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Polymer Process Engineering
Introduction
12/24/2014 1Chapter 1. Primer/introduction
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WHAT IS A POLYMER?
Berzelius (1883)Poly (many) + mer (unit)
Polystyrene polymerized in 1938; polyethylene glycol made in 1860sEarly polymer products were based on cellulose- gun cotton = nitrated
cellulose
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A polymer is
Long chain molecule, often based on organicchemical building blocks (monomers)
Long molecules (Mw ~100,000 Da) have solid-
like properties The chain may be amorphous (no regular
structure), crystalline (a regular repeating
structure), crosslinked, Dendrimers and oligomers have different
properties
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HOW DO YOU BUILD A MOLECULE?
Chemical structure
Chain morphologyconstitution, configuration, conformationDegree of polymerization = number of repeating units
Building block sourceshydrocarbons, renewable materials
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Building blocks
5% of petroleum goes
into polymers
Sustainable use is
possible Energy recovery is
possible if solid
polymers are
combusted
Type C H O
gas NG 3 1 0
liquid Crude 6 1 0
solid Coal 14 1 0
Renew-able
cellulose 6 1 5.3
Hemi-
cellulose
6 1 8
lignin 6.8 1 3
protein
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Building methods
Chain (addition)
Examplepolyethylene (PE)
from ethylene
Small number of reactingchains at any one time,
which can grow into long
molecules prior to
termination Long reaction times needed
to achieve high conversions
Step (condensation)
Examplepoly(ethylene
terephthalate) (PET) from
terephthalic acid andethylene glycol
Endgroups react to build the
chain; long reaction times
needed to achieve highpolymer
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Multiple building blocks
Copolymers, terpolymers,
Using multiple building blocks leads to
polymers with intermediate properties or
unique properties compared to the
homopolymers
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Several copolymer configurations
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Chain configurations
Linearrepeating units are aligned
sequentially
Branchedlarge segments branch off the
main chain/carbon backbone
Crosslinked/networkchemical crosslinks
between chains add mechanical strength
EXAMPLES?
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Multiphase systems
Composites
Structural
Random
Other
Nanocomposites
Blends
Dispersed lamellae, cylinders, spheres
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HOW DO WE CLASSIFY POLYMERS?
Structurechemical, configuration
solid performance (mechanical + thermal properties)
other
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Mechanical + Thermal
Thermoplasticsolidified by cooling andreheated by melting
Thermosetsretain their structure when
reheated after polymerization (usuallycrosslinked)
Elastomersrubbers, deform readily with
applied force Thermoplastic elastomers
other
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WHAT IS IN A COMMERCIALPRODUCT?
Very few commercial products are pureMWDmolecular weight distribution
additives
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Polymers vs. metals
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Why do we use
polymers?
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Polymeric materials
Compete well on a strength/weight basis
Easy to form into 3D shapes
Creep under load is usually poor; this behavioris usually corrected by adding fillers or fibers
Low corrosion in the environment compared
to metals
Generally good solvent resistance
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Thermoplastics
Commodities: 75% of the polymer volumeused is with 4 polymer families, polyethylene,polystyrene, polypropylene and poly(vinyl
chloride) [low cost] Intermediate: higher heat deflection
temperatures
Engineering plastics: can be used in boilingwater
Advanced thermoplastics: extreme properties
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Thermosets
High moduli, high flex strengths, high heat
deflection temperatures
Shape is retained during thermal cycling
Often made with step/condensation
polymerization systems
Crosslinking is usually used
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HOW DO WE MAKE A PART?
