Date post: | 07-May-2015 |
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Plastic Materials
The objective of this training session is to familiarize you with the generally used plastic materials , their properties and applications.
Objective:
Contents:
• Why plastics?• What are plastics?• Classification of polymers• Classification of thermoplastic materials• Fillers, Reinforcement fibers & Additives• Plastic Blends• Commonly used plastics & their properties• Plastic material selection
Take away ... basics about plastic materials
Why Plastics???
- Polymers which are very resistant to chemicals.
- Polymers which are thermal and electrical insulators.
- Generally, polymers which are light in weight - with varying degrees of strength.
- Polymers that can be processed in various ways to produce thin and very intricate parts.
Plastic Materials
The origin of the word "plastics" comes from Greek. Meaning “to form”
PLASTICS PLASTICS PLASTICS !!!
THAT IS WHAT WE HEAR . WHY IS IT SO ???
WEIGHT OFPACKING
ENERGY CONSUMPTION WASTE VOLUME
100%
+391%
+208%
+258%
WITH PLASTIC MATERIAL
WITHOUT PLASTIC MATERIAL
Plastic Materials
Comparison of plastics as packaging materials
PLASTICS ARE A MERE 4% OF THE USES OF OIL
FUELSOTHERS PETROCHEMICALS
PLASTICS
MISC.
7% 86% 7%
4%
3%
Plastic Materials
100Kg Of plastics in a motor car replaces 200 to 300 Kg Of traditional material
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PLASTICS
Use of Plastics in Western Europe
Plastic Materials
The consumption of energy reduced by 50% in appliances from past 20 years
Plastics 8% Paper/Cardboard27% Miscellaneous 17%
Metals 5% Glass 9% Organic Material 34%
Household waste in western Europe (129 million tons/year)
Land Fill
MehanicalRecyclingEnergy Recovery
IncinerationW/OEnergy Recovery
72%
3%16.8%
8.2%
Plastic Materials
Recycling is the major advantage in plastics to reduce the waste
Plastic Materials
Applications:
• Automotive
• Medical
• Appliances
• Electrical
• Sports
Advantages:
• Greater design freedom (part complexity)
• Less number of parts
• Fewer assembly operations
• No secondary operations
• Weight reduction
• Cost reduction
• Properties tailored to specific applications
What is polymer&polymerization?
The principal structure of plastic is that a unit, or mer, is linked many times to become a polymer.
The chemical process for the formation of polymers is called as polymerization.
• Thermoplastic & Thermoset materials
• Crystalline & Amorphous materials
• Natural & Synthetic polymers
• Copolymers
• Alloys
• Elastomers
Classification:
• Organic polymeric materials .
• Mostly Petrochemical based.
• Polymer : Made of many units.– Generally a few thousand to a few million in
one molecule.
Plastic Materials
Classification of plastic materials
Thermoplastics
are resins that repeatedly soften when heated and hardened when cooled.
Nylon, Acrylic, Acetal, Polystyrene, Polyvinyl chloride, Polyethylene, Cellulose acetate are some examples.
Thermoplastic elastomers known as highly elastic and flexible resins.
Thermosets(cross-linked plastics)
Initially a liquid or a semisolid or a powder, which solidify on heating for first time, and then will only decompose on heating to a high temperature.
Phenolic, Amino, Epoxy, Polyurethane are few examples.
Vulcanization is process to convert from rubbers to thermoset plastics.
Thermoplastics materials are major contribution to engg. applications
The thermal behavior of thermoplastics leads toMelt processing techniques such as
• Injection molding - suitable for precision & complex parts • Extrusion - suitable for single cross section parts• Thermoforming - suitable for complex big parts• Blow molding - suitable for bottle shape parts• Roto molding - suitable for big components like water tanks
The thermal solidification of thermosets leads toProcessing methods such as
• Hot compression molding• Resin transfer molding• Pultrusion• Vacuum bagging , pressure bagging
Classification of plastic materials
Injection molding is the dominated process in plastics...
This is what happens to thermoplastics and thermosets, when we process them.
Classification of plastic materials
Classification of plastic materials
Classification of plastic materials
Crystalline Materials:
the chemical structure allows the polymer
chains to fold on themselves and pack
together in an organized manner during
the melting and cooling process.
• The structure the polymer is uniform and Order.• Opaque material• Shrinkage is more(around 2%)• Shrinkage is non-uniform in both direcitons• Warpage is more• Sharp transition in the Melting phase• Very good Chemical resistance• Low gloss and dimensional stability• Acetal, Nylon, Polyethylene, Polypropylene, Polyamides, Polyester(PET, PBT)Acrylic etc.
