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proven membrane systems and specialflame-retardant membranes, initially individ-ually and then in combinations involvingflame-retardant adhesives and textiles.

Adhesive screening Based on research into available reactive PURholt-melt adhesives with flame-retardingcharacteristics, the adhesives alone were sur-ficially applied to silicone paper in a prelimi-nary step, after which the combustion be-havior of the foils produced in this way wasexamined in accordance with ISO 15025. Onthe basis of the findings thus made, a selec-tion was made of adhesives for application tomembranes. A thermostable membranewithout flame-retardant characteristicsserved as a benchmark in this respect alongwith an adhesive without flame-retardantcharacteristics as used by Trans-Textil in pro-tective fabric materials. In each case an adhesive was applied to themembrane by means of gravure roller inSTFI's hot melt multipurpose coating andlaminating machine (Fig. 2) and on a largerscale in Trans-Textil's hot melt lamination unitusing the screen printing method (Fig. 3). Ad-hesive runnability during application and theresulting application pattern were appraised.A test made of the combustion behavior ofthe membrane options with or without ad-hesive showed that combustion behaviorwas influenced by the adhesives to only avery slight extent, this primarily being de-pendent on the properties of the membraneconcerned.

Membrane and laminate development Production of the newly-developed mem-branes was transferred from the bench scaleto a pilot-scale continuous system, wherebya main requirement was to achieve flame- retardance without inclusion of halogen orantimony in the composition. A suitable lamination technique was devel-oped using STFI's hot melt multipurposecoating and laminating machine and thentaken to the lab scale on the basis of screenprinting technology in Trans-Textil’s hot meltlamination unit. The dot bonding techniquewas deployed in both processes, enabling ex-tremely precise process control and adhesive

Flame-retardant breathable moisture barriers for firefighters'protective clothing

In a cooperation project, Trans-Textil GmbH and the STFI developed lami-nates with improved flame-resistance for moisture barriers in firefighters'protective clothing. The composite materials are produced using hotmelttechnology and fulfill the relevant protective clothing standards. Integrated inprotective clothing systems, they protect from extreme heat and externalmoisture, thereby lowering the physiological load on the wearer.

Manfred HänschTrans-Textil GmbH, Freilassing/GermanxRenate BochmannSächsisches Textilforschungsinstitut e.V. (STFI),Chemnitz/Germany

To reduce heat stress and above all to fulfillprotective requirements in choices of weight-reduced textiles, the Saxon Textile ResearchInstitute (STFI) and Trans-Textil GmbH joinedforces to develop new breathable flame-retardant moisture barriers in a project withfunding from the German Central InnovationProgram for SME’s (ZIM). Production wasperformed with the help of hot melt technol-ogy. The goal of the technological develop-ment was to improve the flame-resistance ofthe laminates while fulfilling or surpassingfurther appropriate statutory requirements. As experience shows, the overall perform-ance of a laminate system is due to a combi-nation of synchronized textile components,sophisticated membrane systems incorporat-ing thermostable polyurethane or dual-com-ponent ePTFE, special reactive hot melt ad-hesives and precisely controlled processingtechnologies. In numerous test series, theproject partners developed various mem-brane options and compared them with

Generally speaking, firefighting clothing (Fig.1) and multifunctional protective clothing forindustrial workers exposed to heat containmoisture barriers in the form of breathablemembranes in the laminate system. Thesemoisture barriers provide reliable protectionagainst wind, rain, fire-extinguishing water,liquid chemicals and other dangers of emer-gency situations. Together with the textilecomponents and purposefully selected pro-cessing technology they fulfilll the require-ments of such standards as DIN EN 469 'Pro-tective clothing for firefighters – Require-ments and test methods for protective cloth-ing for firefighting' and DIN EN 343 'Protec-tive clothing – Protection against rain' stan-dards, the HuPF manufacturing and testingspecification for universal firefighters turnoutgear and station wear, the requirements ofindustrial laundry services and other specifi-cations pertinent to the multifunctional con-cept. The moisture barriers fulfill a further functionfor the wearer of the apparel in their abilityto transport moisture vapor away from thebody and pass it to the exterior. In profes-sional personal protective equipment this'breathability' means not only wear comfort,but also helps conserve physical strength andmental acuity in exacting emergency situa-tions, thus making an important contributionto the safety of the wearer. For this reason acentral concern in designing the respectivelaminate systems is to lighten the physiologi-cal load on wearers by incorporating lighterand more breathable textiles and membranesystems.

