Showing papers on "Chemical resistance published in 2021"

Investigation of carbon fiber–reinforced thermoplastic polymers using thermogravimetric analysis:

Abstract: The high chemical resistance of the advanced thermoplastic polymers, such as polyether ether ketone (PEEK), polystyrene (PS), or polyamide (PA), makes methods of the composites’ composition evaluat...

Radiation-Based Crosslinking Technique for Enhanced Thermal and Mechanical Properties of HDPE/EVA/PU Blends.

Abstract: Crosslinking of polyolefin-based polymers can improve their thermal and mechanical properties, which can then be used in various applications. Radiation-induced crosslinking can be done easily and usefully by irradiation without a crosslinking agent. In addition, polymer blending can improve thermal and mechanical properties, and chemical resistance, compared to conventional single polymers. In this study, high-density polyethylene (HDPE)/ethylene vinyl acetate (EVA)/polyurethane (PU) blends were prepared by radiation crosslinking to improve the thermal and mechanical properties of HDPE. This is because HDPE, a polyolefin-based polymer, has the weaknesses of low thermal resistance and flexibility, even though it has good mechanical strength and machinability. In contrast, EVA has good flexibility and PU has excellent thermal properties and wear resistance. The morphology and mechanical properties (e.g., tensile and flexure strength) were characterized using scanning electron microscopy (SEM) and a universal testing machine (UTM). The gel fraction, thermal shrinkage, and abrasion resistance of samples were confirmed. In particular, after storing at 180 °C for 1 h, the crosslinked HDPE-PU-EVA blends exhibited ~4-times better thermal stability compared to non-crosslinked HDPE. When subjected to a radiation dose of 100 kGy, the strength of HDPE increased, but the elongation sharply decreased (80%). On the other hand, the strength of the HDPE-PU-EVA blends was very similar to that of HDPE, and the elongation was more than 3-times better (320%). Finally, the abrasion resistance of crosslinked HDPE-PU-EVA was ~9-times better than the crosslinked HDPE. Therefore, this technology can be applied to various polymer products requiring high heat resistance and flexibility, such as electric cables and industrial pipes.

Resistance to Sulfuric Acid Corrosion of Geopolymer Concrete Based on Different Binding Materials and Alkali Concentrations

Abstract: Geopolymer binder is expected to be an optimum alternative to Portland cement due to its excellent engineering properties of high strength, acid corrosion resistance, low permeability, good chemical resistance, and excellent fire resistance. To study the sulfuric acid corrosion resistance of geopolymer concrete (GPC) with different binding materials and concentrations of sodium hydroxide solution (NaOH), metakaolin, high-calcium fly ash, and low-calcium fly ash were chosen as binding materials of GPC for the geopolymerization process. A mixture of sodium silicate solution (Na2SiO3) and NaOH solution with different concentrations (8 M and 12 M) was selected as the alkaline activator with a ratio (Na2SiO3/NaOH) of 1.5. GPC specimens were immersed in the sulfuric acid solution with the pH value of 1 for 6 days and then naturally dried for 1 day until 98 days. The macroscopic properties of GPC were characterized by visual appearance, compressive strength, mass loss, and neutralization depth. The materials were characterized by SEM, XRD, and FTIR. The results indicated that at the immersion time of 28 d, the compressive strength of two types of fly ash-based GPC increased to some extent due to the presence of gypsum, but this phenomenon was not observed in metakaolin-based GPC. After 98 d of immersion, the residual strength of fly ash based GPC was still higher, which reached more than 25 MPa, while the metakaolin-based GPC failed. Furthermore, due to the rigid 3D networks of aluminosilicate in fly ash-based GPC, the mass of all GPC decreased slightly during the immersion period, and then tended to be stable in the later period. On the contrary, in metakaolin-based GPC, the incomplete geopolymerization led to the compressive strength being too low to meet the application of practical engineering. In addition, the compressive strength of GPC activated by 12 M NaOH was higher than the GPC activated by 8 M NaOH, which is owing to the formation of gel depended on the concentration of alkali OH ion, low NaOH concentration weakened chemical reaction, and reduced compressive strength. Additionally, according to the testing results of neutralization depth, the neutralization depth of high-calcium fly ash-based GPC activated by 12 M NaOH suffered acid attack for 98 d was only 6.9 mm, which is the minimum value. Therefore, the best performance was observed in GPC prepared with high-calcium fly ash and 12 M NaOH solution, which is attributed to gypsum crystals that block the pores of the specimen and improve the microstructure of GPC, inhibiting further corrosion of sulfuric acid.

