Medical Fibres & Biotextiles Flashcards
Potential polymer problems?
Leaching of additives (dyes, stabilisers, antioxidants)
surface reactions
adsorption
texture and form
Polyethylene
Bioinert
Hydrophobic
LDPE - low crystallinity
HDPE - high crystallinity - both mouldable
UHMWPE - particles toxic! - bone necrosis and osteolytic lesions
melt spun into..
woven or nonwoven fabrics
ligament prostheses, and load-bearing composites
PTFE (Teflon)
Bioinert
Cannot mould
Low yield stress
melt spinning
Vascular prostheses coatings, heart valve sewing rings, orthopedic ligaments
Polyamides (Nylon)
Partially crystalline
hydrophillic - properties change with added water
monofilament, braids
sutures
PET (Darcon)
Hydrophilic protein adsorption
Good for blood contact
Doesn’t degrade due to aromatic ester
Multifilament yarn for weaving, knitting, and braiding
Sutures, hernia repair meshes, and vascular grafts
Melt Spinning
Heat above Tm and extrude through spineret
holes = filaments
Wet Spinning
polymer dissolves in solution
extruded through spineret
washed, drawn, dried
Electrospinning
Solution or melt exposed to high V
Applications: filtration membranes, wound dressing, TE scaffolds
Polymer fibre selection criteria
Duration mechanical properties fabrication limitations sterilisation CREEP
Polymer fibre selection options
absorbable polymer fibres
modified natural polymer fibres
hybrid bicomponent polymer fibres (sheath/core, integrate drugs)
Wovens
Stronger
Lower porosity
Low permeability
Vascular grafts, preclotting
Knits
Higher permeability/porosity Easier to suture Dilate post implantation (dis?) Softer more flexible hernia repair, patches
Braids
Great flexibility
unstable in longitudinal loading
sutures
Processing and finishing
remove cytotoxic additives coat yarns with sizing agents prior to weaving cleaning bleaching shrinking
