Hydrophilic Filler Research Articles

Enhancement of Industrial Effluents Quality by Using Nanocomposite Mg/Al LDH Ultrafiltration Membranes

In this paper, Mg–Al-Acr LDH and Mg–Al-Amps LDH nanocomposites were synthesized via reacting of acrylic acid and 2-acrylamido2-methylpropansulfonic acid with Mg–Al LDH by chelation technique. The nanocomposite LDHs were applied as a hydrophilic fillers for modification of polysulfone (PSf) ultrafiltration membrane. The Mg–Al LDH/PSf, Mg–Al-Acr LDH/PSf and Mg–Al-Amps LDH/PSf membranes were fabricated using induced phase-blending method. The chelated LDHs and UF membranes were characterized using Atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analyses. In contrast to the neat PSf film, the Mg–Al-Acr LDH/PSf and Mg–Al-Amps LDH/PSf nanocomposite membranes exhibited higher pore size, porosity, hydrophilicity and lower surface roughness. The finger-like structures demonstrated for neat PSf membrane in cross-section SEM images were collapsed in Mg–Al-Acr LDH/PSf and Mg–Al-Amps LDH/PSf nanocomposite membranes. The synthesized PSf films were optimized in the presence of suitable content of hydrophilic LDHs (0.1 wt%). Not only the modified PSf membranes, when compared with the neat membrane, show a higher pure water flux of 300 and 390 l m−2 h for 0.1 wt% Mg–Al-Acr LDH/PSf and Mg–Al-Amps LDH/PSf membranes, respectively, but also the antifouling of the optimal nanocomposite films was enhanced. Moreover, the TOC of the wastewater decreased from 140.8 to 44 and 30.8 mg l−1, correspondingly. Finally, with a higher water permeation and humic acid rejection, those equipped films turned to be more attractive and excellent for effluent features enhancement.

Development and Characterization of Sustainable Composites from Bacterial Polyester Poly(3-Hydroxybutyrate-co-3-hydroxyhexanoate) and Almond Shell Flour by Reactive Extrusion with Oligomers of Lactic Acid.

Eco-efficient Wood Plastic Composites (WPCs) have been obtained using poly(hydroxybutyrate-co-hexanoate) (PHBH) as the polymer matrix, and almond shell flour (ASF), a by-product from the agro-food industry, as filler/reinforcement. These WPCs were prepared with different amounts of lignocellulosic fillers (wt %), namely 10, 20 and 30. The mechanical characterization of these WPCs showed an important increase in their stiffness with increasing the wt % ASF content. In addition, lower tensile strength and impact strength were obtained. The field emission scanning electron microscopy (FESEM) study revealed the lack of continuity and poor adhesion among the PHBH-ASF interface. Even with the only addition of 10 wt % ASF, these green composites become highly brittle. Nevertheless, for real applications, the WPC with 30 wt % ASF is the most attracting material since it contributes to lowering the overall cost of the WPC and can be manufactured by injection moulding, but its properties are really compromised due to the lack of compatibility between the hydrophobic PHBH matrix and the hydrophilic lignocellulosic filler. To minimize this phenomenon, 10 and 20 phr (weight parts of OLA-Oligomeric Lactic Acid per one hundred weight parts of PHBH) were added to PHBH/ASF (30 wt % ASF) composites. Differential scanning calorimetry (DSC) suggested poor plasticization effect of OLA on PHBH-ASF composites. Nevertheless, the most important property OLA can provide to PHBH/ASF composites is somewhat compatibilization since some mechanical ductile properties are improved with OLA addition. The study by thermomechanical analysis (TMA), confirmed the increase of the coefficient of linear thermal expansion (CLTE) with increasing OLA content. The dynamic mechanical characterization (DTMA), revealed higher storage modulus, E’, with increasing ASF. Moreover, DTMA results confirmed poor plasticization of OLA on PHBH-ASF (30 wt % ASF) composites, but interesting compatibilization effects.

