Poly(β-pinene) as an efficient biobased tackifier for metallocene poly(ethylene) based hotmelt adhesives

In this work, poly(β-pinene) was used for the first time as a biodegradable and renewable tackifier for hot melt adhesives (HMA) based on poly(ethylene) catalyzed by metallocenes (mPE). The HMA formulations were prepared using only poly(β-pinene) as tackifier or using mixtures of the terpene with the hydrocarbon resin C5 ((poly(β-pinene): C5: 80:20; 60:40; 50:50; 40:60; 20:80). An HMA formulation containing only C5 was also prepared for comparison purposes. The results of the thermal analysis showed that the addition of poly(β-pinene) to the formulations increased their thermal stability as well as the value of melting temperature (Tm) and crystallization temperature (Tc). Dynamic mechanical thermal analysis (DMTA) showed that the formulation containing both tackifiers in a weight ratio of 50% had a higher degree of homogeneity compared to the other formulations. Regarding the mechanical properties, the results showed that the addition of higher amounts of poly(β-pinene) resulted in stiffer materials. The values for modulus of elasticity, tensile strength, and elongation at break were similar to those obtained with poly(ethylene-co-vinyl acetate)-based HMA (EVA), the most commonly used HMA. Regarding viscosity, the results show that increasing amounts of poly(β-pinene) increase the viscosity of the formulation. When both tackifiers are used in a weight ratio of 50%, the viscosity is very similar to the formulation with the C5 resin.