Effect of Eco-Friendly Peanut Shell Powder on the Chemical Resistance, Physical, Thermal, and Thermomechanical Properties of Unsaturated Polyester Resin Composites

Abstract: The paper investigates the synthesis of eco-friendly composites and their properties before and after immersion in solvents of different chemical natures. For their preparation, unsaturated polyester resin (UPR) based on recycled poly (ethylene terephthalate) (PET) and peanut shell powder (PSP) were used. Polymerization was carried out in the presence of environmentally friendly polymeric cobalt. Distilled water, acetone, 10% hydrochloric acid, 40% sodium hydroxide, toluene, and 2% sodium carbonate were used as solvents in the chemical resistance test. Changes in the structure, properties, and appearance (morphology) of composites after 140 days of immersion in solvents were investigated. The results show that both the resin and its composites show resistance towards 10% HCl and toluene. The immersion in water has no significant effect on the resin, but for PSP composites, the plasticizing effect of water was observed. In acetone, after only one day, the resin and its composite with 10% PSP shrink and fall into pieces. However, the most destructive is an alkaline environment. After the immersion test, a huge increase in mass and a deterioration of gloss and thermomechanical properties were observed. The destructive influence of the 40% NaOH environment mainly concerned the resin.

Ternary composite films of natural rubber, cellulose microfiber, and carboxymethyl cellulose for excellent mechanical properties, biodegradability and chemical resistance

Abstract: Fast and facile preparation of composite films containing natural rubber and Eucalyptus cellulose microfiber was achieved by the addition of carboxyl methyl cellulose to yield advantage properties such as chemical resistance, biodegradability and excellent tensile strength. It was found that carboxyl methyl cellulose can be employed as pre-agglomeration stabilizer to obtain high dispersion of hydrophilic cellulose fibers in hydrophobic natural rubber latex. The incorporation of cellulose fibers into the natural rubber matrix significantly improved the crystallinity of the composite films. At the highest loading content of cellulose at 50% w/w, the uptake toluene of the film was reduced to only 5%, whereas its tensile strength was increased to 100 times higher than the neat rubber film. Thermal stability was decreased slightly, depending on cellulose fiber loading content, but the glass transition temperature remained constant at about − 64 °C. According to the hydrophilic nature of cellulose, the water absorption capacity and water vapor transmission of the composite films were enhanced. In addition, it was shown that the biodegradability was considerably improved; the composite films degraded sufficiently in soil within 2 weeks.

Binary blended fly ash concrete with improved chemical resistance in natural and industrial environments

Abstract: This study reports the enhanced chemical resistance of a blended concrete mix (CFNI) made with 40 wt.% fly ash, 2 wt.% nanoparticles, and 2 wt.% sodium nitrite inhibitor as partial replacement of cement against calcium leaching, acid and sulfate attacks. The concrete test specimens of four different compositions were fabricated and immersed in natural seawater, 3% sulfuric acid solution, and 10% magnesium sulfate solution for 120 days. Long-term chemical deterioration of the concrete systems is evaluated by assessing visual changes of the specimens and solutions along with the changes in percentage mass loss, compressive strength of the concrete, pH of the solution, and dimensions. The results indicate that CFNI concrete exhibits a superior resistance against chemical attack under all the three aggressive environments. Detailed chemical characterization of the specimens, carried out using XRD, FTIR, and thermogravimetric analysis, reveal a reduced CaO content, absence of deterioration phases like ettringite, brucite, and enhanced C-S-H content in the CFNI concrete. The addition of nanoparticles and inhibitors into fly ash concrete has lowered w/c ratio, increased surface pH, enabled conversion of soluble calcium hydroxide into insoluble calcium silicate hydrate, filled pores/voids, and reduced shrinkage and cracking. The compact microstructure of the CFNI prevented leaching and reduced the ingress of aggressive chemical ions into the concrete. Our results demonstrate that incorporation of nanoparticles and inhibitor into the fly ash concrete composition is ideally suited for the design of high-quality, low-permeable concrete structures that is the key for enhanced chemical resistance in natural and industrial environments.

