AN INTRODUCTION TO PLASTICS - Plastics and Environmental Sustainability - page 114

process has to be therefore carefully controlled. 11 PVC has been under
intense attack by environmental groups for decades. The risk 12 of volatile
emissions as well as the invariable need to handle and transport large
quantities of chlorine to manufacturing plants has contributed to the
negative image of PVC. Vinyl chloride monomer is carcinogenic and its
release into air is a potential hazard. If the temperature is not carefully
controlled, the side reactions that yield by-products such as dioxins can
occur. The emission load of polychlorinated dibenzo- p -dioxins and
polychlorinated dibenzofurans fromthemanufacturing facilities totheopen
environment in the United States was estimated at 12 g International
Toxicity Equivalents (Carroll et al., 2001) per year. Also, the chlorine
production for PVC manufacture is a particularly energy-intensive
operation. 13 There are 17 PVC production facilities in the United States, and
these are regulated by the USEPA as to the maximum allowable emissions.
Table 3.6 summarizes the properties of PVC in comparison to those of PS
and PET.

Table 3.6 A Comparison of Properties For Polyolefins

Property Rigid

PVC

Soft
PVC *

PS PET

Specific gravity 1.4 1.22 1.04 0.959-0.965

Crystallinity (%) ~10-30 ~6

Tensile strength (psi) ×
1000

6-7 1.5-3.5 5-7 5-6

Tensile modulus (psi) ×
1000

165-225 25-40 150-160

Extensibility (%) ~15 200-450 2-3 11-1300

Water absorption (% in 24
h)

0.06 - 0.08 0.10

* Plasticized PVC or flexible PVC.