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Microsoft PowerPoint - Laura Par

VIEWS: 11 PAGES: 38

									The New Generation of
    Green Plastics

 How New? How Green?


         Laura Park, DFO
     Newfoundland and Labrador
           Presentation Outline

Brief overview of conventional plastics
and associated environmental concerns.

Overview of major types of green plastics.

Comparison of green plastics and conventional
plastics in relation to major environmental
concerns.

Presentation of original data on conventional
and green plastics in relation to buoyancy and
degradation in sea water, acute toxicity of
leachate, MFO induction.
                         Conventional Plastics
    Polyethylene terephthalate (PETE)    Clear bottles for beverages, cooking oil, cleaners

    High density Polyethylene (HDPE)     Toys, plastic bags, food & beverage bottles and tubs

    Polyvinylchloride (PVC)              Pipes, well liners, IV bags, food & beverage bottles

    Low density Polyethylene (LDPE)      Shopping bags, trash bags, film packaging, bottles

    Polypropylene (PP)                   Tupperware, rope, food tubs & bottles

    Polystyrene (PS)                     Hard plastic, insulation, cutlery, clear trays, packaging

    Nylons                               Fabric, rope, netting

    Polymethyl methacrylate              Hard, clear plastic “Plexiglas”

    ABS plastic                          Pipes, car parts, toys, LEGO

O   Polytetrafluoroethylene “Teflon"     No stick pans, stain resistant coatings on carpet,
T                                        textiles, leather, Goretex, tents, dental floss
H
E
    Polyvinylacetate                     Films and coatings
R   Melamine-formaldehyde                Resins & laminates like Formica

    Silicone/Synthetic Rubber (various   Sealants, gaskets, toys, shoes, teething rings, nipples,
    types)                               snorkels, tires, gaskets, shoes
    Nalgene polycarbonate                Baby bottles, microwave cookware, syringes, test tubes,
                                         dental products, compact discs, water cooler bottles
    Urea-formaldehyde resins             Used in fiberglass and particle board

    Many others, and literally thousands of variations and polymer blends
  Conventional Plastics–Environmental Concerns:
                         Persistence
Conventional plastics don’t biodegrade, which means they
can’t be used as a food source by any living creature or
even softened by the digestion process.
All large food molecules must be broken down into small
molecules before animals can absorb them. This is
accomplished by specific enzymes which have evolved over
billions of years.
Plastic biodegradation is hampered by a number of factors:

• Plastics are giant molecules – chains (polymers) of millions
of small molecules (monomers).
• Specific plastic degrading enzymes have not evolved.

• Plastic polymers are incompatible with water.
• Most plastics will start to biodegrade to some extent once
the polymer chain length is reduced to ~5,000 units. If
degradation products are polar, degradability improves.
  Conventional Plastics–Environmental Concerns:
                           Persistence
Heat, UV radiation and mechanical stress can cause
degradation of the plastic polymer:
• Heat – melting/burning temperature varies with plastic type.

• Some plastics are more brittle than others – effects of
mechanical stress vary. Plastizers are common additives.

• Catalysts and other trace components of plastic absorb UV
radiation initiating oxidative degradation of the polymers – UV
stabilizers are common additives.

Over time, these processes lead to embrittlement,
fragmentation and eventual biodegradation of plastics, but
the process takes centuries.

As a result, persistent plastic is accumulating in our
landfills, oceans, soils and food chain. Persistence plastic
debris has major impacts on the marine ecosystem.
Conventional Plastics-Environmental Concerns:
                    Toxicity
  Conventional Plastics-Environmental Concerns:
                             Toxicity
     Burning plastic can release toxic chemicals:

       PVC        Dioxins & HCL (acid rain)
       Teflon releases toxic chemicals when heated.

     Toxic releases during plastic production.

     Small molecules can leach out of the plastic:
• Unreacted monomers – some (styrene, vinyl chloride) are toxic

• Production chemicals - may include solvents, catalysts,
lubricants, additives which speed setting time, etc.

