An Investigation into the Characteristics of Polyurethane Foam for Medical Applications Produced Using Additive Manufacturing Technology

Oppon, Charles (2016) An Investigation into the Characteristics of Polyurethane Foam for Medical Applications Produced Using Additive Manufacturing Technology. Doctoral thesis, Northumbria University.

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Abstract

Polyurethane (PU) foam has unique characteristics making it suitable for many applications such as: aeronautics, automotive, building construction, marine, and many house-hold applications. PU’s biodegradability, biocompatibility, lightweight, and durability make it suitable for several medical applications. The porous structure of PU foams enables them to be used for lightweight components and for medical applications where the permeability allows nutrients to reach cell growth areas. The foam components are currently mainly manufactured by material removal i.e. subtractive machining or a casting/moulding processes.

Additive Manufacturing (AM) processes (3D printing), build components in 2D layers and have been utilised to manufacture a range of products for many applications including: jewelry, footwear, industrial design, architecture, engineering and construction, etc. The additive processes have the ability to generate internal hollow structures or scaffolds.

The nature of parts produced by AM technologies makes it fit for lightweight products such as aerospace parts, medical scaffolds, etc., in metals and polymers, however the technology has not been used to produce objects using PU as its material, due to the foaming nature of the material when its two base materials (polyol and Diisocyanate) encounter with each other.

This research has undertaken a critical review of PU foaming processes, medical applications, and characteristics of AM technology processes. The effect of resins mixing ratios, temperature, and foaming direction on the physical and mechanical properties of PU foam have been investigated and used as a base to establish a platform for further development.

The research has evaluated the suitability of Additive manufactured PU foam structures for further application such as medical scaffolds by comparing the foams produced using traditional method and have developed an AM production method (In-flight mixing system) for the material (PU). Based on the evaluations, a new technique has been pro-posed and tested which is able to generate PU 3D structures.

Foam produced by the designed system has average pore size of 689μm which will allow the following: the flow of fluid such as blood, diffusion of waste products out of the scaffold, and cell infiltration and can therefore be suggested for the production of medi-cal scaffolds.

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