14.1 Introduction

Schematic & Perspective Representation of Polyethylene Molecule

14.2 Hydrocarbon Molecules

14.2 Hydrocarbon Molecules …Cont’d

14.2 Hydrocarbon Molecules …Cont’d

14.2 Hydrocarbon Molecules …Cont’d

In Table 14.1 the nomenclature is as follows:

Isomerism

Other common organic groups are presented in Table 14.2.

In Table 14.2, R and R′ represent organic radicals – groups of

atoms that remain as a single unit and maintain their identify during

chemical reactions.

Examples of singly bonded hydrocarbon radicals include the CH3

(methyl), C2H5 (ethyl), and C6H5 (phenyl) groups.

Table 14.3

Effect of molecular weight on polymer characteristics

• Melting or softening temperature is raised with increasing molecular weight.

• At room temperature polymers

– with short chains having molecular weights on the order of 100g/mol exist as liquids or gasses.

– with molecular weights of approximately 1000g/mol exist as waxy solids or soft resins.

– with molecular weights of 10,000 g/mol to several million g/mol exist as solid polymers. These polymers sometimes are called high polymers.