250
R. Tesser et al.
8.5.5 Vegetable Oils Based Plasticisers
Vegetable oils represent a valid resource for bio-plasticizers, because they are
biodegradable, renewable and no toxic. Due to their cheap and sustainable feature,
they are taking on a remarkable role in the chemical industry as raw material. They
are obtained from plants and trees such as sunflowers, rapeseed, soybean. The principal components of the vegetable oils are triglycerides, made up of three fatty acids
joined at a glycerol structure. The composition in terms of fatty acids, according to the
number of carbons atoms in the length and of unsaturations for chain, can be variable
depending on the crops, the growth conditions and the method of purification.
The reasons why oils have the potential to be applied as plasticizers have to be
found in the length and complexity of the fatty acid chains: these can occupy the
intermolecular space between the polymers macromolecules and in this way, they
can enhance the mobility, making softer the plastic. Moreover, the presence of the
esters groups, which can interact with polymer chains through secondary forces, van
der Waals, for example, can aid to solve the compatibility problems, preventing the
migration of plasticizer. Modification reactions of triglyceride molecules are able to
further influence the compatibility of vegetable oils with the polymers.
The most important modifications of vegetable oils generally involve two main
reactive sites of fatty acids: carboxyl group and double bonds. Therefore, esterification, transesterification, epoxidation and acetylation are the primary reactions
suitable to the scope.
Castor and soybean oil esters are recognized as PVC plasticizers due to excellent
compatibility. The HallGreen plasticizer, sold by Hallstar Company, is one of the
commercially manufactured plasticizers completely based on fatty acids esters and
used in PLA resins. Danisco patented a bio-plasticizer, with a bio-component of
100%, obtained by acetylation reaction of castor oil [148]. Diels–Alder adducts,
derivatives by tung oil and alcohols, are reported as excellent PVC plasticizers.
8.5.6 Epoxidized Soybean Oil
Epoxidized soybean oil (ESBO) is one of the oldest bio-based plasticizer of PVC. It
acts as a secondary plasticizer; notwithstanding it was initially tested as the primary
one during the 1950s [132]. At that time, it was reported to have efficient plasticizing
action for PVC, however, it suffered from exudation after a long time of UV-exposure,
pointed out by too sticky surface of the plastics. This drawback was ascribed to the
presence of remaining unsaturations in the oil, hailed from the incomplete epoxidation reaction. It was demonstrated a correlation between the amount of remaining
double bonds and the ESBO permanence in PVC (lifetime) [33, 108].
Other vegetable oils have been applied to prepare epoxidized compounds. The
most important, in addition to soybean, are linseed and rapeseed oil. It is evident
that the double bonds content, expressed as Iodine Number (I.N., namely grams of
R. Tesser et al.
8.5.5 Vegetable Oils Based Plasticisers
Vegetable oils represent a valid resource for bio-plasticizers, because they are
biodegradable, renewable and no toxic. Due to their cheap and sustainable feature,
they are taking on a remarkable role in the chemical industry as raw material. They
are obtained from plants and trees such as sunflowers, rapeseed, soybean. The principal components of the vegetable oils are triglycerides, made up of three fatty acids
joined at a glycerol structure. The composition in terms of fatty acids, according to the
number of carbons atoms in the length and of unsaturations for chain, can be variable
depending on the crops, the growth conditions and the method of purification.
The reasons why oils have the potential to be applied as plasticizers have to be
found in the length and complexity of the fatty acid chains: these can occupy the
intermolecular space between the polymers macromolecules and in this way, they
can enhance the mobility, making softer the plastic. Moreover, the presence of the
esters groups, which can interact with polymer chains through secondary forces, van
der Waals, for example, can aid to solve the compatibility problems, preventing the
migration of plasticizer. Modification reactions of triglyceride molecules are able to
further influence the compatibility of vegetable oils with the polymers.
The most important modifications of vegetable oils generally involve two main
reactive sites of fatty acids: carboxyl group and double bonds. Therefore, esterification, transesterification, epoxidation and acetylation are the primary reactions
suitable to the scope.
Castor and soybean oil esters are recognized as PVC plasticizers due to excellent
compatibility. The HallGreen plasticizer, sold by Hallstar Company, is one of the
commercially manufactured plasticizers completely based on fatty acids esters and
used in PLA resins. Danisco patented a bio-plasticizer, with a bio-component of
100%, obtained by acetylation reaction of castor oil [148]. Diels–Alder adducts,
derivatives by tung oil and alcohols, are reported as excellent PVC plasticizers.
8.5.6 Epoxidized Soybean Oil
Epoxidized soybean oil (ESBO) is one of the oldest bio-based plasticizer of PVC. It
acts as a secondary plasticizer; notwithstanding it was initially tested as the primary
one during the 1950s [132]. At that time, it was reported to have efficient plasticizing
action for PVC, however, it suffered from exudation after a long time of UV-exposure,
pointed out by too sticky surface of the plastics. This drawback was ascribed to the
presence of remaining unsaturations in the oil, hailed from the incomplete epoxidation reaction. It was demonstrated a correlation between the amount of remaining
double bonds and the ESBO permanence in PVC (lifetime) [33, 108].
Other vegetable oils have been applied to prepare epoxidized compounds. The
most important, in addition to soybean, are linseed and rapeseed oil. It is evident
that the double bonds content, expressed as Iodine Number (I.N., namely grams of