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Commodity Thermoplastics_ LDPE, HDPE, PP, PVC, PS

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Title: Commodity Thermoplastics_ LDPE, HDPE, PP, PVC, PS


1
Commodity Thermoplastics_ LDPE, HDPE, PP, PVC, PS
Professor Joe Greene CSU, CHICO
2
Polyolefin Definition
  • Olefins Unsaturated, aliphatic hydrocarbons made
    from ethylene gas
  • Ethylene is produced by cracking higher
    hydrocarbons of natural gas or petroleum
  • Olefin means oil forming
  • Historically given to ethylene because oil was
    formed when ethylene was treated with Cl.
  • Now applies to all hydrocarbons with linear CC
    double bonds (not aromatic CC double bonds)
  • Polyethylene discovered around 1900, though using
    an expensive process
  • LDPE commercialized in 1939
  • HDPE commercialized in 1957

3
Principal Olefin Monomers
  • Ethylene
    Propylene
  • Butene-1
    4-Methylpentene

4
Several Olefin Polymers
  • Poly Ethylene Poly
    Propylene
  • PolyisoButene
    PolyMethylpentene

5
Polymers Derived from Ethylene Monomer

6
Addition Polymerization of PE
  • Polyethylene produced with low (Ziegler) or high
    pressure (ICI)
  • Polyethylene produced with linear or branched
    chains

OR
n
7
Mechanical Properties of Polyethylene
  • Type 1 (Branched) Low Density of 0.910 - 0.925
    g/cc
  • Type 2 Medium Density of 0.926 - 0.940 g/cc
  • Type 3 High Density of 0.941 - 0.959 g/cc
  • Type 4 (Linear) High Density to ultra high
    density gt 0.959

8
Physical Properties of Polyethylene

9
Processing Properties of Polyethylene

10
Special Low Versions of PolyethyleneProduced
through catalyst selection and regulation of
reactor conditions
  • Very Low Density Polyethylene (VLDPE)
  • Densities between 0.890 and 0.915
  • Applications include disposable gloves, shrink
    packages, vacuum cleaner hoses, tuning, bottles,
    shrink wrap, diaper film liners, and other health
    care products
  • Linear Low Density Polyethylene (LLDPE)
  • Densities between 0.916 and 0.930
  • Contains little if any branching
  • Properties include good flex life, low warpage,
    and improved stress-crack resistance
  • Applications include films for ice, trash,
    garment, and produce bags

11
Special High Versions of PolyethyleneProduced
through catalyst selection and regulation of
reactor conditions
  • High Molecular Weight- High Density Polyethylene
    (HMW-HDPE)
  • Densities are 0.941 or greater
  • MW from 200K to 500 K
  • Properties include improved toughness, chemical
    resistance, impact strength, and high abrasion
    resistance.
  • High viscosities
  • Applications include trash liners, grocery bags,
    industrial pipe, gas tanks, and shipping
    containers

12
Special High Versions of PolyethyleneProduced
through catalyst selection and regulation of
reactor conditions
  • Ultra High Molecular Weight Polyethylene (UHMWPE)
  • Densities are 0.96 or greater
  • MW from 3M to 6M
  • Properties include improved high wear resistance,
    chemical inertness, and low coefficient of
    friction.
  • High viscosities result in material not flowing
    or melting.
  • Processed similar to PTFE (Teflon)
  • Ram extrusion and compression molding are used.
  • Applications include pump parts, seals, surgical
    implants, pen tips, and butcher-block cutting
    surfaces.

13
Copolymers of Polyethylene
  • Ethylene-ethyl acrylate (EEA)
  • Properties range from rubbery to tough
    ethylene-like properties
  • Applications include hot melt adhesives, shrink
    wrap, produce bags, bag-in-box products, and wire
    coating.
  • Ethylene-methyl acrylate (EMA)
  • Produced by addition of methyl acrylate monomer
    (40 by weight)with ethylene gas
  • Tough, thermally stable olefin with good
    elastomeric characteristics.
  • Applications include food packaging, disposable
    medical gloves, heat-sealable layers, and coating
    for composite packaging

