Mechanical Stiffness of Polycaprolactone as a Function of Fiber Porosity and Fiber Alignment

S. Tasmim, N. Bodiford, J. Coffer, T. Tayag
Texas Christian University,
United States

Keywords: polycaprolactone, Young's modulus, biomaterials, mechanical properties


Polycaprolactone (PCL) is a biodegradable polymer that can be used as a long-term implantable matrix for controlled and targeted drug delivery. When polymeric biomaterials are used in such applications, they must show the ability to perform with an appropriate host response. For instance, they must have the same mechanical properties as that of the environment in which they will be used. Therefore, knowing the mechanical properties, such as Young’s Modulus, for these materials is important. Here, we will characterize samples of PCL based on their fiber porosity and fiber alignment. The PCL samples characterized in this paper were fabricated via the electrospinning technique. These samples had either solid (non-porous) fibers or porous fibers. Solid PCL fibers had a diameter of ~4µm and porous PCL fibers had a diameter of ~4.5µm and a pore size of ~0.5µm. The solid fibers were oriented either all in one direction, or in multiple directions and the fibers in porous samples were randomly oriented. Solid aligned PCL (S-A PCL), solid randomly oriented PCL (S-R PCL), and porous randomly oriented PCL (P-R PCL) samples had sheet thicknesses of 73.75µm +/- 11.10µm ,77.50µm +/- 2.50µm, and 120µm +/- 18.3µm respectively. To measure their Young’s Modulus, the samples were first cut into a dog-bone shape using a 50W CO2 laser engraver (Epilog Laser, 800 Laser System). A tensile test was then performed on samples to collect stress and strain data. A least squares fit was applied to the most linear portion of the data (with an R2 value between 0.999 – 0.966) within the elastic region of the stress strain graph, to extract the Young’s Modulus of the sample. Our data resulted in a Young’s Modulus of 10.568 MPa +/- 0.512 MPa for the S-A PCL, 0.497 MPa +/- 0.079 MPa for the S-R PCL, and 0.312 MPa +/- 0.046 MPa for the P-R PCL. S-A PCL samples were tensile tested along the fibers; since all fibers in a S-A PCL sample are in the direction of the applied load, they are all able to contribute in supporting the load, resulting in a high stiffness. However, fibers in S-R PCL and P-R PCL are oriented in different directions, thus only a number of the fibers are in the direction of the applied load and are able to support the load. Our results are consistent with our expectations as the S-A PCL sample has the highest stiffness among the three samples. The Young’s Modulus of the S-R PCL is higher than that of P-R PCL. The next steps for this project will be to better understand the reason behind the stiffness difference between S-R PCL and P-R PCL and to see whether or not aging affects the stiffness of porous fibers.