Complex sentence: Flubber is a non-Newtonian fluid, easily made from polyvinyl alcohol--based glues and borax, that flows under low stresses but breaks under higher stresses and pressures.
Split into simpler sentences: Flubber is a non-Newtonian fluid, easily made from polyvinyl alcohol--based glues and borax. It flows under low stresses but breaks under higher stresses and pressures.