CHEM0012 Assessment Part 1 of 3 2022-23
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CHEM0012 Assessment Part 1 of 3
2022-23
Polymers
This coursework is due at Noon on 23rd November. Submission is via Moodle.
You are asked to submit answers to questions on polypropylene, as described below.
Instructions
You must submit a typed answer: handwritten answers are not permitted. The maximum length of your submission is strictly two A4 pages including all figures. Your report must be in single column format, single spaced (or greater if you wish), with a minimum font size of 11 point (Calibri is recommended) for the main text and minimum margins of 0.5 cm on each side. Text can wrap around Figures. As a guide, this page is ~580 words.
A third page is permitted for a list of abbreviations used and bibliography ONLY. These must be complete citations and formatted consistently using any recognized style.
Over-length reports will be penalised by 10% and any work beyond two pages will not be read. Late submissions will be subject to UCL regulations.
You may use figures from the lecture notes or open literature with correct attribution. However, original figures are encouraged (and rewarded), so that they illustrate your work and answer accurately. Chemical schemes should be your own, preferably using a chemical drawing package, although scanned hand-drawn images may be used. Anything pasted (such as an equation) should be attributed – you are encouraged to write you own, increasing your ability in using Word etc which will serve you well next year. Layout and readability will account for 20% of the mark. For example, this document has no grammar / spelling errors indicated by Word, nor by me reading it, the text is spaced out (including between paragraphs), the headings are consistent in style, abbreviations defined, symbols and chemistry corrected formatted etc. – not a “100%” but close.
Any quoted values of properties (e.g. Tg) must be fully attributed and you should consider whether they are from reliable sources before using them.
No concepts, published literature or any websites, beyond the lecture notes, discussions in face-to- face sessions and the course textbook Polymers by Walton and Lorimer (on Bibliu) are required to complete this work, but if further sources are consulted and their content used, these must be cited in your bibliography. An answer based on your knowledge – not material you find – is likely to read far better and answer the actual question!
An indicative length for each part of the question is provide as an approximate guide. But the report will be marked as a whole and you can draw on material from the remainder of your answer to illustrate another part as appropriate.
A strong reminder: All material will be passed through Turnitin. You are directed to past material in CHEM0006, the student handbook, Chemistry Student Hub on what constitutes plagiarism.
A single file must be submitted and be in one of the following file formats: pdf, Microsoft Word .doc or .docx, or ODF.
Polypropylene
Polypropylene is one of the most widely used polymers used in a wide range of applications.
1. Polypropylene is synthesised via a chain-growth (free radical) mechanism from propene. The monomers add in a head-to-tail configuration (refer to Polymers by Walton and Lorimer page 7-8). Using polypropylene as an example, explain, drawing chemical structures, what is meant by polymer tacticity. If synthesised with a molecular catalyst, atactic polypropylene is formed, whilst when a catalyst that is bonded to a solid surface is used, isotactic polypropylene is formed. Provide an explanation. Note there is no need to do any further research beyond Polymers by Walton and Lorimer, just think about it – additional information from sources will not give additional marks.
[2 x 3 marks, 1/3 page]
2. Isotactic polypropylene is considered semi-crystalline. Consider a hypothetical series of polypropylene samples: four isotactic polypropylenes that have been determined to have crystallinities of 10, 50 and 80 % (relative to amorphous regions by mass), labelled iPP-10, iPP-50 and iPP-80, and a further sample that is atactic and purely amorphous and labelled a- PP. Sketch a DSC trace (on the same axes) for each carefully noting any key differences. Explain these differences.
[10 marks, 2/3 page]
3. A co-polymer can be formed from the monomers ethene and propene. Consider a hypothetical series of the co-polymers made from a monomer mixture in the molar ratio 10:90, 50:50 and 80:20 ethene to propene, together with samples of polythene and polypropene. State and explain the general trend in Tg, Tm and the crystallinity of these samples. Illustrate your answer with sketches of the chemical structure and / or the DSC curves as you find appropriate to explain your reasoning.
[10 marks, ½ page]
4. Explain how you could make a polypropylene-based material biodegradable through co-polymerisation. Give specific examples, explaining your rationale.
[10 marks, ½ page]
2022-11-22