neil edmonds presentation - wasteminz · abbreviations for plastics abs...
TRANSCRIPT
Introduction
Abbreviations for PlasticsABS Acrylonitrile-Butadiene-StyreneEVA Ethylene-Vinyl Acetate HDPE High-Density PolyethyleneLDPE Low-Density PolyethyleneLLDPE Linear Low-Density
PolyethylenePA Polyamide (nylon)PC PolycarbonatePE PolyethylenePET/PETE Polyethylene TerephthalatePETG Glycol Modified Polyester
TerephthalatePMMA Polymethyl methacrylate (acrylic)
PMP Polymethyl Pentene (TPX)POM Polyoxymethylene (acetal) PP PolypropylenePS PolystyrenePSU PolysulfonePTFE PolytetrafluoroethylenePU/PUR PolyurethanePVC Polyvinyl ChloridePVDF Polyvinylidene FluorideSAN Styrene AcrylonitrileTPE Thermoplastic ElastomerUHMW-PE Ultra High Molecular
Weight Polyethylene
Thermosetting polymers cannot be recycled
Classification of PolymersNatural Synthetic
Carbohydrates Thermoplasticseg. Cellulose, Starch Commodity Plastics (PE, PP, PS, PVC, PET)
Engineering Plastics (PA, POM, ABS,)Proteins Specialty Plastics (PTFE)eg. Wool, Silk
ElastomersThermoplastic (SBS, TPU)Thermosetting (NR, SI)
Thermosetting (3D, Network, Crosslinked)Epoxy Resins (EP)Unsaturated Polyester Resins (UP)
Thermoset polymers
resin + catalyst
Mix
CureReaction
Solidified thermosetThermoplastic polymers
Solid Stock or Granules Finished Product
Heat,Reshape,Mix, etc…
Elastomers (or rubbers) are flexible thermoplastic or thermoset polymers
Examples of simple polymers:
Ethylene Mer Polyethylene
Propylene PolypropyleneMer
ØDuring polymerization, monomers join together forming large molecules from multitudes (poly) of small repeating segments (mers).
ØThe behaviour of a plastic when molten depends on the monomers used. For example, nylons and polyesters have very low viscosity melts while HDPE and PS are high viscosity. This means they must be handled and processed differently.
Manufacture of Polymers
Thermoplastic polymers are typically received from the supplier in solid form, with the polymerisation reaction complete.
ØVery long polymer chains are already formed, these can be repeatedly melted, shaped and cooled with very little degradation of the polymer.
Ø Plastics manufacturers mould pellets, sheets or powder into products.
Properties of different polymers
Polyesters - PET Poly(ethylene terephthalate)
Key material properties:• high tensile strength and rigidity• very high heat resistance• excellent electrical insulation • chemical resistance• very good dimensional stability
Disadvantages:• high processing temperatures• careful drying required before processing
Applications:• packaging• electrical and electronic connectors and components• appliance components
Recyclability:• limited commercial recycling• main kerbside collection in NZ is of PET used for packaging which is largely
exported for reprocessing
Identification Code
High Density Polyethylene (HDPE)Key material properties:• translucent• high tensile strength• rigid• excellent chemical resistance
Disadvantages:• difficult to bond• stress cracking• poor weathering resistance
Applications:• household goods (basins, sieves, dishes, rubbish bins)• transport cases• pipes• electrical fittings• sports equipment• food and freezer containers
Recyclability:• highly recyclable• most common material for kerbside collection in NZ – milk bottles• also commercial recycling
Identification Code
Poly(vinyl chloride) – PVCKey material properties:• very good weathering resistance• resistant to a range of chemicals.• rigidity and strength properties • good electrical insulation• resistance to abrasion• clarity
Disadvantages:• contains chlorine• limited thermal capability• higher density than many other plastics
Applications:• pipes for external use • extruded profiles and frames• sheet for roofing or panelling• blown bottles for oil, wine
Recyclability:• limited commercial recycling of flexible PVC and PVC films in NZ• no household or kerbside PVC collection in NZ due to low volume & contamination risk
PVC
Identification Code
Polyethylene Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE)
Key material properties:• excellent chemical resistance• moisture transmission resistance• excellent electric insulation properties• low cost• excellent flexibility and toughness• low heat resistance, tensile strength and rigidity
Disadvantages:• difficulty in bonding• stress cracking• high gas transmission
Applications:• film for packaging• food containers, especially lids• pipes
Recyclability:• highly recyclable• high level of commercial LDPE film recycled in NZ – but little household
