How does the degassing step in a vacuum oven influence the quality of molded F-LSR components? Enhance Material Strength

The degassing step is a critical preventive measure that directly determines the structural integrity and reliability of molded fluorosilicone rubber (F-LSR) components. By subjecting the rubber mixture to a vacuum oven at 100°C for approximately two hours prior to adding catalysts, manufacturers effectively purge trapped air and moisture that would otherwise compromise the material during curing.

Degassing is not merely about achieving a smooth surface finish; it is the fundamental driver of internal structural density. Without this step, trapped volatiles expand during vulcanization, inevitably causing pinholes, cracks, and a significant reduction in mechanical strength.

The Mechanics of Defect Prevention

Eliminating Volatiles and Micro-bubbles

The process of stirring and mixing fluorosilicone rubber inevitably introduces micro-bubbles into the viscous material. Furthermore, the raw mixture may contain residual trace moisture. The vacuum oven treatment targets and extracts these volatile elements before the material moves to the molding stage.

Controlling Expansion During Vulcanization

The subsequent stage of production involves thermal compression vulcanization, which subjects the rubber to high heat. If gas bubbles or moisture remain trapped within the mixture, the heat causes them to expand rapidly. This expansion disrupts the material matrix, leading to internal ruptures and surface defects.

Impact on Material Performance

Maximizing Structural Density

The primary goal of the degassing phase is to ensure the internal consistency of the rubber. By removing voids created by air or steam, the vacuum process ensures high internal structural density. A dense material is essential for consistent performance in demanding applications.

Ensuring Mechanical Strength

Defects caused by trapped gas manifest as pinholes or cracks in the final product. These discontinuities act as stress concentrators, significantly weakening the component. Proper degassing eliminates these flaws, preserving the inherent mechanical strength of the fluorosilicone rubber.

Critical Process Parameters

Adhering to Temperature and Time

The specific parameters of 100°C for approximately 2 hours are essential for success. This combination provides sufficient energy and time to drive out moisture and air without degrading the base polymer. Rushing this step or lowering the temperature risks leaving residual volatiles deep within the mixture.

The Importance of Sequencing

It is vital to note that this vacuum treatment must occur before the addition of catalysts. Degassing the base mixture first ensures that the material is pure and dense before the chemical cross-linking process begins.

Making the Right Choice for Your Goal

To ensure your F-LSR components meet industrial standards, apply these principles to your manufacturing workflow:

• If your primary focus is Visual Quality: Rigorously apply the vacuum step to eliminate surface pinholes and visible bubbles that mar the finish.
• If your primary focus is Durability: Ensure the full 2-hour duration is met to maximize internal density, preventing hidden cracks that lead to premature failure.

Treat the vacuum oven cycle not as a preliminary option, but as the defining step for the material's final physical properties.

Summary Table:

Process Parameter	Recommended Setting	Impact on Quality
Temperature	100°C	Effectively drives out moisture and trapped volatiles.
Duration	~2 Hours	Ensures complete extraction of micro-bubbles from viscous rubber.
Timing	Before Catalyst Addition	Prevents premature curing while ensuring material purity.
Environment	Vacuum Oven	Creates the pressure differential needed to collapse internal voids.

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References

1. Jae Il So, Yingjie Qian. Improvement of Heat Resistance of Fluorosilicone Rubber Employing Vinyl-Functionalized POSS as a Chemical Crosslinking Agent. DOI: 10.3390/polym15051300

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