PLASTIC PRODUCTS - Plastics and Environmental Sustainability - page 156

Figure 4.13 Dependence of the modulus of PVC on plasticizer content.
DODP and DIDP are types of phthalates TPU is a thermoplastic PU.
Source: Reproduced with permission from Pita et al. (2002).
Most plasticizers including phthalates are not covalently linked (bonded or
grafted) to PVC molecules and are free to leach out of the plastic product. 16
With plasticized packaging films in direct contact with food, leaching of
plasticizer is a concern.
4.6 BIOPOLYMER OR BIO-DERIVED PLASTICS
A biopolymer or bioplastic 17 is a polymer produced by a living organism.
Cellulose is the most common biopolymer constituting about a third of
all plant biomass. All living things produce other biopolymers such as
polynucleotides and proteins. An example of a class of useful biopolymers
are the so-called bacterial polyesters that are harvested from bacteria grown
under specific conditions.