▁paste . ▁Their ▁addition ▁highly ▁impro ves ▁concrete ▁and ▁mort ar ▁properties . ▁ ▁Fil led ▁polym er ▁r he ology ▁ ▁The ▁incorpor ation ▁of ▁various ▁types ▁of ▁fill ers ▁into ▁polym ers ▁is ▁a ▁common ▁means ▁of ▁reducing ▁cost ▁and ▁to ▁im part ▁certain ▁des irable ▁mechanical , ▁thermal , ▁elect rical ▁and ▁magnetic ▁properties ▁to ▁the ▁resulting ▁material . ▁The ▁advantages ▁that ▁filled ▁polym er ▁systems ▁have ▁to ▁offer ▁come ▁with ▁an ▁increased ▁complexity ▁in ▁the ▁r he ological ▁behavior . ▁ ▁Usually ▁when ▁the ▁use ▁of ▁fill ers ▁is ▁considered , ▁a ▁comprom ise ▁has ▁to ▁be ▁made ▁between ▁the ▁improved ▁mechanical ▁properties ▁in ▁the ▁solid ▁state ▁on ▁one ▁side ▁and ▁the ▁increased ▁difficulty ▁in ▁m elt ▁processing , ▁the ▁problem ▁of ▁ach ieving ▁uniform ▁disp ersion ▁of ▁the ▁fill er ▁in ▁the ▁polym er ▁matrix ▁and ▁the ▁econom ics ▁of ▁the ▁process ▁due ▁to ▁the ▁added ▁step ▁of ▁comp ounding ▁on ▁the ▁other . ▁ ▁The ▁r he ological ▁properties ▁of ▁filled ▁polym ers ▁are ▁determined ▁not ▁only ▁by ▁the ▁type ▁and ▁amount ▁of ▁fill er , ▁but ▁also ▁by ▁the ▁shape , ▁size ▁and ▁ ▁size ▁distribution ▁of ▁its ▁particles . ▁The ▁vis cos ity ▁of ▁filled ▁systems ▁generally ▁increases ▁with ▁increasing ▁fill er ▁fraction . ▁This ▁can ▁be ▁partially ▁am el ior ated ▁via ▁broad ▁particle ▁size ▁distributions ▁via ▁the ▁F arr is ▁effect . ▁An ▁additional ▁factor ▁is ▁the ▁stress ▁transfer ▁at ▁the ▁fill er - pol ym er ▁interface . ▁ ▁The ▁inter fa