The Effect of Silanized Halloysite Nanotubes on the Structure of Polyethylene-Based Composite.

Chemical modification of the surface of halloysite nanotubes (HNT) by alkalization (with sodium hydroxide (NaOH)) and grafting with silanes (bis(trimethylsilyl)amine (HMDS)) was carried out. The efficiency of the alkalization and grafting process was evaluated by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and the nitrogen adsorption method were used. XRD and FTIR analysis confirmed the formation of bonds of trimethylsilyl groups to the HNT surface which changed the nature of the surface from hydrophilic to hydrophobic. In addition, it was noted that grafting with silanes decreases by 7.2% the specific surface area of the halloysite compared to the alkalized material. High-density polyethylene (HDPE) composites with halloysite (HNT), alkalized halloysite (alk-HNT), and HMDS-modified halloysite (m-HNT) were processed in the molten state in a Brabender mixer chamber. On SEM/EDS micrographs of HDPE composites with silanized HNT, a change in surface characteristics from smooth to ductile was observed. Higher melting point values based on differential scanning calorimetry (DSC) analysis of HDPE composites with 5%wt silanized halloysite in comparison with HNT and alk-HNT of, respectively, 2.2% and 1.4% were found, which indicates a slight beneficial influence of the filler on the quality of ordering of the crystalline phase of the matrix.

Hydroxyapatite-lignin hybrid systems as improved poly(vinyl chloride) fillers: From preparation to application.

In this study, new, functional hydroxyapatite-lignin hybrid systems were designed and characterized. The efficacy of the mechanical method utilized to obtain these systems was confirmed by Fourier transform infrared spectroscopy. The hybrid materials were also noted for their good electrokinetic stability and thermal stability. The introduction of 2.5 to 10 wt% hydroxyapatite-lignin systems into an unplasticized PVC blend using a two-step kneading and pressing method resulted in composites with relatively homogeneous distribution, as confirmed by SEM observations. The processing properties of the filler-containing blends were investigated using plastographometric analysis and MFR tests. The introduction of a lignin-predominant hybrid system into the PVC matrix results in a significant improvement of thermal stability, softening temperature, and tensile strength, while maintaining sufficient impact strength for numerous applications. Hybrid materials containing higher amounts of added lignin are promising materials with bacteriostatic properties. This can be utilized to stabilize and prevent the deposition of microorganisms, as well as the formation of biofilms, on material surfaces, thereby limiting the spread of pathogens. New eco-composites based on PVC and a hybrid filler containing lignin show promise in producing components with surfaces resistant to bacterial colonization. Hence, these materials could be used in medical and hospital equipment.

Graphene Modification by Curcuminoids as an Effective Method to Improve the Dispersion and Stability of PVC/Graphene Nanocomposites.

A large amount of graphene-related research is its use as a filler for polymer composites, including thin nanocomposite films. However, its use is limited by the need for large-scale methods to obtain high-quality filler, as well as its poor dispersion in the polymer matrix. This work presents polymer thin-film composites based on poly(vinyl chloride) (PVC) and graphene, whose surfaces were modified by curcuminoids. TGA, UV-vis, Raman spectroscopy, XPS, TEM, and SEM methods have confirmed the effectiveness of the graphene modification due to π-π interactions. The dispersion of graphene in the PVC solution was investigated by the turbidimetric method. SEM, AFM, and Raman spectroscopy methods evaluated the thin-film composite's structure. The research showed significant improvements in terms of graphene's dispersion (in solutions and PVC composites) following the application of curcuminoids. The best results were obtained for materials modified with compounds obtained from the extraction of the rhizome of Curcuma longa L. Modification of the graphene's surface with these compounds also increased the thermal and chemical stability of PVC/graphene nanocomposites.

Preparation, Characterization and Tailoring Properties of Poly(Vinyl Chloride) Composites with the Addition of Functional Halloysite-Lignin Hybrid Materials.

In this article, halloysite-lignin hybrid materials (HL) were designed and obtained. The weak hydrogen bonds found between the components were determined based on Fourier transform infrared spectroscopy (FTIR), proving the achievement of class I hybrid systems. The HL systems were characterized by very good thermal stability and relatively good homogeneity, which increased as the proportion of the inorganic part increased. This was confirmed by analyzing scanning electron microscope (SEM) images and assessing particle size distributions and polydispersity indexes. Processing rigid poly(vinyl chloride) (PVC) with HL systems with a content of up to 10 wt% in a Brabender torque rheometer allowed us to obtain composites with a relatively homogeneous structure confirmed by SEM observations; simultaneously, a reduction in the fusion time was noted. An improvement in PVC thermal stability of approximately 40 °C for composites with HL with a ratio of 1:5 wt/wt was noted. Regardless of the concentration of the HL system, PVC composites exhibited inconsiderably higher Young's modulus, but the incorporation of 2.5 wt% of fillers increased Charpy impact strength by 5-8 kJ/m2 and doubled elongation at break. This study demonstrated that favorable mechanical properties of PVC composites can be achieved, especially with an HL system with a ratio of 5:1 wt/wt.

