martin keppert department of materials engineering and...
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Macromolecular compoundsMartin KeppertMartin Keppert
Department of materials engineering and chemistryDepartment of materials engineering and chemistryOffice A 329, office hours Monday 14Office A 329, office hours Monday 14--1616
[email protected]@fsv.cvut.cz
web: web: tpm.cvut.cztpm.cvut.cz
Outlinenatural and synthetic macromolecules
raw materials for organic chemistry
chemistry of wood and paper
asphalt, tar
production and properties of synthetic polymers on C basis
synthetic polymers on Si basis
Bio-MacromoleculesMacromolecule = „large molecule“
usually with a repeating structure motive
Bio-macromolecules:
proteins chains of amino acidsAlaninThe simplest amino acid
polysacharides chains of saccharidesGlucose
nucleic acids DNA and RNA
Synthetic polymers
Macromolecules based on:
a) carbon basischains of (simple) organic molecules
Poly-propylene
b) silicon basis
PDMS poly-dimethyl-silicone
Raw materials for organic chemistry
Fossil: crude oil – mixture of hydrocarbons and other organiccompounds – phenols, heterocycles…
natural gas – mostly methane CH4, small amouts of other gaseous hydrocarbons, H2S, He…
coal – sedimentary rock formed by organic (aromatic)compounds, 80-90 % of C
Renewable: wood (or biomass in general)
PhotosynthesisConversion of CO2 gas from air to saccharides-Takes place in plants-Needs energy – photosynthesis isconversion of ligth energy of sunto chemical energyof saccharides
6 CO2+6 H2O → C6H12O6 + 6 O2
Energy of light
Glucose
The only process for conversionof light to chemical energy →responsible also for oil and coal
Chemistry of woodOrganic matter: contains C (49 %), O (44 %), H, N, S..
Structure of wood: cellulose - structurehemicellulose - structurelignin – filler of celulose structure
Properties of wood: inhomogenity and anisotropy – mechanicalproperties depends on direction (tree rings) and position
E.g. tensile strength: 250 and 10 MPa (along x transversalto the fibres)
CellulosePrincipal building material of plant cellsPolymer of monosaccharide β-D-glukopyranoseLong chains (to 10 000 units; i.e. to 4 mm) – bonded also
transversaly by hydrogen bonds → large, insoluble molecules
Polymer chain
Transversal hydrogen bonds
Hemi-cellulosePoly-saccharide formed by various mono-saccharides
Similar to cellulose, but:
Smaller molecules than cellulose (to 250 units)
Lower strength and higher solubility than cellulose
LigninVarious large organic compounds, it fills the structure madeby cellulose
Soluble in alkaline solutions
Use of wood in buildingsDirect – wooden constructions, roof constructions…
Wood-based boards – glued pieces (small, large…) of wood
plywood
OSB oriented strand board
chip-board
Production of cellulose (pulp)
Pulp = technical cellulose
1. pulp-wood is chipped
2. chips are cooked in alkaline solution (NaOH+Na2S orCa(HSO3)2+SO2) at 150 ˚C and 6 hours
3. lignin and hemi-cellulose dissolve → cellulose remains
4. bleaching of cellulose by H2O2 or Cl2
Production of paper
1. pulp is grinded in water solution to suspension of cellulosefibres
2. addind of recycled paper, binder, filler, pigment….
3. processing on paper machine: from cellulose suspensionto dry paper
AsphaltBlack, sticky, viscous liquid or semi-solidRest after destilation of crude oil
Dispersion of two phases: maltenes liquid organic compounds (oil)M=500-1000 g/mol
asphaltanes solid, insoluble blackspecies, M=5000–10000 g/mol
Use: binder of aggregates in road construction
Tarby-product of coal cokingliquid, black organic matter
hydrofobic: use for roofing shingles,insulation tar paper
Synthetic polymers on C basis
Elastomers PlastomersElastic deformation Plastic deformation
Thermosettingplastics
Rubbers Thermoplastics
May be reversiblyformed by heating
After curing are notformable any more
General properties of polymersphysical and chemical properties depend on the chemical
composition (type of monomers), length of chains,1D or 3D structure
are easily formed and modified (e.g. increase adhesion)
usually low price
low heat resistance and flammability (not true for Teflon)
PVC membrane
Structure of polymers 1
Monomer: principal, repeating unit
Molar mass of polymer: up to 300 000 g/mol
Degree of polymerization:
polymer
monomer
Mn
M=
Polyethylene
Structure of polymers 2
a) linear polymer
b) branch polymer
c) cross-linked polymer – 3D structure (rubber)
Formation of polymeric structure
a) polymerization joining of alkenes (double bond) to chain-no by-product-polymer has the same chemical composition as monomers
b) polycondensation joining of monomers by condensationby-product: water
c) polyaddition addition of monomer to a growing chain by-proper functional group-polymer contains the same elements as monomers,but in different possitions
Polymerization
Monomers have double bond – converts to a new bondbetween monomers → formation of polymer
Poly-styreneStyrene (vinyl benzene)
Mechanism of polymerization: monomer(s) are dissolvedin solution, polymerization takes place by radical, cationic oranionic mechanism
Homopolymers and co-polymersHomopolymer: onyl one kind of monomer (poly-styrene)Co-polymer: two kinds of monomers
Alternating co-polmer: ABABABABABPeriodic co-polmer: AAAABBBBAAAABBBBRandom co-polymer: ABBAAABAABABAAABBBBABBA
PolycondensationReaction of two different monomers, the new bond is formedbetween two functional groups. By-product (water, HCl) is formed.
