Page 50 - Fall2020

Technology as Servant

PLASTICS:

A FLEXIBLE MATERIAL FOR AN INCREASINGLY INFLEXIBLE WORLD
By James Kirkpatrick

“There is a great future in plastics,” Mr. WHY PLASTICS?
McGuire warmly explains to Dustin Hoffman’s What is it about plastics that have made
Ben character in the often-quoted scene from the them so ubiquitous in our society and so
iconic 1969 movie, The Graduate. Who could sought after as a material of construction? The
have foreseen the accuracy of Mr. McGuire’s main benefit that plastics bring to the table is
prediction from a half-century ago? Fast forward a straightforward engineering one: plastics
to the present. We’ve become a society utterly sit in a “Goldilocks Zone” in terms of their
wrapped in plastic, or more accurately, we’ve strength-to-weight ratio. “Stronger than wood,
become a society wholly dependent on synthetic lighter than metal,” would be the easiest way
materials, mostly derived from hydrocarbons to explain this sweet spot in non-engineering
(oil and natural gas), of which plastic is the terms. Furthermore, unlike wood, steel and
most prevalent. other metals, plastic is easily tailored to specific
In 1970, total worldwide petrochemicals end-use requirements, which explains the amaz-
demand (consumption) measured approximately ing variety of end-use applications. Think of
To put fifty million metric tonnes (MMT); today this the intricate parts involved in a child’s (or adult
consumption has grown steadily to almost eight
child’s) flying drone toy. Making this device out
this in hundred MMT, a sixteen-fold increase in fifty of wood requires hundreds of hours of a skilled
perspective, years or a compound annual growth rate of just carpenter’s time; made out of metal, this device
would be too heavy to fly on battery power
among the under 6 percent. Although all synthetic materi- alone. The light weight, strength and infinite
als are included in this current demand figure
primary of eight hundred MMT, plastics constitute the moldability of plastics solve both of these design
building bulk of synthetic material consumption. The challenges simultaneously.
The following list of desirable engineering
remainder includes synthetic fibers (such as ny-
materials, lon, polyester and related derivatives), solvents, properties explains the usefulness of plastics
plastic adhesives and direct-use petrochemicals. and their widespread usage in modern society:
The majority of the five hundred twenty-five
demand is MMT of annual plastic demand comes in one • Strength-to-weight ratio bridges the gap
now about of five compounds: low density polyethylene between wood and metals;
one-eighth (LDPE), linear low-density polyethylene (LL- • Excellent electrical properties (non-conduct-
ing);
DPE), high density polyethylene (HDPE), poly-
of global propylene (PP) and polyvinyl chlorine (PVC). • Superior chemical resistance, especially to
concrete To put this in perspective, among the pri- strong acids and bases;
demand, mary building materials, plastic demand is now • Easily tailored cosmetic properties, coloring
about one-eighth of global concrete demand,
and moldability;
one-third of one-third of global steel and about half of global • Resistant to weathering and UV degrada-
global steel and wood demand. Given the staggering growth in tion;

about half of plastics production over the past fifty years, • Highly suitable for mass production;
several fundamental questions naturally arise: • Generally non-toxic, inert to human contact
global why do we use so much plastic, what did plas- and consumption, although this is still a
wood tic replace in our daily lives before the 1960s matter of some scientific debate.

and what makes plastics so challenging from a
demand. disposal and recycling perspective? These advantages are offset by several
48 Wise Traditions FALL 2020