Biodegradable packing films using Guar Gum – Plastic alternative
Overview :- Petroleum based packaging materials are threat to environment due to their non-biodegradability and non-renewability. Biopolymers based films could provide suitable alternatives for these petroleum based products. BARC has developed biodegradable films using Guar gum a widely available biopolymer and various additives such as nanoclays, fynol, epoxy, beeswax, glycerol and tween-80. It is an intelligent technological advancement for the economical & environmental solution for the plastics packaging films. It has a comparable mechanical and barrier properties with commercially available stretch wrap films and no specific environment is required for degradation.
Matter :- Serious environmental hazards posed by conventional petroleum-based packaging materials have led to an increased interest in recent years towards development of biodegradable packaging materials. Suitable candidates for developing biodegradable films include natural polymers such as carbohydrates, proteins and lipids. Most promising among these are carbohydrates due to their excellent film forming properties. Guar gum (GG) is a water soluble galactomannan, which is extracted from the seeds of a legume plant Cyamopsis tetragolonoba. Chemically, guar gum has a backbone of β-D-1, 4-linked mannose residues, with side chains of α-D-galactose residue
s linked to O-6 of every second mannose residue. Wide availability and excellent film forming properties has led to the use of this biopolymer as a promising raw material for development of biodegradable packaging films.
Lower mechanical strength and high permeability to water vapor as compared to petrochemical-based plastics are some of the drawbacks, which limit commercial use of biopolymers. Several physical methods such as UV curing, thermal processing, gamma irradiation, and addition of various additives have been demonstrated to be useful for overcoming these limitations. We had earlier demonstrated that guar gum subjected to low dose gamma radiation (500 Gy) resulted in 33% improvement in tensile strength as compared to control gaur gum based films. This improvement was noted due to ordering in polymer chains as a result of low dose gamma radiation. GG nano-composites with natural refined bentonite clay (Nanofil-16) had 104% higher tensile strength and 24% lower water vapor transmission rate in comparison to control. In a recent study, concentration of various additives such as glycerol, beeswax, nanoclay and tween-80 was optimized using response surface methodology to improve mechanical and barrier properties of GG films. Enzymatic modification has also been used for improving mechanical properties of GG film.
Highly polar nature of carbohydrate based biopolymers including GG results in films with poor mechanical strength, barrier properties and sealability, thereby restricting their use as packaging material. Chemical modification of GG using various reagents for improving its hydrophobicity has been reported. Guar galactomannan chemically modified with benzamide resulted in formation of water resistant film. Partial methylation of guar gum has also been attempted for preparation of non-ionic derivative of guar gum. These derivatives have, however, not been investigated so far for their suitability for packaging applications.
Chemical modifications could possibly lead to changes in conformation of polymer in solutions and its thermal behavior. Several investigations have shown that the conformation and morphology of polymer chains affect the physical properties of the polymer. In the present study, the effect of methylation on thermal, mechanical and barrier properties of GG films were therefore taken up for detailed investigation.