Preparation of chemical resistance two-component epoxy-based adhesive used in epoxygraphite composite of fuel cells

In environments such as fuel cells which include chemicals (acids and bases), adhesives can degrade overtime and during a long period when exposed to harsh chemical conditions, and do not achieve the requiredfinal application. Therefore, the preparation of adhesives resistant to harsh chemical conditions is verynecessary for applications such as batteries and fuel cells. Epoxy adhesives are chemical compounds thatbond components between two surfaces. Epoxy adhesive can offer a wide range of final properties and avariety of applications. The epoxy adhesive has a high degree of adhesion due to good wettability, highadhesion strength due to polar and ether hydroxyl groups, and high chemical resistance properties.In this paper, the mechanical and chemical properties of developed epoxy adhesive with three differentcuring systems (۱۱ phr DETA, ۲۸ phr PACM, and ۲۸+۲۰ phr PACM+ Phenolic resin) were investigatedby lap-shear and acidic media (Sulfuric acid ۲۵%) chemical resistance tests, respectively.Fuel cells are a new technology for energy production that produces high-efficiency electrical energy froma direct combination of fuel and oxidizer without causing environmental or noise pollution [۱-۲]. Fuel cells consist of parts in which composite is one of them. Two-component epoxy systems have a verifiedtrack record for providing excellent mechanical properties, chemical resistance, and adhesion to a widerange of substrates [۳]. They are frequently chosen over other technologies especially when chemicalresistance is an important feature [۴]. Chemical resistance is required in a variety of applications fromconstruction and infrastructure to marine and protective metal coatings In this research, epoxy-graphitecomposite (EGC) is an essential part that the goal is to increase the sealing property of fuel cells made ofepoxy-graphene composite. Exposure to solvents and harsh liquids over time can damage adhesives andbinders, weakening the bond between two points or surfaces, including fuel cells [۵]. Therefore, themechanical and chemical properties of utilized dual-component epoxy-based adhesive in acidic solutionduring a time (three weeks) was investigated.Epoxy resin based on diglycidyl ether of bisphenol A, (KER ۸۲۸), with epoxy group content of ۵,۳۰۰mmol/kg and molar mass of ۱۸۵ g/mole, and curing system of Diethylenetriamine (DETA), ۴,۴-Diaminodicyclohexylmethane (PACM) and Phenolic resin (PR) hardeners, were supplied by KUMHOP&B Chemicals Inc., Nouryon, and Evonik, respectively. To study the mechanical properties of theprepared adhesive, the adhesion strength was measured using a lap-shear-joint test and single-lap-joint testwas performed according to ASTM D۱۰۰۲. In order to measure the chemical resistance of the desiredadhesive, the samples were immersed in ۲۵% sulfuric acid at room temperature for ۷۰ hrs. According toASTM D۴۷۱, Equation (۱) shows the rate of change in sample weight in which M۱ is the initial sampleweight and M۲ is the sample weight after immersion (....)The stress-strain diagram from the lap-shear test is shown in Figure ۱. The results of this test are also listed inTable ۱. The results revealed that the adhesive containing PACM curing agent has a higher shear strength thanthe sample containing DETA and the highest mechanical strength is obtained when ۲۸ phr of PACM and ۲۰phr of phenolic resin are used simultaneously Also, the results of the immersion of samples in sulfuric acid are listed in Table ۲. The outcomes revealed the chemical resistance of the samples is in accordance with the mechanical test