Acid Composites Research Articles

3D‐printing continuous plant fiber/polylactic acid composites with lightweight and high strength

AbstractContinuous plant yarn‐reinforced polylactic acid (PLA) composites were produced through in situ 3D printing, focusing on how plant fiber attributes influence the crystallization, mechanical, and rheological properties of the printed composites. The aim of this study was to assess the viability of plant fibers as substitutes for synthetic ones in engineering additive manufacturing. Plant fibers promoted the crystallization of PLA due to their shear induction and nucleation agent induction effects. The inherent triangular void defect during printing decreased with increasing plant fiber‐volume fraction. Rheological analysis revealed a transition to more elastic behavior post‐fiber addition, indicating solid‐like properties. The tensile strength of flax fiber‐yarn/PLA composite (volume fraction of 50.79%) was 342.37% higher than that of pure PLA, with a 22.2% lower density than pure PLA. Flax fiber demonstrated a superior reinforcement effect than carbon fiber in compressive strength for 3D printed honeycomb sheets with lower energy consumption and footprint. Optimizing fiber characteristics holds promise for high‐performance 3D‐printed natural fiber composites, particularly in vehicle applications.Highlights Plant fiber/polylactic acid (PLA) composites were in situ printed with a volume fraction of 50.79%. Plant fibers promoted the crystallization of PLA during the printing process. The tensile strength of flax fiber/PLA increased by 342.3% with a 22.2% lower density than PLA. Flax fiber showed a better reinforcement than carbon fiber in a compressive test of printed honeycomb.

Facile fabrication of 3D-printed cellulosic fiber/polylactic acid composites as low-cost and sustainable acoustic panels

This work presents a green, cost-effective and eco-friendly strategy to reduce noise pollution by developing biopolymer-based 3D-printed acoustic panels. We successfully fabricated two series of composites by varying the weight percentage (wt%) of cellulose fibers of water hyacinth (WH) and pineapple leaf (PAL), with polylactic acid (PLA) as the matrix via the heat-press method. All samples were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Physico-mechanical properties, including hardness, tensile, and impact strength, were improved with increasing fiber loading. Filaments of 1 wt% water hyacinth fibers (WHFs) in PLA (1 WHF/PLA) and 1 wt% pineapple leaf fibers (PALFs) in PLA (1 PALF/PLA) were prepared and tested for 3D printability. The sound absorption coefficients (α) of the 3D-printed panels were investigated from 500 to 5000 Hz sound frequency range. The 3D-printed 1 WHF/PLA and 1 PALF/PLA acoustic panels achieve a maximum α (α-max) of 0.55 and 0.83 at 5000 and 4000 Hz, respectively, featuring the first work to report α-max > 0.5 at low fiber loadings in the high-frequency sound range. The tensile strength of the 3D-printed versions is significantly higher than non-3D-printed counterparts and commercial acoustic absorbers. Our data suggest the prepared 3D-printed panels are excellent candidates for acoustic applications at high-frequency noises. This study exhibits a facile, environmentally benign and sustainable approach to construct highly efficient and mechanically robust biopolymer-based 3D-printed sound-proof panels, which have promising potential as green engineering materials. Interestingly, this research also proposes a mitigation technology for the freshwater invader, Eichhornia crassipes (water hyacinths).

Effect of plasma treatment and graphite/carbon black addition on bending and electromagnetic shielding of hemp fiber/polylactic acid composites

Effect of plasma treatment and graphite/carbon black addition on bending and electromagnetic shielding of hemp fiber/polylactic acid composites

Outstanding electromagnetic interference shielding of bamboo fiber/carbon nanotubes/polylactic acid composites with biodegradability and corrosion resistance

To cope with the increasing electromagnetic waves and environmental pollution, it is imperative for exploring environmentally friendly electromagnetic interference (EMI) shielding materials with prime shielding effectiveness (SE). In this study, a biodegradable bamboo fiber/carbon nanotubes/polylactic acid (BF/CNTs/PLA) composite with abundant pore structures were successfully produced by mixing, melting and hot-pressing approach by utilizing hydrophobically treated bamboo fiber (BF), carbon nanotubes (CNTs) with efficient electrical conductivity and biodegradable polylactic acid (PLA) with exceptional thermal stability. Specially, with the addition of 12 wt% CNTs, the BF/CNTs/PLA composite displayed excellent EMI SE of 47.7 dB at X-band due to the uniform dispersion of conductive CNTs in consecutive BF/PLA composite. In addition, the value of SEA/SET was 79.9 %, illustrating absorption was the primary shielding mechanism. what’s more, BF/CNTs/PLA presented superior thermal stability and EMI SE of 89.7 %, 84.5 %, and 81.3 % after immersion of BF/CNTs/PLA in HCl, NaCl, and NaOH solution, respectively, demonstrating its prime corrosion resistance. Therefore, BF/CNTs/PLA composites have enormous application potential in the field of high-temperature resistance, biodegradability, and biomass based electromagnetic shielding materials.

