SOCIETAL BENEFITS OF PLASTICS - Plastics and Environmental Sustainability - page 181

increasingly substitute for metal components in automobiles with plastic or
composite replacements.
The percentage of plastics in American automobiles has consistently
increased over the years. But today's automobile is still over 60% iron/
steel in construction, with plastics contributing only 9.3% to the weight
but to about 50% of its volume (American Chemical Council, 2012). The
most used plastics in passenger cars are PP (37%), PU (17%), and HDPE
(11%) accounting for more than half of all plastics used in a vehicle. 3 The
surface of the vehicles is protected by polymer-based coatings: usually a
base electrocoat, a primer surface, and a top clear coat. It is the transparent
clear coat that protects the vehicle surface from scratches (marring) and
retain the gloss and color ( Figure 5.1 ) .
As seen in Table 5.1 , the mechanical properties of polymer composites
compare very well with those of other materials, and further substitution
for at least some of the metal in an automobile is feasible. Functionally
equivalent plastic components that can replace metal counterparts weigh
50-75% less. Typically, a 10% reduction in vehicle weight is estimated to
reduce its fuel consumption by about 5-8%. Therefore, this weight
advantagetranslatesintoverysignificantimprovedfuelefficiency,fossilfuel
conservation,andavoidedcarbonemissions,giventhesizeoftheworldfleet
of vehicles.