Environmental Engineering Reference
In-Depth Information
It is also possible to produce biobased polyester thermoplastics [48, 49];
Petrovic
et al.
produced a high-molecular-weight linear polyester utilizing a self-
transesterification reaction of 9-hydroxynonanoic acid, a hydroxyl acid produced
from castor oil [49]. The polymer produced from 9-hydroxynonanoic acid
(PHNME) is analogous to polycaprolactone (PCL), but has a longer hydrocarbon
chain between the ester groups [49]. PCL is a conventional polyester with wide
use in the biomedical industry. The longer carbon chain in PHNME results in a
higher melting point and better thermal stability than PCL [49]. Polyesters
formed with ricinoleic acid (from castor oil) and lactic acid also show promise for
biomedical applications [45]. It was shown that by manipulating the composition
of ricinoleic acid, the polymers produced could be tuned from solid to liquid at
room temperature [50, 51].
As with polyurethanes, polyesters from vegetable oils are well suited for
ecologically friendly, water-based coatings. These systems typically use alkyd
resins with high acid numbers, neutralized with amines [52]. The alkyd resins can
be used in water-based coatings and paints [53, 54].
5.2.6
Polyamides
Polyamides based on vegetable oils are used in the ink and paint industry [55, 56].
Polyamides are thixotropic, which improves film appearance and allows for easy
application of coatings [4]. Vegetable-oil-based polyamides can be produced by
condensation reaction of fatty-acid-based dimer acids and diamines [56]. An
important polyamide from a vegetable oil is Polyamide 11 (PA 11), derived from
castor oil [57, 58]. PA 11 exhibits good dimensional stability, electrical properties,
a wide range of flexibility, low cold brittleness temperature, and good chemical
resistance [7].
5.2.7
Vegetable Oil Conclusion
Although this was by no means a comprehensive review of the topic of polymers
based on vegetable oils, the reader may have gained an appreciation of their
potential; vegetable oils have the ability to replace fossil-based feedstocks in a
large capacity using familiar chemistries and technologies. Virgin vegetable oils
can be cross-linked with vinyl monomers to produce thermosets comparable
to fossil-based materials in a number of ways [19-22]. Modified vegetable oils
obtain reactivities similar to traditional monomers and are capable of producing
materials suitable for structural applications [2, 30]. Polyurethanes produced from
vegetable oils have shown promise for foam and coating applications as well as a
route to renewable thermoplastics [35, 38-42]. Polyesters from vegetable oils
have applications in coatings and biomedical products [4, 45]. Polyamides from
vegetable oils can be used for the synthesis of PA 11, and have been shown to have
properties suitable for paints [55, 56, 58].
