Amorphous and SemiCrystalline

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• Amorphous and Semi-Crystalline
• Commodity Thermoplastics
• Materials, properties and applications.

Prepared by the IAPD Education Committee (Module
3) Presented courtesy of Modern Plastics, Inc.
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Amorphous Commodity ThermoplasticsKey
Characteristics

• Low cost
• Low temperature resistance
• Low strength
• Good dimensional stability
• Bonds well
• Typically transparent

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Amorphous Commodity ThermoplasticsMaterials

• Polymethyl methacrylate (PMMA)
• Polystyrene (PS)
• Acrylonitrile butadiene styrene (ABS)
• Polyvinyl chloride (PVC)
• Polyethylene terephthalate glycol (PETG)
• Cellulous acetate butyrate (CAB)

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Acrylic (PMMA) Strengths

• Availability of all ranges of optical
  transparency, including opacity
• Rigidity
• Surface hardness
• Half the weight of glass
• Heat resistance

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Acrylic (PMMA) Limitations

• Grain effect
• Discolor with high UV exposure
• Attacked by organic solvents
• Limited chemical resistance
• Poor wear and abrasion resistance
• Low impact strength

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Acrylic (PMMA) Applications

• Protective glazing
• Windows
• Toys
• Point of purchase (POP) displays

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Polystyrene (PS) Strengths

• Inexpensive
• Easy to bond
• Quick to bond
• Easy to decorate

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Polystyrene (PS) Limitations

• Low impact resistance
• Brittle after UV exposure
• Cannot be used at elevated temperatures
• Mechanical stress

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Polystyrene (PS) Applications

• Refrigeration
• Disposable beverage glasses
• Medical devices
• Disposable laboratory products
• Wood replacement products

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Acrylonitrile Butadiene Styrene (ABS)Strengths

• Good impact resistance
• Easily formable
• Many different formulations

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Acrylonitrile Butadiene Styrene (ABS)Limitations

• Grain effect
• Will discolor with high UV exposure
• Attacked by organic solvents
• Hygroscopic (absorbs moisture)

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Acrylonitrile Butadiene Styrene (ABS)Applications

• Aircraft interiors
• Computer housings
• Cassette holders
• Mass transit components
• Wall coverings
• Consumer electronics
• Appliances
• Automotive

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Polyvinyl Chloride (PVC)Strengths

• Low cost
• Good chemical resistance
• Versatile
• Naturally UV resistant
• Good strength

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Polyvinyl Chloride (PVC)Limitations

• Heat sensitive
• Low impact strength
• Poor wear resistance

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Polyvinyl Chloride (PVC)Applications

• Pipe, valves and fittings
• Thermoformed parts for transportation, exhibits
  and machinery parts
• Point of purchase displays
• Pollution control equipment parts
• Packaging

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Modified Polyethylene Terephthalate Glycol
(PETG)Strengths

• Optical transparency
• Good toughness
• Easy to fabricate
• Easy to form
• Ability to be sterilized

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Modified Polyethylene Terephthalate Glycol
(PETG)Limitations

• Limited UV resistance
• Cannot be used above 60-66C/140-150F range
• Low softening point precludes sterilization

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Modified Polyethylene Terephthalate Glycol
(PETG)Applications

• Packaging
• Graphic arts
• Point of purchase (POP) displays

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Cellulose Acetate Butyrate (CAB)Strengths

• Tough at low temperatures
• Compounded easily for unique applications

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Cellulose Acetate Butyrate (CAB)Limitations

• Not compatible with other materials
• Not self-extinguishing

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Cellulose Acetate Butyrate (CAB)Applications

• Cash register keys
• Tool handles
• Windshields
• Thermoformed signs
• Trim stripping
• Window well covers

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Semi-Crystalline Commodity PlasticsKey
Characteristics

• Low cost, strength and temperature resistance
• Excellent chemical resistance
• Low COF
• Near zero moisture absorption
• Very good electrical properties
• Good toughness

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Semi-Crystalline Commodity PlasticsMaterials

• Polyethylene (PE)
• High density polyethylene (HDPE)
• Low density polyethylene (LDPE), (LLDPE)
• Polypropylene (PP)
• Polymethylpentene (PMP)

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Polyethylene (PE), Polypropylene (PP)
Polymethylpentene (PMP)Key Characteristics

• Partially crystalline, partially amorphous
• Largest family are the polyolefins
• Cost, benefits and limitations are different for
  each

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Polyethylenes (PE)Key Characteristics

• Classified by density and molecular weight
• Excellent chemical resistance
• Zero moisture absorption
• Light weight (1/8 weight of steel)
• Excellent insulator
• Low COF
• High impact strength

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Polyethylenes (PE)Applications

• Packaging
• Wire and cable
• Industrial

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Low Density Polyethylene (LDPE)Key
Characteristics

• Good chemical resistance
• Very flexible
• High impact strength
• Low heat resistance (60-79C/140-175F)
• Used extensively in packaging industry and for
  prosthetic devices

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High Density Polyethylene (HDPE)Key
Characteristics

• Higher rigidity and tensile strength than low and
  medium density polyethylenes
• Good formability
• Slightly lower impact strength than LDPE
• Virgin grades are FDA and USDA approved

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Low Density Polyethylene (LDPE)High Density
Polyethylene (HDPE)Applications

• Films
• Industrial trash bags
• Liners
• Shipping bags
• Marine industry
• Playgrounds
• Bathrooms
• Pipe
• Automotive

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Polypropylenes (PP)Key Characteristics

• Excellent chemical resistance
• Excellent fatigue strength referred to as
  living hinge
• Lower impact strength than polyethylenes
• Available in homopolymer and co-polymer
• Co-polymer offers better impact, clarity and cold
  temperature properties

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Polypropylenes (PP)Applications

• Packaging
• Automotive
• Consumer/durable goods
• Vacuum formed parts
• Fiber/carpet

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Polymethylpentene (PMP)Key Characteristics

• High transparency, even in thick sections
• Very light weight (.83 specific gravity)
• Higher heat resistance than other grades in this
  groupcompares favorably to PTFE up to
  148.89C/300F
• Good electrical properties
• Low-temperature impact strength
• Very brittle
• Poor UV resistance
• USDA compliant

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Polymethypentene (PMP)Applications

• Medical products
• Food processing equipment
• Microwavable packaging

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