March 2019 Abstracts

Polyanionic Bio-emulsifier: A Heteropolysaccharide Based Bio-composite for Leather Post Tanning Process

by Sharmila Selvaraju, Sathya Ramalingam and Jonnalagadda Raghava Rao

Biopolymer-based composites are attracting significant interest in leather processing due to their incremental substitution of petrochemical products as raw materials in the retanning stage. Several polymeric bio-composites were developed and studied as alternatives to synthetic tanning agents (syntans). Bio-composite was prepared by simultaneously dispersing cellulose (acting as syntan) and emulsifying soybean oil with a bio-emulsifier termed Emulsan (acting as fatliquor). The resultant dual propertied of fullness and softness is endowed as a leather supplement to reduce the negative impact on the environment. Hence polymeric bio-composites were prepared through ultrasonication by blending different amounts of cellulose with soybean oil with an optimised Emulsan ratio. In order to enhance the biocompatibility of this bio-composite, the Emulsan surfactant we chose was extracted from Acinetobacter calcoaceticus. The poly-anionic nature of Emulsan serves as a stable surfactant to emulsify soybean oil into cellulose in the composite preparation. The resultant composites were characterised for functionality and physical properties by FTIR, DSC, TGA, and DLS. The value of an example composite in leathers’ post tanning processes was evaluated by utilising it as a retanning agent. Leather treated with a bio-polymeric composite showed improved strength and physical properties versus control leathers.

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Polyacrylate Ester-based Policarboxilate (PCE) as a New Leather Retanning Agent

by Miquel Canudas, Nicola Menna, Antoni Torrelles, Joan De Pablo and Josep Maria Morera

Acrylic resins are extensively used as retanning products because of their affinity with chrome tanned leather. However, their anionicity changes the cationic leather surface becoming a problem for the subsequent uses of fatliquoring and dyeing agents. As a result of changing charges, a leather with lower color intensity and poorer structural properties is obtained.

This paper presents an initial study which analyses the use of polyacrylates esters based polycarboxylates (PCE) superplasticizers as a new retaining agent compared to traditional wet end acrylic resins. Properties of PCEs in leather were compared to acrylic resins. For the applying assays, PCEs with different molecular weight were synthetized and characterized using a gel permeation chromatography (GPC). Experimental results indicate that PCEs improve leather properties avoiding the dyeing and fatliquoring problems of the acrylic resins.

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Study on the Microstructure of Crocodylus Niloticus Skins During Leather Making Process

by Qiang Tao-Tao and Han Mi-Mi

The variation on the microstructure of Crocodylus niloticus skins in the tanning process was observed and analyzed by using frozen section staining, which provide the reliable theoretical basis for Crocodylus niloticus leather production. The research on aldehyde fuchshin staining method showed that elastic fiber will receive a lot of damage in the bating and bleaching process. Through the observation of wet blue leather by scanning electron microscopy, the preparation work section and tanning process design are reasonable, also, inter-fibrillary substances had been well removed. The crosscut microstructure of Crocodylus niloticus hides before and after fatliquoring was observed by nile blue sulphate staining method, and the results showed that fatliquor could penetrate into the skin uniformly.

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Deciphering the Role of Individual Retanning Agents on Physical Properties of Leathers

by Murali Sathish, Bhuvana Subramanian, Jonnalagadda Raghava Rao and Nishter Nishad Fathima

In post-tanning different types of retanning agents are used in combination to improve the functional properties of leather and therefore understanding the individual effect of each retanning agents on final properties is difficult. This work mainly focuses toward quantifying the individual effect of different weight percentages (4, 8 and 16%) of phenol-formaldehyde resin (PFR), melamine-formaldehyde resin (MFR), acrylic resin (AR) and biopolymers (BP) on physical properties of leather. It was found that the strength characteristics are greatly affected when the retanning agents offer increased above 8% where the effect of phenol-formaldehyde resin is higher than other re-tanning agents. Melamine-formaldehyde resin and biopolymer is predominantly affecting the belly region. It has also been observed that the phenol-formaldehyde resin improves the fullness whereas grain tightness and flatness are improved with increasing the percentages of melamine-formaldehyde resin offer. Biopolymer improves the grain smoothness and the ability of improving the roundness of leather is similar for all kind of retanning agents. A meaningful conclusion could not be drawn in the porosity results obtained due to the heterogeneous nature of leather matrix. Thus, a conventional triplicate method of measurement as done in this study would not suffice to provide a conclusive interpretation of results obtained using capillary flow porometry technique.

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