Macromolecular materials

Ing.Martin Keppert, Ph.D.

Department of materials engineering and chemistryDepartment of materials engineering and chemistry

keppert@fsv.cvut.cz

Outline

natural and synthetic macromolecules

chemistry of wood and paper

raw materials for organic chemistry

asphalt, tar

production and properties of synthetic polymers on C basis

synthetic polymers on Si basis

Silicone bake mould

homopolymer copolymer

•

Macromolecular compound (polymer)matter

which

structure

is

formed

by chain

of

repeating

units

–

identical

or

similar

structure

units

(monomers)

Fundamental

terms

Fundamental

terms

biopolymersnatural compound, founded in organisms (proteins, saccharides)

natural polymer materialsmaterials produced from natural polymeric raw materials (timber, natural rubber, asphalt)

synthetic polymerssynthetic polymers produced from simple organicmolecules(plastics, rubbers)

DNA

(deoxi-ribo-nucleic

acid)

and

RNA

(ribo-nucleic

acid)Genetic

code

–

sequence

of

4 kinds

of

monomer units

H3

PO4

ribosa(sacharid)

A,G,C,TOrganic

heterocycles

BiopolymersNucleic

acids

BiopolymersProteins

condenstation

of

amino

acids

protein: contains

hundreds

amino

acidsfunction: enzymes, mechanical

motion, skin …

kolagen – fiber protein – skin, ligaments, cartilages(10% of human body)Tensile strength 50 MPaflexible, non-elastic, insoluble in water

Kolagen structure

BiopolymersProteins

–

Kolagen

Monosacharides – simple sugarsHydoxy-rich

hydrocarbons

(ketones, aldehydes) = high

content

of

energy

in C-O chemical

bond

Glucose

Inner ether

BiopolymersSacharides

-H2

O

polysacharidy polymer from

monosacharides

glucose

Polysacharide –

more than 10 monosacharides2-10 monosacharides = oligosacharide

Function in organisms: construction of plant bodies

(celulose)storage of energy (starch, sacharose)

Glycosid bond

BiopolymersPoly-sacharides

Photosynthesis

Conversion of CO2

gas from air to saccharides-Takes place in plants-Needs energy –

photosynthesis is

conversion of ligth energy of sun

to chemical energy

of saccharides

6 CO2

+6 H2

O → C6

H12

O6

+ 6 O2

Glucose - chemical energy

Energy of light

The only process for conversionof light to chemical energy →responsible also for oil and coal

Chemistry of wood

Organic matter: contains C (49 %), O (44 %), H, N, S..

Structure of wood: cellulose –

long-fiber structurehemicellulose –

short-fiber structure

lignin –

filler of cellulose structurewater, pitch…

Cellulose

Principal building material of plant cells

Polymer of monosaccharide β-D-glukopyranose

Long chains

–

fibers (to 10 000 units; i.e. to 4 mm) – bonded also transversaly by hydrogen bonds →

large, insoluble molecules

cotton

Hemi-cellulose

Poly-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(polyphenols), it fills the structure

made

by cellulose

Soluble in alkaline solutions

Thermoplastic –

enablewood flexibility

Properties of wood: inhomogenity and anisotropy –

mechanicalproperties depends on direction (tree rings) and positionE.g. tensile strength: 250 and 10 MPa (along x transversal to the fibres)

Properties of wood

Hygroscopitcity –

absorption andDesorption of water –

volume

changesA:R:T0,1 % : 2-4 % : -8 %

Tangential

Axial

Radial

Wood flexibilty

Wood is flexible at elevated temperature and humidity (by water vapor)Due to lignin –

thermoplastic behaviour

Burning of wood

Burning = oxidation of wood components by oxygen from air

over 100 C: dehydration of cellulose to water and carbon130-150 C:

decomposition of lignin –

browning of wood

180-200 C:

fast wood dehydration to water steam and CO2270-280 C:

burning exotermic oxidation by oxygen

Pyrolysis of wood

Thermal decomposition without oxygendehydration of cellulose, decomposition of lignine, partial oxidationproduct: charcoal fuel with higher caloricity (about 95 % pure carbon, the rest is water and ash)

Charcoal pile

Preservation of wood

wood is harmed by: wood-destroying fungusinsectsmoisture (fungus, volume canges)

wood protective chemicals (fungicides+insecticides): Cu-based chemicals, boron compounds (H3