14
Copolymers of Polyethylene
  • Ethylene-Vinyl Acetate (EVA)
  • Repeating groups is ethylene with an acetate
    functional
  • Part of the pendent group are highly polar.
  • Vinyl acetate reduces crystallinity and increases
    chemical reactivity because of high regions of
    polarity.
  • Resultflexible polymer that bonds well to other
    materials
  • Excellent adhesive (Elmers Glue)
  • Other applications include flexible packaging,
    shrink wrap, auto bumper pads, flexible toys, and
    tubing

n
m
15
Copolymers of Polyethylene
  • Ethylene-Propylene (EPM)
  • Ethylene and propylene are copolymerized in
    random manner and causes a delay in the
    crystallization.
  • Thus, the copolymer is rubbery at room temp
    because the Tg is between HDPE (-110C) and PP
    (-20C).
  • Ethylene and propylene can be copolymerized with
    small amounts of a monomer containing 2 CC
    double bonds (dienes)
  • Results in a ter polymer, EPDM, or thermoplastic
    rubber, TPO

16
Mechanical Properties of PE Blends

17
Processing Properties of PE Blends

18
Polypropylene History
  • Prior to 1954 most attempts to produce plastics
    from polyolefins had little commercial success
  • PP invented in 1955 by Italian Scientist F.J.
    Natta by addition reaction of propylene gas with
    a sterospecific catalyst titanium trichloride.
  • Isotactic polypropylene was sterospecific
    (molecules are arranged in a definite order in
    space)
  • Polypropylene is similar in manufacturing method
    and in properties to PE

19
Chemical Structure
  • Propylene
  • Isotactic- CH3 on one side of polymer chain
    (isolated). Commercial PP is 90 to 95 Isotactic

n
20
Polypropylene Stereostatic Arrangements
  • Atactic- CH3 in a random order (A- without
    Tactic- order) Rubbery and of limited commercial
    value.
  • Syndiotactic- CH3 in a alternating order (Syndio-
    Tactic- order)

21
Addition Polymerization of PP
  • Polypropylene produced with low pressure process
    (Ziegler)
  • Polypropylene produced with linear chains
  • Polypropylene is similar in manufacturing method
    and in properties to PE
  • Differences between PP and PE are
  • Density PP 0.90 PE 0.941 to 0.965
  • Melt Temperature PP 176 C PE 110 C
  • Service Temperature PP has higher service
    temperature
  • Hardness PP is harder, more rigid, and higher
    brittle point
  • Stress Cracking PP is more resistant to
    environmental stress cracking

22
Advantages of Polypropylene
  • Advantages
  • Low Cost
  • Excellent flexural strength
  • Good impact strength
  • Processable by all thermoplastic equipment
  • Low coefficient of friction
  • Excellent electrical insulation
  • Good fatigue resistance
  • Excellent moisture resistance
  • Service Temperature to 126 C
  • Very good chemical resistance

23
Disadvantages of Polypropylene
  • Disadvantages
  • High thermal expansion
  • UV degradation
  • Poor weathering resistance
  • Subject to attack by chlorinated solvents and
    aromatics
  • Difficulty to bond or paint
  • Oxidizes readily
  • flammable

24
Molecular Weight Review
  • Molecular Weight estimates the average length of
    the polymer chain and is similar to the DP
    (degree of polymerization)
  • MW (MW of mer) x DP
  • Example MW 100,000 for PS then the DP 1000.
    (PS 104 amu)
  • Example MW 50,000 for PE then the DP 1800.
    (PE 28 amu)
  • Molecular Weight is measured by osmometry, light
    scattering and solution viscosity
  • Molecular Weight is characterized by Weight
    Average, Mw, and Number Average, Mn.
  • Polydispersity, PD
  • Ratio of Mw / Mn

25
Mechanical Properties of Polypropylene

26
Physical Properties of Polyethylene

27
Processing Properties of Polyethylene

28
Copolymers of Polypropylene
  • Ethylene-propylene copolymers
  • Small amount of PP can lower crystallinity of
    linear HDPE
  • Polyallomers (block copolymers)
  • Blocks of PE and PP polymers allows
    crystallization to take place
  • Properties are similar to HDPE and PP
  • Ethylene-propylene rubbers
  • Random co-polymerization of ethylene and
    propylene prevents crystallization of the chains
    by suppressing regularity of molecules
  • Resulting polymers are amorphous having low Tg
    (between -110C and -20C depending on of PE and
    PP)
  • Polymers are rubbery at room temperature
  • Conventional vulcanization allows for use as
    commercial rubber, thermoplastic rubbers, TPR