Modulating water mobility in comminuted meat protein gels using model hydrophilic filler particles

Glass microspheres (3–6 μm and 30–50 μm diameter) and diamond particulates (1–3 μm, 3–7 μm, and 30–50 μm diameter) were employed as model hydrophilic fillers in comminuted poultry meat protein gels to evaluate the contribution of surface characteristics. The irregular surface morphology and more mild hydrophilic nature of the diamonds contrasted with the high sphericity and strong hydrophilicity of the glass microspheres. For comminuted meat protein gels prepared with both low and high protein content (9.5% and 10.2%), substantial liquid expulsion was observed in the absence of filler. The 3–6 μm glass fillers enhanced the large deformation and recovery properties of the low protein gels, while both protein levels displayed a significant reduction in thermally-induced liquid expulsion. The diamond particles had no significant impact on liquid retention or gel strength at either protein level; however, the smaller particulates decreased the recoverable energy of the high protein composite gels. Light microscopy and T2 relaxometry support the hypothesis that the 3–6 μm glass microspheres reduce water mobility by supporting water-filled capillary channels within the gel network. In contrast, the diamond particles are unable to immobilize the aqueous phase by this mechanism due to their weaker hydrophilic nature and irregular surface morphology.

Development of nanofiltration PES membranes incorporated with hydrophilic para hydroxybenzoate alumoxane filler for high flux and antifouling property

The PES nanofiltration membranes incorporated with hydrophilic para hydroxybenzoate alumoxane (PHBA) filler were prepared with enhanced pure water flux, dye removal, and antifouling property. The fabricated membranes were characterized in terms of average pore radius, porosity, surface roughness, water contact angle, active layer thickness, and zeta potential. The surface roughness of the nanofiltration membranes decreased and the surface hydrophilicity of the nanofiltration membranes increased with the increase of the PHBA content. According to nanofiltration experiments, the highest pure water flux of the PES membranes incorporated with PHBA reached up to 80.47 kg/m2h under operation pressure of 0.4 MPa, which was nearly 5.8 times as much as that of the neat PES membrane. The PES membranes incorporated with PHBA filler also exhibited excellent antifouling performance and dye removal capability. In the best PHBA content with the P-PHBA 0.3 % membrane, the highest rejection of 99.21 and 98.53% were achieved for DR 16 and MB, respectively. Furthermore, the P-PHBA membranes exhibited good long-term operational pH stability for DR 16 rejection. P-PHBA 0.3 % membrane also exhibited the highest flux recovery ratio (98.50%) and the lowest irreversible fouling ration (1.50%). Moreover, the dominant fouling mechanism was determined using Hermia–"s model. This superior antifouling behavior and relatively high dye rejection combined with remarkable stability show the potential of the organic-inorganic fillers embedded nanofiltration membranes in sustainable water treatment technology.

Enhanced Dielectric Permittivity of Optimized Surface Modified of Barium Titanate Nanocomposites.

High permittivity polymer-ceramic nanocomposite dielectric films take advantage of the ease of flexibility in processing of polymers and the functionality of electroactive ceramic fillers. Hence, films like these may be applied to embedded energy storage devices for printed circuit electrical boards. However, the incompatibility of the hydrophilic ceramic filler and hydrophobic epoxy limit the filler concentration and therefore, dielectric permittivity of these materials. Traditionally, surfactants and core-shell processing of ceramic fillers are used to achieve electrostatic and steric stabilization for adequate ceramic particle distribution but, questions regarding these processes still remain. The purpose of this work is to understand the role of surfactant concentration ceramic particle surface morphology, and composite dielectric permittivity and conductivity. A comprehensive study of barium titanate-based epoxy nanocomposites was performed. Ethanol and 3-glycidyloxypropyltrimethoxysilan surface treatments were performed, where the best reduction in particle agglomeration, highest value of permittivity and the lowest value of loss were observed. The results demonstrate that optimization of coupling agent may lead to superior permittivity values and diminished losses that are ~2–3 times that of composites with non-optimized and traditional surfactant treatments.

