Chapter 23: Environmental Aspects of Plastics

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Chapter 23 Environmental Aspects of Plastics
Professor Joe Greene CSU, CHICO
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Topic

• Source Reduction
• Recycling
• Regeneration
• Degradation
• Landfill
• Incineration
• Total Product Life Cycle
• Future
• Chemical Hazards
• Sources of Chemical Hazards
• MSDS

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Topic

• Source Reduction
• Reduce the amount of material that is used in any
  application
• Combine parts into larger parts, e.g., 1 liter
  soda uses 40 less packaging than (2) 0.5 liters
• Reduce thickness of plastic part, e.g., trash
  bags had 0.08mm thickness (0.003 in) with LDPE,
  was reduced to 0.025mm (0.001 in) thickness with
  stronger and tougher LLDPE
• Reduce thickness by process imporvements
• Substitution of plastics for paper have reduced
  weight of packaging
• 1000 grocery bags from paper weighs 140 lbs and
  stacks 46 inches
• 1000 grocery bags from plastic weighs 15.6 lbs
  and stacks 3.5 in
• Recycle in house plastic from sprues and runners
  back into product.

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Topic

• Recycling
• Collection plastic listed with recycled number
• Codes for plastics
• 1 PET
• 2 HDPE
• 3 Vinyl/PVC
• 4 LDPE
• 5 PP
• 6 PS
• 7 Other
• Handling/Sorting
• Maximum economic is obtained when each material
  is sorted
• Aluminum must be separated from metals since it
  cant be readily separated from zinc and brass
• Plastics are sorted mostly by sight. Machines can
  sort by light absorption

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Topic

• Recycling
• Reclamation and Cleaning
• Plastic is shredded and cleaned
• End-Uses- Sorted PCR (Post Consumer Recycle)
• LDPE for new bags and film
• PS in insulation and instrument packaging
• PP in automotive parts, e.g., interior door inner
  panels, head liners, etc.
• Mechanical properties drop with use of regrind
  plastic versus virgin plastic. Max use of 50
  regrind, Typical 20.
• End-Uses- Comingled PCR with several plastics
  regrind
• Other plastics include thermoset materials,
  elastomers, and composites
• Plastic wood with use of comingled PCR that is
  compression molded and not injeciton molded
  usually.

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Topic

• Regeneration
• Process of breaking down polymer molecule into
  basic chemicals or chemical recycling.
• Easiest to regenerate is condensation polymers,
  PET and nylon.
• Under high pressure and heat in the presence of a
  catalyst the molecule unzips and regenerates the
  monomers.
• Thermoset composites use process of pyrolysys,
  which is the decomposition of a material using
  heat in the absence of oxygen.
• Advantage of this process is it is more effective
  for mixed plastics than PCR
• Disadvantages is the generation of air and water
  pollution and large amounts of energy required

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Topic

• Landfills
• 90 of all solid waste (by weight) in US is
  sanitary landfill.
• Plastics comprise 8 by weight and 20 by
  volume.
• Paper products comprise 40 by weight and 34 by
  volume.
• Percentage of plastics in landfill has not grown
  in the last 20 years.
• Inceration
• Controlled burning is an option for disposing of
  a large percentage of municipal solid waste.
• Paper, plastic, and other flammables are
  separtaed from solid waste and pressed into
  pellets and burned at a separte facility.
• Burning generates electricity
• Environmental concerns includes creation of
  toxins (dioxins), ash problems, and carbon
  dioxode releae for global warming

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Topic

• Inceration
• Burning generates electricity
• Energy content of various solid waste
• Material Energy Value (BTU/pound)
• PET 10,900
• HDPE 18,700
• Rubber 12,800
• Newspaper 8,000
• Wood 7,300
• Yard Waste 2,900
• Fuel oil 20,900
• Coal 9,600

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Topic

• Total Product Life Cycle
• What is the total impact of a particular product
  or product type on the environment over the total
  life cycle of the product from the creation of
  the product, its use, and disposal impact.
• Example,
• Polystyrene versus paper cups, Table 23.3

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Topic

• Energy Requirements
• Example,
• Paper sack versus Polyethylene sack, Fig 23.3
• Refrigerators and freezers. Plastics are replace
  of glass and metal
• Plastics saved 700 million pounds and require a
  total of 15.8 trillion BTUs during production
  versus 23 trillion BTUs for metal and glass.
  (Savings of 7.2 trillion)

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Topic

• Energy Requirements
• Plastic pipe
• More tonnage of plastics hoes into pipe than any
  other single use.
• Weight of pipe was 2 billion pounds versus metal
  pipe of 17.5 billion pounds.
• Energy consumption of plastic was 84 trillion
  BTUs versus 408 trillion BTUs for metal pipe,
  Savings of 324 trillion BTUs
• Beverage Bottles
• PET was introduced in mid 1970s to a market full
  of glass bottles.
• Energy consumption for plastic is 18.2 trillion
  BTUs versus 24.2 trillion BTUs for glass. Savings
  of 16 trillion BTUs, or equivalent to 2.8
  millions barrels of crude oil.

