Paper Packaging · Technical Guide
How to Select Molded Fiber Barrier Additives
Barrier chemistry for molded fiber should be selected around the medium that must be resisted, the point of addition, compliance requirements and the actual forming and drying process. A good formulation is not simply the product with the highest nominal barrier claim; it is the one that delivers the required performance reliably inside the mill process.
1. Start with the barrier requirement
The first question is whether the package needs resistance to water, oil and grease together, or mainly oil and grease. Food trays, bowls, lids and other molded-fiber formats can face very different exposure conditions. Temperature, contact time, food composition, product thickness and fiber furnish all influence the level of treatment required.
For projects that require both water and oil resistance, a dual-function wet-end additive can simplify the formulation. For applications focused primarily on oil and grease resistance, an oil-focused chemistry may be more efficient. Where fluorine-free specifications are mandatory, that requirement should be defined at the beginning rather than treated as a late-stage substitution.
2. Understand the three wet-end barrier options
XIAOJU groups three products under Molded Fiber Barrier Additives. RETERRA RT901 is positioned as a PFAS-free wet-end water and oil repellent. RETERRA RT326 is a PFAS-free oil and grease barrier additive. FluoRight 660 is a fluorinated wet-end oil and grease barrier additive. These products address different performance and compliance priorities rather than serving as interchangeable names for the same chemistry.
The practical selection therefore starts with the target barrier profile and market requirement, then moves to dosage optimization under the customer’s actual pulp system and forming process.
3. Validate the process, not only the laboratory result
Wet-end additives interact with the complete pulp-molding process. Furnish composition, consistency, retention, mixing time, pH, drainage, mold temperature, drying profile and final wall thickness can all affect performance. Foam control and additive compatibility should also be checked because a chemistry that performs well in a simple beaker test may behave differently in a recirculating production system.
A useful validation plan keeps the required barrier test constant while changing one process variable at a time. This makes it easier to distinguish chemistry limits from process-related losses and helps establish a stable production window.
4. Know when surface treatment or reinforcement is a separate need
Wet-end barrier chemistry is only one part of the paper-packaging additive system. RETERRA RT940 belongs to the Paper Barrier Coating Agents series and is intended for surface application when post-forming or post-papermaking treatment is preferred. RETERRA C101 belongs to Molded Fiber Reinforcement Additives and addresses mechanical integrity, fiber bonding and surface durability rather than acting as the primary barrier chemistry.
Separating these functions helps avoid overloading a single additive with unrelated expectations. Barrier, reinforcement and surface coating can be optimized as independent layers of the overall package design.
Selection reference
| Primary need | Series / product direction |
|---|---|
| PFAS-free water + oil resistance | RETERRA RT901 |
| PFAS-free oil & grease resistance | RETERRA RT326 |
| Fluorinated oil & grease resistance | FluoRight 660 |
| Surface-applied paper barrier | RETERRA RT940 |
| Mechanical reinforcement / lint & dust reduction | RETERRA C101 |