Classification of thermoplastics
Amorphous Materials:
the chemical structure of the Amorphous materials is random and not in order after the melting and cooling process.
• The structure of the polymer is no-uniform and random.• Transparent material • Shrinkage is less (around 0.5%)• Shrinkage is uniform in both the directions• Warpage is less• Gradual transition in the Melting phase• Low Chemical resistance• High gloss and dimensional stability• Polystyrene, ABS, PC, SAN, PVC etc.
Liquid crystalline materials are one having amorphous regions between and connecting the crystalline regions
Classification of thermoplastics
Classification of thermoplastics
Classification of thermoplastics
Classification of thermoplastics
Relative polymer properties
Property Crystalline Amorphous Liquid CrystallineSpecfic Gravity Higher Lower HigherTensile Strength Higher Lower HighestTensile Modulus Higher Lower HighestDuctility, Elongation Lower Higher LowestResistance to creep Higher Lower HighMax usage temp. Higher Lower HighShrinkage & warpage Higher Lower LowestFlow Higher Lower HighestChemical resistance Higher Lower HighestCreep resistance Higher Lower HighestHeat resistance Higher Lower HighestImpact resistance Lower Higher Highest
Liquid crystalline materials are best...
Plastic fillers, Reinforcing fibers & Additives
Fillers
• Glass spheres
• Carbon black
• Metal powders
• Silicon sand
• Wood flour
• Ceramic powders
• Mica flakes
• Molybdenum Disulfide
Reinforcing fibers
• Glass fibers
• Carbon fibers
• Aramid fibers
• Jute
• Nylon fibers
• Polyester fibers
Additives
• UV Stabilizers
• Plasticizers
• Loubricants
• Colorants
• Flame retardants
• Antioxicants
• Antistatics
“Fillers/Fibers/Additives” maybe any substances that is added to the polymer in small concentration in order to alter their physical properties either to facilitate processing or to change physical, chemical or electrical properties of the material.
Fillers/fibers/additives improves the properties by 30-40%
•Preservatives
• Processing aids
•Fungicides
• Smoke suppressants
• Foaming agents
• Viscosity modifiers
• Impact modifiers
Blends are mechanical mixtures of chemically different polymers or co- polymers.
What is expected of a blend?
• High performance at reasonable price.• Modification of performance as market develops.• Extending the performance of expensive resins.• Generation of unique materials.• They should be economical, competitive and should not affect other needed properties.• They should be easy to process.
Plastic Blends
Most commonly used blends:
•ABS/PVC Blends• PC/ABS Blends• PBT/PC Blends• EPDM/PP
Blending of plastics is innovative in the competitive market
Plastic Material Selection
• Identify application requirements - mechanical (load, impact, stiffness, etc.), thermal (temperature range, maximum use temperature, etc.), environmental considerations
• Identify the chemical environment - define the chemical stress, temperature, contact time and type
• Identify specific loads - regulatory (UL, FDA, etc.), outdoor or UV exposure, light transmission (clear or opaque), fatigue and creep requirements
• Define processing considerations - Injection molding, blow molding, extrusion, thermoforming, foam molding etc.
• Assembly - painting, plating, shielding, adhesion, snap fit, welding etc.
• Finish & gloss
• Cost
• Availability
Material section is the key factor in the design phase
Plastic Material Selection
Material performance• Modulus• Strength/Ductility• Thermal Conductivity• Viscosity• Material Cost
Part Performance Requirements• Load/Deflection• Time/Temperature• UV Stability, Transparency, • Chemical Compatibility, etc.
