What Is The Function Of A Laboratory Hydraulic Press In Pet And Cnt Film Preparation? Engineering Durable Battery Films

The primary function of a laboratory hydraulic press in the preparation of PET and PET-carboxylated CNT composite films is to apply precise, high-magnitude pressure to densify the material structure. Specifically, the press subjects vacuum-filtered fiber films to pressure (e.g., 4 MPa) to physically compress the interleaved hydrophilic and hydrophobic fiber layers. This process transforms a loose fiber arrangement into a compact, mechanically robust film with high structural density.

Core Insight: The hydraulic press serves as a critical structural enforcer. By compacting the film to a high density, it equips the material with the mechanical strength necessary to physically constrain the volume expansion of zinc anodes, thereby ensuring the long-term stability of the battery during charge and discharge cycles.

Optimizing Microstructural Integrity

Densification of Interleaved Layers

Before pressing, the composite material exists as a vacuum-filtered fiber film, which naturally contains voids and loose connections. The hydraulic press applies vertical force to collapse these voids.

Eliminating Porosity

This physical compression forces the interleaved hydrophilic and hydrophobic fiber structures to merge more tightly. The result is a substantial reduction in the film's internal free volume.

Enhancing Mechanical Strength

By bringing the fibers into closer proximity, the press increases the physical points of contact within the matrix. This directly translates to improved mechanical strength, transforming a potentially fragile filter cake into a durable structural component.

The Critical Role in Battery Performance

Inhibiting Anode Volume Expansion

The most specific application of this pressing process is to prepare the film for use in batteries with zinc anodes. Zinc anodes suffer from significant volume expansion during cycling. The pressed film acts as a mechanical barrier that is strong enough to suppress this swelling.

Maintaining Interface Stability

If the film were left unpressed, it would lack the rigidity to contain the anode. The hydraulic press ensures the film is dense enough to maintain a stable electrode interface, preventing the degradation that typically comes from repetitive expansion and contraction.

Improving Cycle Life

By mechanically constraining the anode, the compacted film preserves the battery's internal geometry. This leads to better long-term stability and reliability over many charge and discharge cycles.

Understanding the Trade-offs

The Balance of Pressure

While the primary reference highlights the benefits of 4 MPa pressure, it is vital to note that pressure must be "precise." Insufficient pressure will fail to achieve the required density to stop anode expansion.

Risk of Over-Compression

Conversely, excessive pressure beyond the optimal point can crush the fiber structure or close off pore pathways too completely. In battery applications, while mechanical suppression is key, the material must often remain permeable to ions; finding the exact pressure window is essential to balance strength with electrochemical function.

Making the Right Choice for Your Goal

To maximize the effectiveness of your laboratory hydraulic press for these composite films, consider the following strategic priorities:

If your primary focus is mechanical suppression of anode expansion: Prioritize higher pressure settings (around 4 MPa) to maximize the compaction density and stiffness of the film.
If your primary focus is process repeatability: ensure your press is capable of maintaining the target pressure precisely across the entire surface area to prevent localized weak points in the film.

Ultimately, the hydraulic press is not just shaping the film; it is engineering the physical properties required to survive the harsh mechanical environment inside a cycling battery.

Summary Table:

Process Phase	Function of Hydraulic Press	Impact on Material Properties
Structural Compaction	Collapses voids in vacuum-filtered fiber films	Increases density and reduces porosity
Interface Bonding	Forces hydrophilic/hydrophobic layers together	Enhances internal structural integrity
Mechanical Reinforcement	Increases physical contact points between fibers	Boosts tensile strength and rigidity
Anode Stabilization	Creates a mechanical barrier for zinc anodes	Suppresses volume expansion during cycling

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References

Yuanyue He, Zhe Peng. Simultaneous Inhibitions of Volume Variation and Water Decomposition via Interwoven Structure of Hydrophilic/Hydrophobic Fibers for Stable Zn Electrode. DOI: 10.1002/smll.202504282

This article is also based on technical information from Kintek Press Knowledge Base .