Identification Code
Polypropylene (PP)Key material properties:• greater hardness and stiffness than HDPE• excellent chemical resistance• electrical insulation properties• higher tensile strength and heat resistance than HDPE• good fatigue and abrasion resistance• high impact and flexural strength
Disadvantages:• poor weathering resistance• poor low temperature impact and flexural strength
Applications:• tool and travel cases• automotive parts - bumper bars, ducts, fuel tanks• food/packaging containers and boxes• sterilisable hospital items• appliance components• ropes and fibres
Recyclability:• commercial waste commonly recycled in NZ• very limited household/kerbside collection in NZ due to variety of applications & low volumes
Identification Code
Polystyrene - General Purpose Polystyrene (GPPS) Key material properties:• clarity• rigidity• low cost• high gloss• dimensionally stable
Disadvantages:• flammable• poor weatherability• poor solvent resistance• brittleness
Applications:• food containers - egg cartons, produce trays• disposable drinking cups and glasses
Recyclability:• limited commercial recycling in NZ• no NZ household/kerbside collection due to lower volumes and low material value
Identification Code
END USES Ø Thermoformed bowls, plates, dairy containers (HIPS)Ø Foamed packaging (HIPS)Ø Refrigerator liners (HIPS, ABS)Ø Automotive interiors (HIPS, ABS)Ø Injection moulded disposables (razors, pens) Ø Tools and computer housings (ABS)
STYRENE COPOLYMERSCopolymers are plastics containing more than one type of polymer (eg. ABS) Sometimes different polymers/copolymers are blended/alloyed eg. PC/ABS
Polyamides – NylonKey material properties:• excellent abrasion resistance• good chemical resistance• easy colouration• good impact strength after moisture saturation • good lubricity• high heat resistance• toughness, durability and very good fatigue resistance• properties frequently enhanced with additives
Disadvantages:• high moisture absorption• some dimensional instability• high shrinkage in moulded sections
Recyclability:• limited commercial recycling only
Identification Code
PA
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Polymer AdditivesAdditives may limit recycling options:
Ø Pigments and Fillers - Increase Strength and StiffnessØ Impact Modifiers - Improve ToughnessØ Flame Retardants - Make Polymers More Difficult to BurnØ Stabilizer Systems:
• Oxidative Stabilizers - Reduce Oxidation• Ultraviolet Stabilizers - Improve Weathering• Thermal Stabilizers - Allow High Temperature
Processing
Plastics processing technologiesMany ways to convert plastics materials into products, most common methods are:
Ø extrusionØ thermoformingØ blow moulding Ø blown film Ø injection moulding Ø rotational moulding
Extrusion
Ø process used to make continuous shapesØ a wide range of different continuous shapes can be
produced
Injection MouldingØ a way to make solid, shaped, individual productsØ used to produce a very wide range of different shapes
and sizes
Thermoforming
Ø a way to make solid, shaped, individual productsØ suitable for very thin-walled products, very large or small
products or a small numbers of products
Blow MouldingØ a way to make enclosed, hollow shaped productsØ used to produce products like bottles and drums in a
wide range of sizes
Blown Film A process known as blown film extrusion uses an industrial blower to expand a hot plastic tube into a light, strong plastic bag. The air inflates the plastic tube like a balloon until a bag with the desired size and wall thickness is formed. The balloon moves slowly up a tower,the bubble being contained by rollersthat fold the film and roll it into a cylindrical shape. The final product can have multiple layers.
Rotational MouldingØ a way to make a wide range of enclosed, hollow shaped
productsØ large industry in New Zealand
Why are polymers selected for particular products?
Ref: SABIC Innovative Plastics
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DimensionsGeometry, Weight,
Warpage (inner or outer part)Dimensional stability
Amorph/Semicrystallinefilled/unfilled
AestethicsTransparency (wavelength?), Opaque,
Color, Gloss, TextureFlow Lines, Scratch Resitance
Part visible?
MechanicalImpact, Stiffness, Abrasion, Fatigue
Additives, lifetime?
RegulatoryFood (FDA, FCEU), Water (KTW)Toys, Medical (ISO10993, EUP),
Flame retardancy (UL, ..), RoHS, WEEE,Forbidden Additives?
ElectricalUL, GWT, GWIT,
HAI, HWI, RTI, CTI Wall Thickness?EMI shielding?
AcousticsWhat Frequencies?Noise reduction?
