Polyethylene (PE) VMSE: Repeat Unit Structures Poly(vinyl chloride) (PVC) Polytetrafluoroethylene (PTFE) Polypropylene (PP) Polystyrene (PS) Poly(methyl methacrylate) (PMMA) Phenol-formaldehyde (Bakelite) Poly(hexamethylene adipamide) (nylon 6,6) Poly(ethylene terephthalate) (PET, a polyester) The density of totally crystalline nylon 6,6 at room temperature is 1.213g/cm3. Also, at room temperature the unit cell for this material is triclinic with lattice parameters: a=0.497nmb=0.547nmc=1.729nma=48.4=76.6y=62.5 If the volume of a triclinic unit cell, Vtri, is a function of these lattice parameters as Vtri=abc1cos2cos2cos2+2coscoscos determine the number of repeat units per unit cell. Click on the link to access Table 14.3. Atomic weights for several elements are included in the following table