-H2O
PolyadditionThe chain is formed by addition reaction of (at least) twocompounds with functional groups suitable for addition.
Most important polyaddition: di-alcohol + di-iso-cyanate = poly-urethan
Urethan bond
Important thermo-plasticsThermo-plastics: produced as pellets or powder, which may
be melted and formed and modified to the final product
Properties: + resistant to atmosphere and corrosion, light- thermally unstable
Technically important thermoplastics: poly-ethylene,poly-propylnene, poly-vinylchloride, poly-butene,poly-vinylacetate, poly-styrene, poly-carbonate, poly-amide, poly-urethane, fluoropolymers
PE bottles
Forming and modificationof thermo-plastics
Modification of properties: plasticizer, softening, thermaland light stabilization, pigment, filler….
Forming of thermo-plastics: extrusion, mould pressing,rolling, injection molding
Extrusion
Poly-ethylene PE
Several types of PE:
LDPE low density PEbags, bottles
HDPE high density PE fuel tanks, foils, water piping, corrosion protection
HDXLPE high density cross-linked PEhigh strength – large tanks
Poly-propylene PP
Use: ropes, car plastic parts, tubing
Poly-vinyl-chloride PVC
Vinyl flooring PVC siding
Poly-vinyl-acetate PVA
Emulsion of PVA in water or acetone: adhesive for wood, paper..
Interior paintings
Poly-styrene PS
Cups, food containers
Expanded poly-styrene EPS: solid foam made from PS pelletsby pentane and steam (heat to evaporate pentane)
EPS thermal insulation
Poly-carbonate PC
Condenstation ofbisphenol-a andphosgene
Very stable, hard, resistant
Use: DVD, bullet-resistant glass, sun-glasses, construction
Poly-methyl-methacrylate PMMA
Acrylic glass and acrylic fibers, cheaper than poly-carbonate
Acrylic paints suspension of PMMA in water
Poly-amide PAPolycondensate of aminoacids or amines with acids
Hard, resistant to chemicalsUse: fibers, construction elements
Poly-urethans PURpoly-adducts of di-alcohols and di-iso-cyanates
PUR foams insulation, packaging, steering wheels
Fluoro-polymers
Teflon poly-tetra-fluoro-ethylene PTFE
High thermal (250 ˚C) and chemical resistance
Use: chemical equipment, frying pans, Gore-Tex
Teflon bearings
Important thermo-setting plastics
Polymers, which are cured irrversibly to a solid form(not possible to melt and form again)
Before curing: thermoset is liquid or shapeable
Curing = cross-linking by heat or chemical reaction to a solid
Important thermosets: phenol-formaldehyde resins,urea-formaldehyde resin, epoxy-resins
Processing of thermosets: injection molding, pressing
Phenol-formaldehyde resins
e.g. Bakelit Dr. Leo Baekeland 1909 first industrial plastic
+
use: as electric insulators,snooker balls, paintings, adhesives
Urea-formaldehyde resinUrea-melamin resin
Condensates of formaldehyde and an amino-compound
+Urea
Melamin
H
H
Adhesives for wood fibre boards
plywood
Epoxy resin
+
Epi-chlor-hydrin Bis-phenol A
Curing: after mixing with „hardener“
Use: adhesives, paintings, electronics
Poly-addition
Elastomers - rubbersElastic deformation
Synthetic rubber
polymers and co-polymers
SBR styrene-butadiene rubber
CR chloro-prene rubber
Vulcanization: cross-linkingby sulphur and heat– brings the elasticity1/3 of rubber production
is from „Latex tree“
Isoprene rubber IR
Natural rubber, also made synthetically
Polymerization
Styrene-butadiene rubber SBR
Co-polymer of butadiene and styrene – most commonsynthetic rubber
Polymers on Si basis
PDMS poly-dimethyl-silicone
very high heat and chemical resistance, elastic deformation
Use: tubings, sealant, medical use, adhesive…
Paintings formulation
a) binder – a polymer substance – makes the volume of paint
b) pigment – color
c) solvent – to improve the application
d) filler – for higher volume and lower price