Polyurethanes & Silicones Flashcards
(37 cards)
Who developed Nylon 6,6?
Du Pont
What changes were made to Nylon to create Polyurethanes?
Added two oxygens, leading to:
Lower melting point
Toughness
Elastomeric properties
Fatigue resistance
What type of polymer is polyurethane?
Block polymer
What are the two segments of polyurethane?
- Hard segment – Glassy/crystalline, provides strength/toughness
- Soft segment – Rubbery
Is polyurethane homogeneous or non-homogeneous?
Non-homogeneous
What are the two main types of polyurethanes?
- Thermosets – Used in injectable/moldable biomedical devices
- Thermoplastic elastomers – Reformed through cooling, used in coatings
Why are thermoplastic elastomers useful in biomaterials?
They have good blood-contacting properties
What forms the hard segments of polyurethane?
Diisocyanates and chain extenders
What forms the soft segments of polyurethane?
Diols
What forms thermosets?
Polyisocyanates and polyols
What forms thermoplastic elastomers?
Diisocyanates and diols
Why must some diisocyanates be substituted in tissue engineering?
MDI and TDI can be toxic
What are silicones?
Synthetic materials with a silicon-oxygen backbone and organic side groups
What allows silicones to be customized for different applications?
Their unique chemical properties
Name three types of silicone materials.
Fluids, elastomers, adhesives
What is the monomer unit of silicones?
Siloxane
What is the general formula for silicones?
(R₂SiO)x
What are the three forms of silicone structures?
Linear, cyclic, or cross-linked
How do silicones handle temperature?
Can withstand extreme cold and heat (e.g., steam autoclaving)
Why are silicones chemically stable?
They resist water, oxidation, and UV radiation
What makes silicones useful in drug delivery and wound healing?
High gas permeability
Why are silicones biocompatible?
Low surface tension and chemical stability
Why do silicones reduce hemolysis?
They are hydrophobic
How does high molecular weight affect silicone toxicity?
Reduces toxicity
