“One‐pot” synthesis of crosslinked silicone‐containing macromolecular charring agent and its synergistic flame retardant poly(l‐lactic acid) with ammonium polyphosphate

A crosslinked silicone‐containing macromolecular charring agent (CSi‐MCA) was synthesized via “one‐pot” process, and it was combined with ammonium polyphosphate (APP) to synergistically improve the flame retardancy of poly(l ‐lactic acid) (PLA). The chemical structure of synthesized CSi‐MCA was characterized by Fourier transform infrared spectroscopy and solid‐state ¹³C nuclear magnetic resonance. The thermal gravimetric analyzer indicated that the CSi‐MCA displayed good thermal stability and high residue via the catalytic crosslinking. Furthermore, the flame retardant effect of CSi‐MCA and APP as intumescent flame retardants in PLA system was investigated by limited oxygen index, UL94, and cone calorimeter test. When the content of CSi‐MCA was 5 wt% and APP was 10 wt% (CSi‐MCA/APP = 1/2), the limited oxygen index value of composites was 33.6 and UL94 classed a V‐0 rating. The peak heat release rate and total heat release of PLA composites containing both APP and CSi‐MCA decreased significantly in comparison with those with APP or CSi‐MCA alone. The flame retardancy mechanism was investigated via analyzing residual chars by scanning electron microscopy and X‐ray photoelectron spectroscopy as well as the possible chemical reaction between APP and CSi‐MCA by thermal gravimetric analyzer and Fourier transform infrared spectroscopy. The results showed that the enhanced flame retardancy was attributed mainly to synergistic effect of CSi‐MCA and APP, which could form a compact, continuous, and protective layer during combustion. Copyright © 2017 John Wiley & Sons, Ltd.     

Flame‐retardant behavior of bi‐group molecule derived from phosphaphenanthrene and triazine groups on polylactic acid

The flame‐retardant polylactic acid (PLA) has been prepared via mixing the flame retardant TGIC‐DOPO derived from phosphaphenanthrene and triazine groups into matrix. The flame retardancy of TGIC‐DOPO/PLA composites was characterized using the limiting oxygen index (LOI), vertical burning test (UL94), and cone calorimeter test. Results reveal that the 10%TGIC‐DOPO/PLA composite obtained 26.1% of LOI and passed UL94 V‐0 rating. The flame‐retardant mechanism of PLA composites was characterized via thermogravimetric analysis (TGA), pyrolysis gas chromatography/mass spectroscopy, and TGA‐Fourier transform infrared. It discloses that TGIC‐DOPO promoted PLA decomposing and dripping early, and it also released the fragments with quenching and dilution effects. These actions of TGIC‐DOPO contribute to reducing the burning intensity and extinguishing the fire on droplets, thus imposing better flame retardancy to PLA. When TGIC‐DOPO was partly replaced by melamine cyanuric with dilution effect and hexa‐phenoxy‐cyclotriphosphazene with quenching effect in composites respectively, the results confirm that TGIC‐DOPO utilize well‐combination in dilution effect and quenching effect to flame retard PLA. Copyright © 2015 John Wiley & Sons, Ltd.     

Additive manufacturing of fire‐retardant ethylene‐vinyl acetate

Thermocompression (with also extrusion and injection molding) is a classical polymer shaping manufacturing, but it does not easily allow designing sophisticated shapes without using a complex mold, on the contrary to 3D printing (or polymer additive manufacturing), which is a very flexible technique. Among all 3D printing techniques, fused deposition modeling is of high potential for product manufacturing, with the capability to compete with conventional polymer processing techniques. This is a quite low cost 3D printing technique, but the range of filaments commercially available is limited. However, in some specific 3D printing processes, no filaments are necessary. Polymers pellets feed directly the printing nozzle allowing to investigate many polymeric matrices with no commercial limitation. This is of high interest for the design of flame‐retarded materials, but literature is scarce in that field. In this paper, a comparison between thermocompression and 3D printing processes was performed on both neat ethylene‐vinyl acetate (EVA) copolymer and EVA flame retarded with aluminum triHydroxyde (ATH) containing different loadings (30 or 65 wt%) and with expandable graphite (EG), ie, EVA/ATH (30 wt%), EVA/ATH (65 wt%), and EVA/EG (10 wt%), respectively. Morphological comparisons, using microscopic and electronic microprobe analyses, revealed that 3D printed plates have lower apparent density and higher porosity than thermocompressed plate. The fire‐retardant properties of thermocompressed and 3D printed plates were then evaluated using mass loss calorimeter test at 50 kW/m². Results highlight that 3D printing can be used to produce flame‐retardant systems. This work is a pioneer study exploring the feasibility of using polymer additive manufacturing technology for designing efficient flame‐retarded materials.     

