{"id":11553,"date":"2026-09-22T10:01:07","date_gmt":"2026-09-22T08:01:07","guid":{"rendered":"https:\/\/www.zfoam.com\/hermetic-sealing-for-cbrn-warfare\/"},"modified":"2026-09-22T10:01:07","modified_gmt":"2026-09-22T08:01:07","slug":"hermetic-sealing-for-cbrn-warfare","status":"publish","type":"post","link":"https:\/\/www.zfoam.com\/en\/hermetic-sealing-for-cbrn-warfare\/","title":{"rendered":"Hermetic sealing for CBRN warfare"},"content":{"rendered":"

High-compression gaskets for military shelters and bunkers<\/span><\/h3>\n

A seal failure of just a few microns in a<\/span> shelter’s perimeter gasket<\/b> negates the filtration system’s overpressure, leaving the crew exposed to chemical agents.<\/span><\/p>\n

In a combat scenario, survival depends on maintaining<\/span> constant positive internal pressure\u2014<\/b>as required by specifications\u2014and that pressure relies on the perimeter gasket. When the gasket fails, everything else fails. <\/span><\/p>\n

Conventional elastomers do not hold up. Under high closure pressures, they suffer from elastic fatigue and lose performance after months of stowage (prolonged storage) at extreme temperatures. A crushed gasket no longer seals, regardless of the quality of the surrounding metalwork. <\/span><\/p>\n

That is why we utilize<\/span> the BISCO\u00ae L3-XX40<\/b> range of high-resilience silicones\u2014a medium-density <\/span>(465 kg\/m\u00b3)<\/b> microcellular polymer that recovers its original thickness after years of extreme compression and maintains the seal throughout the equipment’s service life.<\/span><\/p>\n

 <\/p>\n\n\n\n\n\n\n\n
Engineering material<\/b><\/th>\nNominal density<\/b><\/th>\nResidual deformation (ASTM D1056)<\/b><\/th>\nBehaviour during prolonged stowage<\/b><\/th>\n<\/tr>\n<\/thead>\n
BISCO\u00ae L3-XX40 silicone<\/span><\/td>\n465 kg\/m\u00b3<\/span><\/td>\n <5 %<\/b><\/td>\n

<\/span><\/p>\n

Excellent long-term elastic memory<\/td>\n

\n<\/tr>\n

PORON\u00ae 4701-60 Very Firm polyurethane<\/span><\/td>\n240 kg\/m\u00b3<\/span><\/td>\n

<<\/p>\n

 10 % (70 \u00b0C)<\/span><\/td>\nFirm, continuous elastic support<\/span><\/td>\n<\/tr>\n
Standard cellular rubber (EPDM \/ neoprene<\/span><\/td>\n150 kg\/m\u00b3<\/span><\/td>\n >40 % (irreversible collapse)<\/span><\/td>\nAccelerated fatigue and loss of seal integrity<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 
\n <\/p>\n

Collapse due to compression set in traditional gaskets<\/span><\/h2>\n

Armoured hatches on command shelters require high<\/span> deflection force<\/b> to counteract the torsion transmitted to the frame during transport across hostile terrain.<\/span><\/p>\n

Subjected to constant closure,<\/span> cellular rubber or neoprene gaskets<\/a><\/strong> undergo permanent flattening\u2014a <\/span>phenomenon known<\/b> in the industry as <\/span>“compression set.”<\/span><\/i>. The material loses its dimensional memory, microscopic gaps emerge, and pressurized air escapes through them.<\/span><\/p>\n

With<\/span> BISCO\u00ae <\/b>silicones, however, recovery force remains constant<\/span> between -55\u00b0C and +200\u00b0C<\/b>, maintaining over <\/span>95% elastic<\/b> memory throughout the operating cycle, as verified by<\/span> ASTM D1056<\/b> tests.<\/span><\/p>\n

A factory-installed gasket continues to seal effectively two years later\u2014whether in the desert or in temperatures of minus 40\u00b0C\u2014without the need to readjust wedge closures in the field.<\/span><\/p>\n

The reason lies in the physics of the material: open-cell foams rely on trapped air for recovery\u2014air that migrates until the material loses its ability to rebound\u2014whereas in BISCO\u00ae silicones, the polymer network itself performs this function. <\/span><\/p>\n

 <\/p>\n

\"Gaskets<\/p>\n

 <\/p>\n

Outgassing: The Silent Enemy of Optronics<\/span><\/h2>\n

Chemically blown foams can retain process residues and release<\/span> volatile organic compounds (VOCs)<\/b> into the enclosure.<\/span><\/p>\n

This<\/span> outgassing<\/b>generates vapours that condense on communications racks and fog up thermal and infrared vision sensors. In a shelter without forced ventilation, an ill-chosen gasket can compromise thermal vision capabilities long before any external threat does. <\/span><\/p>\n

To eliminate this risk, we process Zotefoams\u2019<\/span> Plastazote\u00ae polyolefins<\/a><\/strong>, which are expanded using<\/span> pure nitrogen<\/b> injection rather than chemical agents. Their closed-cell structure and chemical inertness prevent moisture absorption and gas emission, thereby <\/span>protecting integrated circuit boards<\/b> against corrosion caused by acidic condensation.<\/span><\/p>\n

When extreme mechanical firmness is also required, we turn to<\/span> PORON\u00ae 4701-60 Very Firm polyurethanes<\/b>. These materials exceed<\/span> ISO 6452 and DIN 75201<\/b> fogging<\/span><\/i> test<\/span> standards, ensuring that no volatile residues cloud the<\/span> targeting or guidance optics<\/b>. They contain no plasticizers and are non-corrosive to metal.<\/span><\/p>\n

 <\/p>\n

\"High-compression<\/p>\n

 <\/p>\n

The Hidden Failure Vector in Bonded Joints<\/span><\/h2>\n

Tactical transport subjects the shelter to constant vibration and shear forces that stress any bonded joint.<\/span><\/p>\n

A perimeter gasket made from strips mitre-bonded at the corners possesses a critical weakness: these joints eventually fail under frame torsion, creating an <\/span>entry point for CBRN (Chemical, Biological, Radiological, and Nuclear) agents.<\/b><\/p>\n

We solve this by machining<\/span> continuous, single-piece gaskets\u2014free of joints\u2014<\/b>directly from CAD designs.<\/span><\/p>\n