In a cross linked polymer, the monomeric units are linked together to constitute a three dimensional network. Which of the following is a cross-linked polymer ?

A. Nucleic acids e.g. RNA and DNA
B. Polysaccharides
C. Polyisoprene
D. Polyurethane

A. Polymethyl methacrylate (PMMA)
B. Polytetrafluroethylene (PTFE)
C. Polycarbonates
D. Phenolic resins

A. Decreases its tensile strength
B. Increases its ozone & oxygen reactivity
C. Increases its oil & solvent resistance
D. Converts its plasticity into elasticity

A. Thiokol
B. Plexiglass or Lucite
C. Dacron
D. Teflon

A. Are made by addition polymerisation reaction only
B. Contain an epoxy group (fig bellow) at the ends of the polymer
C. Are cross-linked polymers only
D. Use emulsion polymerisation methods

A. Polymer termination step
B. Condensation of siloxane to silicone
C. Initial hydrolysis of silicone monomer
D. None of these