Reinforcing and protecting leather-based relics using gelatin/tannic acid composites

Subject to environmental influences such as temperature, humidity, light, and microorganisms, leather-based relics are easily be deteriorated, which will damage their historical value. In this work, gelatin/tannic acid composites (Gel/TA) was prepared and characterized to investigate their potential as a novel approach for reinforcing and protecting leather-based relics. According to the characterization, it was found that hydrogen bonds was formed between gelatin and TA, and Gel/TA presented increases in the antioxidant capacity(82.12 %), compared to the gelatin. After reinforcing the aged leather with Gel/TA, the cross-linking between leather collagen fibers is more closely interconnected. The mechanical properties and antibacterial activity of leather-based relics are significantly improved. The oxidation resistance of leather-based relics increased from 20.72 % to 63.03 %. Under the condition of accelerated simulated aging, the time to reduce the mechanical properties of reinforced leather by 50 % was extended from 7.6 days to 10 days. At the same time, the color of leather-based relics changed slightly. This result suggested that the Gel/TA composites play an important role in the filling and reinforcement protection of leather artifacts. This work will put forward a feasible way to producing sustainable multifunctional materials for leather-based relics.

Primary amine-catalyzed enantioselective 1,4-Michael addition reaction of pyrazolin-5-ones to α,β-unsaturated ketones.

The enantioselective 1,4-addition reaction of pyrazolin-5-ones to α,β-unsaturated ketones catalyzed by a cinchona alkaloid-derived primary amine-Brønsted acid composite is reported. Both enantiomers of the anticipated pyrazole derivatives were obtained in good to excellent yields (up to 97%) and high enantioselectivities (up to 98.5% ee) under mild reaction conditions. In addition, this protocol was further expanded to synthesize highly enantioenriched hybrid molecules bearing biologically relevant heterocycles.

Synergistic preparation of a straw fiber/polylactic acid composite with high toughness and strength through interfacial compatibility enhancement and elastomer toughening

Plant fiber-reinforced polylactic acid (PLA) composites are extensively utilized in eco-friendly packaging, sports equipment, and various other applications due to their environmental benefits and cost-effectiveness. However, PLA suffers from brittleness and poor toughness, which restricts its use in scenarios demanding high toughness. To expand the application range of plant fiber-reinforced PLA-based composites and enhance their poor toughness, this study employed a two-step process involving wheat straw fiber (WF) to improve the interfacial compatibility between WF and PLA. Additionally, four elastomeric materials—poly (butylene adipate-co-terephthalate) (PBAT), poly (butylene succinate) (PBS), polycaprolactone (PCL), and polyhydroxyalkanoate (PHA)—were incorporated to achieve a mutual reactive interface enhancement and elastomeric toughening. The results demonstrated that Fe3+/TsWF/PLA/PBS exhibited a tensile strength, elongation at break, and impact strength of 34.01 MPa, 14.23 %, and 16.2 kJ/m2, respectively. These values represented a 2.4 %, 86.7 %, and 119 % increase compared to the unmodified composites. Scanning electron microscopy analysis revealed no fiber exposure in the cross-section, indicating excellent interfacial compatibility. Furthermore, X-ray diffraction and differential scanning calorimetry tests confirmed improvements in the crystalline properties of the composites. This work introduces a novel approach for preparing fiber-reinforced PLA-based composites with exceptional toughness and strength.

