Characterization of Novel Magnesium-Doped Citrate Polymer Composites for Injection Molding
Open Access
- Author:
- Venable, Matthew
- Area of Honors:
- Engineering Science
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Jian Yang, Thesis Supervisor
Melik C Demirel, Thesis Honors Advisor - Keywords:
- citric acid
biomaterials
rheology
mechanics
engineering
biomedical engineering
orthopedics
injection molding
implants - Abstract:
- Current commercial options for orthopedic biomaterials come with a plethora of shortcomings that render them unideal for clinical use. While their mechanical strength may be similar to that of bone, other properties limit their applicability and benefit to patients. The purpose of this study was to design a novel citrate-based orthopedic composite consisting of poly(octamethylene citrate) (POC) as a foundational polymer, hydroxyapatite (HA) as a bone-like mineral phase, and magnesium oxide (MgO) as a bioactive setting agent. A qualitative setting comparison was included, illustrating that MgO can set all tested POC-based polymers, suggesting niche applications beyond orthopedics with the addition of unique constituent monomers. Mechanical properties of the composites, namely viscosity, compressive strength, setting time, and injection force, were analyzed to determine fitness for orthopedic use. Viscosity and setting time were tunable with MgO, HA, and hexamethylene diisocyanate (HDI) concentrations. Moreover, in the presence of a realistic, slow-injection shear rate, POC and POC- HA exhibited intense shear-thinning on the order of 11% for the former and 96% for the latter. Compressive strength, Young’s modulus, and peak strain were characterized, demonstrating MgO’s significant improvements in POC-HA composite strength. Lastly, injection force measurements reflected the composites’ shear thinning behavior as all break-loose and glide forces were less than 20 N at 0.5 mL/s several minutes into the setting process. A novel application of MgO-setting citrate polymers for injection molding biomaterials was explored given the mechanics of the POC composites, showing that POC-MgO/HA shows promise in this field and is worthy of further study.