Polymerization
Formulation
Fabrication
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Formulation
Additives are used to modify properties
and/or lower costs
Additives: heat stabilizer, light stabilizer,
lubricant, colorant, flame retardant, foaming
agent, plasticizer
Reinforcement: particulate minerals, glass
spheres, activated carbon, fibers
Blends, alloys, laminates
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Additives can change:
Processing properties
Performance properties
Composites: polymers with fiber fillers Packaging: multiple layers often used
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Formulation operations
Thermoplastics: melting or solvent processing
Thermosets: additive addition to monomers
or to prepregs
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Fabrication
Varies by industry sector
Adhesive
Coating
Elastomer
Plastic
fiber
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Overview of the polymer industry
Industry General product requirements
adhesive Strong surface forces; epoxy, superglue
coatings Film-forming; LDPE with good impact
composites Structural materials; epoxy + fibers
elastomers Large deformation and recovery; rubber in tire and seals
fibers High strength/area; polyacrylonitrile
foams Light weight, low thermal conductivity; polyurethane
plastics Stable deformation under static load; HDPE, PP, PVC
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Commodity plastics
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Polymer Major uses
LDPE Packaging film, wire and cable insulation, toys, flexible bottles,
housewares, coatings
HDPE Bottles, drums, pipe, conduit, sheet, film, wire and cable
insulation
PP Automobile and appliance parts, rope, cordage, webbing,
carpeting, film
PVC Construction, rigid pipe, flooring, wire and cable insulation,
film, sheet
PS Foam and film packaging, foam insulation, appliances,
housewares, toys
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Film blowing
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High strength films are achieved by
orienting the crystallites. The film is
biaxially oriented; the wind-up rolls
stretch the film in the machine direction
and the expansion of the film radially
provides a hoop stress force.
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Wire coating
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Wire coating speeds can be high, and process start-up is challenging. Metal wires may need sizing,
or wetting agents in the polymer melt for good adhesion.
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Calendaring
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Thin and thick section calendaring is used to make wide sheets (8-12 ft).
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Bottle blowing
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The parison is inflated,
developing biaxially
orientation similar to that of
blown film. The sides of the
mold provide cooling, quickly
freezing in the orientation
developed during the
blowing process. When this
process is used to make soda
bottles of PET, the
orientation is critical to
achieving low carbon dioxide
permeation rates (and longbottle shelf life).
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Compression molding
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Thermoset applications
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Polymer Major uses
Phenol-
formaldehyde resins
(PF)
Electrical equipment, automobile parts, utensil handles,
plywood adhesives, particleboard binder
Urea-formaldehyde
resins (UF)
Similar to the above; textile coatings and sizings
Unsaturated
polyester (UP)
Construction, vehicle parts, boat hulls, marine accessories,
corrosion-resistant ducts, pipes and tanks, business equipment
Epoxy (EP) Protective coatings, adhesives, electrical parts, industrial
flooring, highway paving materials, composites
Melamine-
formaldehyde resins
(MF)
Similar to UF resins; decorative panels, counter and table tops,
dinnerware
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Elastomers
The polymers used for elastomers usually have
very low heat deflection and melt temperatures
Solids with good mechanical properties are made
by crosslinking polymer chains together
The molecular weight of elastomer parts is the
size of the object
Vulcanization of rubber uses sulfur to providecrosslinks between the C=C bonds of natural
rubber.
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Fibers
Fibers are based on highly crystalline polymers
that can be oriented axially to have great
strength. Orientation (cold drawing) develops
crystal structure in the solid.
Most natural fibers from biomass are based
on cellulose; spider silk has different
compositions and is based on a set ofcopolymers
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Elastomer polymers
Polymer family description
Styrene-butadiene Copolymers with a range of constitutions; SBRstyrene-
butadiene rubber
Polybutadiene Cis-1,4-polymer
Ethylene-propylene EPDethylene-propylene-diene monomer; the small amountsof diene provide unsaturation
Polychloroprene Poly(2-chloro-1,3-butadiene); this polar elastomer has excellent
resistance to non-polar organic solvents (gasoline, diesel)
Polyisoprene Poly(cis-1,4-isoprene); synthetic natural rubber
Nitrile rubber Copolymer of acrylonitrile and butadieneButyl rubber Copolymer of isobutylene and isoprene
Silicon rubber Rubber based on polysiloxanes
Urethane rubber Elastomer with polyethers linked via urethane groups
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Synthetic fibers
Fiber type description
Cellulosic
acetate rayon Cellulose acetate
viscose rayon regenerated cellulose
Non-cellulosic
Polyester Mostly poly(ethylene terephthalate)
Nylon Nylon 6,6; nylon 6, nylon 10; other aliphatic, aromatic
polyamides
Olefin Polypropylene; copolymers of vinyl chloride + acrylonitrile, vinyl
acetate, vinylidene chloride
Acrylic > 80% acrylonitrile; modacrylic = acrylonitrile + vinyl chloride or
vinylidene chloride
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Coatings
Coatings. Major area for expansion; solar cells,
windows, Supplier base is highly
fragmented.
