Immiscible polymers, adhesion

Char, K., Brown, H.R. and Deline, V.R., Effects of a diblock copolymer on adhesion between immiscible polymers, 2. PS-PMMA copolymer between PPO and PMMA. Macromolecules, 26(16), 4164-4171 (1993). 

Janarthanan et al. [67] have employed roughness on a micron scale to enhance the adhesion between two immiscible polymers, polycarbonate and styrene-acrylonitrile copolymer, SAN. Grooves of depths between 5 and 35 p,m were scribed in the polycarbonate surface before laminating the two polymers. The... 

Additionally, some properties unique to both systems may result. The majority of homopolymer blends are immiscible with one another and often experience poor interfacial adhesion between the separate phases. Since block copolymers are covalently linked together, macroscopic incompatibility at the interface is minimized. The macroscopic incompatibility of a two-polymer blend may be eliminated by the addition of a block copolymer derived from the two systems. Hence, copolymers can be used to strengthen blends of immiscible polymers by serving as emulsifiers (7-9). 

Figures 20.13 and 20.14 describe the effect of dibutyltin dilaurate (DBTDL) on the tensile strength and tensile modulus for the 25/75 LCP/PEN blend fibers at draw ratios of 10 and 20 [13]. As expected, the addition of DBTDL slightly enhances the mechanical properties of the blends up to ca. 500 ppm of DBTDL. The optimum quantity of DBTDL seems to be about 500 ppm at a draw ratio of 20. However, the mechanical properties deteriorate when the concentration of catalyst exceeds this optimum level. From the previous relationships between the rheological properties and the mechanical properties, it can be discerned that the interfacial adhesion and the compatibility between the two phases, PEN and LCP, were enhanced. Hence, DBTDL can be used as a catalyst to achieve reactive compatibility in this blend system. This suggests the possibility of improving the interfacial adhesion between the immiscible polymer blends containing the LCP by reactive extrusion processing with a very short residence time.

Creton, C, Kramer, E. /., Brown, H. R. and Hui, C.-Y Adhesion and Fracture of Interfaces Between Immiscible Polymers From the Molecular to the Continuum Scale. Vol. 156, pp.53-135. 

Capability of the individual component substances in either an immiscible polymer blend or a polymer composite to exhibit interfacial adhesion. 

Figure 10.7 shows that the tensile strength is improved as polystyrene is incorporated. Data for conventional melt-blended samples (Fayt et al., 1989) are provided for comparison. We note that the ductile-to-brittle transition for our system is shifted toward much higher polystyrene content. Fayt and others have shown that conventionally prepared polyethylene/ polystyrene blends are relatively poor materials (Barentsen and Heikens, 1973 Wycisk et al., 1990). Blends of most compositions are weaker than polystyrene or polyethylene homopolymers because of the poor interfacial adhesion between the two immiscible polymers. The electron micrographs and the mechanical data for the blends described here indicate that poly-... 

Brown HR, Krappe U, Stadler R (1996) Effect of ABC triblock copolymers with an elastomeric midblock on the adhesion between immiscible polymers. Macromolecules 29 6582-6588... 

Chain functionalized polymers or graft copolymers are of great technological importance. They are used as compatibilizing agents for immiscible polymer blends (8) and adhesive layers between polymer-polymer co-extruded surfaces (8). Currently, of all polymers sold, about 30% are in the form of compatibilized immiscible blends (9-12). Next we discuss a few examples of chain functionalization. 

Adhesion and Fracture of Interfaces Between Immiscible Polymers from the Molecular to the Continuum Scale... 

Since we will focus below primarily on adhesion at interfaces between two immiscible polymers, it is appropriate to describe briefly what is known about such interfaces. The Gibbs free energy of mixing (per segment) of any two homopolymers A and B is given approximately by the Flory-Huggins expression ... 

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