Preparation of novel, liquid, solvent-free, polyolefin-based adhesives

An innovative procedure for functionalization of polyolefins was developed. It was found that synthesized polyolefins end-capped with trimethoxysilane (silylated polyolefins) are new polyolefin-based adhesives. To prepare the mentioned materials,1-octene as a higher alpha-olefin was cooligomerized with two linear, nonconjugated dienes (ie, 1,5-hexadiene and 1,7-octadiene) by using metallocene catalyst system, Cp2HfCl2/MAO, at room temperature. Then, amine-terminated trimethoxysilane (3-aminopropyltrimethoxysilane) was reacted with unsaturated bonds of synthesized cooligomers in the presence of palladium(II) acetate. Embedding of the dienes on 1-octene oligomeric chains was explored by Fourier transform infrared (FTIR), H-1, and C-13-NMR spectroscopy. On the basis of the results, 1,5-hexadiene showed both 1-butene branch and five-member ring. On the other hand, 1,7-octadiene was incorporated by 1,2-addition, forming both 1-hexene branch and seven-member ring in the cooligomer backbone. Mole percentage of C(sic)C and cyclic moieties reached to a value of 28.54, 18.59% mol in 1-octene/1,5-hexadiene, and 38.04, 6.71% mol in 1-octene/1,7-octadiene cooligomers, respectively. Reaction of synthesized cooligomers with 3-aminopropyltrimethoxysilane was confirmed by FTIR spectroscopy, which yielded targeted adhesives. To study the adhesion properties, resulting adhesives were applied to different substrates. Obtained results demonstrated that tensile shear strength of synthesized adhesives to polar substrates was 2.21% to 2.84% more than nonpolar substrates. Among studied systems, the best performance was achieved by1-octene/1,7-octadiene-based adhesive and Al substrate with tensile shear strength of 1.45 N/mm(2).