Natural Polymers Flashcards
Common natural polymers: (6)
cellulose, lignin, starch, chitin/chitosan, protein
Other less common natural polymers: (4)
alginic acid
hyaluronic acid
xanthum gum
curdlan
What does the traditonal viscose processing method of cellulose involve?
dissolve pulp with NaOH + CS2 -> used to spin fibre
major problem with procesesing cellulose:
difficult to process in solution or as a melt
cellulose is made of repeating ______ units
B 1,4 glucan
What are some new cellulose solvents? (4)
NMMO
DMAc
Ionic liquid
NaOH/urea aqueous solvent
Starch is made of what monomers?
a 1,4 glucan (and a-1,6 glucan)
the 2 forms of starch:
amylose (linear)
amylopectin (branched)
characteristics of starch: (2)
gelatinization
poor wet mechanical property
chitin is made of what units?
N-acetylglucosamine units connected by B-1,4 linkages
Good source of natural chitin:
arthropod exoskeletons
How is chitin converted to chitosan?
deacetylation (>55%) using NaOH
Good properties of chitin & chitosan:
antibacterial, antiinflammatory
How are amino acids polymerized into proteins?
condensation reactions -> form peptide bond
the general structure of an amino acid:
amino end, carboxyl end R group (variable)
What is a bioplastic?
biopolymer that can be shaped/molded via plastication or crosslinking
problems with conventional plastics (synthetic) that bioplastics aim to address: (4)
limited recycling
limited landfill space
toxins from incineration
fossil fuel consumption
some bioplastic examples (and their sources)
PLA (Polylactic acid) from corn PHA from bacteria soy/casein/corn protein Cereplast - starch based SoyOyl - veg oil based
How can bioplastics be combined with conventional plastics?
composite materials
Are all bioplastics biodegradeable?
No:
soy oil plastics, soy protein-formaldehyde, casein-formaldehyde are NOT biodegradeable
What is a material that is biodegradeable but not renewable?
PCL (polycaprolactone)
and other biodegradeable synthetics
biopolymers that are both renewable + biodegradeable:
PGA PLA soy protein plastics starch based plastics PHA
advatnages of biopolymers: (6)
renewable feedstock (raw materials) domestically grown CO2 neutral biodegradeable biocompatible energy-saving (lower process temp)
disadvantages of biopolymers: (4)
more $$$
low mechanical properties
lower functional temperatures
less durable in harsh environments
proteins are usually ____polymers
hetero
T/F: starch based polymers are more diverse than protein based
false: proteins have very large variety of polymer network structures -> large spectrum of chem functionalities
Common plant proteins (4)
common animal proteins (4)
corn zein
wheat gluten
soy protein
sunflower proteins
caseins
whey
gelatin/collagen
myofibrillar
Wheat gluten is majorly sourced from where?
starch industry (co-product)
advantages of gluten based materials:
good film formation high availability + low $ biodegradable/nontoxic adhesive properties high gas barrier + perm selectivity
How does energy usage and CO2 emissions for wheat gluten compare to LDPE?
over 5x less!
What happens to the barrier properties of wheat gluten if Aw is increased?
increases by thousands of times!
very poor barrier at high moisture
Increasing Aw will (increase/decrease) the gas permeation selectivity of wheat gluten
increase
better selectivity at high moisture
downside of wheat gluten materials (2)
poor water resistance
poor mechanical properties
Where is barley protein obtained from
byproduct of starch or beta glucan processing
How is barley protein made into a film?
barley protein + glycerol
hot pressing (>100C, 20MPa, 10 min)
forms barley protein film
How can properties of protein bioplastics be modulated? (3)
crosslinking
lamination
composites (mix with other materials)
What is a common crosslinking agent for protein bioplastics? What does it achieve, and what is a concern?
formaldehyde
improve mechanical and barrier properties
concern: toxicity
How is lamination used to enhance protein bioplastics?
apply onto another material (paper) as coating agent; paper acts as support
coating will provide functionality: give MAP/selectivity properties to paper, or controlled release of antimicrobial compounds, etc
What are some natural antimicrobial compounds that could be emitted by protein bioplastics?
carvacrol menthol cinnamaldehyde AITC Eugenol
How is SPI/cellulose nanocrystal composite made?
cotton pulp -> sulfuric acid -> cellulose nanocrystals
combine with SPI (soy protein isolate) + glycerol
hot pressing
cellulose/soy composite material
the molecular structure of natural polymers:
fibre (made of microfibrils connected by interfibrillar tie molecules)
made of crystalline regions + amorphous regions
What are natural polymer nanocrystals used for? (4)
reinforces mechanical properties
improves barrier properties
stabilizes food emulsions
swelling properties
polyurethane can be reinforced with _____ nanocrystals
starch (or starch + cellulose)
____ nanocrystals are used as a Pickering emulsion stabilizer
cellulose
biopolymer microspheres can be used as a:
edible delivery vehicle
What can be used to make edible delivery vehicle?
barley protein
alginate-whey
oat protein gels
Why are edible delivery vehicles useful? (2)
protect enzymes/probiotics/vitamins from harsh stomach condition
or controlled release of some active substances
How are micro/nanofibres produced?
electrospinning
polymer solution ejected through syringe/spinneret connected to high voltage - draws out long thin threads
Uses for electrospun micro/nanofibres: (2)
gas sensors for food safety
‘smart’ food preservation (atmosphere, pH, light, temp)
