I had some time on my hands (this lazy Sunday morning), so I thought I'd help a brother out.
Elasticity: When creating the mold of the armor, certain types of rubber are used. They are very pliable, with high tensile strength, and are known for their ability to retain details.
Luster: Depending on your sanding, painting, and sealing techniques, your finished armor can have anywhere from a dull sheen to a mirror-like finish.
Porosity: Several steps in the armor-making process deal with material porosity. At some stages (such as fiberglassing), you rely on the porosity of the cloth to soak up the resin. At other steps (such as mold-making), you must get rid of as much porosity as possible, or else your mold might stick to the rubber.
Hardness: Depending on your type of armor and materials used, your hardness will vary. Hardness also becomes a factor when picking out suitable mold products, such as hardness of rubber (rated on a scale called "Shore A"), or hardness of plastic (rated on a scale called "Shore D").
Viscosity: The viscosity of your materials is very important to your armor, especially to determine whether you can brush the liquid on, or if you have to pour it. Thickeners can be added at certain stages, if you require higher viscosities.
Density: There are several ways to create your armor, and of course, the different methods have different end results as well as differing densities. The amount of plastic you pour into your molds will determine their density, as will the amount of layers of resin and fiberglass you apply.
Conductivity: Normally, plastics and resins aren't very good conductors, but some armor makers like to add professional details such as lights, fans, and speakers to their pieces. These not only give the finished item a more realistic look, but also require a working knowledge of electricity, resistance, and conductivity.
Solubility: When using certain products, it's very helpful to note what other products and compounds to keep away from when making your armor. Layering a type of rubber or resin over certain tapes, glues, or papers can result in the bonds dissolving. The item then ends up as a sticky mass on your table, and is hard (if not impossible) to salvage.
Flammability: It's very important to keep away from any heat source or open flames when creating your armor. Almost all of the products in their unhardened states are flammable, sometimes combustible, and often a carcinogen or respiration hazard.
Corrosiveness: As with solubility, mixing or layering incorrect products can result in disaster. Weakness, holes, collapse, and failure to cure are all telltale signs of improper use. As with many chemicals, it's best to wear protection over your eyes and hands at all times, as many of the unhardened products can be harmful if touched, swallowed, or inhaled for long periods of time.
Let me know how these work out dude, and hopefully I helped.