Bioplastic can be categorized in numerous ways based, for example, on their sources, chemical compositions, synthesis techniques, and usage.
There below three things to understand Bioplastic:
- Bioplastic includes biodegradable and compostable plastic based on renewable (Bio-based) and non-renewable (fossil resource) as certified according to EN13432, ASTM D-6400, and ISO17088.
- Copolymers, combinations, or biocomposites can be produced from two or more of these materials. Many commercially known bioplastics are made to complete technical requirements and lower costs. Specific examples are starch-based bioplastics, where starch is compounded or mixed with other bioplastics.
- Materials from yearly renewable plant fibers, e.g., molded pulp, are usually comprised of bioplastics. Still, wood-fiber-based materials, such as paper and paperboard, are traditionally considered a separate group of materials and hence are omitted.
1. Bioplastic is directly extracted from biomass.
Polysaccharides or polyose are a class of carbohydrates polymerized in various forms
from monosaccharides. It exists inherently as starch and cellulose in plants and can be extracted in the form of starch granules or cellulosic fibers for industrial applications.
- Starch (Corn, Potato, and Wheat)
- Cellulose (Cellulose fiber, Cellulose derivatives, Lignocelluloses, and Fibre composites)
Starch is a readily available, renewable, low-cost natural polymer source, making it the best raw material for the production of bioplastics. The starch is found as granules in numerous plants, such as wheat, corn, rice, and potatoes, and is a carbohydrate polymer of D-glucose organized into two substantial constitutes:
a. amylose – a linear or sparsely branched polymer.
b. amylopectin – a highly multiple-branched polymer attached to amylose starch with a much higher molecular weight.
These molecules are readily digestible by microorganisms directing to outstanding biodegradability or compostability of bioplastics containing a significant amount of starch.
Cellulose is a linear homo-polymer of glucose and is the most abundant natural polymer on Earth. Direct utilization of cellulose in packaging can be placed in a few categories relying on the improvement of the cellulose ranging from micro-fibrils, the pulp (short fiber), textile fibers, or engineering fiber (long ultimate fiber or fiber bundles) to relatively unrefined lignocellulosic biomass, as in wood flour, straws, etc.
- Animal (Collagen Wool)
- Plant (Soy Gluten)
Proteins are natural chains of amino acids linked by amide and can be degraded by enzymes, e.g., proteases. Earlier discovered its usage for encapsulates, coatings, adhesives, and surfactants. From their origins, they can be separated into animal and plant proteins. The nutritious value of proteins is meant for producing edible food packaging.
The physicochemical properties can be modulated by plasticization, e.g., glycerol, or mixing with other polymers, e.g., PVOH.
Soy protein and oil can be used to make biodegradable high-stiffness thermoset polymers as a replacement for urea formaldehyde (UF) adhesive in the production of wood fiber boards.
2. Bioplastics are synthesized from bio-derived monomers
In this classification, polylactic acid (PLA) is one of the most commercially available and controlled bioplastics. In addition to Natureworks LLC, the largest PLA manufacturer, many others, such as the Purac and Sulzer partnership, are also producing PLA. In a more recent development, polyethylene, a non -biodegradable polymer, has also been made from bio-ethanol fermented from sugar.
3. Biodegradable polymers from petrochemicals
- Polyesters (Aliphatic & Aromatic)
- PVOH, EVOH
This set of materials, consisting of aliphatic polyesters, aromatic co-polyesters, and polyvinyl alcohols (PVOH), is specialty polymers synthesized from petrochemical monomers and have weak linkages and are vulnerable to enzymic attack leading to biodegradation of the polymer chains.
They are often combined with starch, cellulose, or copolymers to produce compostable packaging materials.
4. Polyesters directly produced from natural organisms
- PHA (PHB, PHV, PHH)
Some aliphatic polyesters can be synthesized by certain microbes and are produced commercially using bioengineering techniques to collect and extract the polymers. They are collectively remarked as polyhydroxyalkanoates.
(PHAs), has polyhydroxy butyrate (PHB), polyhydroxy valerate (PHV), polyhydroxyalkanoate (PHH), and its copolymers.
Most polymers are biocompatible and bioresorbable and hence have seen medical applications, e.g., implants.
Multiple grades of PHA exist with various degrees of crystallinity and can be processed with traditional melt flow technologies.