ALBERT

Description: Esterification was used to improve the thermal stability of nanocellulose to extend its application as reinforcing filler to polymer matrices with high melting point. The effect of the structure of ester groups on thermal stability was studied in detail. Various types of nanocellulose esters (straight-chain, C2–C14; cyclic adamantoyl, ADM; aromatic benzoyl, BNZ; and branched pivaloyl, PIV) with degree of substitution values in the range of 0.40–0.47 were prepared from bacterial cellulose nanofibers and nanocrystals. The reaction conditions used to prepare the esters maintained the viscosity-average degree of polymerization (DPv) and crystallinity of the starting materials. Thermogravimetric analysis showed that the temperature at maximum weight loss rate (T max ) increased after esterification. The structure of the ester groups and the DPv, however, showed no varying effect on T max . The 5 % weight loss temperature (WLT) which was used to assess the thermal stability at the onset of thermal degradation varied with the type of ester. Lower 5 % WLT was observed in straight-chain esters than those of the bulky esters of ADM, BNZ and PIV; which also showed high resistance to weight loss when subjected to isothermal heating. To understand the event at the onset of thermal degradation, low temperature pyrolysis was conducted. The evolved gases were separated and identified by gas chromatography–mass spectrometry technique. Results showed that at the onset of thermal degradation, levoglucosan (LG) is produced from the untreated BC nanocrystals. After esterification, LG formation was inhibited. The removal of the ester groups or deprotection is the main event at the onset of thermal degradation of nanocellulose esters. From the structure of the pyrolysis products, the mechanism of thermal deprotection of nanocellulose esters is proposed for the first time.

Description: Sugar palm fiber (SPF) is one of the prospective fibers used to reinforce polymer composites. The aim of this study is to evaluate the physicochemical, thermal, and morphological properties of SPF after alkali and sea water treatments. The chemical constituents group and thermal stability of the SPF were determined using scanning electronic microscopy (SEM) along with energy dispersive X-ray spectroscopy and thermogravimetric analysis (TGA). Fourier transform infrared spectroscopy was carried out to detect the presence of functional groups in untreated and treated SPF. The SEM images after both treatments showed that the external surface of the fiber became clean as a result. However, the sea water treatment affected the fiber properties physically, while the alkali treatment affected it both physically and chemically by dissolving the hemicellulose in the fiber. The TGA results showed that untreated fiber is significantly more stable than treated fiber. In conclusion, the results show that the fiber surface treatment significantly affected the characterization of the fiber.

Description: Viscose fiber was oxidized with sodium periodate to prepare a reactive dialdehyde viscose fiber (DAVF) containing abundant aldehyde groups. A solid amine adsorbent (DAVF-PEI) with high amino density for CO 2 capture was then prepared by modifying DAVF with polyethylenimine (PEI). Response surface methodology (RSM) based on a three-level, three-factorial design was used to optimize the synthesis conditions of DAVF, in which multiple linear regression equations of aldehyde content and fiber mass loss degree were constructed. The well-designed DAVF was then employed as a support to graft with PEI via Schiff base reaction to prepare a solid amine fiber (DAVF-PEI) for CO 2 adsorption. The experimental results verified that DAVF-PEI possessed good thermo-stability and high CO 2 adsorption capacity (4.11 mmol/g). DAVF-PEI also showed promising regeneration performance, which could maintain almost the same adsorption capacity for CO 2 after ten adsorption and desorption recycles.

Description: Encapsulation of various materials on textiles is an interesting task because of the controlled release and higher stability. Here, a robust cotton fabric was prepared through novel simultaneous treatment and nano-encapsulation of Chamomile extract using Tragacanth gum (TG) as the wall material and an environmentally friendly binder with hydrogel properties. The nano-encapsulated and treated cotton (NE&TC) fabric was characterized by FESEM, FT-IR and UV-Vis spectrophotometry, which indicated the successful encapsulation of the plant extract within the TG and material and linkage on the cotton fabric. The peaks at 1736 and 1777 cm −1 related to the TG and Chamomile extract in the FT-IR spectrum and a strong peak around 270–400 nm in the UV-Vis spectrum of the NE&TC fabric confirmed the nano-encapsulation and treatment. The prepared NE&TC fabric indicated a relatively good washing and rubbing durability with reasonable release behavior. The DSC pattern of the NE&TC fabric showed a peak at 162 °C confirming the presence of  Chamomile extract in the nanocapsules. This article proposes a novel method for the application of TG as a natural polymer on cotton fabric for obtaining multifunction purposes including in-situ synthesis of encapsulated Chamomile extract, stabilization of nanocapsules and introduction of hydrogel properties.

Description: Recyclable and transparent nanocomposite films based on bacterial cellulose (BC) and hemiaminal dynamic covalent network polymer (HDCN) have been synthesized by in situ polymerization of 4,4′-diaminodiphenyl ether (ODA) with paraformaldehyde. Transparency and structural and mechanical properties of such nanocomposite films are investigated. It was found that BC/HDCN nanocomposite films exhibits a high optical transparency (86 % at 550 nm). Scanning electron microscopy reveals excellent compatibility of the reinforcement of BC nanofibers and HDCN matrix, which leads to the improvement of 20 and 200 % in tensile strength and storage modulus, respectively, as compared to neat HDCN films. BC hydrogels are readily recoverable from nanocomposite films by the sulphuric acid treatment and ODA monomer is deposited and also recycled.

