Homogeneous and porous modified bacterial cellulose achieved by in situ modification with low amounts of carboxymethyl cellulose

Abstract In situ modification of bacterial cellulose allows structural and morphological tuning which determines the crucial properties such as water absorption/retention and rheological behaviour. This work reports the effect of in situ modification carried out by adding of two biopolymers - Agar and Chitosan - to the standard culture media for bacterial cellulose synthesis. The agar modified BC (Agar-BC) frames the Bacterial cellulose (BC) network as reduced pore volume, and a much denser network, leading to lesser water absorption and further lower retention time than BC. Agar-BC also demonstrates a higher storage modulus, while the yield point is observed at a lower shear strain. This indicates densely packed behaviour of crosslinked polymer with low strain onset of plasticity. On the other hand, chitosan modified BC (Chitosan-BC) also exhibits a lower pore volume with lower densly packed structure and with lower swellability and water retention reduced to 1 hour (7 hours for BC). Chitosan-BC presents a lower modulus with a yield strain similar to that of unmodified BC. The water absorption-retention behaviour is discussed in details on the basis of relative pore shape-size distribution, fibre dimension and surface area. The mechanism of viscoelatic deformation for each of the cases is explained using a schematic illustrations of the presumed fiber morphologies.

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In-situ Modification of Graphene Oxide by Insoluble Sulfur and Application for Nitrile Butadiene Rubber

International Polymer Processing ◽

10.3139/217.3910 ◽

2020 ◽

Vol 35 (2) ◽

pp. 221-228

Author(s):

S.-B. Chen ◽

T.-X. Li ◽

S.-H. Wan ◽

X. Huang ◽

S.-W. Cai ◽

...

Keyword(s):

Graphene Oxide ◽

Butadiene Rubber ◽

Nitrile Butadiene Rubber ◽

In Situ Modification

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Seawater Absorption and Adhesion Properties of Hydrophobic and Superhydrophobic Thermoset Epoxy Nanocomposite Coatings

Nanomaterials ◽

10.3390/nano11020272 ◽

2021 ◽

Vol 11 (2) ◽

pp. 272

Author(s):

Ayman M. Atta ◽

Mohamed H. El-Newehy ◽

Meera Moydeen Abdulhameed ◽

Mohamed H. Wahby ◽

Ahmed I. Hashem

Keyword(s):

Thermal Stability ◽

Oleic Acid ◽

Salt Spray ◽

Adhesion Properties ◽

In Situ Modification ◽

Long Time ◽

Seawater Environment ◽

Thermoset Epoxy ◽

The Cost

The enhancement of both thermal and mechanical properties of epoxy materials using nanomaterials becomes a target in coating of the steel to protect it from aggressive environmental conditions for a long time, with reducing the cost. In this respect, the adhesion properties of the epoxy with the steel surfaces, and its proper superhyrophobicity to repel the seawater humidity, can be optimized via addition of green nanoparticles (NPs). In-situ modification of silver (Ag) and calcium carbonate (CaCO3) NPs with oleic acid (OA) was carried out during the formation of Ag−OA and CaCO3−OA, respectively. The epoxide oleic acid (EOA) was also used as capping for Ca−O3 NPs by in-situ method and epoxidation of Ag−OA NPs, too. The morphology, thermal stability, and the diameters of NPs, as well as their dispersion in organic solvent, were investigated. The effects of the prepared NPs on the exothermic curing of the epoxy resins in the presence of polyamines, flexibility or rigidity of epoxy coatings, wettability, and coatings durability in aggressive seawater environment were studied. The obtained results confirmed that the proper superhyrophobicity, coating adhesion, and thermal stability of the epoxy were improved after exposure to salt spray fog for 2000 h at 36 °C.

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