29
Polyolefin_Polybutylene
  • History
  • PB invented in 1974 by Witco Chemical
  • Ethyl side groups in a linear backbone
  • Description
  • Linear isotactic material
  • Upon cooling the crystallinity is 30
  • Post-forming techniques can increase
    crystallinity to 55
  • Formed by conventional thermoplastic techniques
  • Applications (primarily pipe and film areas)
  • High performance films
  • Tank liners and pipes
  • Hot-melt adhesive
  • Coextruded as moisture barrier and heat-sealable
    packages

30
Properties of Polybutylene

31
Polyolefin_Polymethylpentene (PMP)
  • Description
  • Crystallizes to 40-60
  • Highly transparent with 90 transmission
  • Formed by injection molding and blow molding
  • Properties
  • Low density of 0.83 g/cc High transparency
  • Mechanical properties comparable to polyolefins
    with higher temperature properties and higher
    creep properties.
  • Low permeability to gasses and better chemical
    resistance
  • Attacked by oxidizing agents and light hydrogen
    carbon solvents
  • Attacked by UV and is quite flammable
  • Applications
  • Lighting elements (Diffusers, lenses reflectors),
    liquid level
  • Food packaging containers, trays, and bags.

H3C-CH-CH3
32
Properties of Polymethylpentene

33
PVC Background
  • Vinyl is a varied group- PVC, PVAc, PVOH, PVDC,
    PVB
  • Polyvinyls were invented in 1835 by French
    chemist V. Regnault when he discovered a white
    residue could be synthesized from ethylene
    dichloride in an alcohol solution. (Sunlight was
    catalyst)
  • PVC was patented in 1933 by BF Goodrich Company
    in a process that combined a plasticizer,
    tritolyl phosphate, with PVC compounds making it
    easily moldable and processed.
  • PVC is the leading plastic in Europe and second
    to PE in the US.
  • PVC is made by suspension process (82), by mass
    polymerization (10 ), or by emulsion (8)
  • All PVC is produced by addition polymerization
    from the vinyl chloride monomer in a head-to-tail
    alignment.
  • PVC is amorphous with partially crystalline
    (syndiotactic) due to structural irregularity
    increasing with the reaction temperature.
  • PVC (rigid) decomposes at 212 F leading to
    dangerous HCl gas

34
PVC and Vinyl Products
  • Rigid-PVC
  • Pipe for water delivery
  • Pipe for structural yard and garden structures
  • Plasticizer-PVC or Vinyl
  • Latex gloves
  • Latex clothing
  • Paints and Sealers
  • Signs

35
PVC and PS Chemical Structure
  • Vinyl Groups (homopolymers produced by addition
    polymerization)
  • PVC - poly vinylidene - polyvinylalcohol
    (PVOH)
  • chloride (PVDC)
  • polyvinyl acetate (PVAc) - PolyStyrene (PS)

n
36
Mechanical Properties of Polyvinyls

37
Physical Properties of Polyvinyls

38
Processing Properties of Polyvinyls

39
PS Background
  • PS is one of the oldest known vinyl compounds
  • PS was produced in 1851 by French chemist M.
    Berthelot by passing benzene and ethylene through
    a red-hot-tube (basis for today)
  • Amorphous polymer made from addition
    polymerization of styrene
  • Homopolymer (crystal) (2.7 M metric tons in
    1994)
  • Clear and colorless with excellent optical
    properties and high stiffness.
  • It is brittle until biaxially oriented when it
    becomes flexible and durable.
  • Graft copolymer or blend with elastomers- Impact
    polystyrene (IPS)
  • Tough, white or clear in color, and easily
    extruded or molded.
  • Properties are dependent upon the elastomer ,
    but are grouped into
  • medium impact (Izodlt1.5 ft-lb), high impact (Izod
    between 1.5 to 2.4 ft-lb) and super-high impact
    (Izod between 2.6 and 5 ft-lb)
  • Copolymers include SAN (poly styrene-acrylonitrile
    ), SMA (maleic anhydride), SBS (butadiene),
    styrene and acrylic copolymers.
  • Expandable PS (EPS) is very popular for cups and
    insulation foam.
  • EPS is made with blowing agents, such as pentane
    and isopentane.
  • The properties are dependent upon cell size and
    cell size distribution