Potential of Attapulgite/Humic Acid Composites for Remediation of Cd-Contaminated Soil

Stabilizing materials were prepared by different ratios of attapulgite/humic acid composites, and the optimum proportion for the remediation of Cd-polluted soils was found. The results suggested that the bioavailability of Cd in soil was decreased by the application of material prepared with humic acid and attapulgite in a ratio of 1:5. CaCl2-Cd, diethylenetriaminepentaacetic acid (DTPA-Cd) and the toxicity characteristic leaching procedure (TCLP-Cd) were reduced by 34.03%, 26.62% and 43.66%, and the ecological risk was depressed accordingly. The addition of stabilizing materials could transform the acid-soluble and reducible speciation to residue speciation, with a ratio of 1:5, significantly increasing the residue proportion of Cd in soil. The content of the residue state was increased by 63.13%, and the content of the acid-soluble state was significantly decreased by 34.10% compared with the control. The bioavailability, acid-soluble and reducible speciation of Cd had a highly negative correlation with the growth of corn, and the accumulation of Cd in corn had a significantly negative correlation with the residue speciation. Attapulgite/humic acid composites can reduce the bioavailability and increase the ratio of residue Cd in soil effectively, and they have the potential to remediate the pollution of heavy metals in soil.

Biodegradable implant of magnesium/polylactic acid composite with enhanced antibacterial and anti-inflammatory properties.

Addressing fracture-related infections (FRI) and impaired bone healing remains a significant challenge in orthopedics and stomatology. Researchers aim to address this issue by utilizing biodegradable biomaterials, such as magnesium/poly lactic acid (Mg/PLA) composites, to offer antibacterial properties during the degradation of biodegradable implants. Existing Mg/PLA composites often lack sufficient Mg content, hindering their ability to achieve the desired antibacterial effect. Additionally, research on the anti-inflammatory effects of these composites during late-stage degradation is limited. To strengthen mechanical properties, bolster antibacterial efficacy, and enhance anti-inflammatory capabilities during degradation, we incorporated elevated Mg content into PLA to yield Mg/PLA composites. These composites underwent in vitro degradation studies, cellular assays, bacterial tests, and simulation of the PLA degradation microenvironment. 20wt% and 40wt% Mg/PLA composites displayed significant antibacterial properties, with three composites exhibiting notable anti-inflammatory effects. In contrast, elevated Mg content detrimentally impacted mechanical properties. The findings suggest that Mg/PLA composites hold promise in augmenting antibacterial and anti-inflammatory attributes within polymers, potentially serving as temporary regenerative materials for treating bone tissue defects complicated by infections.

Structural characteristics and emulsifying properties of linear dextrin/eicosapentaenoic acid composites: Effect of the degree of polymerization

This work aimed at building functional emulsions based on the linear dextrins (LDs) emulsion system. The gradient polyethylene glycol (PEG) precipitaion method was used to fractionate LDs into fractions with different degrees of polymerization (DP). A package, and co-precipitation procedure of LDs, and eicosapentaenoic acid (EPA) was used to fabricate LDs-EPA composites. The gas chromatograph, Fourier transform infrared spectroscopy, X-ray diffraction and differential scanning calorimetry analyses affirmed the formation of the LDs-EPA composites. The sizes of these composites were 38.55 nm, 59.14 nm to 80.62 nm, respectively, and they had good amphiphilicity. Compared with LDs, these LDs-EPA composites stabilized Pickering emulsion had higher stability and antioxidant capacity. Their emulsifying ability was positively correlated with the DP values of LDs. Furthermore, the oxidation stability results showed that LDsF10-EPA emulsion had the lowest lipid hydroperoxide (LHs) content, malondioxide (MDA) content and hexal concentration, which were 138.75 mmol kg−1 oil, 15.50 mmol kg−1 oil and 3.83 μmol kg−1 oil, respectively. The study provided a new idea and application values for the application of LDs in emulsion.

Optimization of extrusion-based additive manufacturing of bronze metal parts using a CuSn10/Polylactic acid composite

As additive manufacturing gains widespread adoption across various industries, its application to traditional materials such as bronze remains relatively underexplored. Through a comprehensive assessment, this research investigates the extrusion-based additive manufacturing of bronze, utilizing a CuSn10/Polylactic Acid (PLA) composite filament for printing bronze green parts, followed by thermal debinding and sintering processes to produce metal parts. By systematically varying 3D printing, debinding, and sintering parameters, optimized conditions for manufacturing bronze metal parts are identified. The study evaluates key material properties including density, ultimate tensile strength, surface morphology, and electrical conductivity of the produced metal parts. Additionally, the influence of printing parameters on dimensional deviation and shrinkage for both bronze green and metal parts is analyzed. Overall, this research highlights the potential of additive manufacturing to revolutionize bronze production, offering valuable insights into optimized process parameters and the enhancement of bronze component properties for a wide range of industrial applications.