Adjusting cell structure of polypropylene composite foams by controlling the size and dispersed state of NaCl particles during CO2 batch foaming process

In this work, a novel method for regulating cellular structure of polypropylene (PP) foam under CO2 batch foaming with water as disperse medium was established by addition of hydrophilic fillers (Such as NaCl). The presence of NaCl increased adsorption amount of water in PP/NaCl composites. As a result, both CO2 and adsorbed water acts as blowing agents during CO2 batch foaming. Thus the dispersed state and size of NaCl particles directly affect the mixed state of two blowing agents (water and CO2) and the competition between two types of heterogeneous nucleation from NaCl particles and PP crystals during foaming, which are the fundamental reasons for the formation of the foamed materials with different cellular structures, such as isolated large cell surrounded by uniform small cell structure, bimodal cell structure and homogeneous cell structure. Another unexpected finding was that the water absorption of PP/NaCl composites increased with the decrease of NaCl particle size, which is beneficial to play the in-situ cooling effect and co-blowing agent of absorbed water to control the foaming behavior of PP, and avoid the damage of foam mechanical properties due to the high content of filler.

LIGHTWEIGHT ELASTOMER COMPOUNDS REINFORCED WITH CELLULOSE NANOFIBRILS AND A CARBON BLACK HYBRID FILLER SYSTEM

ABSTRACT Cellulose is found in the walls of plant cells, making it the most common biopolymer in the world. It is mechanically stable, resistant to hydrolysis, and boasts—especially in its nanoscopic state—a large reactive surface area and low density. To realize reinforcement in rubbers, the large and polar cellulose surface must interact with the nonpolar elastomer matrix. The dispersion of hydrophilic fillers is, however, still a major challenge in rubber technology. In this work, commercially available nanofibrillated cellulose (NFC) was incorporated into a nonpolar BIIR via latex mixing. Transmission electron microscopy, tensile testing, swelling, and rheometry were used to characterize the compound properties and the reinforcing potential of NFC. The compounds were compared with the established and highly dispersible standard carbon black N550 with a medium specific surface area. In addition, hybrid filler systems with both particle types were prepared. This yielded well-dispersed nanocomposites of a new kind exhibiting high stiffness, good tensile properties, and reduced material weight.

Influence of nanofillers on the properties of siloxane elastomers

In this study, the influence of nanosilicon(IV)-oxide (with hydrophobic and hydrophilic functionalized surfaces) on the properties of siloxane elastomers was studied. The elastomers were prepared from vinyl and hydrogen oligosiloxanes, while the nanocomposites were obtained by addition of nanofillers at different concentrations (1, 5, 10 and 20 wt%). The chemical structure of the obtained materials was analyzed by Fourier transform infrared spectroscopy. Transmission electron microscopy confirmed good dispersion of the hydrophobic filler within the polymer matrix, while the hydrophilic filler formed a net on the siloxane sample. Type of the filler modification did not affect hardness of the siloxane hybrid materials, while the samples with the highest content of hydrophobic nanosilica have shown the highest value of tensile strength. Influence of the nanosilica type on thermal degradation of elastomeric materials was investigated by using thermogravimetric analysis, while the influence of the fillers on the phase transition temperature was analyzed by differential scanning calorimetry. Lower compatibility of the hydrophobic matrix and hydrophilic filler caused a decrease in the crystalline melting temperature with the lowest value determined for the sample with the highest filler loading. Increase in the nanofiller content resulted in the improved thermal stability of the obtained hybrid materials.

Highly selective filler–polymer gaps in situ fabricated in mixed matrix membranes for gas separation

We report an interface self-assembly strategy to build high speed gas transport channels throughout mixed matrix membranes in situ using the gaps between hydrophilic polymers and hydrophobic fillers (normally considered as defects that lower the gas separation performance).

Investigation of Piezoelectricity and Resistivity of Surface Modified Barium Titanate Nanocomposites.

