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

keppert@fsv.cvut.czkeppert@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