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Cummings, Laura

Publications and source records attributed to Cummings, Laura.

5 records
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DOE OSTI2023

Microporous structure in silicone polymers with polylactic acid and polyethylene glycol microspheres: Synthesis and characterization

Porosity in polymer parts could improve mechanical properties while reducing weight and density. Individual pores must be small enough that bulk mechanical properties are retained but significant enough to reduce the density of the material. Filler materials can be incorporated into polymer matrices and removed to create voids. Here, this paper focuses on creating spherical pores in silicone matrices by inserting and removing core materials or fillers during post-cure. A method was developed to incorporate pore formers into an uncured polymer resin and remove the pore former materials from the matrix. Polyethylene glycol (PEG) and polylactic acid (PLA) microspheres were created and incorporated into silicone matrices as pore formers. Microspheres with controllable size distributions were formed via an emulsion formation. Microspheres are removed from the matrix by solvent extraction and calcination. Thermogravimetric Analysis (TGA), Dynamic Mechanical Analysis (DMA), and optical imaging characterize and determine the successful creation of micropores in the polymer matrices.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Porous Polymeric Materials FY24 PDRD Final Report

Fillers and pore formers are used in many materials at Kansas City National Security Campus (KCNSC) to fine tune density and stiffness. Current off-the-shelf options such as urea and Expancel do not always provide the desired properties. This project investigated several methods for introducing porosity in rigid polymers such as epoxy and polyurethane. This work was done at partnering universities to identify a variety of methods to create porous polymeric materials. The University of Oklahoma (OU) investigated emulsion templating of epoxy, where the epoxy is mixed with a surfactant and water to form an emulsion. The emulsion is then molded and cured. During the cure process, water droplets evaporate to form porous structures. Total porosity can be tuned by changing the concentration of water added to the polymer. The University of Kansas (KU) investigated the synthesis of phenolic microballoons by spray drying, as well as methods of incorporating removable porogens into epoxy and polyurethane materials to create polymeric foams.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Synthesis and characterization of polylactic acid microspheres via emulsion-based processing

Polylactic acid (PLA) microspheres are primarily used in drug delivery applications and rarely manufactured commercially. In encapsulation, the drug encapsulation and microsphere synthesis process happen simultaneously. Simultaneous synthesis necessitates conditions that ensure the drugs to be encapsulated remain viable in the synthesis process. Here, in the present work, solid pure PLA microspheres are prepared using a repeatable centrifugal mixing method to create a single emulsion system. A planetary thinky mixer is used to achieve centrifugal mixing. PLA acts as the dispersed phase of the emulsion, whereas Polyvinyl alcohol (emulsifier) dissolved in deionized water serves as the bulk phase. The emulsions are stirred for about 4 min at 2000 rpm. Microspheres prepared by mechanical mixing are compared with microspheres prepared by centrifugal mixing. The microspheres prepared by centrifugal mixing proved to be narrower and closer to a normal distribution with a mean size (D x 50) of 30 microns. The size distribution of planetary mixed microspheres did not change from one batch to another.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