Polymer-ceramic nanocomposite piezoelectric and dielectric films are of interest because of their possible application to advanced embedded energy storage devices for printed wired electrical boards. The incompatibility of the two constituent materials; hydrophilic ceramic filler, and hydrophobic epoxy limit the filler concentration, and thus, their piezoelectric properties. This work aims to understand the role of surfactant concentration in establishing meaningful interfacial layers between the epoxy and ceramic filler particles by observing particle surface morphology, piezoelectric strain coefficients, and resistivity spectra. A comprehensive study of nanocomposites, comprising non-treated and surface treated barium titanate (BTO), embedded within an epoxy matrix, was performed. The surface treatments were performed with two types of coupling agents: Ethanol and 3-glycidyloxypropyltrimethoxysilan. The observations of particle agglomeration, piezoelectric strain coefficients, and resistivity were compared, where the most ideal properties were found for concentrations of 0.02 and 0.025. This work demonstrates that the interfacial core-shell processing layer concentration influences the macroscopic properties of nanocomposites, and the opportunities for tuning interfacial layers for desirable characteristics of specific applications.

Highly selective sodium alginate mixed-matrix membrane incorporating multi-layered MXene for ethanol dehydration

The single/double-layered MXene nanosheets with two-dimensional intergaps and good hydrophilicity have been known as promising porous fillers for preparing high-performance mixed matrix membranes for pervaporation dehydration. However, the single/double-layered MXene nanosheets must be exfoliated from multi-layered MXene (mMXene) through long-time ultrasonication and then be collected through high-speed centrifugation, which limits the facile and large-scale application of single/double-layered MXene nanosheets in membrane fabrication. In this study, mMXene particles with intergaps were directly obtained under mild conditions and then used to fabricate the sodium alginate (SA) mixed matrix membranes. The effects of mMXene content on membrane structure properties and pervaporation dehydration performance were studied. Compared with the pure SA membrane, the SA/mMXene mixed matrix membrane hydrophilicity increases but the degree of swelling decreases with increasing the mMXene content, and the mixed matrix membrane containing 0.12 wt% mMXene in SA shows the 10 times higher separation factor of 9946 and the 24.5% lower permeate flux of 505 g m−2 h−1 for dehydration of ethanol/water (90 wt%) solution. The hydrophilic mMXene fillers attribute to the enhancement in the preferential sorption of water and the constraint in the selective diffusion of ethanol, giving the significant improvement in membrane selectivity.

Poly(methyl methacrylate)-induced Microstructure and Hydrolysis Behavior Changes of Poly(L-lactic acid)/Carbon Nanotubes Composites

Poly(L-lactic acid) (PLLA)-based composites exhibit wide applications in many fields. However, most of hydrophilic fillers usually accelerate the hydrolytic degradation of PLLA, which is unfavorable for the prolonging of the service life of the articles. In this work, a small quantity of poly(methyl methacrylate) (PMMA) (2 wt%–10 wt%) was incorporated into the PLLA/carbon nanotubes (CNTs) composites. The effects of PMMA content on the dispersion of CNTs as well as the microstructure and hydrolytic degradation behaviors of the composites were systematically investigated. The results showed that PMMA promoted the dispersion of CNTs in the composites. Amorphous PLLA was obtained in all the composites. Largely enhanced hydrolytic degradation resistance was achieved by incorporating PMMA, especially at relatively high PMMA content. Incorporating 10 wt% PMMA led to a dramatic decrease in the hydrolytic degradation rate from 0.19 %/h of the PLLA/CNT composite sample to 0.059 %/h of the PLLA/PMMA-10/CNT composite sample. The microstructure evolution of the composites was also detected, and the results showed that no crystallization occurred in the PLLA matrix. Further results based on the interfacial tension calculation showed that the enhanced hydrolytic degradation resistance of the PLLA matrix was mainly attributed to the relatively strong interfacial affinity between PMMA and CNTs, which prevented the occurrence of hydrolytic degradation at the interface between PLLA and CNTs. This work provides an alternative method for tailoring the hydrolytic degradation ability of the PLLA-based composites.