Preparation and properties of nano SiO2 modified cellulose acetate aqueous polymer emulsion for leather finishing

Abstract: Poor water solubility of cellulose acetate is a key factor limiting its application in leather finishing field. Herein, a self-emulsifying aqueous emulsion was synthesized by using cellulose diacetate (CDA) as the substrate, dimethylolbutyric acid (DMBA) as the hydrophilic agent, and hexamethylene diisocyanate (HDI) as the bridging agent. Because the flexible carbon chain of HDI has the advantages of easy bending and deformation, the problem of large steric hindrance and low reactivity of -OH during water-based CDA can be solved by using the method of converting reactive functional groups and transferring reactive sites. At the same time, the flexible molecule 1,4-butanediol (BDO) and propylene glycol polyether (N210) are used as chain extenders to increase the molecular stretch and curl ability by adjusting the ratio of molecular soft and hard segments, and improve emulsion stability and coating flexibility. And through the reaction of -NH2 and -NCO on the surface of nano SiO2 modified by KH550, the nano SiO2 is evenly distributed in the CDA water-based polymer to improve the comprehensive performance of the emulsion coating. Thus the nano-SiO2 modified cellulose acetate water-based polymer emulsion (SiO2/WCDA) is obtained for leather finishing. The emulsion particles show an oil-in-water (O/W) core–shell structure, and the average particle size and dispersion coefficient (PDI) of the particles are 88.79 nm and 0.150, respectively. The surface of the coating film is compact, flat, and hydrophobic, with the contact angle is 104.3 °. In addition, the coating film has good adhesion, water resistance, heat resistance, yellowing resistance, chemical resistance, flexibility and mechanical properties.

High Performance Electrospun Polynaphthalimide Nanofibrous Membranes with Excellent Resistance to Chemically Harsh Conditions

Abstract: Polynaphthalimide (PNI) with six-membered imide ring (6-PI) has better chemical resistance than five-membered imide ring (5-PI), but is difficult to be processed into nanofibers due to the poor processability. In this work, we proposed a template strategy to fabricate nanofiber 6-PI membranes and their composite membranes. Neat 6-PI and 6-PI composite fibrous membranes were prepared using high-molecular-weight polymers 5-PAA and PVP as templates by electrospinning. FTIR, DMA, TGA and tensile tests were used to characterize their chemical structures, thermal stability and mechanical properties. Further eye-observation, micro-morphology investigation and tensile tests were applied to evaluate the chemical resistance of nanofibrous membranes in strong acid, strong alkaline, and concentrated salt. The results demonstrated that 6-PI nanofibrous membranes possessed the best thermal stability, best acid, alkaline, and salt resistance with the highest mechanical retention. This study will provide basic information for high-performance electrospun 6-PI nanofiber membranes and provide opportunities for applications of PIs in different chemically harsh environments.

Comparative Study of the Impact Wedge-Peel Performance of Epoxy Structural Adhesives Modified with Functionalized Silica Nanoparticles

Abstract: Epoxy structural adhesives have strong adhesion, minimal shrinkage and high thermal and chemical resistance. However, despite these excellent properties, their high-energy impact resistance should be improved to satisfy the increasing demands of the automotive industry. For this reason, we used four types of silica nanoparticles with different surface groups, such as polydimethylsiloxane (PDMS), hydroxyl, epoxy and amine groups, as toughening agents and examined their effect on the glass transition temperature (Tg), crosslinking density and phase separation of epoxy structural adhesives. High-energy impact resistance, mode I fracture toughness and lap shear strength were also measured to explain the effect of surface functional groups. Silica nanoparticles with reactive functional groups increased the mode I fracture toughness of epoxy structural adhesives without sacrificing the crosslinking density. Although the mode I fracture toughness of epoxy structural adhesives could not clearly show the effect of surface functional groups, the dynamic resistance to cleavage obtained by impact wedge-peel tests showed quite different values. At a 0.3 vol% content, epoxy-functionalized silica nanoparticles induced the highest value (40.2 N/mm) compared to PDMS (34.1 N/m), hydroxyl (34.9 N/mm), and amine (36.1 N/m). All of these values were significantly higher than those of pristine epoxy structural adhesive (27.7 N/mm).