A feasible strategy to constructing hybrid conductive networks in PLA‐based composites modified by CNT‐d‐RGO particles and PEG for mechanical and electrical properties

Carbon nanotubes (CNTs) and reduced graphene oxide (RGO) were successfully assembled by chemical reaction to obtain CNT‐d‐RGO particles. Then, a home‐made dynamic impregnating device was used to prepare hybrid CNT‐d‐RGO/polyethylene glycol (PEG). Next, the different modifiers, including CNTs, GO, CNT‐d‐RGO, PEG, and CNT‐d‐RGO/PEG, were, respectively, added into poly‐(lactic acid) (PLA) matrix via melt‐compounding. The dispersed morphology for these different modifiers within the PLA matrix was confirmed by SEM and TEM observations. Especially, compared with the identical weight ratio of CNT‐d‐RGO, the hybrid CNT‐d‐RGO/PEG within the PLA matrix exhibited an excellent exfoliated and interconnected networks morphology. Moreover, compared with pure PLA, not only the crystallinity of all PLA‐based composites notably improved, but half‐crystallization time was also shortened. Furthermore, despite the addition of different modifiers, the crystal form of PLA‐based composites remained unchanged. Noticeably, compared with those of pure PLA, the tensile stress, strain, and modulus of PLA composite added with CNT‐d‐RGO/PEG increased by 29.4%, 4.1%, and 56.1%, respectively, and the V‐notch impact strength slightly improved. In addition, compared with pure PLA, volume resistivity of the PLA composite added with 1 wt% CNT‐d‐RGO/PEG decreased by 93.1%, and its volume conductivity increased by five orders of magnitude.     

Effect of polyethylene glycol on the crystallization and impact properties of polylactide‐based blends

Polylactide (PLA) was plasticized by polyethylene glycols (PEGs) with five different molecular weights (M_w = 200–20,000 g/mol). The effects of content and molecular weight of PEG on the crystallization and impact properties of PLA were studied by wide‐angle X‐ray diffraction, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy, and V‐notched impact tests, respectively. The results revealed that PEG‐10,000 could significantly improve the crystallization capacity and impact toughness of PLA. When the PEG‐10,000 content ranged from 0 to 20 wt%, the increases in both V‐notched Izod and Charpy impact strengths of PLA/PEG‐10,000 blends were 206.10% and 137.25%, respectively. Meanwhile, the crystallinity of PLA/PEG‐10,000 blends increased from 3.95% to 43.42%. For 10 wt% PEG content, the crystallization and impact properties of PLA/PEG blends mainly depended upon PEG molecular weight. With increasing the M_w of PEG, the crystallinity and impact strength of PLA/PEG blends first decreased and then increased. The introduction of PEG reduced the intermolecular force and enhanced the mobility of PLA chains, thus improving the crystallization capacity and flexibility of PLA. Copyright © 2015 John Wiley & Sons, Ltd.     