The Influence of Mechanical and Mechanochemical Activation of Hardwood Wood Waste on Biocomposite Properties

As the demand for sustainable environment friendly materials increases, the biocomposites such as wood-polymer composite (WPC) have gained more attention in past years. Wood wastes and by-products like sawdust, chips, bark and wood residues as well as recycled polymers can serve as raw materials for production of WPC. However, there are still many issues obtaining WPCs, mainly a poor compatibility between a hydrophobic polymer matrix and a hydrophilic wood filler. In the present study, mechanical and mechanochemical activation of aspen wood waste were performed to increase their compatibility with recycled polypropylene matrix in the WPC, and the impact of both methods on the biocomposite properties were studied. It was found, that mechanochemical activation (MCA) of aspen wood particles leads to increased hydrophobicity of the obtained WPC compared to the WPC with mechanically activated (MA) particles. Work of adhesion with water was remarkably lower for the WPC modified by MCA which also correlates with moisture sorption results. Surface free energy of the WPC modified by MCA was lower compared to the WPC modified by MA, mostly due to decreased the polar component of surface free energy. The modulus of elasticity (MOE) were competitive for both the WPC formulations, however, MCA led to increased flexural strength of WPC compared to MA.

Modified Silica Incorporating into PDMS Polymeric Membranes for Bioethanol Selection

In this work, polydimethylsiloxane (PDMS) polymeric membranes were fabricated by incorporating fumed silica nanoparticles which were functionalized with two silane coupling agents—NH2(CH2)3Si(OC2H5)3(APTS) and NH2(CH2)2NH(CH2)3Si(OC2H5)3(TSED)—for selective removal of ethanol from aqueous solutions via pervaporation. It was demonstrated that large agglomerates were not observed indicating the uniform distribution of modified silica throughout the PDMS matrices. It is noted that the ethanol diffusivity and the water contact angles were both increased remarkably, being beneficial to the preferential permeation of ethanol through the membranes. The pervaporation results showed that the addition of the two types of modified silica nanoparticles dramatically enhanced both the permeability and selectivity of hybrid membranes. Compared to APTS, silica modified by TSED at the concentration of 4 wt. % resulted in the optimum pervaporation membranes with the maximum separation factor of 12.09 and the corresponding permeation flux of approximately 234.0 g·m−2·h−1in a binary aqueous mixture at 40°C containing 10 wt. % ethanol. The observation will benefit the choice of coupling agents to improve the compatibility between hydrophilic fillers and hydrophobic polymers in preparing mixed matrix membranes.

Glycopolymer Grafted Silica Gel as Chromatographic Packing Materials.

The modification of the surface of silica gel to prepare hydrophilic chromatographic fillers has recently become a research interest. Most researchers have grafted natural sugar-containing polymers onto chromatographic surfaces. The disadvantage of this approach is that the packing structure is singular and the application scope is limited. In this paper, we explore the innovative technique of grafting a sugar-containing polymer, 2-gluconamidoethyl methacrylamide (GAEMA), onto the surface of silica gel by atom transfer radical polymerization (ATRP). The SiO2-g-GAEMA with ATRP reaction time was characterized by Fourier infrared analysis, Thermogravimetric analysis (TGA), and elemental analysis. As the reaction time lengthened, the amount of GAEMA grafted on the surface of the silica gel gradually increased. The GAEMA is rich in amide bonds and hydroxyl groups and is a typical hydrophilic chromatography filler. Finally, SiO2-g-GAEMA (reaction time = 24 h) was chosen as the stationary phase of the chromatographic packing and evaluated with four polar compounds (uracil, cytosine, guanosine, and cytidine). Compared with unmodified silica gel, modified silica gel produces sharper peaks and better separation efficiency. This novel packing material may have a potential for application with highly isomerized sugar mixtures.

The Effect of Varying Almond Shell Flour (ASF) Loading in Composites with Poly(Butylene Succinate (PBS) Matrix Compatibilized with Maleinized Linseed Oil (MLO).