40
Mechanical Properties of PS, ABS, SAN

41
Physical Properties of PS, ABS, SAN

42
Processing Properties of PS, ABS, SAN

43
Section Review
  • Major Topics
  • Vinyl is a varied group- PVC, PVAc, PVOH, PVDC,
    PVB.
  • PVC is the leading plastic in Europe and second
    to PE in the US.
  • PVC is produced by addition polymerization from
    the vinyl chloride monomer in a head-to-tail
    alignment.
  • PVC is partially crystalline (syndiotactic) with
    structural irregularity increasing with the
    reaction temperature.
  • PVC (rigid) decomposes at 212 F leading to
    dangerous HCl gas
  • X1
  • Vinyls have (CH2CX2) repeating link
  • PS is Amorphous and made from addition
    polymerization
  • PC is amorphous and made from condensation
    polymerization
  • Effects of reinforcements on PP and PS

44
Homework Questions
  • 6. Four typical Physical Properties of PVC are
    Optical _______, Resistance to moisture ______
    , UV resistance _____, solvent
    resistance_______
  • 7. The Advantages of PP are ________, ________,
    _______, and __________.
  • 8. The Disadvantages of PP are ________,
    ________, _______, and __________.
  • 9. Glass fiber affects PP by (strength) ________,
    (modulus)________, (impact)_______, (density)
    __________, and (cost) ____________.
  • 10. Two Blends PVC are ___________, and
    __________.

45
Section Review
  • Major Topics
  • Isotactic, atactic, sydiotactic polypropylene
    definitions
  • Differences between PP and PE
  • Molecular Weight definition and forms (Weight
    Average, Mw, and Number Average, MA )
  • Polydispersity definition and meaning
  • Relation between Molecular weight and Degree of
    Polymerization (DP)
  • Mechanical, physical, and processing properties
    of PP, Polybutylene, and polymethylpentene
  • PP is produced with linear chains

46
Section Review
  • Key Terms and Concepts
  • Polyolefin
  • Molecular weight
  • Number average molecular weight, weight average
    MW
  • Polydispersity
  • Polymer shrinkage
  • Polymer blends
  • Tensile Modulus
  • Izod Impact Strength

47
Homework Questions
  • 1. Define Polyvinyls, PS, PP, HDPE, chemical
    structure.
  • 2. Compare the density PVC, PVB, PS, and PVDC
    which is higher/lower than PP.
  • 3. Compare the density of HDPE, LDPE, UHMWPE,
    LLDPE to PP?
  • 4. What is the tensile strength of PP with 0,
    30 glass fibers? What is the tensile modulus?
  • 5. Plot tensile strength and tensile modulus of
    PVC, PS, PP, LDPE and HPDE to look like

50
xHDPE
Tensile Strength, Kpsi
xLDPE
10
200
500
Tensile Modulus, Kpsi
48
Homework Questions
  • 1. Define Polypropylene chemical structure
  • 2. Does commercial PP have Isotactic, atactic,
    sydiotactic form.
  • 3. If MW of PP is 200,000, what is the approx.
    DP?
  • 4. Polydispersity represents the distribution of
    _______and _____
  • 5. Density of PP is _____ which is higher/lower
    than HDPE.
  • 6. PP mechanical properties are higher/lower than
    LDPE and HDPE
  • 7. Plot tensile strength and tensile modulus of
    PP, LDPE and HPDE to look like the following

50
xHDPE
Tensile Modulus, Kpsi
xLDPE
10
2
5
Tensile Strength, Kpsi
49
Homework Questions
  • 8. Four typical Physical Properties of PP are
    Optical _______, Resistance to moisture ______
    , UV resisance _____, solvent resistance_______
  • 9. The Advantages of PP are ________, ________,
    _______, and __________.
  • 10. The Disadvantages of PP are ________,
    ________, _______, and __________.
  • 11. Glass fiber affects PP by (strength)
    ________, (modulus)________, (impact)_______,
    (density) __________, and (cost) ____________.
  • 12. Five polyolefins are ________, ________,
    _______, ______, and __________.
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