Polymers Flashcards
What is a polymer?
A large molecules built from small repeating units (has high molecular weight)
What is a monomer?
A repeating unit comprised of a simple molecule
What is polymerisation?
The process of converting a monomer to a polymer
What are natural polymers? Give examples.
Produced in nature by plants and animals (e.g. silk, hair, wool)
What are synthetic polymers? Give examples.
Produced in a lab (e.g. plastic, PVC)
What is HDPE?
High density polyethylene
What is LDPE?
Low density polyethylene
What bonds exist between a polymer?
Single bonds
What is addition polymerisation?
Where monomers react (add together) to form a polymer(with no byproducts)
What does thermoplastic mean?
A polymer that is flexible and can be softened and remoulded by heating
What does thermosetting mean?
A polymer that is rigid and cannot be reshaped by heating (chars instead)
What structure do thermoplastics have?
Minimal cross-linking between chains
Why can thermoplastics be remoulded?
The minimal crosslinks between chains allow them to slide past one another an form new shapes
Why can’t thermosetting plastics be remoulded?
The high degree of cross-linking between chains restricts the polymer chains from moving once heat is introduced, setting the plastic firmly into shape
What bonds exist in thermoplastics?
Strong covalent bonding in polymer chain
What bonds exist in thermosetting plastics?
Strong covalent bonds within chain and between the polymer chains
What secondary interactions exist within thermoplastics?
Can be dispersion (nonpolar) or dipole-dipole or hydrogen bonds (polar)
Are thermoplastics or thermosetting plastics easier to recycle?
Thermoplastics are easier as the weak secondary bonds between the chains allow them to be reshaped
Why are thermosetting plastics difficult to recycle?
Strong covalent bonds exist between polymer chains, cannot be reshaped
What occurs to a thermosetting plastic if the number of cross-links increases?
The material becomes harder