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Chemical Hazards

• Materials
• Resins (See MSDS)
• Thermoplastic resins- low toxicity and low health
  hazard
• Thermoset resins- moderate toxicity and moderate
  health hazard
• Reinforcements- low toxicity and moderate health
  hazards (dust)
• Fillers- low toxicity and moderate health hazards
  (dust)
• Solvents- moderate to high toxicity with moderate
  to high health hazards
• Catalyst- moderate to high toxicity with moderate
  to high health hazards
• Plasticizers- low toxicity and moderate health
  hazards

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Material Safety Data Sheet(MSDS)

• Hazardous materials are common in the plastics
  industry
• MSDS are required to accompany any purchased
  hazardous industrial raw material.
• Plastics are defined as potentially hazardous
  because in the course of normal use, plastics may
  produce dusts, mists, gases, fumes, vapors, or
  smokes which are dangerous.

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Material Safety Data Sheet(MSDS)

• Section I General Information
• Section II Composition
• Section III Physical Properties
• Section IV Fire and Explosion Hazard Data
• Section V Health Hazard Data
• Section VI Reactivity Data
• Section VII Spill or Leak Procedure
• Section VIII Occupational Protective Measures
• Section IX Special Precautions
• Section X Transportation

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Section I General Information

• Product name
• Manufacturers Identity
• Emergency telephone numbers
• Trade name of chemical
• Chemical family name of the material
• Example
• Lexan
• General Electric
• 1-800-gecares
• Lexan PC Resin
• Poly(Bisphenol-A carbonate)
• Chemical Abstracts Services (CAS) Number-
  Unambigous identification of materials. Lexan
  25971-65-5 (same as Merlon)

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Section II Composition

• Hazardous Ingredients
• Major constituents
• hazardous additives, fillers, or colorants
• Example for ABS
• 3 Carbon black (solid- trapped in polymer)
• 0.2 residual styrene monomer (gas- released
  during processing)

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Section II Definitions

• Definitions
• OSHA- Occupational Safety and Health
  Administration
• ACGIH- American Conference of Governmental
  Industrial Hygienists
• PEL- Personal Exposure Limits (TWA)
• TWA- Time weighted average. Exposure level
  considered acceptable in an 8 hour day as part of
  a 40 hour week.
• REL- Recommended exposure
• TLV- Threshold Limit Value. Recommended by the
  American congress of Governmental industrial
  Hygienist. (TWA for 8 hours)
• STEL- Short term exposure limit. Acceptable
  exposure for 15 minutes and should not be
  exceeded any time during the 8 hour work day.

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Section II Styrene

• Styrene as a health hazard
• Building block for thermoplastic styrenics, e.g.,
  polystyrene, ABS, SAN, and others.
• Cross-linking building block for thermoset
  styrenics, e.g., polyesters, vinyl esters.
• ABS has 0.2 residual styrene plus other sources
  (styrenic plastics)
• One study found a range of 1 to 7 ppm styrene in
  an injection molding plant
• Thermosets
• Manufacturing of large boat hulls, boats, large
  tanks, tubs, shower stalls, body panels for cars
  and trucks.
• Polyester is 35 styrene by weight.
• Processing methods include fiber spray with resin
  in stream, handlayup by roller, closed mold RTM
  operations, compression molding of polyester
  sheet.
• Ventilation is essential to keep exposure within
  limits.

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Section III Physical Properties

• Properties of material as one substance
• Evaporation Rate
• Melting point
• Boiling point
• Specific gravity
• Solubility in water
• Physical form

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Section IV Fire and Explosion Hazard Data

• Section for fire fighting
• Most plastics are not explosive
• Upon burning most plastics will yield water and
  CO2
• Many plastics are self-extinguishing
• All thermosets are self-extinguishing
• Water is recommended as the best medium for
  extinguishing fires
• Toxic fumes from plastics include
• black smoke, CO, hydrogen cyanide, and ammonia
• Flash point is very high for many plastics

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Section V Health Hazard Data

• Routes of entry of toxic substances
• Ingestion
• Oral LD-50 in rats. Lethal Dose 50 percentile of
  fatalities in rats
• Many pelletized plastics are rather inert.
• Extremely toxic LD-50 less than 1 mg/kg or 10
  ppm
• Highly toxic LD-50 less than 50 mg/kg or 100 ppm
• Moderately toxic LD-50 less than 500 mg/kg or
  1000 ppm
• Slightly toxic LD-50 greater than 500 mg/kg or
  1000 ppm
• Example
• LD-50 for guinea pig is 264mg/kg (264mg x mass of
  pig)
• Assuming equal response from human 264mg x 70kg
  for mass of human 18480mg or 18.48g to be
  ingested.