Part design• part Stiffness• Optimal Ribbed Geometry• Wall Thickness• Part Volume/Weight
Manufacturing• Maximum Flow Length• Minimum Wall Thickness• Cycle Time• Manufacturing Cost
Material SelectionGoal: Minimize System Cost =
(Material Cost) x (Part Volume) + (Machine Cost) x (Cycle Time)
Design based material selection
Plastic Material Abbreviation
Material Abbreviation Trade name TypePOM Poly oxy methylene or Polycetal Delrin CrystallinePPS Poly phenylene sulphidePC Poly carbonate Lexan AmorphousPTFE Poly tetra fluro ethylene Teflon AmorphousPEEK Poly ethyl ether ketone Victrex AmorphousPBT Poly butylene terephthalate Arnite AmorphousPMMA/Acrylic Poly methyl propenate Lucite, Plexiglass CrystallinePVC Poly chloro vinyl Indovin AmorphousNylon Polyamide Zytel, Perlon CrystallineABS Acrylonitrile butadiene styrene Abstron AmorphousPE Poly ethylene CrystallineLDPE Low density poly ethylene CrystallineHDPE High density poly ethylene CrystallinePS Poly styrene AmorphousHIPS High impact poly styrene AmorphousSAN Styrene acrylonitrile AmorphousPP Poly propylene CrystallineCA Cellulose acetate AmorphousCAB Cellulose acetate butyrate AmorphousCP Cellulose propionate AmorphousPPO Poly phenylene oxide Nyrol Amorphous
Common properties of plastic materials
Physical properties
• Density
• Specific gravity
• Refractive index
• Water absorption
• Mold shrinkage
• Rheology
• Transparency
• Elasticity
• Plasticity
• Ductility, Toughness
• Brittleness
• Notch sensitivity
• Lubricity
• Coefficient of linear expansion
Mechanical properties
• Tensile strength
• Flexural Modulus
• Elongation
• Creep
• Impact strength
• Fatigue resistance
• Hardness
• Coefficient of friction
Electrical properties
• Conductivity
• Volume resistivity
• Surface resistivity
• Dielectric strength
• Arc resistance
Thermal properties
• Melting point
• Glass transition temp
• Thermal conductivity
• Aging at elevated temp
• Flammability
Environmental conditions
• Stress level
• Temperature
• Chemical compatibility
• Weathering resistance
Chemical Properties• Molecular weight• Melt viscosity(MFI)• Glass transition temperature• Heat distortion temperature(HDT)
Commonly used plastics and propertiesMateial/Properties
Density(g/cc)
Tensile Strength(Mpa)
Elongation(%)
Impact Strength(ft-lb/in)
HDT(Deg C)
VST(Deg C)
Melting point(Deg C) Tg(Deg C)
Shrinkage(cm/m) LOI(%) Applications
Polyacetol HOMO 1.42 70 25-75 1.4 100-110 175 -13 0.02 15Polyacetol CO 1.41 58 40-75 1-1.5 100-110 105 0.035
PPS 1.88 92 1 27.5 350 300-360 85-950.001-0.005 44-53
Connectors, Coil formers, Bobins, Rey equipments, Metal replacement in the automotove industry, Street lamp reflectory, PH meter components, Encapsulation components
PC 1.2 65 6 to 7 9 to 16 135-140 158-160 220-230 1450.006-0.008 26
Insulating areas, f lame resistance, durability, impact resistance,heat resistance
PPO 1.06 48-76 5 to 10 80-149 257 116-1500.005-0.007 29-35
Water w ashing machines, dish w ashes, w ater pumps, elctronic, automotive and structural foam
PTFE 2.1-2.3 17-21 200-300 2 121 327 1150.030-0.060 90
High chemical inertness exceptional w eather properties, seals, gasket, packaging, pump parts, laboratory equipment, PCB, w ire insulation, aircraft components, non-stick w oven w are, f lexible steam hose, unsintered tape for pipes sealings.
PEEK 1.265 92 >40 8(kj/m) 150 334 1430.012-0.020 35
Heat resistance, hydrolytic stability, chemical plants, pump impeller & aircraft components
PBT 1.31 52 200 1 54 220 22-430.015-0.02 18
Automotive, electrical, electronics, homew are,pow er tools, toys & machine parts
PETP 1.4 130-150 2 to 3 77-90(J/m) 205-210 265 70-800.018-0.021 21
House hold appliances, elctrical, electronic components, coffee maker, medical devices & gear w heels
Acrylic 1.17-1.20 8,000-11,600 3 to 7 0.4-0.5 70-95 90 160 990.004-0.007 17
High optical clarity, soft contact lenses, unbreakable w atch crystals, artif icial eyes, contact lenses, artif icial dnetures, acrylic emulsions
PVC 1.36-1.42 58 5
2.18-119.68(Kgcm/cm) 92 170-220 65-80 0.004 23-43
Building frames, pipes, blow moldes parts, vinyl leather cloth, w all paper f inishing, play ball, toys, mine belting, garden hose, f looring
Nylon 1.13 12,000(lb/in) 300 1.2 90-97 204 215 500.01-0.015 21-34
Nylon 6,6 1.14 11,000(lb/in) 90 2 70-100 230-250 264 60 0.01-0.02 21-30
Nylon 6,10 1.09 8,000(lb/in) 100 1.4 65-85 193 215 30
ABS 1.01-1.07 31-45 5-200 1 to 8 87-107 95-101 200-210 110-1250.004-0.008 29-35
toughness, rigidity and good appearance
toughness, abrasion resistance
Handles, sw itch parts, gears and plumbing applications