In this work poly(butylene succinate) (PBS) composites with varying loads of almond shell flour (ASF) in the 10–50 wt % were manufactured by extrusion and subsequent injection molding thus showing the feasibility of these combined manufacturing processes for composites up to 50 wt % ASF. A vegetable oil-derived compatibilizer, maleinized linseed oil (MLO), was used in PBS/ASF composites with a constant ASF to MLO (wt/wt) ratio of 10.0:1.5. Mechanical properties of PBS/ASF/MLO composites were obtained by standard tensile, hardness, and impact tests. The morphology of these composites was studied by field emission scanning electron microscopy—FESEM) and the main thermal properties were obtained by differential scanning calorimetry (DSC), dynamical mechanical-thermal analysis (DMTA), thermomechanical analysis (TMA), and thermogravimetry (TGA). As the ASF loading increased, a decrease in maximum tensile strength could be detected due to the presence of ASF filler and a plasticization effect provided by MLO which also provided a compatibilization effect due to the interaction of succinic anhydride polar groups contained in MLO with hydroxyl groups in both PBS (hydroxyl terminal groups) and ASF (hydroxyl groups in cellulose). FESEM study reveals a positive contribution of MLO to embed ASF particles into the PBS matrix, thus leading to balanced mechanical properties. Varying ASF loading on PBS composites represents an environmentally-friendly solution to broaden PBS uses at the industrial level while the use of MLO contributes to overcome or minimize the lack of interaction between the hydrophobic PBS matrix and the highly hydrophilic ASF filler.

Evaluation and Characterization of Sildenafil 50 mg Orodispersible Tablets Using Sublimation Technique

Objective: The aim of this work focused on formulation and evaluation of sildenafil 50 mg orodispersible tablets by sublimation technique. Methods: Active ingredient and excipients mixtures were evaluated for physicochemical changes of the drug utilizing FTIR spectroscopy and DSC thermal analysis. Nineteen proposed formulae N1-N19 were prepared by sublimation technique using menthol as a sublimating agent. Three different types of superdisintegrants (sodium starch glycolate, croscarmellose sodium and plasidone XL) were used in three different ratios (3, 6 and 9 % w/w), percentage of inter-granular and intragranular disintegrant. Hydrophilic filler such as mannitol and hydrophobic filler such as microcrystalline cellulose were used in the ratio (1:1, 2:1 and 4:1 w/w).Elimination of bitterness using sucralose as a potent sweetener. Granulation was achieved by alcoholic solution of PVP K25 as binder at Diosna® high shear mixer. Lubricant (hydrophobic magnesium stearate and hydrophilic sodium stearyl fumarate). Un-lubricated granules were characterized for bulk density, tapped density, true density, particle size distribution, Carr'sindex, Hausner ratio, flow rate and angle of repose. Tablets were firstly compressed on rotary machine then subjected to vacuum oven at 60ᵒC for 6 hours. Post compression characterization for tablets after sublimation including content uniformity, average weight, hardness, thickness, In-vitro disintegration, friability, wetting time, assay and dissolution profile of the proposed formulae against the immediate release marketed tablet Viagra ® 50 mg tablet. Results: The formula (N 16) which granulated using 1% PVP k25 with 9% plasidone XL (60% of it is inter-granular while 30% intra-granular), menthol 1%, Microcrystalline cellulose: Mannitol 1:1 and magnesium stearate was the most effective formulation as it showed wetting time of 30.7 seconds, disintegration time of 25 seconds and cumulative % drug release of 92.8 and 95.8 % after 1 and 3 minute respectively. Conclusion: Sildenafil 50 mg ODT successfully was prepared by sublimation technique with better wetting time, disintegration time, assay dissolution profile, hardness and friability.