Description: This article describes a facile route, which combines mild maceration of waste pulp sludge and a mechanical shearing process, to prepare microfibrillated cellulose (MFC) with a high storage modulus. In the maceration, the mixture of glacial acetic acid and hydrogen peroxide was used to extract cellulose from never-dried waste pulp sludge. Then, two different mechanical processes including disc refining (DR) and ultrasonication plus homogenization (UH) were applied to the cellulose after maceration and resulted in MFC with a highly tangled fibril network. All of the resultant cellulosic suspensions (2 % w/w) exhibited a gel-like and shear-thinning behavior with storage moduli ( G ′) ranging from 200 to 4000 Pa. Among them, the 30-min DR-treated MFC gels had the maximum G ′, which was much higher than for previously reported MFC gels at the same concentration. Additionally, after mechanical processing, specific surface areas and water retention values of MFC were accordingly increased with the enhancement of shear force, while the storage moduli ( G ′) were not consistently increased. Finally, a strong MFC gel was successfully prepared from never-dried waste pulp sludge via a one-step disc refining process and using cost-effective chemicals. The obtained hydrogels will have potential as low-density reinforcing fillers or as a template for further surface modification.

Description: A kind of viscose fiber fabric with permanent flame retardancy has been prepared by grafting polymerization of phosphorus and nitrogen-containing monomer, i.e. 2,2-dimethyl-1,3-propanediol acrylamide methoxyl phosphate (DPAMP) onto viscose fiber fabric (VF-g-DPAMP). The effects of the initiator concentration, DPAMP concentration, temperature, pH and time on grafting polymerization were studied, and the structure of VF-g-DPAMP was determined with Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy. The surface morphology of viscose fiber fabric and VF-g-DPAMP were studied by scanning electron microscope. The thermal property and fire retardant performance of VF-g-DPAMP were assessed by thermogravimetric analysis, limited oxygen index measurements and cone calorimeter test, respectively. The results show that DPAMP has been successfully grafted onto viscose fiber fabric, and VF-g-DPAMP has good char-forming ability and better fire retardancy. The pkHRR and THR of the grafted fabric decrease from 150 to 98 kW/m 2 and 5.70 to 1.73 MJ/m 2 , respectively.

Description: Paper-based devices enable low-cost mass production, wide availability and useful technical aspects such as light weight, mechanical bendability and natural integration in existing paper-based creations such as educational books, administrative documentation and artwork. While magneto-electronics and spintronics play an important role in delivering sensing, communication and data storage solutions, especially necessary in the framework of the internet of things, it is beneficial to achieve compatibility between this technology and paper materials. As a first example of paper-based magneto-electronics, we investigate the manufacturing of well performing anisotropic magneto-resistors on paper by means of low power sputter deposition of permalloy \((\hbox {Py:Ni}_{81}\hbox {Fe}_{19})\) , shadow mask patterning and magnetic clamping of the shadow mask. A range of commercially available papers were studied by varying most significant mechanical, chemical and geometrical attributes of the paper to this application. The dependence of magnetic properties (coercivity, saturation remanence and relative permeability) on the paper properties (surface roughness, stiffness and paper making process) was studied based on magnetic characterization, surface profilometry and elemental analysis. Subsequently, conclusions on the optimal magnetic \(\hbox {Py:Ni}_{81}\hbox {Fe}_{19}\) -on-paper system were drawn.

Description: In this work, wheat bran was used as cellulosic filler in biocomposites based on natural rubber. The impact of wheat bran content [ranging from 10 to 50 parts per hundred rubber (phr)] on processing, structure, dynamic mechanical properties, thermal properties, physico-mechanical properties and morphology of resulting biocomposites was investigated. For better characterization of interfacial interactions between natural rubber and wheat bran, achieved results were compared with properties of biocomposites filled with commercially available cellulosic fillers—wood flour and microcellulose. It was observed that wheat bran, unlike commercial cellulosic fillers, contains high amount of proteins, which act like plasticizers having profitable impact on processing, physical, thermo-mechanical and morphological properties of biocomposites. This is due to better dispersion and distribution of wheat bran particles in natural rubber, which results in reduction of stiffness and porosity of the biocomposites. Regardless of cellulosic filler type, Wolff activity coefficient was positive for all studied biocomposites implying reinforcing effect of the applied fillers, while tensile strength and elongation at break decreased with increasing filler content. This phenomenon is related to restricted strain-induced crystallization of NR matrix due to limited mobility of polymer chains in the biocomposites. Furthermore, this explains negligible impact of particle size distribution, chemical composition and crystallinity degree of applied cellulosic filler on static mechanical properties of highly-filled NR biocomposites. The conducted investigations show that wheat bran presents interesting alternative for commercially available cellulosic fillers and could be successfully applied as a low-cost filler in polymer composites.

Description: Guar gum (GG) fracturing fluids were studied by incorporating cellulose nanofibrils (CNFs) in anhydrous borax crosslinked guar gum gels. To fully understand the impact of CNF on the proppant suspension capability of developed fracturing fluids, their shear rate-dependent viscosity and viscoelasticity were investigated. The shear rate dependencies of fluids was fitted to the Carreau model. The zero shear rate viscosity and elasticity of fracturing fluids increased significantly by incorporating CNF in guar gum gels. On the other hand, the viscosity at high shear rates (〉100 s −1 ) decreased as desired. The proppant settling velocities through fracturing fluids were evaluated by modeling the terminal falling velocity of proppants moving through a Carreau model fluid. The experimental results of the rheological behavior and the modeling results of the proppant settling rate indicated that the fracturing fluids containing CNF had better suspension capabilities. In addition, the lower viscosities of CNF formulated GG gels at higher shear rates will make them more pumpable.