Curcuma longa L. Rhizome Extract as a Poly(vinyl chloride)/Graphene Nanocomposite Green Modifier.

In this work, a method to increase the dispersion of graphene (GN) in the matrix of rigid poly(vinyl chloride) (PVC) by using a natural plant extract from Curcuma longa L. (CE) is proposed. Currently, despite the increasing number of reports on the improvement of GN dispersion in PVC blends, still there is a need to find environmentally friendly and economical dispersion stabilizers. We proposed a stabilizer that can be easily obtained from a plant offering thermal stability and high effectiveness. PVC/GN nanocomposites stabilized with the proposed extract were investigated by SEM, AFM (structure), TGA, and Congo red test (thermal properties). Additionally, static and dynamic mechanical properties and electrical resistivity were measured. The use of CE as a graphene dispersant improved its dispersion in the PVC matrix, influenced tensile properties, increased the storage modulus and glass transition temperature, and extended the thermal stability time of nanocomposites. In this work, a CE extract is proposed as an efficient eco-friendly additive for the production of nanocomposites with an improved homogeneity of a nanofiller in the matrix and promising characteristics.

Review of Recent Developments of Glass Transition in PVC Nanocomposites.

This review addresses the impact of different nanoadditives on the glass transition temperature (Tg) of polyvinyl chloride (PVC), which is a widely used industrial polymer. The relatively high Tg limits its temperature-dependent applications. The objective of the review is to present the state-of-the-art knowledge on the influence of nanofillers of various origins and dimensions on the Tg of the PVC. The Tg variations induced by added nanofillers can be probed mostly by such experimental techniques as thermomechanical analysis (TMA), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and dielectric thermal analysis (DETA). The increase in Tg is commonly associated with the use of mineral and carbonaceous nanofillers. In this case, a rise in the concentration of nanoadditives leads to an increase in the Tg due to a restraint of the PVC macromolecular chain's mobility. The lowering of Tg may be attributed to the well-known plasticizing effect, which is a consequence of the incorporation of oligomeric silsesquioxanes to the polymeric matrix. It has been well established that the variation in the Tg value depends also on the chemical modification of nanofillers and their incorporation into the PVC matrix. This review may be an inspiration for further investigation of nanofillers' effect on the PVC glass transition temperature.

Plasticized Poly(vinyl chloride) Modified with Developed Fire Retardant System Based on Nanoclay and L-histidinium Dihydrogen Phosphate-Phosphoric Acid.

The current work assessed the burning behavior of plasticized poly(vinyl chloride) (PVC-P) modified with a two-component composition, consisting of L-histidinium dihydrogen phosphate-phosphoric acid (LHP) and nanoclay (n). The thermal and thermodynamical properties of the PVC-P containing from 10 to 30 wt% of the fire retardant system (FRS) were determined by thermogravimetric analysis (TG) as well as by dynamic mechanical thermal analysis (DMTA). In contrast, fire behavior and smoke emission were studied with a cone calorimeter (CC) and smoke density chamber. The research was complemented by a microstructure analysis, using a scanning electron microscope, of the materials before and after burning CC tests. The effects were compared to those achieved for PVC-P, PVC-P with a commercially available fire retardant, the substrate used for the produced LHP, and the mixture of LHP and zinc borate, both of which contained the same share of nanoclay. Based on a notable improvement, especially in smoke suppression suggests that the n/LHP system may be a candidate fire retardant for decreasing the flammability of PVC-P.

Composites of Poly(vinyl chloride) with Residual Hops after Supercritical Extraction in CO2.

