Evaluating the mechanical performance of supercritical CO₂ fabricated polymide 6,6/PMMA, fiber reinforced composites

Abstract

Recent advancements in SC CO, mediated synthesis and material processing have led to polymer-polymer blends and composite materials with complex morphologies, exhibiting long-range order and orientation on multiple length-scales from the nanometer to the centimeter scale. The material under consideration in this work is a polyamide 6,6 (nylon)/poly (methyl methacrylate) (PMMA) fiber-reinforced composite that was fabricated in a unique SC CO, assisted process. The tensile and flexural properties of these unique composites are studied and the evolution of damage and energy dissipation are monitored through cyclic loading and microscopic analysis of post-stressed composite cross sections. I t is shown that this morphology leads to improved flexural modulus and increased ultimate strength with only a small decrease in tensile modulus. These composites also exhibited significant improvements in stress distribution and load transfer without the use of fiber sizing agents for fiber/matrix compatibilization. 546FYg. I . Schematic diagram of high pressure CO, fabrication facility.

Supercritical carbon dioxide as a green solvent for processing polymer melts: Processing aspects and applications

“…The few systems that have been reported so far are (polymeric matrix is reported first): polylactide-(PLA), poly(lactide-co-glycolide)-(PLGA), poly-3-caprolactone-(PCL) or poly(vinyl alcohol)-(PVOH) and calcium hydroxyapatite particles [138], PMMA-or PS-and nylon-6, PP, PET or PE fibers [139]. Other binary combinations are PMMA and clay particles [140], PP and ZnS particles [141], PE and clay particles [142], poly(trimethyleneterephthalate) (PTET) and clay particles [143], and, HDPE and Pd or Rh particles [144].…”

“…In such cases supercritical CO 2 acts not only as a plasticizer for the synthesized polymer matrix, but also as a carrier facilitating the absorption of the monomer into the fibers or the particles. In other examples [138,[141][142][143][144] the composite is prepared by blending the matrix with the other component in the presence of supercritical CO 2 . In these examples the role of supercritical CO 2 is yet to be systematically investigated.…”

“…Finally, it must be mentioned that after processing, release of CO 2 often results in foaming, leaving the composite in the form of a porous (micro) material. This is of course very important in supporting the growth of blood vessels and collagen fibers in the matrix of biodegradable polymers [138] or when the final product is intended to be used as catalyst [144].…”

Anisotropic cellular structures from semi‐crystalline polymer templates

“…Polymerization of the second phase then leads to partitioning within the substrate (since scCO 2 is a weak solvent for most polymers), leading to the formation of interpenetrating networks. 23,[32][33][34][35][36][37] Fine blending of two polymers can be achieved by this technique and is superior to conventional methods like melt mixing, where gross phase separation can occur especially between immiscible polymers. 27,38 Control over cell anisotropy can be challenging since conventional scCO 2 processing limits the available cell geometries, their orientation, and their mechanical and physical responses since it is well established that the cell structure and geometry govern the physical and mechanical properties of the foam.…”

“…In this process, semi‐crystalline or amorphous polymers are utilized as substrates, and monomer (such as styrene) and free radical initiator are allowed to diffuse into the substrate assisted by scCO 2. Polymerization of the second phase then leads to partitioning within the substrate (since scCO 2 is a weak solvent for most polymers), leading to the formation of interpenetrating networks 23,32–37 . Fine blending of two polymers can be achieved by this technique and is superior to conventional methods like melt mixing, where gross phase separation can occur especially between immiscible polymers 27,38 …”