• Additives – Can make up as much as 50% of the final product –
Not part of the polymer structure - loosely bound and can leach
out. Most of these additives are not well tested or regulated.
These include dyes, plasticizers, stabilizers, anti-static agents,
flame retardants, etc.
         Toxicity of Conventional Plastics
#         Plastic Type        Components of Concern
    Polyethylene            Acetaldehyde
    terephthalate (PETE)
    High density            BHT, Chimassorb 81, irganox
    Polyethylene (HDPE)     PS 800,1076, and 1010
    Polyvinylchloride       Lead, cadmium, mercury,
    (PVC)                   nonylphenol, Diethylhexyl
                            phthalate, Bisphenol A
    Low density             BHT, Chimassorb 81, irganox
    Polyethylene (LDPE)     PS 800,1076, and 1010
    Polypropylene (PP)      BHT, Chimassorb 81, irganox
                            PS 800,1076, and 1010
    Polystyrene (PS)        Styrene, Deca-BDE (related
                            to PCBs)
    Polycarbonate (Nalgene) Bisphenol A (BPA)
    Teflon pans, stain
    resistant coatings      Perfleurochemicals (PFCs)
Conventional Plastics - Environmental Concerns:
          Use of non-renewable fossil fuels
Conventional plastics are made from dwindling non-
renewable fossil fuels – mostly natural gas – 4% of world’s
oil production is used as raw material for plastics.

Plastics are the world’s most used material – an
estimated 350 billion pounds of new plastic is produced
annually, and this number is growing.

Only a small percentage of plastic is recycled and
most recycled products (plastic lumber, clothing) are
not recycled.

Impediments to recycling include Quality Control
issues, health risk (food packaging), very labour
intensive, thermoset plastics cannot be melted – grind
up as filler.
Major Concerns – Conventional plastics:

        Greenhouse gas emissions:


An estimated 4% of the world’s oil production is
used to produce plastic. This could be avoided by
using renewable energy sources.


 Conventional plastics act as a carbon sink, but so
 did the crude oil when we left it in the ground so
 there is no real net gain.
             What makes a plastic green?
Should degrade completely (to carbon dioxide,
methane, water, inorganic compounds) in a range of
natural environments (compost, soil, marine and fresh
water/sediments).
Should be non-toxic and leave no toxic or
persistent residues (i.e. metals, plastic particles).
Should disappear rapidly (3-6 months).

Should ideally be produced from a renewable resource.
Is natural source genetically modified? Is it competing with food
production?

To be a viable alternative, green plastics must:
• Possess and maintain appropriate performance
properties during anticipated life of the product.
• Be processed using existing technology/equipment.
• Be produced at a competitive price.
 Overview of major types of green plastics
    Biodegradable plastic from natural polymers

              Cellulose-based plastics:

Cellophane was the first biodegradable plastic –
initially produced in 1908.
Cellulose is also the basis for rayon, and celluloid.

The rapid growth of plastics from fossil fuels largely
replace cellulose-base products, although still used
for some applications – celluloid – table tennis balls.

As interest in biodegradable plastics increased in
recent years, difficulty processing cellulose-based
plastic using current technology has restricted
interest in this polymer.
 Overview of major types of green plastics
    Biodegradable plastic from natural polymers

              Starch-based plastics:

Thermoplastic starch-based polymers made of at least
90% starch from renewable resources such as corn,
potato, wheat or tapioca are now on the market.

By using specific plasticizing solvents, gelatinized
starch can be converted into a thermoplastic
material.

To improve some of the properties of the plastic, the
biopolymer may be modified, and blended with
additives such as plasticizers, but no synthetic
polymers are added.

 Examples: Novon, Eco-FOAM, Paragon
 • Fully biodegradable, renewable source, non-toxic.
  Overview of major types of green plastics
 Biodegradable plastic polymers produced by microbes:

Various types of bacteria synthesize polymers as an
energy storage molecule (similar to starch). Some of
these are useful for plastic production.


Polyhydroxybutyrate (PHB) is the most common - brittle,
has poor thermal stability, difficult to process. In 2000,
cost was 10x more than traditional plastic, largely due
to cost of the glucose. Cheaper feed stock options are
being explored including whey.

