Chapter 6B Flashcards
What are the key properties of an ideal degradable plastic?
ideal degradable plastic should have mechanical properties, undergo hydrolysis or oxidation, and eventually convert into biomass, CO₂, and water.
What happens during the first, second and third stage of degradation of a biodegradable plastic?
1st- The product remains strong and tough, able to withstand stresses.
2nd- Go through chemical and physical modification.
3rd- The bulk of the polymer is converted into biomass, CO₂, and water by environmental microflora.
What is the difference between polymer degradation and biodegradation?
Polymer degradation refers to changes in properties (e.g., tensile strength, color) due to environmental factors,
- while biodegradation refers to chemical processes that alter the molecular weight or solubility of the polymer.
What is bioerosion?
Bioerosion refers to physical processes that result in weight loss of a polymer device, and it can be either bulk erosion or surface erosion.
- Bulk erosion occurs when degradation takes place throughout the entire sample, and water ingress is faster than the rate of degradation (e.g., PLA).
- Surface erosion occurs when the sample is eroded from the surface, and mass loss is faster than water ingress (e.g., polyanhydrides).
What are the three main mechanisms of biodegradation?
Enzymatic degradation, hydrolysis, and a combination of both.
What is enzymatic degradation?
Enzymatic degradation is the breakdown of polymers with the help of enzymes, such as those from fungi, yeast, or moulds.
What is Type I, II, III erosion?
- Type I erosion occurs in water-soluble polymers cross-linked to form a 3D network, where solubilization happens by cleavage of the backbone or crosslinking.
- Type II erosion occurs when water-insoluble polymers are converted to water-soluble by reaction with pendant groups.
- Type III erosion occurs when high molecular weight polymers are broken down into smaller water-soluble molecules.
What factors affect the biodegradation of polymers?
Chemical structure (functional groups, hydrophobicity: hydrophilic degrade faster bcs water, enzyme),
- morphology (tensile strength and branching), and
- particle size. (Larger particle sizes result in slower degradation.)
What are the main steps in the production of bioplastics?
- Mixing raw materials, heating, and converted into homogenous substance.
- extrusion, at the end of extruder, molten T/plastic starch discharge through nozzle.
- Cooling
What technologies are used for processing bioplastics?
Extrusion, blowing, thermoforming, and injection molding.
What are the advantages and disadvantages of bioplastics?
Advantages:
Reduced CO₂ emissions, cheaper alternative, reduced waste generation, reduced carbon footprint, and multiple end-of-life options.
Disadvantage:
Not decomposable with other plastics, made from GM foods, use of agricultural land, and difficulty in recycling.
What are some applications of bioplastics in food packaging and automotive?
FP:
Bottles, edible coatings, wrapping films, and containers/trays.
Automotive:
Door panels, instrument panels, and seat upholstery made from natural fibers and biopolymers.
What are biocomposites?
Biocomposites are materials made from natural fibers (reinforcement) and biobased or synthetic polymer matrices.
What are the two main components of biocomposites?
Reinforcement (natural fibers)
- Hemp, jute, sisal, flax, and kenaf.
and matrices (biobased or synthetic polymers).
- PLA (Polylactic acid), PHBV (Polyhydroxybutyrate-co-valerate), and PBS (Polybutylene succinate).
Requierement for high quality biocomposites?
- Good mechanical properties
- Good fibber for matrix adhesion
- Low viscosity of polymer matrix.
What are the limitations of biocomposites?
Moisture absorption, limited mechanical performance, durability issues, and thermal sensitivity.
What is a major factor limiting the use of biopolymers and biofibers?
Thermal sensitivity and flammability.
What are some applications of biocomposites in the building industry and medical field ?
Building:
Particleboards made from sunflower stalks and urea-formaldehyde adhesives.
Medical:
used in medical devices and implants due to their biocompatibility and biodegradability.
What are some common manufacturing techniques for biocomposites?
Hand lay-up, filament winding, pultrusion, extrusion, press molding, injection molding, and compression molding.
How can the properties of biocomposites be enhanced?
By promoting adhesion through surface modification, coating, derivatization, and careful selection of polymer matrix and fillers.
What are some barriers to the uptake of biocomposites?
Technical commercial consumer bariers, poor adhesion, fiber variability, limited availability, and irregular fiber shape.