In-situ cooling of adsorbed water to control cellular structure of polypropylene composite foam during CO2 batch foaming process

The fixation stage of cellular structure during polymer foaming process is difficult to control due to difficult removing of internal heat, especially for crystalline polymers such as polypropylene (PP). In order to control cellular structure in the fixation stage, we established an universal method by introducing water as an in-situ internal cooling agent during the foaming process of PP. Particularly, hydrophilic fillers were added into the high melt flow index polypropylene (HMI-PP) with poor foaming ability to study the effect of adsorbed water on the foaming process of PP/filler composites during sc-CO2 batch foaming process. Compared to pure HMI-PP, HMI-PP/hydrophilic filler composites showed increased adsorption amount for water and melt viscosity. The water within the composites played a key role in the foaming process, which not only served as a physical foaming agent to increase the volume expansion ratio of PP composite foam, but also showed the function of rapid cooling foam proved by thermal imaging technology. As a result, the presence of some hydrophilic fillers within HMI-PP matrix significantly improved the foaming properties of HMI-PP, including preventing internal bubble collapse and significantly increasing the volume expansion ratio of the foam. The applicability of this method was validated using other PP materials besides HMI-PP, including high molecular weight PP (HMW-PP), high melt strength PP (HMS-PP).

Effect of organic/inorganic nanoparticles on performance of polyurethane nanocomposites for potential wound dressing applications

This study focuses on the evaluation and modification of polyurethane (PU) membranes containing organic and inorganic nanoparticles for potential use as a wound dressing. For the purpose of PU nanocomposite preparation, chitosan (CS) was converted into nanoparticles by the ionic-gelation method to improve its blending capability with the PU matrix. These CS nanoparticles (nano-CS) were obtained as a hydrophilic organic filler with different contents and were utilized along with inorganic titanium dioxide (TiO2) nanoparticles in the nanocomposite membrane preparation. The membranes were prepared using phase inversion technique and their microstructure was controlled by manipulating the solvent non-solvent exchange rate. Obtained results demonstrate that addition of polymer solvent to nonsolvent induced a microstructure alteration from finger-like to sponge-like, which is more suitable for fluid uptake and consequently more useful for wound dressing applications. Similar results were obtained by introduction of nanoparticles to membranes. Due to the polar nature of nanoparticles and their effects on PU structure, prepared membranes showed 71.5% improve in swelling when compared to neat PU. Moreover, the reinforcement effect of nanoparticles caused an 18.94% increase in ultimate tensile strength in comparison with bare PU film, while elongation at break was not affected considerably. In addition, prepared PU nanocomposite films showed suitable antibacterial activity of 69% against Staphylococcus aureus and did not show any toxicity to human fibroblast cells. Based on these results, simultaneous use of TiO2 and chitosan nanoparticles can improve both physical and antibacterial properties of PU as an ideal wound dressing.

Effect of microencapsulated ammonium polyphosphate on the durability and fire resistance of waterborne intumescent fire-retardant coatings

Large-scale addition of hydrophilic solid filler (i.e., ammonium polyphosphate) into waterborne intumescent fire-retardant coatings can cause many problems such as poor compatibility, easy absorption of moisture, and poor durability. In this work, microencapsulated ammonium polyphosphate with melamine formaldehyde resin (MFAPP) was prepared and applied in intumescent fire-retardant coatings to solve the problems mentioned. Due to the hydrophobicity of melamine formaldehyde (MF) resin, MFAPP exhibited better water resistance, thermal stability, and compatibility with polymer matrix, which was confirmed by Fourier transform infrared spectra, scanning electron microscopy (SEM), particle size test, water solubility, water contact angle, and thermogravimetric analysis (TGA). The effect of the MFAPP on durability and fire resistance of the fire-retardant coatings test were investigated by the static immersion test, fire resistance test, TGA, and SEM. Even immersed in distilled water for 12 h, the coatings containing MFAPP did not show obvious damage, indicating microencapsulation improved the water resistance of coatings. Furthermore, the fire-resistant time and thermal stability of the waterborne intumescent fire-retardant coatings were also improved remarkably by utilizing the microencapsulation of ammonium polyphosphate.