Synthesis and characterization of polyesteramide based hot melt adhesive obtained with dimer acid, castor oil and ethylenediamine

Polyesteramide based hot melt adhesives were synthesized from high purity dimer acid (composition: ~1% trimer acid, ~98% dimer acid and ~1% linoleic acid), ethylenediamine and castor oil. The effect of castor oil content on the properties of the hot melts, such as thermal properties: glass transition temperature (Tg), melting temperature (Tm), enthalpy of melting (Hm), crystallization temperature (Tc), enthalpy of crystallization (Hc) and softening point (Ts); mechanical properties: tensile strength, elongation at break and Shore D hardness; adhesion properties: lap shear strength (LSS) and T-Peel strength (TPS); and rheological properties were investigated. Ethylenediamine was replaced by 5%, 10% and 15% (molar basis) of castor oil. It was found that Tg, Tm, Hm, Tc, Hc, Ts, LSS, TPS, tensile strength, Shore D hardness and viscosity, all decreased with increased concentration of castor oil. This is due to the decrease in the crystallinity of the polyesteramide caused by conversion of amide linkages by ester linkages and increased distance between two ester linkages (due to the bulky nature of castor oil).