Paints. Major area for expansion; vehicles,
Materials supplier base is clustered; painting
systems base is clustered; user base is
fragmented
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Adhesives
Highly fragmented market.
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Foams
Major area: insulation
for housing, sound
control,
Materials:
polystyrene,
polyurethanes,
Reaction injectionmolding example
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Composites
Thermosets and thermoplastics
Sheet molding compounds
Filament winding
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HOW DO WE NAME POLYMERS?
Polymer nomenclature is widely varied.
Trademarks and common names may be industry-sector specific.
Nomenclature: Polymer Handbook. Chapter 1.
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Source-based names
Source-based name when the polymer is derivedfrom a single (original or hypothetical) monomer;or random co-/ter-polymers Poly(vinyl alcohola)
Poly(styrene-co-butadiene) Polyformaldehyde (not polyoxymethylene)b
Poly(ethylene oxide) (not poly(ethylene glycol)b
a
when the name is long, parentheses are used toseparate the name from poly
b - actually the second name is quite common
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Structure-based names
Structure-based name when the
constitutional repeating unit (CRU) has several
components
The CRU is independent of the monomers and
polymerization methods
Poly(hexamethylene adipamide)
Poly(ethylene terephthalate)
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copolymers
Type Connective Example
unspecified -co- Poly(A-co-B)
statistical -stat- Poly(A-stat-B)
random -ran- Poly(A-ran-B)
alternating -alt- Poly(A-alt-B)periodic -per- Poly(A-per-B-per-C)
block -block- (-b-) Poly(A-b-B) or Poly A-block-poly B
graft -graft- (-g-) Poly(A-g-B) or Poly A-graft-poly B
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Source-based name Structure-based name Trade name, abbreviation
polyethylene polymethylene PE, LDPE, HDPE, LLDPE
polypropylene Poly(propylene) PP
polyisobutylene Poly(1,1-dmethylethylene) PIB
polystyrene Poly(1-phenylethylene) Styron, Styrofoam
Poly(vinyl chloride) Poly(1-chloroethylene) PVC
Poly(vinylidene chloride) Poly(1,1-dichlorethylene) Saran
polytetrafluoroethylene Poly(difluoromethylene) Teflon
Poly(vinyl acetate) Poly(1-acetoxyethylene) PVAC
Poly(vinyl alcohol) Poly(1-hydroxyethylene) PVAL
Poly(methyl methacrylate) Poly(1-methoxycarbonyl-1-
methylethylene)
PMMA; Lucite, Plexiglass
polyacrylonitrile Poly(1-cyanoethylene) PAN; Orlon, Acrilan fibers
polybutadiene Poly(1-butenylene) BR rubber
polyisoprene Poly(1-methyl-1-butenylene) NR rubber
polychloroprene Poly(1-chloro-butenylene) Neoprene
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Polymers with other backbones
Source-based name Structure-based name Trade name, abbreviation
polyformaldehyde Poly(oxymethylene) POM
Poly(ethylene oxide) Poly(oxyethylene) PEO
Poly(ethylene glycol adipate) Poly(oxyethylene oxyadipoyl) Polyester 2,6
Poly(ethylene terephthalate) Poly(oxyethylene oxy-terephthaloyl) PET; Dacron
Poly(hexamethylene
adipamide)
Poly(iminoadipoyl imino-hexamethylene) Nylon 6,6
Poly(e-caprolactam) Poly(imino[1-oxohexamethylene]) Nylon 6
polyglycine Poly(imino[1-oxoethylene]) Nylon 2
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WHY ARE LONG CHAIN MOLECULESSOLIDS?
Bonding along the backbone is not extraordinary.
With long chains, secondary valence forces, integrated over the entirechain, provide considerable bonding forces.
Chain entanglements provide physical linkages.
