Midterm study for plastics Flashcards
(23 cards)
Environmental
leave a planet (atmosphere, water, land)
that can sustain life
Economic
create long-term sustainable values by
optimal use, recovery and recycling
Social
actively support the capacity of current and future generations to create equitable, healthy and liveable communities
(e.g., what if we replicated the Western way of life across the globe?)
Sustainable development
development that meets the needs
of the present without compromising the ability of future generations to meet their own needs.
Operating point chosen depends on values
of society;
increasingly, consumers and
governments demand consideration of
human and environment impacts
What can shift the curve?
Technological innovations can shift curve
and present new optimal operating points
End-of-Life Options
o Remake high value products
o Downcycle
o Chemically recycle
o Compost
o Waste to energy – Incinerate
o Landfill
How can we decide if a polymer or product is “sustainable”
Need to consider many angles of its application and lifecycle
o Superior materials to reduce plastic used (e.g., thinner gauge films)
o Design for better structural performance
o Design for less complexity (e.g., less heterogeneity)
o Improve manufacturing to reduce scrap and waste
o Materials with less toxicity
o Processes with fewer byproducts
o Renewable feedstocks
o Lower embodied process energy
o Transparency for consumer
decision making
o Attention to unintended consequences
Characteristics of Polymers
- Lightweight (~7 times less dense than steel)
- Moldable into complex shapes
- Wide range of mechanical properties
- Can incorporate color, or can be transparent
- Electrical and thermal insulation
- Chemically resistant
- Cost effective
- “Recyclable”
Units
Common base units
o Mass [kg] [lb]
o Length [m], area [m 2], volume [m 3]
o Time [s]
o Temperature [oC] [oF]
o Force (massacceleration) [N = kg m 2s-2]
o Energy (forcedistance) [J=N m =kg m 3s-2]
o Power (energy/time) [W = J/s]
o Pressure (force/area) [Pa = N/m 2]
More units
Some relevant polymer physical properties
o Molecular weight [g/mol]
o Viscosity (resistance to flow) [Pa s]
o Stress [Pa]
o Strain (length change/original length) [ ]
o Modulus (stiffness) [Pa]
o Tensile strength [Pa]
o Density [g/cm 3 or kg/m 3]
What are Polymers?
o Poly = many Mers = units
o Molecular weight usually > 10,000 g/mol
o Covalently bonded atoms form long chains
o Backbone carbon- or silicon-based
o Oxygen, nitrogen, fluorine, chlorine also found in some
o Molecules interact with weaker forces (hydrogen bonding, Van der Waals interactions)
than ionic, covalent or metallic bonds
Branched polymers
- Ex: Low density polyethylene
- Properties (e.g. viscosity, density)
depend on branch density, branch length
Copolymers
more than one monomer type makes up the main chain
Network polymers
Ex: Vulcanized rubber
Amorphous polymers
no order, “spaghetti bowl” arrangement
- Properties arise from entanglements that cause chains to drag on each other
Crystalline polymers
regular packing of mers to form crystallites linked by regions of amorphous polymer. Need to have regular structure (i.e. isotactic or no pendant groups)
2 recycle HDPE
High density, HDPE
-Somewhat flexible
-Used for bottles, more
“crinkly” bags
4 recycle LDPE
Low density, LDPE
-Very flexible
-More transparent
-Used mostly in film
5 recycle PP
Polypropylene
o High strength and stiffness
o High crystallinity (order in the molecule)
6 recycle PS
o PS is stiffer than other thermoplastics
discussed so far: bulky benzene ring
causes steric hindrance
o Completely amorphous in most cases
o Good clarity, and high tensile strength
Polystyrene
3 recycle V
Poly(vinyl chloride)
o “Vinyl” is name given to PVC (though actually
any monomer with a double bond that reacts
during polymerization is a “vinyl” polymer)
o Extremely versatile, can be processed into many forms
o Almost always amorphous, though some crystallinity possible
o High density: 1.4 g/cm 3 (due to big Cl atom)
o Rigid, hard and low impact strength as pure polymer
o Cl atom causes strong permanent dipole, gives resistance to non-polar
solvents (oil, hexane, etc.)
o Processing temp varies significantly
depending on method and additives
1 recycle PETE
Polyester
o Poly(ethylene terephthalate) referred to as “polyester”,
though this is really a whole class of step-growth polymers
o Highly crystalline (given time & temperature to crystallize)
o Great water stability at use temps, poor water stability at
melting/processing temps (reverse polymerization)
o Good resistance to organic solvents but not to bases
o Good oxygen and water vapor barrier
o Great fiber former, drawn to increase crystal alignment and tensile strength
o Used in carpet, clothing, packaging, films, tapes
o Highly recyclable, including both mechanical and
chemical recycling
