Polyurethanes & Silicones Flashcards

1
Q

Who developed Nylon 6,6?

A

Du Pont

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2
Q

What changes were made to Nylon to create Polyurethanes?

A

Added two oxygens, leading to:

Lower melting point
Toughness
Elastomeric properties
Fatigue resistance

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3
Q

What type of polymer is polyurethane?

A

Block polymer

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4
Q

What are the two segments of polyurethane?

A
  1. Hard segment – Glassy/crystalline, provides strength/toughness
  2. Soft segment – Rubbery
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5
Q

Is polyurethane homogeneous or non-homogeneous?

A

Non-homogeneous

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6
Q

What are the two main types of polyurethanes?

A
  1. Thermosets – Used in injectable/moldable biomedical devices
  2. Thermoplastic elastomers – Reformed through cooling, used in coatings
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7
Q

Why are thermoplastic elastomers useful in biomaterials?

A

They have good blood-contacting properties

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8
Q

What forms the hard segments of polyurethane?

A

Diisocyanates and chain extenders

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9
Q

What forms the soft segments of polyurethane?

A

Diols

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10
Q

What forms thermosets?

A

Polyisocyanates and polyols

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11
Q

What forms thermoplastic elastomers?

A

Diisocyanates and diols

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12
Q

Why must some diisocyanates be substituted in tissue engineering?

A

MDI and TDI can be toxic

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13
Q

What are silicones?

A

Synthetic materials with a silicon-oxygen backbone and organic side groups

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14
Q

What allows silicones to be customized for different applications?

A

Their unique chemical properties

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15
Q

Name three types of silicone materials.

A

Fluids, elastomers, adhesives

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16
Q

What is the monomer unit of silicones?

17
Q

What is the general formula for silicones?

A

(R₂SiO)x

18
Q

What are the three forms of silicone structures?

A

Linear, cyclic, or cross-linked

19
Q

How do silicones handle temperature?

A

Can withstand extreme cold and heat (e.g., steam autoclaving)

20
Q

Why are silicones chemically stable?

A

They resist water, oxidation, and UV radiation

21
Q

What makes silicones useful in drug delivery and wound healing?

A

High gas permeability

22
Q

Why are silicones biocompatible?

A

Low surface tension and chemical stability

23
Q

Why do silicones reduce hemolysis?

A

They are hydrophobic

24
Q

How does high molecular weight affect silicone toxicity?

A

Reduces toxicity

25
Q

Why do most silicones pass biocompatibility tests?

A

High purity and chemical stability

26
Q

What can affect silicone biocompatibility?

A

Impurities in the material

27
Q

What is biodurability?

A

material’s ability to resist the body’s attempts to break it down or reject it

28
Q

Why are silicones long-lasting in the body?

A

Excellent thermal and chemical durability

29
Q

What is the one part of the body where silicone breaks down?

A

The stomach (due to acids)

30
Q

What are the three main types of silicone adhesives?

A
  1. Bonding adhesives – Attach components, used in insulation and sealing
  2. Pressure-sensitive adhesives – Stick to skin and flexible surfaces
  3. Gel adhesives – Soft skin adhesives, easy to remove
31
Q

Name three medical uses of silicone.

A
  1. Hypodermic needle coatings
  2. Silicone tubing for fluid transport
  3. Medical implants (pacemakers, joint replacements)
32
Q

Where is silicone used in surgery?

A

Implanted prosthetics in plastic surgery, breast implants, etc

33
Q

Why are silicones used in electronics?

A

Insulation and protection

34
Q

What industrial use do silicones have?

A

Lubricants for machinery

35
Q

What role do silicones play in construction?

A

Waterproof coatings and adhesives

36
Q

How are silicones used in consumer products?

A

Found in shampoos, conditioners, and cosmetics

37
Q

What is a common cookware use for silicone?

A

Heat-resistant potholders