the present invention discloses processes and apparatus for the efficient and rapid conversion of an elastomeric monomer to a polymerized elastomer , and conjointly , reaction of the resultant rubbery polymer into a monovinylaromatic polymerization reaction to form a rubber - modified polymer ; and more specifically teaches a method of polymerizing butadiene and reacting it with styrene monomer to form a transparent rubber - modified impact - resistant polystyrene material exhibiting elastomer concentrations that range from as low as 6 weight percent or lower , to as high as about 50 percent .