A Brief Analysis of the Critical Role of Seals in Fine Chemical Production

A Brief Analysis of the Critical Role of Seals in Fine Chemical Production
In fine chemical production, the sealing performance of dynamic equipment plays a crucial role in ensuring the stability of production. This article aims to systematically review the common materials of various seals and the basis for their selection. In modern industry, most rubbers used are synthetic rubbers, including common types such as styrene-butadiene rubber (SBR), butadiene rubber (BR), butyl rubber (IIR), and nitrile rubber (NBR), while specially modified rubbers include chloroprene rubber (CR), ethylene propylene diene monomer (EPDM), fluoroelastomers (FKM), silicone rubber (VMQ), and polyurethane rubber (AU). The performance of rubber mainly depends on its molecular structure characteristics:
- Main chain structure: Saturated main chains (such as EPDM, IIR) have better resistance to ozone and oxidation compared to unsaturated main chains containing C=C double bonds (such as NR, SBR).
- Side group polarity: The introduction of strong polar groups (such as F atoms in FKM, -CN groups in NBR) significantly improves the oil resistance and chemical resistance of rubber.
- Chain regularity: Highly regular cis structures (such as NR, BR) allow rubber to crystallize during stretching, thereby achieving higher strength.
- Molecular chain flexibility: Flexible chain segments (such as the cis configuration of BR, Si-O bonds in silicone rubber) endow rubber with good elasticity and low-temperature resistance.
If the material of the seal is improperly selected, it can lead to various production problems. For instance, seals containing active C-H bonds may undergo decomposition reactions in organic solvents or acidic environments, causing swelling, aging, and loss of sealing function, resulting in material leakage and posing serious safety risks. Meanwhile, seals with C-O-C bonds are prone to chain breakage in organic solvents and alkaline conditions, leading to hardening, aging, and subsequent internal or external leakage.
During routine inspections in the workshop, if equipment shows signs of "leakage", the possibility of mismatch between the seal material and process conditions should be considered first. At this point, methods such as the binary search and mind mapping can be used to systematically identify the cause. Especially in high-pressure equipment, the durability of sealing elements is of critical importance, and any negligence can lead to serious consequences.
To avoid incorrect selection, one can refer to existing rubber corrosion resistance manuals, which typically list the resistance of different rubbers to various chemical media and their applicable temperature ranges. However, in actual production, materials are often complex mixtures containing organic solvents, acidic components, and metal ions. Therefore, the most reliable method is to conduct small-scale experiments, immersing the seals in actual materials for soaking tests (adjusting temperature and simulating wear conditions), and comprehensively evaluating their resistance through dimensional measurement, weight change, tensile elasticity testing, and time-based assessment.
In conclusion, in chemical production, the rational selection of seals should be highly valued. When leakage occurs, the compatibility of the material should be considered first, and the resistance of the seal under actual working conditions should be verified through experiments, with practice serving as the best basis for selection.