Masters Theses

Date of Award

12-1994

Degree Type

Thesis

Degree Name

Master of Science

Major

Polymer Engineering

Major Professor

J.E. Spruiell

Committee Members

R.S. Benson, E.S. Clark

Abstract

The introduction of synthetic polymers in the 1940's has revolutionized the field of biomaterials. Currently, applications for polymeric biomaterials include surgical implants, prosthetic devices, artificial ligaments, synthetic blood vessels, and controlled drug release systems. A great deal of work has been focused on developing surgical suture implants, which will provide adequate strength while the tissues heal and will be absorbed in the body over a reasonable amount of time. Several synthetic absorbable sutures are currently on the market, but improvements over the properties observed for these materials is desired. 3M company has recently developed a The new class of bioabsorbable polymers for potential surgical suture applications, known as the "poly (ester-amide)s". It is the purpose of the present research to obtain preliminary information on these materials and conduct experimental and analytical studies on its processing into fibers.

The melting and glass transition temperatures of these materials were determined. Additionally, attempts were made to estimate the values of amorphous and crystalline densities for PEA 6,2. These values were used to estimate the crystallinity of PEA 6,2 fibers and films by measuring their densities. A PEA 6,2 copolymer was also studied in relation to the PEA 6,2 homopolymer.

Melt spinning studies were performed on PEA 6,2 and a copolymer of PEA 6,2. These melt spun fibers were drawn under several drawing conditions to study the effect of different processing variables on the structure and properties of these fibers. Previously reported information on the processing and properties of PEA 10,2 are included for comparison purposes only.

In previous studies, a large drop in molecular weight was observed during processing, which adversely affected the properties of the final fibers. Improvements in the molecular weight retention were achieved by reducing the polymer's residence time using the Maxwell extruder. Further improvements in molecular weight retention achieved by redrying the polymer prior to processing to remove any moisture absorbed. Many difficulties were encountered with the processing of these materials; many of these problems appear to result from problems in the synthesis of these polymers and in their basic properties. For example, additional cooling devices were required to expedite the solidification of PEA 6,2 and PEA 6,2 copolymer monofilaments, resulting from the materials glass transition temperature, which is close to room temperature, and its sluggish crystallization kinetics.

It was observed from x-ray studies on PEA 10,2, PEA 6,2 and the PEA 6,2 copolymer that they all form the same basic crystal structure with annealing. The crystallographic repeat distance for PEA 10,2 is higher than that observed for PEA 6,2 and the PEA 6,2 copolymer, which is attributed to the four additional methylene groups present in PEA 10,2. The crystallographic repeat distance for PEA 6,2 and the PEA 6,2 copolymer were not significantly different from each other. Furthermore, little difference between crystals formed from these two materials was observed, indicating that they are essentially the same material.

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