The common applications of poly(vinyl chloride) (PVC) in many industries mean that the topic of recycling and disposal of post-consumer waste is still very important. One of the methods of reducing the negative impact of PVC waste on the natural environment is to use technological or post-consumer waste of this polymer to produce new composite materials with favorable utility properties, with the addition of natural fillers, among which agro-waste, including hop residue, is deserving of special attention. In this study, the effect of the addition of residual hops (H) on the mechanical and physicochemical properties of poly(vinyl chloride) was investigated. PVC blends containing 10, 20 and 30 wt % of hop residue were mixed in an extruder, while the specimens were obtained by the injection molding method. It was observed that the addition of H increased their thermostability, as shown by a Congo red test. Furthermore, thermogravimetric analysis showed that the degradation rate of PVC/H composites in the first and second stages of decomposition was lower in comparison with unmodified PVC. In turn, composite density, impact strength and tensile strength decreased significantly with an increasing concentration of filler in the PVC matrix. At the same time, their Young's modulus, flexural modulus and Rockwell hardness increased. Flame resistance tests showed that with an increasing residual hop content, the limiting oxygen index (LOI) decreased by 9.0; 11.8 and 13.6%, respectively, compared to unfilled PVC (LOI = 37.4%). In addition, the maximum heat release rate (pHRR) decreased with an increasing filler content by about 16, 24 and 31%, respectively. Overall, these composites were characterized by a good burning resistance and had a flammability rating of V0 according to the UL94 test.

Thermal Stability of Nanosilica-Modified Poly(vinyl chloride).

The thermal stability of PVC with 1 wt % of spherical porous nanosilica, prepared by roll milling at processing time varied from 1 to 20 min, was investigated by means of visual color changes, Congo red, and thermogravimetric tests (TGA and DTG), as a function of rolling time and composition of PVC matrix. The melt flow rate (MFR) measurements were realized to identify the degradation-induced changes of processing properties. A high level of gelation of the PVC matrix for all samples was verified by DSC (differential scanning calorimetry). It was found that the addition of porous nanosilica to absorb a certain volume of HCl, produced by dehydrochlorination reaction, leads to an improvement of thermal stability, an effect observed in a form of minor color changes of the samples, lower evolution of gas hydrogen chloride, and slight changes of the MFR value. It was demonstrated that the TGA measurements are not sufficiently sensible to detect the degradation of PVC at the processing conditions, i.e., at the temperature equal to 220 °C and below this temperature.

Biofilm on the polymer composites - qualitative and quantitative microbiological analysis.

BACKGROUND: Modern technology, which has been getting more and more recognition in the world for the last several years, is the moving bed biofilm reactor (MBBR) technology. Currently, movable biofilters made of basic polymeric materials, polyethylene and polypropylene. METHODS: An innovative solution in the field, mainly because of the large active surface area for biological membrane can be wood polymer composites (WPC). In the research polypropylene (PP) and polyvinyl chloride (PVC) was used as the matrix. Two types of commercial wood flour also, selected from conifers, were selected for the study: Lignocel C 120 with particle sizes in the range of 70 µm-150 µm and L9 with dimensions of 0.8-1.1 mm and wood chips, which are used on an industrial scale for the production of chipboards, were used as a filler. A quantitative and qualitative analysis of newly formed biofilms was performed. RESULTS: The study showed a direct effect of the filler and its particle size on the susceptibility to the formation of the biofilm of on the composites surface. CONCLUSIONS: Polypropylene PPH 648 T and 40% wt. of L9 type wood flour was the most susceptible to biofilm formation. Pure polypropylene PPH 648 T was the least susceptible material.

Poly(vinyl chloride) Composites with Raspberry Pomace Filler.

This study examined, the effect of chemically extracted raspberry pomace on the thermal stability, mechanical properties, flammability, chemical structure and processing of poly(vinyl chloride). It was observed that the pomace in this study was used to extract naphtha, thereby permitting the removal of bio-oil as a factor preventing the obtaining of homogeneous composites. Furthermore, adding 20% raspberry pomace filler after extraction extended the thermal stability time for the composites by about 30%. It was observed that composite density, impact strength, and tensile strength values decreased significantly with increasing concentrations of filler in the PVC matrix. At the same time, their modulus of elasticity and Shore hardness increased. All tested composites were characterized by a good burning resistance with a flammability rating of V0 according to the UL94 test. Adding 20 to 40% of a natural filler to the PVC matrix made it possible to obtain composites for the production of flame resistant elements that emitted less hydrogen chloride under fire conditions while ensuring good rigidity.

Adsorption of Sr(II) ions and salicylic acid onto magnetic magnesium-zinc ferrites: isotherms and kinetic studies.

