mention two properties of synthetic polymers / plastics which make them acceptable to the users?

Some of the synthetic polymers are plastic, synthetic fibre like nylon 6,6 , synthetic rubbers like Buna-S. These are the examples of man-made polymers. Synthetic polymers which includes nylon is used in textiles and fabrics, teflon used in non-stick coatings in utensils, bakelite used in electrical switches , polyvinychloride used in pipes, dacron used in safety helmets , melamine resin used in the manufacture of unbreakable crockery. 
These polymers are cheaper and their manufacturing is cost-effective. These polymers have highly desirable properties like strength, flexibility, resistivity, chemical inertness etc.