Answer to Question 1
A burn test will show polystyrene gives off a thick black smoke because of the benzene group. A flexural test will show PS being much more brittle than the PE and the PS will fracture long before the PE. PS will also be much more susceptible to chemicals. Some possible chemicals for the resistance test could be gasoline or acetone. PE will not be susceptible to either.
Answer to Question 2
Ionic crosslinking occurs in ionomers such as EAA and arises when an acid is a pendent group on a polymer. When the acid reacts with a base, the acid loses a hydrogen ion and becomes negatively charged. These negative charges can be attracted to metallic ions that are added to the plastic mixture that are part of the reactive base. The attractions between the metal ions and the acidic groups are ionic. When the acid groups on more than one polymer are all attracted to the same metal ion, the polymers are crosslinked with the metal ion forming a bridge. These ionic crosslinks increase the stiffness, toughness, and strength of the plastic because they increase the energy needed to cause the molecules to slide past each other and because they network the molecules together resulting in a better transfer of impact energy. Melting point and glass transition point are also increased, but the plastic is not a thermoset because heating will cause the ionic crosslinks to break.
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