Polyhydroxyvalerate (PHV) - small amounts improve
properties of PHB
eg. Biopol (copolymer PHB/PHV with addition of a
softener (triacetine/estaflex) and titanium dioxide and
boron nitrate.
   Overview of major types of green plastics
 Biodegradable plastic polymers produced by microbes:


These products are not widely available – Still trying
to work the bugs out of the process.



E. coli bacteria have been genetically modified (GM)
produce PHB more efficiently.


Corn has been genetically modified to produce PHB in
their cells.
    Overview of major types of green plastics

       Biodegradable plastic from natural monomers:
       PLA – Polylactic Acid   eg.   Lacea, Lucty, Galactic

Lactic acid is produced by fermentation of sugar. A
solvent-free melt process is used to synthesize a lactic
acid polymer.
              • Fully degradable, but degrades poorly at
              less than 60C (ocean)
              • Non-toxic and can be recycled
Generally good performance characteristics:

•   PLA is naturally clear, and can be formulated to be
    rigid or flexible and formed using most conventional
    techniques and equipment (films, sheets, fibers, molds)
Production cost has been prohibitive, but with oil prices on
the rise, and recent innovations leading to reduced costs,
interest in this polymer has increased – Large plant
recently constructed in Nebraska (300 million lbs PLA/yr.)
Overview of major types of green plastics
  Biodegradable plastic synthesized from fossil fuels:

   Polycaprolactone (PCL)
   fully biodegradable, degrades in human body
   (used for sutures), non-toxic
   Compatible with starch and a range of other
   resins – used as a plasticizer for PVC

   A number of other related products from fossil
   fuels mostly produced in Japan/Korea.

   Polyvinyl alcohol and ethylene vinyl alcohol
      • Water soluble
      • Vinex, Elvanol (made in USA)
Overview of major types of green plastics
     Degradable plastics made from conventional
   polymers with additives which promote degradation:
  Typically polyethylene or polypropylene with a thermal
  and/or UV prodegradant additive “oxo-degradable”

 Once the material is discarded, oxidative degradation is
 initiated by heat, UV light or mechanical stress in
 presence of oxygen. Metals are frequently used to
 promote oxidation. Degradation products are more water
 soluble, which improves biodegradability.

  e.g. BIO-SOLO (used for compost collection in PEI)
  Recycled PE + additives. (cobalt)
  • degradation activated by heat and oxygen - Probably will
  not degrade in a cold ocean
Other examples include EcoSafe, BioMax, TDPA, PDQ,
Addiflex, DegradeTM, Totally Degradable PlasticTM and Entec.
Overview of major types of green plastics
       Blends of natural and/or synthetic polymers

  5-50% starch blended with synthetic polymers such
  as polyethylene, polypropylene or polystyrene.
  The starch portion degrades and the plastic
  disintegrates into small particles that will persist,
  but are not visible.
  e.g. Earthstrength, Polystarch, Entec and MEBI


  Thermoplastic starch blended with polyvinyl alcohol
  e.g. Plantic (Australia)
Overview of major types of green plastics
       Blends of natural and synthetic polymers

  Thermoplastic starch blended with biodegradable
  polymers from renewable or non-renewable sources

           NatureWorksTM - Starch/PLA
  Fully biodegradable, non-toxic, renewable source


   Mater-BiTM, BioFlexTM - Starch/PCL or PVA
   Fully biodegradable, non-toxic, renewable and non-
   renewable sources.

                          Capron
   Blend of Polyhydroxybutyrate (PHB) with Polycapro-
   lactone (PCL)
        Green plastics Vs traditional plastics
      Type      Source     Toxicity        Persistence
Traditional    Non-        Toxicity a 400-600 years or
               renewable   Concern    more – Some say
                                      never!
Starch-based   Renewable Non-toxic     Compost 4-8 weeks
                                       Ocean 20-30 weeks off
                                       Australia (temp dependent)

PLA            Renewable Non-toxic     Compost 2-6 weeks
                                       Ocean – unknown - degrades
                                       poorly at temp< 60C

PHB/V          Renewable Non-toxic     Compost 4 weeks
                                       Ocean- unknown but may be
                                       digestible

