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The Properties and Parameters of Experimental Bioplastics
Transcript of The Properties and Parameters of Experimental Bioplastics
are a long chain of molecules formed from monomers in a chemical reaction.
forces hold the monomers together whilst
forces hold the polymer chains together. These secondary bonds are heat dependent, and will break with energy input.
Unlike elements with defined temperature points (freezing, melting etc) plastics have a
fluid transition range
Plastics disintegrate (burn) before becoming gaseous.
are created from a range of different raw materials, the main renewable sources of biopolymers are proteins, polysaccharides and lipids.
are polymers of amino acids.
are polymers made of fatty acids and glycerol.
are made from chains of charbohydrates (monosaccharides) Starch, glycogen and cellulose are all polysaccarides made up of glucose.
A way of processing protein-based biomaterials is the mechanical method, which consists of mixing proteins and plasticizer to obtain a dough-like material
The testing procedures to categorize plastics are intense and expensive. This is one of the reasons innovative products do not appear in the wider market. There are hundreds of tests controlled by bodies such as,
which can be us to define the properties and therefore the identity of the new material. To understand the properties of basic commercial bioplastics I interpreted some of the ASTM's tests, trying to cover a wide range of properties.
Or Blended bio polymers
- Materials with long molecular chains (monomers) of natural or fossil raw materials, produced by chemical or biochemical reactions
4 types of plastic
: elastomers, thermosets, thermoplastics and thermoplastic elastomers.
which soften or melt when heated and harden when cooled. They have an uncross-linked structure.
Wide range of properties
and source materials, can be blended or additives can be used.
Lack of interest in innovation
All of the most popular commercial plastics were invented before 1940.
The Morphology of Macromolecules
can come from many sources animal, bacteria, and plant. Many proteins are inexpensive, wasted, and abundant raw materials. Animal protein can be found in gelatine, a product usually made from pig and bovine skin and bones - waste products from animal farming. Plant protein can be derived from waste too, certain seeds, stalks etc contain more protein than the equivalent weight of animal material
such as starch and
such as glycerol can also be used. Polysaccarides and monoscaccarides can be derived from bacteria, plants and animals so again, there is a lot of potential for
sustainable raw materials
Semi-crystalline plastics are harder and more heat resistant (although do expand more when heated). Their chains have some structured crystalline regions
Amorphous plastics can be dissolved and their chains are random.
The plastics are poured into a mold
and left to dry. Different
create plastics with different properties. This is because of how the molecular chains are organized, (un)crossed, and their length.
Water absorption, thermo-insulation, tensile strength and flexibility tests for
Gelatine based polymers absorbed the most water, was the best insulator and had the greatest tensile strength. These properties make sense considering its molecular structure: uncross-linked chains which are semi-crystalline.
Chemical Structure of plastics
In The Laboratory
Production of Plastic Components
The most important manufacturing methods for plastics are injection molding, extrusion, calendering (rolling), compression molding, foaming and casting.
Working methods such as thermal reforming, sawing and milling are also common post production.
Layered blended plastics using injection, compression casting, foamed unset plastic
For in-materio ballistic analogue... one can not change the laws of physics, so one changes the structure and dynamics of the substrate S. Stepney
How does temperature change effect the physical properties of thermoplastic biopolymers?
0. How does the plastic react to high temperatures?
1. What happens if the plastic is heated and re-set at various temperatures?
2. How does plastic change if set at different temperatures?
3. How does the plastic change if frozen and left to thaw at different temperatures?
Melting and freezing can be reversible processes
Heating and cooling are reversible processes
Extreme temperature swings cause scarring to the plastic
Setting in a cool environment produces unblemished plastics
The gelatine based bio polymer can be re-set after melting but has a very low glass transition temperature
Blended Biopolymer 1
vegetable oil and gelatine based polymer
protein and polysaccharides
High Glass transition temp (80-90)
Strong yet flexible sheet casting.
High water absorption.
High tensile strength.
Blended biopolymer 2
vegetable oil, starch and glycerine based bio polymer
protein and polysaccharides
rigid form, yet flexible.
Absorbs less water
High Compressive strength
preparing the specimens for testing, experiment 0, experiment 1 [gly], experiment 2. [oil], experiment 3. [gel]
There are certain difficulties associated with creating bio-plastics in my "Kitchen Laboratory":
Bioplastics are unfortunately prone to contamination with mold or bacteria. It is imperative that every item used in making the plastic is absolutely clean, that the raw materials have been kept clean and dry and glycerine solutions etc. can not be kept for long periods of time.
I personally have very little space to store sheets of bio plastics. Sheets of plastics are preferable for me as they take up less space, dry quicker and I can cast them in wipe clean baking trays to minimize contamination.
Contamination can also occur if layers of wet plastics are left to dry out together. The plastics need water to evaporate in order to set, if moisture becomes trapped in the casting process then contamination will occur.
If contamination takes place the damage is irreversible and the plastic will begin to break down immediately. The plastic may totally disintegrate in just a few days.
The larger the sheet of plastic, the longer the plastic takes to dry and the greater risk of contamination.
Ideally, laboratory conditions would be used to create the plastics or at least a chilled, clean environment.
(right) Plastics setting in the 'Laboratory'
Before casting into wipe-clean trays I used card formers and plastic trays - these were particularly prone to contamination.
The setting process can take up to 1-2 weeks depending on the formula and size of the plastic sheet.
Ideally the plastics would be set over a long period around 8 degrees centigrade.
Due to lack of storage and the size of wipe-clean baking trays; the majority of sheets I have been creating are 300x300x5mm.