**3.2 Classification of plasticizers**

Several substances, including water, can be used to plasticize the polymer. It is reported that, phthalate, sebacate and citrate esters are among the most commonly used plasticizers (Felton, 2007). Compatibility, general structure (being a monomeric or polymeric), functions and chemical structure are taken into account in classifying the plasticizer substances (Gooch, 2010).

Most used group of the plasticizer substances is the phthalic acid esters which have firstly put into use in 1920. Dioctyl-phthalate is the most commonly used phthalic acid ester and it constitutes 50% of the world's plasticizer consumption (Höfer & Hinrichs, 2010).

Aliphatic ester plasticizers are derived from esterification of adipic, sebacic and azelaic acids with linear or branched monofunctional alcohols of short or medium length of chain (e.g. dioctyladipate and dibutylsebacate). Adipate, azelate and sebacate plasticizers are distinguished from other groups by their low viscosity. They give flexibility to the polymers they are used together at low temperatures (Harper, 2006; Höfer & Hinrichs, 2010; Rahman & Brazel, 2004).

Phosphate esters and various glycol derivatives such as propylene glycol and polyethylene glycol are also employed to plastify the polymeric films (Felton, 2007; Harper, 2006; Meier et al., 2004; Rahman & Brazel, 2004).

It has been reported that, surfactants, preservatives and other compounds also function as plasticizer agent together with cellulosic and acrylic polymers (Felton, 2007).

#### **3.3 Properties of plasticizers**

A plasticizer is firstly expected to be compatible with the polymer substance. This means that, it can fully mix with the polymer and can remain permanently in the polymer.

macromolecular segments increase as a result of loosening of tightness of intermolecular

The plasticizers with lower molecular weight have more molecules per unit weight compared to the plasticizers with higher molecular weight. These molecules can more easily penetrate between the polymer chains of the film forming agent and can interact with the

By adding plasticizer to a polymeric material, elongation at break, toughness and flexibility are expected to increase, on the other hand tensile stress, hardness, electrostatic chargeability, Youngs modulus and glass transition temperature are expected to decrease

Plasticizers with low molecular weight, act by reducing the secondary bonds (e.g. hydrogen bond) of the polymer chains and themselves forming secondary bonds (Gal & Nussinovitch, 2009). While low molecular weight improves miscibility with the polymer, the second factor increasing the compatibility is the realization of strong mutual hydrogen bonding (Harper, 2006). Thus, weakening of interaction of the polymer chains decrease tensile strength and glass transition temperature and so the flexibility of polymer films increases (Felton, 2007;

Several substances, including water, can be used to plasticize the polymer. It is reported that, phthalate, sebacate and citrate esters are among the most commonly used plasticizers (Felton, 2007). Compatibility, general structure (being a monomeric or polymeric), functions and chemical structure are taken into account in classifying the plasticizer substances

Most used group of the plasticizer substances is the phthalic acid esters which have firstly put into use in 1920. Dioctyl-phthalate is the most commonly used phthalic acid ester and it

Aliphatic ester plasticizers are derived from esterification of adipic, sebacic and azelaic acids with linear or branched monofunctional alcohols of short or medium length of chain (e.g. dioctyladipate and dibutylsebacate). Adipate, azelate and sebacate plasticizers are distinguished from other groups by their low viscosity. They give flexibility to the polymers they are used together at low temperatures (Harper, 2006; Höfer & Hinrichs, 2010; Rahman

Phosphate esters and various glycol derivatives such as propylene glycol and polyethylene glycol are also employed to plastify the polymeric films (Felton, 2007; Harper, 2006; Meier et

It has been reported that, surfactants, preservatives and other compounds also function as

A plasticizer is firstly expected to be compatible with the polymer substance. This means that, it can fully mix with the polymer and can remain permanently in the polymer.

plasticizer agent together with cellulosic and acrylic polymers (Felton, 2007).

constitutes 50% of the world's plasticizer consumption (Höfer & Hinrichs, 2010).

forces (Bergo & Sobral, 2007; Höfer & Hinrichs, 2010).

Rahman & Brazel, 2004).

(Gooch, 2010).

& Brazel, 2004).

al., 2004; Rahman & Brazel, 2004).

**3.3 Properties of plasticizers** 

**3.2 Classification of plasticizers** 

specific functional groups of the polymer (Gal & Nussinovitch, 2009).

(Gal & Nussinovitch, 2009; Harper, 2006; Rahman & Brazel, 2004).

Tendency to migration, exudation, evaporation or volatilization of the plasticizers employed in a polymeric system must be low (Felton, 2007; Harper, 2006).

Other properties expected from an ideal plasticizer are its workability, its ability to provide desired thermal-electrical and mechanical characteristics to the end product, its durability at high and low temperature values, its being effective over a wide temperature range and not being affected by ultraviolet radiation, its cost being low and its conformance to the health and safety arrangements (Rahman & Brazel, 2004).