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Chemical bonding in polymers
Most primary bonds along the
backbone are covalent
Secondary valence bonds
Much smaller forces than the
covalent bonds, but become
significant when integrated over the
entire chain
Consider the forces acting on this
macromolecule as it is pulled
through the tube surrounding its
structure in three dimensional space
As each chain segment moves, it
must overcome the local
interactions at the tube surface Longer chains will have more
resistance to motion
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Secondary valence forces
Secondary valence forces affect the glass transition, the
melting temperature, crystallinity, melt flow,
They include: nonpolar dispersion, polar dipoles, polar
induction, and hydrogen bonds
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Secondary bond Bond energy,
kcal/mol
Range of action,
Angstrom
Dispersion 0.1-5.0 3-5 (r-6)
Dipole-dipole 0.5-5.0 1-2 (r-3)
Dipole-induced
dipole
0.05-0.5 1-2 (r-6)
Hydrogen bond 1.0-12 2-3 (r-2)
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WHAT ARE TYPICAL CHAIN LENGTHDISTRIBUTIONS?
Few synthetic polymers are monodisperse, i.e., have one chain length.
Many biological polymers do have specific molecular weights, e.g., proteins,DNA,
The molecular weight distribution has critical effects on polymer propertiesin the melt and solid states.
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T i l ff t f l l i ht
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Typical effects of molecular weight
distributions Homopolymers with different molecular weight distributions may be
insoluble in each other
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# carbon atoms State Use
1-4 Gas Gaseous fuel5-11 Low viscosity liquid gasoline
9-16 Medium viscosity
liquid
kerosene
16-25 High viscosity liquid Oil, grease
25-50 Crystalline solid Paraffin wax
1000-3000 Plastic solid
(crystalline +
amorphous)
polyethylene
Linear
alkane
properties
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MWD - oligomer
Poly(a-olefin); PAO6
Synthetic base oil
vehicle use
Trimer, tetramer,
pentamer, hexamer,
heptamer
Based on 1-decene
Ionic polymerization
Differential distribution
by size exclusionchromatography
PeakFit used for curve
deconvolution
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Two polyethylenes
Weight frequency, differential
distributions
Number-average molecular
weights are the same
Weight-average molecular
weights are different Narrow MWDPD ~ 5.7
Broad MWDPD ~ 15
Differences in flow, tensile and
appearance properties
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Mn
ni Mii
ni
i
Mw
wi Mii
wi
i
ni Mi2
i
ni M
i
i
PD
Mw
Mn
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HOW DOES CHAIN LENGTH AFFECTPROCESSING?
In-class exercise
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HOW DOES CHAIN LENGTH AFFECTPERFORMANCE?
In-class exercise
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WHAT ARE IMPORTANT THERMALTRANSITIONS?
Thermal properties are often key criteria used to select polymers for specificapplications.
Five regions of viscoelastic behavior (many polymers have all five): < glasstransition, power law region, rubbery plateau, rubbery flow, fluid flow
Othercrystalline solids, crosslinked elastomers
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Five regions of viscoelasticity
Use amorphous polymers below Tg
Use crystalline polymers below Tm
Crosslinked elastomers at G
Melt processing between B and C
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Typical G vs T plots
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regions
Viscoelasticity: most polymers creep(slow flow) under long-term stress.Creep may not be recoverable, i.e., the sample may not recoil to its
original dimensions. Over short periods of time, polymers are elastic.
Solid yield and fracture: elasticity for e< 0.1%; PS is brittle and fails at low
elongations. PE yields, and then undergoes cold drawing to > 300%
elongation.
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BUILDING A GLOSSARY
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POLYMER SCIENCE DIRECTIONS
Medical applications are arich applications area forpolymers.
Local variations in surfaceroughness at the nanoscalecan induce strains in cellmembranes, leading to thegrowth of F-actin stress
fibers that span the lengthof the cell.W.E. Thomas, D. E. Discher, V. P. Shastri,Mechanical regulation of cells by materialsand tissues, MRS Bulletin, 35(2010), 578-583.
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Cells feel their environment
Tissues are hydrated natural polymers with controlledelasticity
Most animals cells require adhesion to a solid to beviable
Tissue elasticity (~ kPas) is important for regulating cell
growth, maturation and differentiation. Brain0.2 < E