Polylactide/poly(butylene adipate‐co‐terephthalate)/rare earth complexes as biodegradable light conversion agricultural films

Rare earth europium(III) complex with α‐thenoyltrifluoroacetone and triphenylphosphine oxide (Eu (TTA)₃(TPPO)₂, shortened as EuTT) was synthesized in this paper, then blended with polylactide (PLA) and poly(butylene adipate‐co‐terephthalate) (PBAT) to prepare the biodegradable agricultural films. Through the optical performance, mechanical properties, and other research, the results showed that the rare earth complex could convert the sun's ultraviolet light to red light when doped polymer. Moreover, the relative intensity ratio of ⁵D₀/⁷F₂ to ⁵D₀/⁷F₁ of PLA/PBAT/EuTT film could reach 3.79, which implied that the film had strong fluorescence intensity and high color purity. The highest tensile strength of the film could reach 36.7/25.2 MPa, and the elongation at break was 462.8/483.0% in the machine and in the transverse direction when the added amount of Eu (TTA)₃(TPPO)₂ was 0.1 wt%. The tensile strength of the film was 33.3/20.1 MPa, and the elongation at break could reach 535.8/413.6% when the added amount of Eu (TTA)₃(TPPO)₂ was increased up to 0.3 wt%. Gel permeation chromatography showed that the Eu (TTA)₃(TPPO)₂ could cause depolymerization of polylactide, resulting in a decrease in the molecular weight of PLA. Furthermore, the crystallization ability of PLA was also improved. In this paper, the biodegradable films exhibited excellent ultraviolet light conversion ability and mechanical properties.     

Synthesis of a novel polyphosphazene/triazine bi‐group flame retardant in situ doping nano zinc oxide and its application in poly (lactic acid) resin

A novel polyphosphazene/triazine bi‐group flame retardant in situ doping nano ZnO (A4‐d‐ZnO) was synthesized and applied in poly (lactic acid) (PLA). Fourier transform infrared (FTIR), solid state nuclear magnetic resonance (SSNMR), X‐ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), and energy dispersive spectrometer (EDS) were used to confirm the chemical structure of A4‐d‐ZnO. The thermal stability and the flame‐retardant properties of the PLA composites were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), limiting oxygen index (LOI), vertical burning test (UL‐94), and micro combustion calorimeter (MCC) test. The results of XPS showed that A4‐d‐ZnO has been synthesized, and the doping ratio of ZnO was 7.2% in flame‐retardant A4‐d‐ZnO. TGA results revealed that A4‐d‐ZnO had good char forming ability (40 wt% at 600°C). The results of LOI, vertical burning test, and MCC showed that PLA/5%A4‐d‐ZnO composite acquired a higher LOI value (24%), higher UL94 rating, and lower pk‐HRR (501 kW/m²) comparing with that of pure PLA. It indicated that a small amount of flame‐retardant A4‐d‐ZnO could achieve great flame‐retardant performance in PLA composites. The catalytic chain scission effect of A4‐d‐ZnO could make PLA composites drip with flame and go out during combustion, which was the reason for the good flame‐retardant property. Moreover, after the addition of A4‐d‐ZnO, the impaired mechanical properties of PLA composites are minimal enough.     

Structure and wettability relationship of coelectrospun poly (L‐lactic acid)/gelatin composite fibrous mats

Coelectrospun polylactide(PLA)/gelatin (GE) composite fibrous matrixes have been identified to exhibit much improved performances compared to the respective components; however, the reasons for their water contact angles decreasing to zero at proper PLA/GE ratios remain unclear. To get a deep understanding of the phenomenon, PLA and GE were coelectrospun with different PLA/GE ratios in this study. Although the resulting composite fibers were homogeneous in appearance, they were detected different microscopic structures by transmission electron mircroscope (TEM) and via morphological observations after selective removal of either PLA or GE component. Together with the results of degradation study in phosphate buffered solution, a kind of cocontinuous phase separation microstructure could be identified for the PLA(50 wt%)/GE(50 wt%) composite fibers, which also showed the water contact angle of 0°. This value was far lower than those of electrospun PLA (～123°) and GE (～42°) fibrous matrixes. The X‐ray photoelectron spectrometry (XPS) data revealed that the polar side groups of protein macromolecules have moved toward composite fiber surface with solvent evaporation during electrospinning, due to the hydrophobic interaction between PLA and GE. Then the excellent hydrophilicity of PLA(50 wt%)/GE(50 wt%) composite fibers could be suggested as the consequence of: (1) the cocontinuous phase separation structure could provide more interface and void for water molecules penetrating; and (2) the accumulation of polar groups on composite fiber surface significantly increased the surface wettability. Copyright © 2010 John Wiley & Sons, Ltd.     

