INTRODUCTION TO PROCESSING OF BIOMATERIALS - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 248

designing of models for quantitative studies, development of novel forming
processes for providing improved properties, newer formulations for power
synthesis, and optimization at different scale-levels, including nanometer scale
and lower.
8.3.3 Polymers
8.3.3.1 Introduction. Among all available biomaterials, polymeric mate-
rials present the greatest diversity in properties and processing techniques. The
diversity in properties enables the use of polymers in a variety of applications,
including long term implantable devices in neurological, cardiovascular, ophthal-
mic and reconstructive pathologies, as well as for devices to be used in short term
applications such as hemodialysis, coronary angiogenesis, blood oxygenation,
electrosurgery, wound treatment and dental implants. For any given application,
polymers need to be processed into a form that is appropriate for that particular
application. This manipulation of the material can be physical, chemical, thermal
or mechanical, depending on the end application of the polymer.
There are several reported methods for the processing of polymers; for
example, fi bers can be processed by spinning; fi lms and sheets by extrusion and
calendering; and fabrication of specifi c shapes by molding methods. The basic
steps involved in the processing of polymers have been briefl y explained in the
following section. In addition to the processing of polymers to generate specifi c
forms, it is also important to understanding the surface characteristics (composi-
tion and structure) of a polymer as the processed polymer (biomaterial) primarily
interacts with the neighboring microenvironment through its surface. Some of the
important surface modifi cation methods have been briefl y explained later in this
section.
8.3.3.2 Processing
8.3.3.2.1 BASIC STEPS OF PROCESSING [42 - 44] . The basic steps involved in
polymer processing can be can be categorized as follows:
1. Pre - shaping — A form of polymeric material is produced by application of
heat and/or pressure that can be shaped in the further steps.
2. Shaping — The pre - shaped polymeric material can be shaped by the tech-
niques such as die forming, molding and casting, and surface treatments.
3. Post - shaping — The shaped polymeric material is further modifi ed by
processes such as welding, bonding, fastening, decorating, cutting, milling,
drilling, dying and gluing to obtain the desired fi nished product.
To improve the properties of polymers, additional materials are often added
to the polymer during its processing. These additives (i.e., plasticizers, stabilizers,
fi llers, lubricants, and foaming agents) can enhance the physical, chemical and
mechanical properties of the fi nal polymer [45].