Petroleum derived plastics dominate the food packaging industry even today. These materials have brought a lot of convenience and attraction to agro, food and packaging industry. These materials also have brought along with them problems relating to the safe-disposal and renewability of these materials. Due to the growing concern over environmental problems of these materials, interest has shifted towards the development and promoting the use of "bio-plastics". Bio-plastic is a term used for sustainable packaging materials derived from renewable resources i.e. produced from agro/food sources, materials such as starch, cellulose, etc. and which are considered safe to be used in food applications. To enhance the mechanical properties, and water barrier properties, it can be blended easily with other polymer as well as nano fillers. The current paper is a review of the progress of research in starch based sustainable packaging materials.

Polyurethanes (PU) are a general class of polymers prepared by the polyaddition of isocyanates and hydroxyl group containing compounds. PU foams are formed via the reaction of poly-isocyanate and multi-functional hydroxyl compounds resulting in urethane linkages. The foams are formed in wide range of densities and maybe flexible, semi-flexible or rigid in structure. To control the foam structure, blowing agents are employed. These agents are introduced during foam formation through volatilization of low-boiling liquids or through the formation of gas due to chemical reaction. Additionally, surfactants, catalysts, etc. are used during the manufacturing of foams. PU, including PU foams, is one of the most important groups of materials today and hence, their recycling has been of great interest. Many methods of recycling PU are available and many more are being studied further. However, no method has seen large scale commercialization or is brought into regular practice. The objective of this review is to bring to light the various technologies available and their current status of development as well as newer upcoming methods that may be available in the future.

Increasing global energy crisis and scarcity of petroleum resources has shifted focus of chemical industries to look for alternative raw material resources. The main focus of raw materials in wood adhesives, such as petroleum and natural gas [1] [2], would be gradually replaced by renewable biopolymers. Starch is a relatively inexpensive and renewable product from abundant plants, easy processing and it has been extensively used as binders, sizing materials, glues and pastes [3], but its bonding capacity is not strong enough to glue wood [4]. Extensive research has been carried out on improving the cohesive properties, especially water resistance, of starch-based adhesives. In starch-based wood adhesive many new approaches have come forward for effective use it in wood/wood composite adhesive giving comparable performance as synthetic adhesives. This review of starch-based adhesives is made with the focus on starch modification methods for improving properties of starch-based adhesives.

The aim of this study is to analyze the various compositions of polyvinyl alcohol (PVA) and starch (S) blends. The blends have been cross-linked with glutaraldehyde to enhance its properties. The hydroxyl groups of PVA and starch react with glutaraldehyde via formation of acetal bonds hence crosslinking could take place. The cross-linking of glutaraldehyde is observed with the help of various analytical methods such as differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). The presence of two highly reactive alpha protons makes glutaraldehyde more reactive and acidic in nature. The higher reactivity of glutaraldehyde, at higher dosages leads to reduction in H-bonding of PVA and starch. The cross-linked blends showed better thermal and mechanical properties. Viscosity, tensile strength, pencil hardness, and ultimate stress were evaluated to estimate the changes due to cross-linking. It was observed that the mechanical properties are directly proportional to the amount of starch as the starch hydroxyl groups are easily accessible for the cross-linking reaction. The cross-linked blend showed better cohesion between its chains, thereby increasing the glass transition temperature. It was reflected in the subsequent increase in tensile strength properties.

Bio-based materials open a new world of possibilities in every field due to its independence from the petrochemical origin. Moreover, concerns on environmental footprints and toxicity of synthetic adhesives made scientists investigate the utilization of biomaterials for wood adhesives. In this perspective, nanocellulose as a sustainable and cheap bio-nanomaterial provides a better alternative to conventional adhesive based on formaldehyde-containing condensation resins. Property of nanocellulose to act as both binders and as structural reinforcement in various adhesive systems adds to its potential. Besides by reducing the harmful emission of formaldehyde, it also can improve the mechanical properties and enhance performance of adhesives. This review paper aims to point out the potential application of nanocellulose based wood adhesives compared to petroleum-based conventional systems beyond renewability. New functionalities through structural modification in nanocellulose could bring a replacement with the synthetic adhesive systems which will play a significant role in future bio-economy.