Study of mechanical and tribological properties of nylon 66‐titanium dioxide microcomposite

Nylon 66 microcomposites with various weight percentage of titanium dioxide (TiO₂) were prepared by a twin screw extruder and investigated for mechanical and tribological properties. Mechanical properties of the composite such as tensile strength/modulus, flexural strength/modulus, impact, and compressive strength first showed an increase up to 6 wt% TiO₂ followed by a decrease at higher filler loading. The value of heat deflection temperature increased with the increase in wt% of TiO₂. Sliding wear tests were performed on pin‐on‐disk equipment under different loads, sliding velocity, and sliding distance combinations. It was found that micro‐TiO₂‐Nylon 66 composite exhibited reduced wear and coefficient of friction up to 6 wt% TiO₂. Micro‐TiO₂ at 2 wt% was most effective in improving the tribological properties of plain nylon 66. The worn surfaces were examined by scanning electron microscopy to understand the wear mechanism. The optimal combination from 2 wt% to 6 wt% micro‐TiO₂‐Nylon 66 can be used depending upon the application requiring improvement in tribological or mechanical properties, respectively.     

Fabrication and enhanced mechanical properties of porous PLA/PEG copolymer reinforced with bacterial cellulose nanofibers for soft tissue engineering applications

A new class of polylactic acid (PLA)/polyethylene glycol (PEG) copolymer reinforced with bacterial cellulose nanofibers (BC) was prepared using a solvent casting and particulate leaching methods. Four weight fractions of BC (1, 2.5, 5, and 10 wt%) were incorporated into copolymer via silane coupling agent. Mechanical properties were evaluated using response surface method (RSM) to optimize the impact of pore size, porosity, and BC contents. Compressive strength obtained for PLA/PEG-5 BC wt% was 9.8 MPa, which significantly dropped after developing a porous structure to 4.9 MPa. Nielson model was applied to investigate the BC stress concentration on the PLA/PEG. Likewise, krenche and Hapli-Tasi model were employed to investigate the BC nanofiber reinforcement and BC orientation into PLA/PEG chains. The optimal parameters of the experiment results found to be 5 wt% for BC, 230 μm for pore size, and 80% for porosity. Scanning electron microscopy (SEM) micrograph indicates that uniform pore size and regular pore shape were achieved after an addition of BC-5% into PLA/PEG. The weight loss of copolymer-BC with scaffolds enhanced to the double values, compared with PLA/PEG-BC % without scaffolds. Differential Scanning Calorimetric (DSC) results revealed that the BC nanofiber improved glass transition temperature (T_g) 57 °C, melting temperature (T_m) 171 °C, and crystallinity (χ %) 43% of PLA/PEG reinforced-BC-5%.     

Influence of phosphorus‐grafted expandable graphite on the flame‐retardant property of UHMWPE composite

In this paper, an efficient flame retardant, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) was covalently grafted onto the surface of expandable graphite (EG). The resultant DOPO‐grafted expandable graphite (EG‐g‐DOPO) was characterized by Fourier transform infrared spectroscopy, energy dispersive spectroscopy, and X‐ray photoelectron spectroscopy (XPS), respectively. The thermal stability of EG‐g‐DOPO was also evaluated by thermogravimetric analysis (TGA). Moreover, a series of flame‐retardant ultra‐high‐molecular‐weight polyethylene (UHMWPE) composites with various concentrations of EG‐g‐DOPO were prepared and evaluated. The results show that the UHMWPE composite with 20 wt% EG‐g‐DOPO possesses a satisfactory UL‐94 flame‐retardant grade (V‐0) and a high limiting oxygen index (30.6%). The residual char of the UHMWPE composite with higher EG‐g‐DOPO concentration shows more compact and integrated, providing an efficient barrier for heat release.     

