Adhesion to Untreated Polyethylene and Polypropylene by Needle-like Polyolefin Crystals

Abstract

Polyolefins, such as polyethylene and polypropylene, are globally the most widely used plastics and are considered to be essential materials. Because they lack polar groups, polyolefins are poorly adhesive, which poses serious recycling challenges. Here, we describe a novel adhesion system involving a polyurethane adhesive and an untreated polyolefin, in which the interface is tightly bound by needle-like polyolefin crystals in the same way that nails adhere to wood. The polyurethane and polyolefin inter-diffuse at high temperatures to form a mixed interfacial layer, after which the polyolefin recrystallizes in the layer upon cooling. Polyurethanes with optimally balanced non-polar and polar blocks exhibit superior adhesion due to their larger miscibility windows, polyolefin compatibilities, and the resulting long needle-like polyolefin crystals.

Advances in Nonreactive Polymer Compatibilizers for Commodity Polyolefin Blends

“…For PE/PP compatibilization, diblock, linear multiblock, graft multiblock, and random copolymers have all been synthesized and studied in blends (Figure A–D). Noncovalent reinforcement through hydrogen bonding − or ionic interactions , has also been used for compatibilizing various polymer interfaces (Figure E). Such approaches combine the concepts of preformed compatibilizer design and reactive compatibilization.…”

“…This is attributed to the low molar mass and amorphous chains produced from multisite Ziegler–Natta catalysts, which entropically migrate to the interface and prevent cocrystallization across the interfaces. Overcoming this challenge and inducing crystallinity at the interface can be achieved through semicrystalline block copolymers, ,− polyester or polyurethane crystalline phases, , ionic domains, and through stereocomplexesin specific compositions …”

Effect of Corona Treatment on the Adhesion between a Two-Component Polyurethane Adhesive and Polypropylene

“…Polyurethane (PU) adhesive is a highly favored adhesive in various applications which require strong adhesion. − Its robust bulk strength, solvent resistance, and strong adhesion to many different substrates make it an ideal choice for many applications. ,− There are two main types of PU adhesives. The first is the one-part PU adhesive, which contains prepolymers in its formulation, and cures through condensation reactions with moisture in air. − The second type is the two-component PU adhesive: part A, an isocyanate blend, and part B, a resin blend of polyols with different hydroxyl functionalities. − For the two-component PU adhesives, the curing time predominantly depends on the formulation components rather than the environmental factors.…”

Organosilicon Compounds in Hot-Melt Adhesive Technologies

“…The force of adhesion between elastic bodies depends on the geometry and energy of the contacting surfaces [ 1 ]. There are several interactions that contribute to the formation of an adhesive bond, including van der Waals attractive forces [ 1 , 2 , 3 , 4 ], mechanical interlocking [ 2 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ], interdiffusion of polymer chains across the interface [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ], chemical bonds at, or across the interface, and electrostatic interactions [ 11 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. Currently, there is no comprehensive and quantitative theory that can establish a clear connection between the physical and chemical attributes of materials, and effectively explain their adhesion as well as the practical strength of an adhesive bond established with the said materials.…”