Fire Resistant Adhesive from Chitosan

Chitosan is one of the most abundant biopolymers on earth. It is used as a nontoxic alternative in a wide range of medicines, packaging, adhesives, and flame retardants. Chitosan is poorly soluble in neutral or alkaline solutions, but it dissolves in solutions of weak acids, such as acetic acid or citric acid, both of which occur naturally. As a replacement for formaldehyde-containing resins in engineered wood, a chitosan-acid mixture acts as a low-cost, nontoxic adhesive for natural wood that also offers fire protection by forming a char barrier. Pentaerythritol was studied as an additive due to its similarity to glycerol (a common plasticizer for chitosan) and its potential flame retardant benefit. The properties of chitosan adhesives produced with acetic acid and citric acid are compared, and moderate thermal treatment is applied to facilitate covalent bonding (e.g., Maillard reaction) that improves water resistance. Tensile shear strengths of >1 MPa are obtained on lap joints. The unique combination of fire protection and adhesion for wood makes these low cost, biobased systems very appealing.

Structure and properties of chitosan/sodium dodecyl sulfate composite films

In this study, we investigated the effect of sodium dodecyl sulfate (SDS) content on the structure and properties of chitosan films. It is found that the binding of SDS to chitosan was realized through the interactions between -SO4 - and -NH3 +, forming an ionically cross-linked film. Structural analysis revealed that the crystallization was greatly hindered by introducing SDS. With an increase of SDS content, the glass transition temperatures (T g) of chitosan films increased due to the formation of crosslinks. Compared to pure chitosan film, the composite films had lower content of moisture and possessed better thermal stability. In addition, the mechanical properties of the as-obtained composite films were closely related to the content of SDS, and were significantly improved in the biopolymer films with moderate SDS content. These results indicate that the microstructure as well as properties of the chitosan films can be regulated by adding SDS.

Microscopic Image Segmentation and Morphological Characterization of Novel Chitosan/Silica Nanoparticle/Nisin Films Using Antimicrobial Technique for Blueberry Preservation

In the current work, the characterization of novel chitosan/silica nanoparticle/nisin films with the addition of nisin as an antimicrobial technique for blueberry preservation during storage is investigated. Chitosan/Silica Nanoparticle/N (CH-SN-N) films presented a stable suspension as the surface loads (45.9 mV) and the distribution was considered broad (0.62). The result shows that the pH value was increased gradually with the addition of nisin to 4.12, while the turbidity was the highest at 0.39. The content of the insoluble matter and contact angle were the highest for the Chitosan/Silica Nanoparticle (CH-SN) film at 5.68%. The use of nano-materials in chitosan films decreased the material ductility, reduced the tensile strength and elongation-at-break of the membrane. The coated blueberries with Chitosan/Silica Nanoparticle/N films reported the lowest microbial contamination counts at 2.82 log CFU/g followed by Chitosan/Silica Nanoparticle at 3.73 and 3.58 log CFU/g for the aerobic bacteria, molds, and yeasts population, respectively. It was observed that (CH) film extracted 94 regions with an average size of 449.10, at the same time (CH-SN) film extracted 169 regions with an average size of 130.53. The (CH-SN-N) film presented the best result at 5.19%. It could be observed that the size of the total region of the fruit for the (CH) case was the smallest (1663 pixels), which implied that the fruit lost moisture content. As a conclusion, (CH-SN-N) film is recommended for blueberry preservation to prolong the shelf-life during storage.