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Section V Routes of Entry

• Routes of entry of toxic substances
• Inhalation
• Thermosets reactants can be inhaled since they
  are in liquid form and have a vapor pressure that
  indicates relative volatility.
• Example Isocyanates used in polyurethane
  production
• TDI (toluene diisocyanate) used in foams for
  seats or paints.
• MDI (methylene diisocynate) used in RIM body
  panels or in paints.
• Construction projects use foamed polyurethane for
  interior walls and roofs.
• TLV is 0.005 ppm
• STEL for TDI is 0.02 ppm.
• Local and general ventilation are extremely
  important when working with urethanes
• Effects are asthma symptoms

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Section V Routes of Entry

• Routes of entry of toxic substances
• Inhalation
• LC for lethal concentration (normally for a vapor
  or gas)
• Unlikely for peletized plastics
• Heated plastics yield hydrocarbons
• Example
• Overheated PET releases acetaldehyde
• STEL of 25 ppm
• Odor threshold is 0.050 ppm.
• Example
• PVD polymerization uses Vinyl chlorine gas
• TLV of 5 ppm
• Odor threshold of 3000 ppm (no odor warning)
• Known human carcinogen

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Section V Routes of Entry

• Routes of entry of toxic substances
• Dermal (Skin)
• Most pelletized plastics do not affect dermal
• Isocyanates can cause rashes and blistering of
  skin
• Isocyantes can cause discoloring of skin.
• Hot plastic materials can cause skin burns
• Catalyst materials can cause skin abrasions
• Example
• Diethylene Triamine (catalyst) CAS 111-40-0
• ACGIH
• TLV STEL
• 1 ppm (skin) NE
• OSHA
• PEL STEL
• 1 ppm NE

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Section V Routes of Entry

• Routes of entry of toxic substances
• Eyes
• Injured by objects landing in the eye
• glass fibers, fillers, additives, colorants,
  particles of plastic
• liquids and gases can cause severe damage
• Example
• methylene- hardener for epoxy
• Causes irreversible blindness in cats and visual
  impairment in cattle.
• Carcinogenicity
• Pelletized plastics are often not regulated as
  carcinogenic
• Residual monomers have links to cancer (vinyl
  acetate, a residual monomer from PVA and EVA is
  present at 0.3) at levels of 600 ppm caused some
  cancer in some animals (bears A3 notation)
• Some liquid polymers and catalysts can cause
  cancer in some animals

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Section VI Reactivity Data

• Pelletized plastics are very stable and
  non-reactive
• Thermo-oxidative degradation can yield hazardous
  gases
• PVC at 100 ºC releases HCl
• PMMA at 100 ºC releases MMA
• POM at 230 ºC releases formaldehyde
• Teflon (other fluoroplastics) at 250 ºC release
  HF
• PET at 300 ºC releases acetaldehyde
• Nylons at 300 ºC nylons release CO and ammonia
• Nylon 6 at 340 ºC releases e-caprolactam
• Thermoset resin degrade to toxic fumes of CO,
  formaldehyde, isocynates (for urethanes)

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Section VI Reactivity Data_PVC and POM

• Thermal degradation of PVC
• PVC degradation is a serious problem
• Can decompose catastrophically if overheated in
  barrel.
• Remaining materials is tightly packed carbon
• Fumes contain high concentrations of HCl
• Response team must wear air respirator, turn off
  machine, tear down after cooling, remove nozzle
  and end cap.
• Thermal degradation of POM (poly actetal or
  polyoxymethylene)
• Thermally degrades (gt230 ºC )and releases
  formaldehyde
• Exposure can occur at purging of machine
• Local exhaust is essential to minimize exposure
• Thermal degradation of Phenolics
• Major uses in adhesive applications (plywood
  particleboard)
• Compression and transfer molding operations
• Can release small amounts of ammonia,
  formaldehyde, and phenol

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Section VI _Phenolics, Nylon 6, PMMS

• Thermal degradation of Phenolics
• Major uses in adhesive applications (plywood
  particleboard)
• Compression and transfer molding operations
• Can release small amounts of ammonia,
  formaldehyde, and phenol
• Phenol TLV of 5 ppm, LD-50 of 414mg/kg, and
  LC-50 of 821 ppm.
• Formaldehyde ceiling of 0.3 ppm
• Thermal degradation of Nylon 6
• Degrades into monomer_ e-caprolactam, and
  residual caprolactam
• Caprolactam vapor TLV is 5 ppm, LD-50 (rat) is
  2.14 mg/kg
• Molding operation release some caprolactam vapor,
  with more produced during purging and extrusions
• Thermal degradation of PMMA (acrylic)_ Plexiglass
• PMMA degrades into MMA (methyl methacrylate)
• TLV for MMA is 100 ppm (410 mg/m3)

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Section VII Spill or Leak Procedure

• Pelletized materials are swept up.
• Liquid chemicals use absorbent materials
• For isocyanates the absorbent materials need to
  allow reaction of the isocyanate with the water
  in the air. The reacted materials is then
  disposed of according to specified government
  regulations.

Section VIII Occupational Protective Measures

• Workplace protection
• Adequate ventilation
• Personal protective devices include
• safety glasses or goggles for eye and face
  protection
• gloves, long sleeves, face shields, ear plugs
• respirators

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Section IX Special Precautions

• Handling
• Storage

Section X Transportation

• Special instructions for transporting liquid
  chemicals
• Most pelletized plastics have no special
  restrictions