For decades, the plastics industry and science have been working together to find new raw materials to replace petrochemical polymers made from non-renewable resources. Biodegradable bioplastics, made from renewable resources, reduce our dependence on petroleum, reduce waste, and offer products that are as efficient as traditional plastics.
The main difference between synthetic and natural polymers is that natural polymers contain oxygen and nitrogen. It is the oxygen and nitrogen in the polymer structure that allows it to break down. Biobased polymers are proving to be a viable alternative to these fossil-based feedstocks while offering environmental benefits such as reduced emissions of toxic substances.
Since many traditional plastics are inert to microorganisms, there is growing interest in developing biodegradable packaging from renewable natural resources. Target markets for biodegradable polymers include packaging materials such as trash bags, polystyrene, food containers, film packaging and laminated paper, hygiene products such as diapers and cotton swabs, consumer products such as kitchen utensils and fast food containers, egg cartons, toys, and agricultural implements such as mulch film and planters.
Cellulose, lignin, and starch are widely distributed in nature. Cellulose is found in abundance in all plants, but some plants produce more cellulose than others. Lignin is found in wood, while starch is abundant in plants such as corn, potatoes, and wheat. Plants, wood, corn, potatoes, and wheat are all renewable, biodegradable, and readily available raw materials. Biodegradable plastic packaging materials are more expensive than traditional petroleum-based plastics. Packaging made from these natural materials has the potential to solve problems such as environmental pollution from non-biodegradable synthetic polymers.
Biodegradability and compostability
Biodegradable materials are materials that can be degraded by microorganisms such as bacteria and fungi in water, natural gases such as carbon dioxide (CO2) and methane (CH4), and biomass. Biodegradability depends largely on environmental conditions such as temperature, presence of microorganisms, oxygen, and water.
Compostable materials are those that degrade under composting conditions. Industrial composting requires high temperatures (55°C – 60°C), high relative humidity, and the presence of oxygen, which are the most optimal conditions compared to other decomposition conditions such as soil, surface water, and seawater. It is considered a suitable indicator for industrial composting of packaging materials.
Bioplastics as packaging materials
Polylactic acid (PLA).
Polylactic acid (PLA), a 100% bioplastic, is currently used in packaging applications. PLA is ideally suited for the manufacture of compostable packaging products. The particular advantages of PLA as a packaging material are its transparency, gloss, rigidity, printability, processability, and excellent aroma barrier properties. PLA is approved for direct food contact and is used in a wide variety of packaging applications. PLA is often used in combination with other biobased or biodegradable polymers to increase stiffness and strength and reduce costs.
Cellophane film has high transparency and rigidity. And cellophane can be colored and is best known as a candy wrapper. Biodegradable films are available in different grades and can be used for packaging a wide variety of products such as cheese, coffee, and chocolate.
Cellulose can be significantly modified to become thermoplastic. For example, cellulose acetate. This material is very expensive and is rarely used for packaging. The most commonly used biodegradable polyesters are polybutylene adipate terephthalate (PBAT), polycaprolactone (PCL), and polybutylene succinate (PBS).
A flexible starch-based film blended with polyester to improve processing, water, and tear resistance.
Why is starch used as a packaging material?
Starch is used as a raw material for a wide range of environmentally friendly materials. 75% of the organic matter on earth is in the form of polysaccharides. The most important polysaccharide is starch. Plants synthesize starch and store it in their structures as an energy reserve. Starch is found in the seeds and tubers of plants. Most of the starch produced in the world is from corn. Visit also: Starch Bags Manufacturers Pakistan
Starch is usually extracted from plant raw materials by wet milling. Starch is composed of two types of anhydroglucose polymers: amylose and amylopectin. Amylose is a linear polymer composed of anhydroglucose units mainly linked together by α-D-(l, 4) glucoside linkages. Amylopectin is a branched polymer with periodic branches connected to the backbone by α-D-(l, 6) glucoside linkages. The amylose and amylopectin content of starch varies and is highly dependent on the starch source. And starch is found in abundance in plant materials such as corn, wheat, rice, potatoes, tapioca, and peas.
Starch: the future of sustainable packaging
Starch is mixed with a compostable polymer.
Starch-based plastics are a complex blend of starch and compostable plastics such as PLA, PBAT, PBS, PCL, and PHA. Blends of starch with plastics improve water resistance, processability, and mechanical properties. Starch-based trays are not transparent. Other packaging products Starch-based materials are often used in bulk fillers and foams for transport packaging. They are also used for serving utensils such as cups, plates, and cutlery.
Biodegradable films have been developed with a starch matrix reinforced with wheat or corn husks. The addition of rice husk has been shown to stretch the starch matrix and increase its modulus, tensile strength, and impact resistance. Water vapor permeability results show that corn starch reduces water vapor permeability more effectively than wheat husks.
Emulsions inoculated with starch for packaging
Graft polymerization is an important method for modifying the physical and chemical properties of polymers. Graft copolymerization of synthetic starch-based polymers is one of the best ways to improve the properties of starch. Starch grafted onto vinyl emulsions is also biodegradable and can be used as a sustainable packaging material.
By applying sustainable methods, we can minimize our impact on the environment and preserve resources for future generations. In the future, industrial advances in packaging technology will likely move toward new types of biomaterials. For this to happen, the culture of environmental protection and sustainability, which has grown stronger in recent years, must be continued. Some starch-based materials and other biopolymers are not yet competitive with petroleum-based plastics, but this will change if oil prices continue to rise.
Blending starch with other polymers to improve the properties of starch-based plastics, using starch in composite materials, and using starch as a biodegradable feedstock for other biopolymers have all been successfully developed as alternatives to petroleum-based plastics. As the market for environmentally friendly plastics encourages further innovation and development, the prospects for the use of starch in the packaging sector are becoming increasingly promising.