Poly(lactic acid)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer/sepiolite nanocomposites: Investigation of thermo‐mechanical and morphological properties

In this study, sepiolite nanoclay is used as reinforcing agent for poly(lactic acid) (PLA)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer (SEBS‐g‐MA) 90/10 (w/w) blend. Effects of sepiolite on thermal behavior, morphology, and thermomechanical properties of PLA/SEBS‐g‐MA blend were investigated. Differential scanning calorimetry results showed 7% improvement in crystallinity at 0.5 wt% of sepiolite. The nanocomposite exhibited approximately 36% increase in the tensile modulus and 17% increase in toughness as compared with the blend matrix at 0.5 and 2.5 wt% of sepiolite respectively. Field emission scanning electron microscopy and transmission electron microscopy images exhibited sepiolite‐induced morphological changes and dispersion of sepiolite in both PLA and SEBS‐g‐MA phases. Dynamic mechanical analysis and wide angle X‐ray diffraction present evidences in support of the reinforcing nature of sepiolite and phase interaction between the filler and the matrix. This study confirms that sepiolite can improve tensile modulus and toughness of PLA/SEBS‐g‐MA blend.     

Effects of a semi‐bio‐based triazine derivative on intumescent flame‐retardant polypropylene

A semi‐bio‐based synergist (N, N′, N″‐1, 3, 5‐triazine‐2, 4, 6‐triyltris‐glycine [TTG]) was prepared by using glycine and cyanuric chloride. The structure of TTG was characterized by ¹H NMR and Fourier transform infrared spectroscopy. The TTG was applied in polypropylene (PP)/intumescent flame‐retardant compounds to improve its flame retardancy. The flame‐retardant properties of PP compounds were evaluated by limiting oxygen index and vertical burning tests (UL‐94). The results showed that 17 wt% intumescent flame‐retardant and 1 wt% TTG makes PP achieve the UL‐94 V‐0 rating without drippings, and the limiting oxygen index value is increased to 29.5 vol%. The thermal degradation behavior and char morphology of PP compounds were investigated by thermogravimetric analysis and scanning electron microscopy. The results indicated that TTG accelerates the formation of char layer, regulates the porous structure of char layer, and enhances its barrier property. Therefore, the temperatures of PP compound after two ignitions during the UL‐94 test are decreased significantly as shown in infrared thermal imaging. In addition, the combustion characteristics of PP compounds were investigated by cone calorimeter. The peak of heat release rate (PHRR) of PP compound is 67% reduced, and the t_PHRR is delayed from 223 to 430 seconds, indicates that the combustion risk of PP compound is reduced.     

Electrospun hyperbranched polylactic acid–modified cellulose nanocrystals/polylactic acid for shape memory membranes with high mechanical properties

The polylactic acid (PLA) nanofiber membranes reinforced with hyperbranched PLA‐modified cellulose nanocrystals (H‐PLA‐CNCs) were prepared by electrospinning. The H‐PLA‐CNCs and the nanofiber membranes were researched by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The outcomes embodied that the cellulose nanocrystals (CNCs) could be successfully improved by the hyperbranched PLA, which would offer powerful CNCs/matrix interfacial adhesion. Thus, the mechanical and shape memory properties of PLA can be improved by adding the H‐PLA‐CNCs. In particular, when the addition of H‐PLA‐CNCs was 7 wt%, the tensile strength and an ultimate strain of PLA composite nanofiber membranes was 15.56 MPa and 25%, which was 228% and 72.4% higher than that of neat PLA, respectively. In addition, the shape recovery rate of the PLA/5 wt% H‐PLA‐CNCs composite nanofiber membrane was 93%, which was 37% higher than that of neat PLA. We expected that this present study would provide unremitting efforts for the development of more effective approaches to prepare biology basic shape memory membranes with high mechanical properties.     