FinancialsCost Expectation
(Material + Processing costs)System cost
Determination of Material Requirements
Enviroment Heat resistance, (HDT, BPT)
UV, Chemicals, WaterHow long, what temperature,
which chemicals?
ProcessingInjection Molding,Foaming, 2K
Extrusion, BlowmoldingThermoforming
Hot/Coldrunner, Cavities?
What requirements?What Application tests?
Second. Operation(Ultrasonic, Vibration, Laser Welding)
Glueing, Painting, Lasermarking, Powder coating, Metallisation,
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Thermo-oxidativeThermal degradation
under influence of oxygen is significantly accelerated
(feee radical)s
ThermalThrough heat exposure
while drying(extended, too highTemp)
Use Temperature
MechanicalThrough granulation processes,
shear in melt flow.All lead to
material degradation
Mechanical StressInhomogeneous distribution of stresses
through tensile/torsion/bending forces
break molecules
PhotochemicalAbsorbtion of light
Influences stability of molecules- less energy to degrade
(Energy)
RadiationX- Rays, Gammas rays
Will lead to split of unsaturated bonds, build radicals
Chemicals Water, Acids/Basis/Organic media
Attack polymer through wetting, swelling.Dissolving of additives,
chemical reactions on surface
Anti AgeingLight protection (UV Ageing, Gamma),
Antioxidants, Heat stabilizerscan slow down ageing
Life Time TestingLife time of part?
Reasonable accelerated testingon parts necessary for evaluation
AgeingAccelerated and comparable
UV Ageing Hydrolytic and chemical testing
on test speciment(tensile bars, plaques)
Material Ageing:Irreversible chemical and
physical processesthrough degradation of the polymer chains,
crosslinking reactions and uncontrollable changes of the chemical structure
with loss of mechanical propeties, FR properties, color, gloss, brittleness,
chemical resistanceFactors amplify each other!
Material ageing: Example Plastics
Barriers to using recycled content in products
Ref: GH-SITA-Plastics-for-N.E.-Recycling-Forum-26-02-2015-v4
Barriers A:ØPlastics change when processed. Heating and forming of plastics results in changes to the chemical structure.
ØChanges include lowering of chain length and oxidation of polymers, both of which result in restricting recycling options.
ØDifferent types of plastics will not mix together,even different grades of the same plastic may not fully mix.
ØPlastics with additives such as pigments are more difficult to recycle.
Barriers B:Ø Not always a slot-in replacement. Reluctance to
change the specifications of the polymers that currently used.
Ø Variability/inconsistency of the recycled polymers from batch to batch and from different suppliers.
Ø Can be constraints on colour – often darkcolours such as grey, black.
Barriers C:Ø Client specifications not allowing moulder to use
recycled content.
Ø Cost and time implications in changing over from an existing material to a recycled one (e.g. optimising moulding parameters & machine settings).
Ø Security of supply.
Ø Potential damage to reputation.
Problematic Products
1. Black Plastics
Carbon black prevents near infrared sorters identifying polymer types.New pigments look black and enable NIR sorting.
2. Multi Layer/Laminates
Pouches, films, tubes and trays with sealing layers.
Laminates of different polymers or materials are beneficial because:Ø Reduce weight - savings in transport costs and emissionsØ Less material is used so less energyØ Lower weight to landfill.Ø Oxygen and light barriers prolong shelf life.
But..create low quality materials when recycled together
3. Multi Layer/Laminates: Tubes and Pouches
Plastic and Aluminium laminates: Pouches, tubes etc. Materials need to be separated to remain high value and be used again.
ØEnval process uses microwave-induced pyrolysis (no oxygen).
ØAluminium is recovered and oils & gases produced from plastics used for heat and electricity.
ØBeing commercialised.
Benefits of using recycled plasticsØ Some recycled polymers can be cheaper than the virgin
(in some cases by 10 to 20%)
Ø Marketing benefits –showing commitment to the environment -“walking the walk”
Ø Customers want products that reduce carbon impact
Ø Material security –It’s a resource we are producing lots of (>2Mt/yr plastic packaging)
Commercial challengesØ Reprocessing Infrastructure costs $Millions to set up
facilities Ø Access to funding not always easy-riskØ Enough collected to justify investment? Chicken and eggØ Volumes of some polymers too low to justify investment
(e.g. PS and PVC)Ø Recovery yields vs costs of disposal –QUALITY.Ø Low /volatile prices - squeezed margins. Ø ?????
uThank you for your attention
Questions?