Rosin-modified o-cresol novolac based vinyl ester thermosets containing methacrylated lignin model compounds: synthesis, curing and thermo-mechanical analysis

Abstract: In the present research article, a detailed study on the synthesis, characterization, and structure–property correlation study of the vinyl ester resin (AVEOCN) based on the rosin modified o-cresol-formaldehyde epoxy novolac resin has been done. The rosin was condensed with o-cresol formaldehyde novolac resin to obtain the product (AOCN). The AOCN resin was epoxidized and subsequently esterified with methacrylic acid using triphenylphosphine as a catalyst and inhibitor hydroquinone to get vinyl ester resin (AVEOCN) having acid value ~ 7 mg of KOH per gram of solid. The chemical structures were confirmed using FT-IR, 1H-NMR, 13C-NMR, and DEPT-135° spectroscopic techniques, and their number average molecular weights were evaluated using 1H-NMR spectroscopy as well as Gel Permeation Chromatographic technique (GPC). The curing dynamics of synthesized VER with lignin modeled compounds, methacrylated eugenol (ME) and methacrylated guaiacol (MG), and petroleum-based styrene as reactive diluents was studied using Differential Scanning Calorimetry (DSC). The thermal stability analysis and mechanical performance of the VER samples were done using Thermogravimetric analysis (TGA) and Universal Testing Machine (UTM), respectively. Chemical resistance tests of the above VER samples were also assessed via exposing the sample coated panels to the different chemical environments for 90 days and their % weight loss was determined. The surface morphology of exposed samples was also studied using Scanning Electron Microscopy (SEM). The results obtained were compared to VER systems based on petroleum products and epoxy resins systems and the superior performance of rosin-modified VER systems indicate that they are suited for pressing demands for coating applications.

Effect of MWCNT carboxylation on mechanical, thermal and morphological behaviour of phenol formaldehyde nanocomposites:

Abstract: Phenol-formaldehyde resin is an inevitable polymer material because of their excellent properties like heat resistance, chemical resistance, creep resistance, and low water sorption. But the drawba...

Specific crosslinking effects of poly(epichlorohydrin)-triol on urethane polymer matrix of castor seed oil-based coatings

Abstract: The contributions of castor seed oil (CSO) as a useful, nontoxic, and sustainable base material for coating systems cannot be overemphasized. This paper took advantage of the predominant fatty acid composition in CSO (i.e., ricinoleic acid). It blended a synthesized crosslinker, poly(epichlorohydrin-triol) (PECH-triol), in percentages within its polymeric matrix. Physicochemical and spectroscopic (FTIR, 1H-NMR, and 13C-NMR) examinations were carried out on the polyols. Thermal stability, hydrophobicity, anticorrosion, mechanical, and antibacterial properties of the prepared polyurethane (PU) coatings were examined. The 20% PECH-triol–CSO-PU film having its TON and TEND at 230.5 and 511.0°C, respectively, showed improved thermal stability when compared with the pristine film (CSO-PU). The derivative of TGA reveals a three-stage degradation step. Hydrophobicity was seen to increase from 73.3° to 92.2°, a reflection of the crosslinking effect of PECH-triol within the urethane matrix. The improved adhesion of 20% PECH-triol–CSO-PU coating on mild steel gave a better chemical resistance.