Flame retardant poly (lactic acid) biocomposites based on azo‐boron coupled 4,4′‐sulfonyldiphenol and its combination with calcium lignosulfonate—Crystalline and mechanical properties

Poly (lactic acid) (PLA) has become an important biopolymer with excellent properties but has limited engineering applications where fire safety is ultimate. An efficient flame retardant (FR) for PLA biocomposites based on azo‐boron coupled with 4,4′‐sulfonyldiphenol‐(((1E,1′E)‐(sulfonylbis(6‐hydroxy‐3,1‐phenylene))bis (diazene‐2,1‐diyl))bis(3,1‐phenylene))diboronic acid (SBDA) was synthesized and characterized by FTIR, ¹H and ¹³C NMR spectra. SBDA was combined with calcium lignosulfonate (Calig) and compounded with PLA, and the FR, crystallization, and mechanical properties were investigated. The addition of 15 wt% FR (10 wt% Calig and 5 wt% SBDA) into PLA led to important reductions in peak heat release rate (PHRR) approximately 54%, total heat release (THR) approximately 28.6%, and the average effective heat of combustion (AEHC) approximately 29.4%. The fire performance index and fire growth index improved by approximately 56.4% and 33.1%, respectively. A V‐0 rating (vertical burning test) and a limiting oxygen index value of 28.8% were achieved for the FR PLA biocomposites. The combinatory SBDA/Calig reduced the segmental mobility of PLA in the organic‐inorganic interface with insignificant changes in the elongation at break and the Young Modulus. TG‐IR study showed significant reductions in pyrolysis gaseous products for the composites compared with PLA. This research work will expand the frontiers of knowledge on use of boron and calcium functionalized polyaromatic polyols for reducing the flammability of PLA.     

S‐Nitrosoglutathione‐Based Nitric Oxide‐Releasing Nanofibers Exhibit Dual Antimicrobial and Antithrombotic Activity for Biomedical Applications

The novel use of nanofibers as a physical barrier between blood and medical devices has allowed for modifiable, innovative surface coatings on devices ordinarily plagued by thrombosis, delayed healing, and chronic infection. In this study, the nitric oxide (NO) donor S‐nitrosoglutathione (GSNO) is blended with the biodegradable polymers polyhydroxybutyrate (PHB) and polylactic acid (PLA) for the fabrication of hemocompatible, antibacterial nanofibers tailored for blood‐contacting applications. Stress/strain behavior of different concentrations of PHB and PLA is recorded to optimize the mechanical properties of the nanofibers. Nanofibers incorporated with different concentrations of GSNO (10, 15, 20 wt%) are evaluated based on their NO‐releasing kinetics. PLA/PHB + 20 wt% GSNO nanofibers display the greatest NO release over 72 h (0.4–1.5 × 10^?10 mol mg^?1 min^?1). NO‐releasing fibers successfully reduce viable adhered bacterial counts by ≈80% after 24 h of exposure to Staphylococcus aureus. NO‐releasing nanofibers exposed to porcine plasma reduce platelet adhesion by 64.6% compared to control nanofibers. The nanofibers are found noncytotoxic (>95% viability) toward NIH/3T3 mouse fibroblasts, and 4′,6‐diamidino‐2‐phenylindole and phalloidin staining shows that fibroblasts cultured on NO‐releasing fibers have improved cellular adhesion and functionality. Therefore, these novel NO‐releasing nanofibers provide a safe antimicrobial and hemocompatible coating for blood‐contacting medical devices.     

Performance enhancement of thin‐film composite membranes in water desalination process by wood sawdust

In this study, polysulfone/wood sawdust (PSf/WSD) mixed matrix membrane (MMM) was prepared as a novel substrate layer of thin‐film composite (TFC) membrane in water desalination. The main aim was to evaluate how different amounts of WSD (0‐5 wt%) and PSf concentrations (12‐16 wt%) in the porous substrate affect the properties of the final TFC membranes in the separation of organic and inorganic compounds. Morphological and wettability studies demonstrated that the addition of small amount of WSD (less than or equal to 1 wt%) in the casting solution resulted in more porous but similar hydrophobic substrates, while high loading (greater than or equal to 2 wt%) of WSD not only changed the substrate wettability and morphology but also increased and decreased the swelling and mechanical properties of substrate layer. Therefore, PA layer formed thereon displayed extensively varying film morphology, interfacial properties, and separation performance. Based on approximately stable permeate flux (ASPF) and apparent salt rejection efficiency (ASRE), the best TFC membrane was prepared over the substrate with 12 to 14 wt% of PSf and around 0.5 to 1 wt% of WSD. Although notable improvements in permeate flux were obtained by adding a small amount of sawdust, the results clearly indicate that the salt rejection mechanism of TFC membrane was different from the glycerin rejection mechanism. Furthermore, durability results of TFC membranes showed that in continuous operation for 30 days, TFC‐14/0.5 and TFC‐14/01 have the maximum plateau levels of stable permeate flux and salt rejection among the all TFC membranes.     

