28: Addition Polymers Flashcards
What is the definition of a polymer?
A polymer is a compound consisting of very large molecules formed by joining together many small molecules repeatedly.
What is polymerisation?
Polymerisation is the process in which many small monomer molecules join together in a chain to form a polymer.
List 8 advantages of synthetic polymers.
They are lightweight, resistant to chemicals, strong, good thermal and electrical insulators, waterproof, and cost-effective. They can be easily moulded into different shapes and easily coloured.
What is addition polymerisation?
Addition polymerisation is a reaction in which monomer molecules join together repeatedly to form polymer molecules; no atoms are lost from the monomer molecules during the reaction.
What is the molecular structure of polythene, and how does that influence its melting and boiling points?
Although it has a large molecular size, it still forms simple molecular structure, with only weak van der Waals’ forces acting between molecules, resulting in a relatively low melting and boiling point.
What condition is needed to start the addition polymerisation of ethene?
High temperature, and an initiator to turn one ethene molecule into a free radical and start the reaction.
What is the repeating unit?
A repeating unit is the smallest part of a polymer molecule, and the whole polymer molecule can be obtained by repeating it.
What is the structure of a monomer of polythene?
What is the structure of a repeating unit of polythene?
What is the structure of a segment of polythene?
What is the structure of polythene?
Draw the chemical equation showing the polymerisation of ethene.
What are two types of polythene?
Low density polythene (LDPE) and high density polythene (HDPE).
How is low density polythene manufactured?
Low density polythene is manufactured by heating ethene at high pressures and high temperatures with initiators, which are often peroxides.
How is high density polythene manufactured?
High density polythene is manufactured by heating ethene at relatively low pressures and low temperatures with a catalyst.
What is the difference in structure between LDPE and HDPE?
LDPE is more branched, thus it occupies a larger volume and has a lower density. HDPE is a straight chain, so it occupies a smaller volume and has a higher density.
The average chain length of LDPE is much shorter than that if HDPE.
What is the difference in melting and boiling points of LDPE and HDPE?
HDPE has a rod-like shape, thus it has a larger surface area and experiences stronger van der Waals’ forces between its molecules. Meanwhile, LDPE is more spherical, having a smaller surface area so it experiences weaker van der Waals’ forces between its molecules. Therefore, HDPE has a higher melting and boiling point since more energy is required to overcome the van der Waals’ forces between its molecules.
What is the difference in melting and boiling points of HDPE and polypropene (PP) both with 1000 repeating units?
Although the two compounds have the same number of repeating units, PP has a much larger number of electrons per molecule due to one extra carbon on each repeating unit compared to HDPE. Therefore, PP experiences much stronger van der Waals’ forces between its molecules than that of HDPE. PP has a higher melting and boiling point since more energy is required to overcome the van der Waals’ forces between its molecules.
What is the name of the monomer making up polypropene?
Propene