Preparation of alkali-resistant aluminum pigment encapsulated with fluoropolymer by in situ polymerization

Abstract: Flaky aluminum pigments with excellent corrosion resistance have found applications in diverse fields. In this study, a fluoropolymer has been incorporated in the aluminum pigment to effectively enhance its corrosion resistance, along with the improvement in the chemical resistance and thermal stability. Specifically, a uniform dense layer of poly(trifluoroethyl methacrylate) (PTFEMA) has been directly coated on the surface of the flaky aluminum pigment by in situ polymerization. The encapsulated aluminum pigment exhibited high stability upon dipping in the alkaline solution (pH = 13) due to protection imparted by the fluoropolymer layer. The morphology of the fluoropolymer layer on the surface of the aluminum pigment was characterized by scanning electron microscopy (SEM). Moreover, the thermal stability of the encapsulated aluminum pigment was analyzed by thermogravimetric analysis (TG). The structure and composition of the fluoropolymer layer were further characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The stability of the aluminum pigment in alkaline aqueous media was investigated via hydrogen evolution experiments. Overall, the corrosion resistance of the aluminum pigment encapsulated with fluoropolymer was observed to be markedly improved owing to the presence of the PTFEMA layer.

Preparation of a novel poly (ether ether ketone) self-reinforced paper appropriate for harsh conditions

Abstract: It remains a challenge to prepare special engineering paper with excellent mechanical properties, high temperature resistance and chemical resistance. The emergence of high-performance fiber provides support for the technical progress of special engineering paper. Herein, a novel method to obtain a novel self-reinforced poly (ether ether ketone) (PEEK) composite paper (SR-DI-PEEK/paper) by vacuum filtration, impregnation and hot pressing. Specially, PEEK fibers were used as the skeleton fiber and a small amount of aramid pulp was added as the decanted fiber. By optimizing the process of SR-DI-PEEK/paper preparation, the best mechanical properties of SR-DI-PEEK/paper was presented. Compared with the composite paper prepared with Phenolic solution (PF-PEEK/paper) and Polyimide solution (PI-PEEK/paper), the mechanical properties of SR-DI-PEEK/paper was significantly improved. In particular, when the concentration of impregnation was 3 wt%, the tensile index of SR-DI-PEEK/paper reached 51.10 N m g−1 (tensile strength 47.16 kN m−1), which is 16.48 times than that of the un-impregnated PEEK/paper (2.86 kN m−1). SR-DI-PEEK/paper also exhibited excellent chemical resistance among acid, alkali, and polar solvents, while the tensile index maintained 96.3% after 40 wt% H2SO4 treatment. Besides, SR-DI-PEEK/paper showed superior thermal performance, while the temperatures corresponding to the weight loss of 5% were 574 °C.

Characterization, coating and biological evaluation of polyol esters rosin derivatives as coating films

Abstract: Polyol esters materials, which have been developed from ethylene glycol, glycerol, pentaerythritol and sorbitol with rosin, were investigated for their formed films and coating properties. Films were dried and characterized for chemical and mechanical resistances. Their films were highly resistant to water, solvents (acetone, toluene and methanol), and acids (10% hydrochloric acid and 20% sulfuric acid) and poorly resistant to alkali (10% sodium hydroxide) as well as adhesion, tensile strength, elongation test, modulus of elasticity, pinhole test and scratching and flexibility tests. Incorporation of ethylene glycol, glycerol, pentaerythritol and sorbitol with rosin was done to achieve good mechanical characteristics and high chemical resistance to these films. The prepared compounds were tested for antibacterial activity against Trametes versicolor and Gloeophyllum trabeum.

PU-coating performance of bio-based hyperbranched alkyd resin on mild steel and wood substrate

Abstract: In the present research article, a hyperbranched alkyd resin was synthesized by using bio-based material (castor oil based fatty amide) and pyromellitic dianhydride. The synthesized hyperbranched alkyd resin was characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. The polyurethanes (PMFAI and PMFAM) were prepared from hyperbranched alkyd resin and diisocyanates [isophorone diisocyanates (IPDI) and methylene diphenyl diisocyanate (MDI)] maintaining the OH:NCO ratio of 1:1.2. These polyurethanes were used in coating applications on mild steel and wood panels. The performance of cured polyurethane coatings was studied in terms of crosscut adhesion, impact resistance, gloss, scratch hardness, and chemical resistance. The chemical resistance test was performed by immersion method in 2 N HCl, 2 N NaOH, 3.5% NaCl solution, xylene, and water. The corrosion rate and anticorrosion efficiency of the coating panels were determined by a potentiostat. From a study of coating properties, it was found that the PMFAI and PMFAM exhibited better coating properties as compared to reported linear alkyd polyurethanes. The stain test of coatings was performed on wood panels. The thermal behavior of the coatings was determined by thermogravimetric analyzer. The surface morphology of coating films was examined by scanning electron microscopy and atomic force microscopy. It was found that the coating properties of hyperbranched alkyd resin were excellent as compared to linear alkyd resin polyurethanes.