Preparation of carboxymethyl cellulose‐g‐poly (acrylamide)/montmorillonite superabsorbent composite as a slow‐release urea fertilizer

A superabsorbent composite was synthesized through free‐radical graft copolymerization of carboxymethyl cellulose, acrylamide, and montmorillonite by means of a crosslinker such as N,N′‐methylenebisacrylamide and potassium persulfate as an initiator. The preparation mechanism was proposed, and the composite structures were confirmed by using Fourier transform infrared spectroscopy, X‐ray diffraction, thermal gravimetric analysis, and scanning electron microscope. The factors influencing the swelling capacity of the composite were determined to accomplish the highly swelling capacity. The composition (15 wt% carboxymethyl cellulose, 5.4 wt% montmorillonite, 82 wt% acrylamide, 0.07 wt% N,N′‐methylenebisacrylamide, and 1.1 wt% potassium persulfate) exhibited high swelling capacity; it was selected to be loaded with urea fertilizer, and the release was investigated by measuring the conductivity. The results showed that the new controlled release system has good slow release properties.     

Antimicrobial,mechanical, barrier,and thermal properties of bio‐based poly (butylene adipate‐co‐terephthalate) (PBAT)/Ag2O nanocomposite films for packaging application

Bio‐based nanocomposites of poly (butylene adipate‐co‐terephthalate) (PBAT)/silver oxide (Ag₂O) were prepared by the composite film casting method using chloroform as the solvent. The prepared Ag₂O at different ratios (1, 3, 5, 7, and 10 wt%) is incorporated in the PBAT. The PBAT nanocomposite films were subjected to structural, thermal, mechanical, barrier, and antimicrobial properties. The electron micrographs indicated uniform distribution of Ag₂O in the PBAT matrix. However, the images indicated agglomeration of Ag₂O particles at 10 wt% loading. The thermal stability of the nanocomposite films increased with Ag₂O content. The tensile strength and elongation of the composite films were found to be higher than those of PBAT and increased with Ag₂O content up to 7 wt%. The PBAT‐based nanocomposite films showed the lower oxygen and water vapor permeability when compared to the PBAT film. Antimicrobial studies were performed against two food pathogenic bacteria, namely, Klebsiella pneumonia and Staphylococcus aureus.     

Morphology control of poly(lactic) acid/polypropylene blend composite by using silanized cellulose fibers extracted from coir fibers

The objective of this work is the use of cellulose fibers extracted from coir fibers as Janus nanocylinders to suppress the phase retraction and coalescence in poly(lactic) acid/polypropylene bio-blend polymers via prompting the selective localization of cellulose fibers at the interface using chemical modification. The untreated and modified cellulose fibers extracted from coir fibers using a silane molecule (tetraethoxysilane) were used as reinforcement and as Janus nanocylinder at two weight contents (2.5 wt% and 5 wt%) to manipulate the morphology of the bio-blends. Their bio-composites with PLA-PP matrix were prepared via melt compounding (at PLA/PP: 50/50). The treatment effect on component interaction and the bio-composites properties have been studied via Scanning electron microscopy, infrared spectroscopy, and differential calorimetry analysis. The mechanical and rheological properties of nanocomposites were similarly assessed. Young's modulus and tensile strength of PLA-PP nanocomposites reinforced by silanized cellulose fibers show a great enhancement as compared to a neat matrix. In particular, there was a gain of 18.5% in Young's modulus and 11.21% in tensile strength for silanized cellulose fiber-based bio-blend composites at 5 wt%. From the rheological point of view, it was found that the silanized cellulose fibers in PLA-PP at both fibers loading enhances the adhesion between both polymers leading to tuning their morphology from sea-island to the continuous structures with the appearance of PLA microfibrillar inside of bio-composites. This change was reflected in the relaxation of the chain mobility of the bio-blend composites.