BO3

),water glass (soluble sodium silicate)

natural preservatives: Chinese tung oil, bull blood

fire retardants: bromine containing organic compounds

application: spraying, painting

Impregnation of wood

way of insertion of preservatives inside to wood

vacuum+pressure process in autoclave (pressure kettle)1. evacuation of air from wood2. pumping of protective chemicals to the kettle (wood)3. increase of pressure –

better insertion of chemicals to

wood

Wood acetylation (chemical modification)

cellulose

acetic anhydride

chemical treatment of wood for higher waterproofnes (hydrofobization)

replacement of hydrophylic OH

groups in cellulose by hydrophobic acetyl groups:

-O-CO-Rlower water absorptivity = higher durability of wood

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

Phenol-formaldehyderesin (2%)

glueing = pressure + heat

wood chipping

Wood-based boards (e.g. OSB)

oriented strand board

Production of cellulose (pulp)

Pulp = technical cellulose

1.

pulp-wood

is chipped

2.

chips are cooked in alkaline solution

(NaOH+Na2

S or Ca(HSO3

)2

+SO2

) at 150 ˚C and 6 hours

3. lignin and hemi-cellulose dissolve

→ cellulose remains

4. bleaching of cellulose by H2

O2

or Cl2

Production of paper1.

Pulp is milled and mixed with water -

slury

2.

Addmixtures: Recycled paper, grinded wood, fillers (kaolin) and pigments

3.

Filtration of slury

–

dewatering, consolidation

4.

Drying

Production of paper

Papermaking machine

Production of paper

Synthetic polymers

Macromolecules based on:a) carbon basis

chains of (simple) organic molecules

Poly-propylene

b) silicon basis

PDMS poly-dimethyl-silicone

Raw materials for organic chemistry,plastics and fuel production

Fossil: crude oil –

mixture of hydrocarbons and other organiccompounds –

phenols, heterocycles…

natural gas

–

mostly methane CH4

, small amouts of other gaseous hydrocarbons, H2

S, He…

coal –

sedimentary rock formed by organic (mostlyaromatic) compounds, 80-90 % of C

Renewable: wood (or biomass in general)

Utilization of carbon-based raw materials

energy burning in power plants, transport…

Chemical industrycrude oil: liquid fuels, plastics, chemicalsnatural gas: ammonia, fertilizerscoal: in history, in future?

Crude oil distilation

distilation =separation of oil fractionsaccording theirboiling pointtemperature

Larger molecule= higher boiling point

C1

-C4

LPG

C5

-C10chemistrypetrol

C10

-C16jet fuel

C14

-C20diesel

C20

-C50oils

C20

-C70heavy oils

>C70asphalt

Chemical conversion of coal and natural gas

Conversion of natural gas (CH4) and coal to synthes gas – mixture of CO and H2

CH4

+ H2

O ↔

CO + 3 H2

coal + water ↔

CO + H2

next step: synthesis of higher (longer) hydrocarbonsfor fuels or chemicals production

Asphalt

Black, 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

Asphalt = dispersion of asphaltenes in maltenesHydrofobic: used as waterproofing

Other use: binder of aggregates in road construction(asphalt-concrete)

•

Natural asphalt –

rare, low importance•

Crude oil asphalts –

by-product of oil distillation

•

primary asphalt

–

properties depend on kind of crude oil, raw material for technical asphalts

•

oxidized asphalt

–

higher softening point, better ductility, for water proofing and coatings, for asphalt-concrete (roads)

•

modified asphalt

–

mixture of asphalts and rubbers or plastics; higher adhesion, better flexibility,

lower modification = asphalt-concretehigher modification = waterproofing

Asphalts for civil engineering

John McAdam1756-1836

Tarby-product of coal cokingliquid, black organic matter

hydrofobic: use for roofing shingles,insulation tar paper

Synthetic polymers on C basisElastomers

Plastomers

Elastic deformation Plastic deformation

Rubbers Thermoplastics

May be reversiblyformed by heating

Thermosettingplastics

After curing are notformable any more

1844 Charles GoodyearVulcanization of natural rubber

1848 nitration (HNO3

) of cotton to nitrocellulose1907 bakelit –

first synthetic polymer

1935 nylon –

synthetic fibers

History of synthetic polymers

General properties of polymers

physical and chemical properties depend on the chemicalcomposition

(type of monomers), length of chains,

1D or 3D structure

are easily formed and modified (e.g. increase adhesion) usually low pricelow heat resistance and flammability (not true for Teflon)

Higher stregth and stability(thermoseting plastics)