Magnetic magnesium-zinc spinel ferrite Mg1 - xZnxFe2O4 (where x = 0.4, 0.6, and 0.8) was investigated as adsorbent for the efficient removal of Sr(II) ions and salicylic acid (SA) contaminants from aqueous medium. The characterization of ferrites was carried out using XRD, VSM, BET, SEM, and EDS. The surface charge of magnetic adsorbents was measured by the drift method. The determination of SA and Sr(II) ion concentrations in the solution phase was carried out by UFLC and complexometry, respectively. It was shown that varying of the Zn(II) content affected the adsorption capacities of magnesium-zinc ferrites. The increasing of zinc content from x(Zn2+) = 0.4 to x(Zn2+) = 0.6 increased the adsorption of Sr(II) ions from 50 to 65 mg/g, and then it was decreased to 36 mg/g for the sample with x(Zn) = 0.8. The Mg0.4Zn0.6Fe2O4 sample demonstrated the maximum adsorption capacity of 74 mg/g. The adsorption isotherm for Sr(II) was fitted by the Dubinin-Radushkevich, Langmuir, Freundlich, and Sips models. The adsorption kinetics of Sr(II) was analyzed by PFO, PSO, and Elovich models. The adsorption kinetics of SA was also investigated. It was demonstrated that the Mg0.2Zn0.8Fe2O4 sample exhibited 90% removal of salicylic acid from the water solutions. The results demonstrated that magnetic Mg-Zn ferrites with spinel structure are good sorbents for the removal of SA and Sr(II) ions from aqueous solution.

WxC-ß-SiC Nanocomposite Catalysts Used in Aqueous Phase Hydrogenation of Furfural.

This study investigates the effects of the addition of tungsten on the structure, phase composition, textural properties and activities of ß-SiC-based catalysts in the aqueous phase hydrogenation of furfural. Carbothermal reduction of SiO2 in the presence of WO3 at 1550 °C in argon resulted in the formation of WxC-ß-SiC nanocomposite powders with significant variations in particle morphology and content of WxC-tipped ß-SiC nano-whiskers, as revealed by TEM and SEM-EDS. The specific surface area (SSA) of the nanocomposite strongly depended on the amount of tungsten and had a notable impact on its catalytic properties for the production of furfuryl alcohol (FA) and tetrahydrofurfuryl alcohol (THFA). Nanocomposite WxC-ß-SiC catalysts with 10 wt % W in the starting mixture had the highest SSA and the smallest WxC crystallites. Some 10 wt % W nanocomposite catalysts demonstrated up to 90% yield of THFA, in particular in the reduction of furfural derived from biomass, although the reproducible performance of such catalysts has yet to be achieved.

Concept for Recycling Waste Biomass from the Sugar Industry for Chemical and Biotechnological Purposes.

The objective of this study was to develop a method for the thermally-assisted acidic hydrolysis of waste biomass from the sugar industry (sugar beet pulp and leaves) for chemical and biotechnological purposes. The distillates, containing furfural, can be catalytically reduced directly into furfurayl alcohol or tetrahydrofurfuryl alcohol. The sugars present in the hydrolysates can be converted by lactic bacteria into lactic acid, which, by catalytic reduction, leads to propylene glycol. The sugars may also be utilized by microorganisms in the process of cell proliferation, and the biomass obtained used as a protein supplement in animal feed. Our study also considered the effects of the mode and length of preservation (fresh, ensilage, and drying) on the yields of furfural and monosaccharides. The yield of furfural in the distillates was measured using gas chromatography with flame ionization detector (GC-FID). The content of monosaccharides in the hydrolysates was measured spectrophotometrically using enzymatic kits. Biomass preserved under all tested conditions produced high yields of furfural, comparable to those for fresh material. Long-term storage of ensiled waste biomass did not result in loss of furfural productivity. However, there were significant reductions in the amounts of monosaccharides in the hydrolysates.

Preparation and Characterization of Eco-Friendly Mg(OH)2/Lignin Hybrid Material and Its Use as a Functional Filler for Poly(Vinyl Chloride).

A functional magnesium hydroxide/lignin hybrid system was prepared by grinding and mixing the pure precursors using a planetary ball mill. In addition, the thermal stability was assessed based on the total mass loss of the hybrid system within the temperature range of 30⁻1000 °C, which amounted to 38%. Moreover, the average particle size was at 4.9 µm as determined by the laser diffraction method. The effect of addition of the prepared and characterized Mg(OH)2/lignin hybrid filler at concentrations ranging from 2.5 wt % to 10 wt % on the processing as well as mechanical and thermal properties of composites on the matrix of the unplasticized PVC compound was also evaluated. The addition of a filler to the poly(vinyl chloride) matrix causes a significant improvement of its thermal stability, which is approximately three times higher compared to a polymer without a filler. Furthermore, the prepared composites are additionally characterized by advantageous mechanical properties, especially higher Young's modulus. A 10% increase in the oxygen index of PVC composites upon addition of 10 wt % hybrid fillers has also been observed, which contributes to an extended range of their application under conditions that require notable fire resistance.