Structure and Gas Barrier Properties of Poly(propylene-graft-maleic anhydride)/Phosphate Glass Composites Prepared by Microlayer Coextrusion

Abstract

Alternating (A-B-A) n polymer films with individual layer thicknesses in the 3-25 μm range were produced using a robust layer multiplying coextrusion process. Such a film with layers of a poly-(propylene-graft-maleic anhydride) (PPgMA) alternating with layers of PPgMA containing a phosphate glass (Pglass) upon biaxial orientation exhibited percolation of high barrier filler platelets resulting in reduction in gas permeation by two to 3 orders of magnitude. This unprecedented reduction in oxygen permeability was attributed to the high volume fraction of highly aligned Pglass platelets in the polymer matrix resembling a brick wall microstructure. Biaxially oriented films with 20 vol % Pglass content exhibited a microstructure resembling alternating organic and inorganic layers, a close replica of natural biocomposites. Structural models for permeability indicated that enhanced barrier resulted from increased tortuosity of the diffusion pathway provided by the aligned high aspect ratio platelets. Aspect ratios ranging from 40 to 175 were calculated by fitting the experimental data to diffusion models. Mechanical tests revealed that the presence of Pglass platelets increased the modulus of the multilayer composites by as much as 2Â, without any considerable loss in ductility. The improvement in mechanical properties was ascribed to the high aspect ratio of the oriented Pglass platelets. Biaxially oriented films conditioned at high relative humidity (97% RH) maintained their high oxygen barrier properties. With an optical transparency between 60 and 85%, and good flexibility, these films stood out as good candidates for a variety of packaging applications.

Forced assembly by multilayer coextrusion to create oriented graphene reinforced polymer nanocomposites

“…Fig. 4c displays some small or wrinkled graphene nanoplatelets which are still expected to be confined within the thin layers (dashed lines), similar to the results reported by Gupta et al [20] for polypropylene/10 vol. % phosphate glass particle filled polypropylene multilayer films.…”

“…Brune and Bicerano [44] solved the full tensor constitutive equations numerically and, from their graphical solution we estimate that (E/E m ) transverse ¼ 0.75 (E/E m ) axial, closer to the experimental result. Future work should explore the possibility that this imperfect planar orientation could be improved by combining the multilayer coextrusion with an external biaxial stretch [20].…”

“…In pioneering work, Baer and coworkers have used this "forced assembly" technique and have shown that immiscible polymer pairs and filled/unfilled polymers can be forced to combine into a unique multilayer structure, accompanied with interesting confined crystallization effects [19], gas barrier properties [20], and optical properties [21]. In addition, Koets et al report the toughening of immiscible amorphous polymer pairs by multilayer coextrusion [22].…”

Synthesis, molecular characterization, evaluation of polymorphic behavior and indentation response in isotactic poly(propylene-co-1-heptene) copolymers

“…Incorporation of specific fillers or other polymers can allow spreading out even more its application fields. This addition can be performed either by direct blending of the different components, filled polypropylenes [1][2][3][4][5][6] or blends [7,8], or by polymerization in the presence of fillers [9][10][11].…”

Investigation of Mechanical Properties and Morphology of Multi-Walled Carbon Nanotubes Reinforced Cellulose Acetate Fibers

“…Specific surface area is highest in the case of rod-shaped filler CNT compared to any other shape of filler particle. Hence rod-shaped filler in CA fiber will help more in load transfer when properly orientated [25][26][27]. Melt spinning and solution spinning are the standard processing methods used for high volume production of nanocomposite fiber.…”