Structure of polymersMonomer: principal, repeating unit

Molar mass of polymer: up to 300 000 g/mol

Degree of polymerization:

= =polymer

monomer

Mn

MPolyethylenenumber

of monomers

Spatial orientation of monomers in polymer -

tacticity

atactic:softsticky

iso and syndiotactic:higher strengthsolid matters

polystyren

Structure of polymers

Synthetic polymers production scheme

Crude oilrafinery

Length and structure of polymer molecules depends on polymerization conditions: composition of rectiong mixture, temperature, catalyst (increase the polymerization rate)…

monomers Chemical plant forpolymers production

Modification and shaping of raw polymer to the final form

polymer

Formation of polymeric structurea)

polymeration

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

or HCl

c) polyaddition addition of monomer to a growing chain byproper functional group

-polymer contains the same elements as monomers,but in different possitions

PolymerationMonomers have double bond

–

converts to a new bond

between monomers

→ formation of

polymer

Styrene (vinyl benzene) Poly-styrene

Mechanism of polymerization: monomer(s) are dissolved in solution, polymerization takes place by radical, cationic oranionic mechanism

alkenes: one kind → homopolymertwo kinds → copolymer

Three phases of polymeration:initiationpropagation (polymer growth)termination

mechanism: radical, ionic

radical

Polymeration -

mechanism

Polymeration to co-polymer

Alternating co-polmer: ABABABABABPeriodic co-polmer: AAAABBBBAAAABBBBRandom co-polymer:

ABBAAABAABABAAABBBBABBA

n

1,3-butadien styren (vinylbenzene)

SBR styrene butadiene rubber

Polycondensation

Reaction of two different monomers, the new bond

is formedbetween two functional groups. By-product (water, HCl)is formed. -H2

O

PET

poly-ethylen-terephtalate

Modification of polymers

”Tuning” of materials properties

softeningcoloring – pigments (titanium white TiO2)fillers – for lower price (kaolin, sawdust, limestone, carbon black..)Thermal stabilization, antioxidants…

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, fluoropolymers

PE bottles

Forming

of thermo-plasticsForming of thermo-plastics:after preheating

or melting

Extrusion: foils, tubes

Extrusion

calender

Hot

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

PVC (vinyl) sidingFoils for water proofing and roofing

Floor

Poly-vinyl-acetate PVA

Emulsion of PVA in water or acetone: adhesive

for wood, paper..

Interior paintings

Poly-styrene PS

Expanded poly-styrene EPS: solid foam made from PS pelletsby pentane and steam

(heat to evaporate pentane)

Cups, food containers

EPS thermal insulation

EPS expanded poly-styreneC

ompa

ct P

S +

pent

ane

steam

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

methyl-ester of acrylic acid

Poly-amide PAPolycondensate of aminoacids or amines with acids

Hard, resistant to chemicalsUse: fibers, construction elements

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 (soft)

Curing = cross-linking

by heat or chemical reaction to a solid

Important thermosets: polyurethan,

phenol-formaldehyde resins,urea-formaldehyde resin, epoxy-resins

Processing of thermosets: injection molding, pressing

Poly-urethans PU(R)poly-adducts

of di-alcohols and di-iso-cyanates

PUR foams insulation, packaging, steering wheels

Polyaddition

The 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

Wide range of polyurethane foam properties

Phenol-formaldehyde resinse.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

Elastomersamorphopus macromoleculesvulcanization – crosslinked structure – significant

elastic (reversible) deformation

Rubbers

Synthetic rubbersSBR styrene-butadiene copolymerBR butadiene polymerCR chloro-prene do náročných prostředí (olej)

IR isoprene rubber - natural

Poly-isoprenePoly-chloro-prene

Tyres technology

1.

Rubber –

natural (latex) or synthetic linear polymer

2. kalandr –

rolling of soft flat rubber, admixture of filler carbon black, softener(oil), sulphur a vulcanizationcatalysts

3. Assemblage

of tyre

4. vulcanization

(curing) –

30 min, 150 ˚C

calander

vulcanization press

Vulcanization

crosslinking of polymer (to 3-D) by help of sulphur

powder and elevated tempreature

Polymers on Si basis

PDMS

poly-dimethyl-silicone

very high heat and chemical resistance, elastic deformation

Use: tubings, sealant, medical use, adhesive…

Goals

Fundamental terms of polymer chemistryBiomacromoleculesChemical composition of wood, production of pulp and paperAsphalt, tarRaw materials for organic chemistryStructure and production of synthetic polymersImportant synthetic polymers