Fig. 1 Firefighters' turnout gear (Trans-Textil)

application: this optimum distribution of hotmelt adhesive compromised breathability toonly a minimal degree. The flame-resistanceof the trial variants produced in this way wasdetermined, yielding findings for further op-timization of the membranes. One particularmembrane variant that fulfilled the intendedfunctionalities to an outstanding degree wastaken as the basis for further work on trans-ferring the membrane laminating technologyto the industrial scale. Not only the membrane variants and pre-se-lected adhesive types underwent the produc-tion trials but also the lamination of nonwo-vens and woven fabrics based on flame-re-tarding fibrous materials with differing com-positions and weights per unit area; this wasfollowed by testing to determine compliancewith respective requirements. Water vaporpermeability, water impermeability and lam -inate cohesion were tested in the case oflaminate variants with good flame-resist-ance. The majority of the functional samplesmet and surpassed the respective require-ments, even after 5 washing and drying cy-cles. The laminates also displayed excellentcohesion (Fig. 4).

Test resultsSelected functional samples of the moisturebarriers (liners) were laminated together withan outer fabric and an insulating inside liningto form 4 assembly demonstrators. After 5washing and dry cycles each, STFI testedthem in terms of heat transmission on expo-sure to flame according to ISO 9151, radiantheat transfer according to ISO 6942 and water vapor permeability according to DINEN ISO 15496. In the assembly demonstrators, water vaportransmission resistance (Ret value) was deter-mined in accordance with EN 31092 by theSwiss Federal Laboratories for Materials Test-ing and Research (EMPA).

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All the functional samples fulfilled the � 13 m2Pa/W requirement of the GermanHuPF specification for firefighting clothingplus the 4 demonstrator components metthe Ret value envisaged in the specified re-quirement profile. All the combinations achieved performancelevel 2 requirements (heat transfer indexHTI24 � 18 and HTI24-HTI12 � 4). With re-gard to radiant heat transfer 3 of the 4 vari-ants met performance level 2 test require-ments ((RHTI24 � 18, RHTI24-RHTI12 � 4). The flame-retardant membranes examined inthe screening had a good protective effectdue to their flame-resistant components butin contrast to the newly-developed moisturebarriers are not suitable for use as breathablemoisture barriers due to properties such aspoor water vapor permeability. Tests conducted to determine the water im-permeability of seams after 10 washing cy-cles proved positive, plus the alternativeflame-retardant agent used in the membrane

was not shown to have a negative effect onthe water impermeability of the seams.

Summary and outlookDeployment of flame-retardant membranesand adhesives improves reliability in the ful-fillment of statutory requirements applicableto firefighting clothing and protective appar-el for workers exposed to heat, and makes itpossible to compensate for possible fluctua-tions in the flame-resistance of textile carriermaterials. The laminates (Fig. 4) and assem-bly demonstrators produced in the projectdisplayed excellent flame-resistance and verygood values concerning heat transmission onexposure to flame, radiant heat transfer, water vapor transition resistance and waterimpermeability. Developing membrane technology furtheropens up options in terms of reducing theweight per unit area of textile carrier compo-nents, and will thus help provide improvedwear comfort at a high protective effect. On the basis of the findings of the joint proj-ect, Trans-Textil will be pursuing the topicfurther to enable industrial-scale productionof new breathable membrane systems offer-ing flame-retardant characteristics, high water impermeability values, and lastingbond strength in use and care processes.

AcknowledgementsWe would like to thank the German Federal Min-istry for Economic Affairs and Energy for its fund-ing of the research project (KF2034026HG1,KF2857601HG1) as part of the Central InnovationProgram for SME’s (ZIM).

Fig. 4 Flame-retardant breathable moisture barriers forfabric systems were the subject of the joint projectundertaken by STFI and Trans-Textil with fundingfrom the German Central Innovation Program forSME’s (ZIM) (Trans-Textil)

Fig. 3 Laminating line (Trans-Textil)

Fig. 2 STFI's hot melt multipurpose coating and laminating machine