▁due ▁to ▁bal ancing ▁of ▁the ▁F erm i ▁layers , ▁and ▁therefore ▁cause ▁ad hes ion . ▁This ▁theory ▁only ▁works ▁given ▁the ▁assumption ▁that ▁the ▁substr ate ▁and ▁ad hes ive ▁have ▁different ▁electro static ▁surface ▁characteristics . ▁▁ ▁F ract ure ▁theory : ▁F ract ure ▁theory ▁is ▁the ▁major ▁mechanism ▁by ▁which ▁to ▁determine ▁the ▁mechanical ▁strength ▁of ▁a ▁particular ▁mu co ad hes ive , ▁and ▁describes ▁the ▁force ▁necessary ▁to ▁separate ▁the ▁two ▁materials ▁after ▁mu co ad hes ion ▁has ▁occurred . ▁Ult imate ▁tens ile ▁strength ▁is ▁determined ▁by ▁the ▁separ ating ▁force ▁and ▁the ▁total ▁surface ▁area ▁of ▁the ▁ad hes ion , ▁and ▁failure ▁generally ▁occurs ▁in ▁one ▁of ▁the ▁surfaces ▁rather ▁than ▁at ▁the ▁interface . ▁Since ▁the ▁f ract ure ▁theory ▁only ▁de als ▁with ▁the ▁separation ▁force , ▁the ▁diffusion ▁and ▁pen etr ation ▁of ▁polym ers ▁is ▁not ▁account ed ▁for ▁in ▁this ▁mechanism . ▁ ▁St ages ▁of ▁mu co ad hes ive ▁process ▁ ▁The ▁mu co ad hes ive ▁process ▁will ▁differ ▁greatly ▁depending ▁on ▁the ▁surface ▁and ▁properties ▁of ▁the ▁ad hes ive . ▁However , ▁two ▁general ▁steps ▁of ▁the ▁process ▁have ▁been ▁identified : ▁the ▁contact ▁stage ▁and ▁the ▁cons olid ation ▁stage . ▁ ▁Contact ▁stage ▁ ▁The ▁contact ▁stage ▁is ▁the ▁initial ▁wet ting ▁that ▁occurs ▁between ▁the ▁ad hes ive ▁and ▁memb rane . ▁This ▁can ▁occur ▁mechan ically ▁by ▁bringing ▁together ▁the ▁two ▁surfaces , ▁or ▁through ▁the ▁bod