in customer communication.
Next step
Review our barrier coated film platform or send your target WVTR, package structure, and application through our technical inquiry form. We can recommend a starting grade and provide a grade-specific TDS for evaluation.
Disclaimer
This article is provided for general technical information only. It is not regulatory, medical, or legal advice, and it does not confirm that any film, laminate, or package is suitable for a particular application or market. Final material selection, processing conditions, and compliance requirements must be validated for the intended product, production line, and destination market. Performance values are typical and must be confirmed against a grade-specific TDS and finished-package testing.