Karteikarten
Ohne Titel
Karten in diesem Stapel (39)
- 1PlasticsChange shape on application of force. Remain this shape when force is removed.
- 2FibresPolymeric materials forcibly drawn in one direction, changing its properties and giving greater strength in drawn direction
- 3ElastomersRubber-like materials. Return to original shape when force is removed.
- 4ThermoplasticsSoften when heated, harden when cooled. Easy to process
- 5ThermosetsNetwork polymers that become permanently hard once formed. Crosslinked once in mould. Cannot be reformed.
- 6Stress strain graph of a brittle plastic, plastic, elastomer and fibre
- 7MnNumber average molecular weight
- 8MwWeight average molecular weight
- 9Average degree of polymerisationMn/m
- 10Polydispersity indexMw to Mn
- 11MorphologyCrystalline, semi crystalline and amorphous
- 12RegioisomerismHead-to-tail and head-to-head
- 13Geometrictrans tougher than cis
- 14IsotacticAll substituents on one side
- 15AtacticSubstituents alternate
- 16SyndiotacticSubstituents arranged randomly
- 17TgGlass transition temperature below this amorphous polymers behave like glassy solids above this they are plastic/rubbery. Pure crysaline polymers do not have one.
- 18Thermomechanical analyisFollows volume changes as temperature increases
- 19Differential scanning calorimetryFollows energy changes as temperature increased throughout transition. Shows a peak for Tm and a dip for Tc and an upwards slope that then levels for Tg
- 20Thermogravimetric analysisMeasures amount and rate of change in mass of a sample as a function of temperature or time in a controlled atmosphere
- 21Spherulites
- 22Factors affecting crystallisation1. Rate of cooling during solidification
2. Annealing
3. Degree of polymerisation
4. Chain configuration
5. Isomerism
6. Deformation
7. Copolymerisation - 23Factors affecting TgChain flexibility, bulky pendant groups limit rotation and polar groups
- 24Factors affecting TmMostly the same as Tg also should consider secondary forces
- 25Chain entanglementLong chains become entangled and behave as if they were even longer. Critical chain length-larger for polar molecules
- 26LDPELow density polyethylene. From free radical polymerisation reaction of ethylene monomer.
Contains long and short branches.
Easily stretched in to films-plastic bags, cling film - 27LLDPELinear low density polyethylene. Synthesised by copolymerisation of ethylene and longer chain olefin co-polymers. Branches all short. Heavy duty bags, flexible tubing.
- 28HDPEHigh density polyethylene.
Synthesised with Zieglar-Nata catalyst reaction. Very little branching. Can be moulded-toys, chemical containers - 29PolyestersStep growth reaction with carboxylic acid group and alchol group.
- 30PolycarbonatesBisphenol A and phosgene. Spectacle lenses, CD/DVD coating
- 31PolyurethanesBifunctional alcohol and isocynate. Alchol attacks carbon of isocynate followed by a proton shift. printing rollers, shoe soles; Lycra/Spandex;
- 32PolyethersSelf condensation reactions of glycols tend to form cyclic ethers. Nucleophilic aromatic substitutions where leaving group (X) is
activated by strongly electron-attracting groups in Ar’. Example PEEK and polysulfone - 33Step growth polymerisation conversion graph
- 34Carothers' equationDP= 1/(1-p)
p is fraction of functional groups reacted - 35Anionic polymerisationMonomer requires electron withdrawing substituents to form stable carbanion. Intiation by nucleophilic addition to monomer. Terminated by solvent, transfer, addition of impurity or not at all
- 36CationicRequire electron donating substituents to stabilise carbocation. Intiators are protonic acids and lewis acids. Stabilised by counter ion. Termination by dissociation (C-C+ -> C=C) or chain transfer
- 37Free radical polymerisationIntiators are peroxides and hydroperoxides and azo compounds. Terminated by combination, hydrogen abstraction and chain transfer.
- 38Living polymerIn anionic polymerisation in the absence of impurities and under the right conditions no termination step. Low polydispersity. Popular method for synthesising block polymers.
- 39Zieglar Natta catalystGives linear structure (HDPE).
Isotactic addition. TM compound and organometallic complex. Formation of active site needs a catalyst and a co-catalyst. Termination by chain transfer. Double bonds undergo cis addition. Level of regularity depends on exposure of active site.
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- Beschreibung
- Karteikarten am Ohne Titel, erstellt von al44 am 16/12/2013.
- Erstellt von
- al44
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