This is an editorial article. It has no abstract.
Biodegradable polymer films from seaweed polysaccharides: A review on cellulose as a reinforcement material
H. P. S. Abdul Khalil, Y. Y. Tye, C. K. Saurabh, C. P. Leh, T. K. Lai, E. W. N. Chong, M. R. Nurul Fazita, J. Mohd Hafiidz, A. Banerjee, M. I. Syakir
Vol. 11., No.4., Pages 244-265, 2017
Vol. 11., No.4., Pages 244-265, 2017
Seaweed and cellulose are promising natural polymers. This article reviews the basic information and recent developments of both seaweed and cellulose biopolymer materials as well as analyses the feasible formation of seaweed/cellulose composite films. Seaweed and cellulose both exhibit interesting film-forming properties. Nevertheless, seaweed has poor water vapour barrier and mechanical properties, whereas cellulose is neither meltable nor soluble in water or common organic solvents due to its highly crystalline structure. Therefore, modification of these hydrocolloids has been done to exploit their useful properties. Blending of biopolymers is a must recommended approach to improve the desired characteristics. From the review, seaweed is well compatible with cellulose, which possesses excellent mechanical strength and water resistance properties. Moreover, seaweed/cellulose composite films can prolong a product’s shelf life while maintaining its biodegradability. Additionally, the films show potential in contributing to the bioeconomy. In order to widen seaweed and cellulose in biocomposite application across various industries, some of the viewpoints are highlighted to be focused for future developments and applications.
Aromatic disulfide dynamic structures were incorporated as chain extenders in waterborne organic-inorganic polyurethane hybrids in order to provide autonomic healable characteristics. The synthesis was carried out following the acetone process methodology and the influence of the introduction of the healing agents in the polymer dispersion stability was analyzed. After the crosslinking process at room temperature, organic-inorganic hybrid films, which presented autonomic healing characteristics, were obtained. These features were evaluated by means of stress-strain tests and the films showed repetitive healing abilities. Thus, the optimum healing time at room temperature (25 °C) as well as the influence of different parameters in the healing efficiency, such the aromatic disulfide concentration or the physical properties of the polymer matrix were analyzed.
Measurements of the storage modulus, μ', vs. strain amplitude, u, for highly filled rubbers exhibit a pronounced decrease of μ' with increasing u. Unfilled rubbers do not show this so called Payne effect. Even though the effect is known since the 1940s, it continues to play a significant role in the research community focusing on rubber materials in general and automobile tires in particular. The key problem is the elucidation of the dependence of the Payne effect on the chemical composition of the rubber material. Based on a scaling approach we derive the functional form μ' (u,T) – μ'(∞,T) ∝ (1 – (D/d)u)–(σ –df + 1)g(T), where the parameters D/d and σ – df + 1 are directly related to the filler network structure. In addition, we explain the temperature dependence of the Payne effect, g(T), in terms of a distribution of activation energies corresponding to different types of filler-filler interactions. Finally, the model is extended to describe the attendant amplitude dependence of the loss modulus.
This paper reports the rapid synthesis of a dual-responsive copolymer through reversible addition–fragmentation chain transfer (RAFT) polymerization under microwave irradiation. Through use of 2-ethoxycarbonothioylthio acetic acid (ECTA) as a RAFT agent, the microwave-assisted polymerization rate of N-isopropylacrylamide (NIPAM) was approximately 150 times faster than that observed under conventional heating conditions, and the resulting homopolymer can be reactivated as a macroinitiator to produce poly(N-isopropylacrylamide-block-methacrylic acid) (PNIPAM-b-PMAA) block copolymers through a similar method. Research into the detailed polymerization kinetics of the PNIPAM and PNIPAM-b-PMAA revealed living characteristics that included a linear relationship between Mn and conversion, controlled molecular weights, and a relatively narrow molecular weight distribution. The solution of the block copolymers in phosphate-buffered saline buffer displayed a phase transition at a lower critical solution temperature transition of 42 °C, and altering the pH from 7 to 3.5 resulted in various degrees of polymer aggregation in the solution. Cisplatin was loaded to the polymeric carrier through a ligand exchange to form a macromolecular prodrug. The observed critical micelle concentration was 0.25 mg/mL. Overall, these polymers offer considerable potential for developing a new multifunctional drug delivery system.
Presented research shows the results of a study on mechanical properties of materials obtained in the course of innovatory application of epoxidized vegetable oil in the synthesis of new bio-based epoxy resins, crosslinked with curing agents which are not typical for epoxy materials. The product was obtained via modern and pro-ecological modification of a well-known synthesis method of epoxies, namely the epoxy fusion process, then it was crosslinked using polyisocyanates of different structure: toluene-2,4-diisocyanate (TDI), hexamethylene diisocyanate (HDI) and 4,4’-methylene diphenyl diisocyanate (MDI). The obtained epoxy-polyurethane materials are characterized by various mechanical properties, which depend on the type of chosen isocyanate. Compositions based on HDI exhibit better mechanical characteristics than elastic polyurethane materials based on hydroxylated soybean oil. Materials cured with aromatic isocyanates MDI and TDI are characterized by higher mechanical resistance comparable with cast polyurethane based on petrochemical resources. Epoxy fusion product cured with toluene-2,4-diisocyanate in a presence of Dabco T9 appears to have the best mechanical properties among all tested compositions.
This work investigated the sorption and the diffusion properties of CO2 under high pressure and the further modifications induced in Poly(lactic acid) (PLA) thin layers. Poly(ethylene terephtalate) (PET) was also considered for comparative purposes. Firstly, from thermodynamic equilibrium, the CO2 sorption isotherm (two sorption-desorption cycles, up to 25 bar, at 25 °C) gave strong evidence of a physisorption mechanism and of a hysteresis phenomenon. Infrared spectroscopy analysis confirmed that no chemical reaction occurred. Secondly, from the kinetics aspect, the CO2 diffusion coefficient was found around 10–13 m2•s–1 and was slightly faster for sorption compared to desorption. Additionally, when CO2 sorption occurred, the PLA structure and its functional properties were modified due to plasticization and swelling. CO2 plasticization reduced the glass transition temperature of PLA and accelerated the physical ageing of the polymer. These results are therefore of significant importance in industrial processing and applications which involve close contact between CO2 and PLA.
Acrylic polymers have high potential as matrix polymers for carbon fiber reinforced thermoplastic polymers (CFRTP) due to their superior mechanical properties and the fact that they can be fabricated at relatively low temperatures. We focused on improving the interfacial adhesion between carbon fibers (CFs) and acrylic polymers using several functional monomers for co-polymerization with methyl methacrylate (MMA). The copolymerized acrylic matrices showed good adhesion to the CF surfaces. In particular, an acrylic copolymer with acrylamide (AAm) showed high interfacial adhesive strength with CFs compared to pure PMMA, and a hydroxyethyl acrylamide (HEAA) copolymer containing both amide and hydroxyl groups showed high flexural strength of the CFRTP. A 3 mol% HEAA-copolymerized CFRTP achieved a flexural strength almost twice that of pure PMMA matrix CFRTP, and equivalent to that of an epoxy matrix CFRP.