UV Polymerization of Methacrylates-Preparation and Properties of Novel Copolymers.

Abstract: More environmentally friendly polymeric materials for use in corrosive conditions were obtained in the process of UV polymerization of terpene methacrylate monomers: geranyl methacrylate and citronellyl methacrylate and the commercially available monomer methyl methacrylate. Selected properties (solvent resistance, chemical resistance, glass transition temperature, thermal stability, and decomposition course during heating) were evaluated. It was found that the properties of the materials directly depended on the monomer percentage and the conditioning temperatures used. An increase in the geranyl or citronellyl methacrylate monomer content in the copolymers reduced the solubility and chemical resistance of the materials post-cured at 50 °C. The samples post-cured at 120 °C were characterized by high resistance to polar and non-polar solvents and the chemical environment, regardless of the percentage composition. The glass transition temperatures for samples conditioned at 120 °C increased with increasing content of methyl methacrylate in the copolymers. The thermal stability of copolymers depended on the conditioning temperatures used. It was greater than 200 °C for most copolymers post-cured at 120 °C. The process of pyrolysis of copolymers led to the emission of geranyl methacrylate, citronellyl methacrylate, and methyl methacrylate monomers as the main pyrolysis volatiles.

Modification of the Properties of Polymer Composites in a Constant Magnetic Field Environment.

Abstract: In this paper, polymer composites based on polylactide (PLA) and epoxy resin (Epidian 5) were studied in terms of the influence of magnetic induction on their changes in physicochemical properties. The composites contained admixtures in the form of magnetite (Fe3O4) and crystalline cellulose (Avicel PH-1010) in the amount of 10%, 20%, and 30% by weight and starch in the amount of 10%. The admixtures of cellulose and starch were intended to result in the composites becoming biodegradable biopolymers to some extent. Changes in physical and chemical properties due to the impact of a constant magnetic field with a magnetic induction value B = 0.5 T were observed. The changes were observed during tests of tensile strength, bending, impact strength, water absorbency, frost resistance, chemical resistance to acids and bases, as well as through SEM microscopy and with studies of the composition of the composites that use the EDS method and of their structure with the XRD method. Based on the obtained results, it was found that the magnetic induction value changes the properties of composites. This therefore acts as one method of receiving new alternative materials, the degradation of which in the environment would take far less time.

Effect of siloxane chain length on thermal, mechanical, and chemical characteristics of UV (ultraviolet)-curable epoxy acrylate coatings

Abstract: In this research, high-performance epoxy acrylate (EA) coating formulations that contain various acrylate-modified diepoxy siloxane (DESA) intermediates were synthesized and characterized. Firstly, diepoxy siloxane (DES) intermediates, which have varying chain lengths (Mw = 370–3300 Da), were modified by acrylic acid via the ring-opening reaction oxirane group. DESA intermediates were then used in the preparation of ultraviolet (UV)-curable EA formulations. EA was also synthesized via acrylic acid modification of a commercial bisphenol-A-based epoxy resin, used as the standard formulation. EA-based UV-curable formulas were applied on substrates and then cured by UV irradiation for investigating the coating performances. Subsequently, performances of the UV-cured coatings were evaluated by the various test techniques, such as hardness, gloss, cross-cut adhesion force scratch resistance, contact angle, yellowing resistance, abrasion resistance, chemical resistance, and color measurement. The effect of DESA variety on the formations was examined compared to both themselves and the standard formulation. The results showed that the varying amounts and chain lengths of DESA influenced UV-curable coatings’ properties; particularly, the scratch resistance, contact angle, and yellowing resistance significantly enhanced with the increasing chain length of DESA. High-performance UV-curable EA formulations could be produced with the scratch resistance of 4 N, the contact angle of 95°, and high yellowing resistance (ΔE = 0.35).