PCL            Non-        Non-toxic   Compost 2-6 weeks
                                       Ocean – 8 weeks
               renewable
Prodegradant Non-          Unknown     6 weeks to disintegrate in
                                       compost, 3-5 years in dry
additives    renewable                 landfill, biodegradation 5-10
                                       years. Ocean – unknown
Impacts of floating plastic debris in the ocean
  Floating plastic moves long distances on ocean
  currents causing serious environmental problems:

  Degradation of distant beaches, fouling of fishing gear

 Entanglement of sea creatures feeding in the
 pelagic environment (birds, sea turtles, baleen
 whale, fish)

  Mortality/morbidity resulting from ingestion

  Entanglement of ship propellers and other marine
  equipment.

  Clogging of water intakes, oil spill response
  equipment, etc
              Buoyancy of Traditional Plastics
# Type                                        Density   Buoyancy
                                              g/cm3

    Polyethylene terephthalate                1.370     Sinks
    (PETE)
    High density Polyethylene                 0.941     Floats
    (HDPE)
    Polyvinylchloride (PVC)                   1.380     Sinks
    Low density Polyethylene                  0.910-    Floats
    (LDPE)                                    .925
    Polypropylene (PP)                        0.85-     Floats
                                              0.95
    High Density Polystyrene                  1.050     Sinks, but may
    (PS)                                                remain in water
                                                        column
    Polystyrene foam                          0.0017    Floats
                                              and up    Extremely buoyant

Density of seawater varies from 1.020-1.029
PCL + starch      PCL + starch      PE Sobey’s   PE + UV        PE + starch   Distilled H2O
                                    bag          Prodegradant
Mater-bi BioBag   Mater-bi BioBag




                       Six months at room temperature

       Buoyancy and degradation of Green plastics
                     in seawater
BioSak (Mater-Bi) - two months at 0-4 C
     Mixed Function Oxidase (MFO) Induction:
     A general purpose detoxification enzyme system
     which inactivates a wide range of fat soluble toxic
     substances.
     MFO enzyme levels increase (induction) in
     response to exposure of the animal to a toxin –
     Used by researchers as an indicator of the toxicity
     of a substance. Chronic induction is associated
     with a range of pathology.

     In preliminary studies 1 week old cod larvae
     exposed to leachate from black PE garbage bags
     (10g/L) showed an increase in MFO:
                 17 pooled larvae /group    pmol/mg/min

                 Exposed                       4.35
                 Control                       0.07
Work conducted by Jacqueline Guiney, Anne Mathieu (Oceans Ltd.) & St. John’s ACAP
                                  Polystyrene test tubes

           PE + starch


                                       Control 2

       PE + UV Prodegradant




                                     PVC shower curtain
          Control 1




                                  Black Polyethylene garbage bag
   PCL + starch Mater-bi BioBag




100g plastic in 5 L seawater for 10 days at 4-8 C
                                    Specific Activity (pmol/mg/min)




                        0.0
                              0.1
                                       0.2
                                             0.3
                                                   0.4
                                                          0.5
                                                                0.6
                                                                      0.7




 Biodeg
          radable


Photod
         egrada
               b   le

     Contro
           l1


     Contro
           l2


          Biosac
                 k

   Polysty
          rene


  Polyeth
          ylene
                                                                            EROD in cod larvae exposed to various plastics
                   Conclusions

More research is needed on all plastics,
particularly in relation to their toxicity and fate
in the environment.
Conventional plastics are a serious
environmental concern and green plastics offer
a good alternative for many applications.

Green plastics are a rapidly evolving industry –
Wide range of products being marketed as
green. Need to evaluate based on more than the
company’s promotional material.

There is strong disagreement on whether
conventional plastics can ever completely
biodegrade, even in the presence of
prodegradant additives.
         Some useful References:

The Impacts of degradable plastic bags in
Australia (2003) Final report to Department of
Environment and Heritage, ExcelPlas Australia


Environment Australia, Biodegradable Plastics
Development and Environmental Impacts (2002)
ExcelPlas Australia

								
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