Organocatalyzed Asymmetric Michael Addition of 4‐Monosubstituted‐pyrazol‐5‐ones to Enones: Construction of Vicinal Quaternary and Tertiary Stereocenters

AbstractPyrazolone moiety bearing an all‐carbon quaternary stereogenic center is frequent in biologically active products and pharmaceuticals. The catalytic route for the construction of quaternary carbon centers poses a formidable challenge . In this report, catalytic asymmetric Michael addition of 4‐monosubstituted‐pyrazol‐5‐ones to simple enones catalyzed by primary amine‐Brønsted acid composite has been developed. An array of pyrazolone derivatives bearing vicinal all carbon quaternary and tertiary stereocenters, were obtained in moderate to good diastereoselectivities (up to 92 : 8 dr) and good to excellent enantiomeric excess (up to 99 % ee). In addition, antipode for enantiomers of the pyrazolone derivatives were also realized in good to high stereoselectivities (up to 92 : 8 dr and up to 98 % ee).

Preparation of Antimicrobial Polybutylene Succinate/Polylactic Acid Composites with a Promoting Effect on the Growth of Green Vegetables

Preparation of Antimicrobial Polybutylene Succinate/Polylactic Acid Composites with a Promoting Effect on the Growth of Green Vegetables

Analysis of the thermal properties in short sansevieria cylindrica fibre/PLA composites processed by twin screw extruder followed by hot press molding technique

Abstract Short Sansevieria cylindrica fibre/polylactic acid composites (SCFP) were fabricated using a twin screw extruder followed by the hot press technique, with variations in fibre loadings of 10 wt%, 20 wt%, 30 wt% and 40 wt%. The thermal properties of SCFP were assessed through dynamic mechanical analysis (DMA), thermomechanical analysis (TMA), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Notably, the samples loaded with 40 wt% of fibre exhibited an increased storage modulus. In terms of loss modulus, the fibre-loaded samples displayed high values, indicating more heat is released during DMA experiment. Interestingly, the composite trend did not solely rely on increasing fibre loading, highlighting the intricate interplay between reinforcement and matrix crucial for determining viscoelastic properties across various temperatures. The TGA results revealed a decrease in inflection temperature with increasing fibre loadings, accompanied by a proportional rise in residues. The DSC thermograms indicated minimal differences in Tg, Tcc, and Tm values among composites with varying fibre loadings. However, neat PLA showed slightly higher values than the composites. On the other hand, reinforcing SCF into the PLA matrix promoted the crystallization of PLA by 1%–3% with the maximum degree of crystallinity of 25.4% obtained for 30 wt% of SCFP.

Recycle of printed circuit boards from waste electric and electronic equipment and their reusability as filler in 3D printed poly(lactic) acid composites

Recycle of printed circuit boards from waste electric and electronic equipment and their reusability as filler in 3D printed poly(lactic) acid composites

A series of formic acid MOFs/polylactic acid blending composites with the improved dielectric performance in Co(II) systems

In order to improve the limited compatibility of existing polymer/ceramic dielectric composites and further enhance the energy storage density, MOF/polymer composite dielectrics have been explored, which exhibit good compatibility to the polymer matrix from abundant organic groups of the inorganic–organic hybrid metal-organic framework (MOF) fillers. However, they still lack a clear composition–structure–property rule, and the precise design of MOF fillers and polymer matrix becomes a prominent problem in these composites due to the diversity of the metal ions and the organic groups. Thus, in this paper, we present a series of formic acid MOFs/polylactic acid dielectric composites in which ferroelectric formic acid MOFs, namely PDLLA/[NH[Formula: see text](CH[Formula: see text])[Formula: see text]NH[Formula: see text]][M[Formula: see text](HCOO)[Formula: see text]][Formula: see text] and PDLLA/[CH[Formula: see text]NH[Formula: see text]][M[Formula: see text](HCOO)[Formula: see text]][Formula: see text], in which the formic acid MOFs are with different structures and different metal ions as fillers, including [NH3(CH[Formula: see text]NH3][MII(HCOO)3]2 (namely MOF– Co (M [Formula: see text] Co), MOF– Mg(M [Formula: see text] Mg), MOF– Mn (M [Formula: see text] Mn), with 1, 4-butanediamine ion as guest) and [CH3NH3][M[Formula: see text](HCOO)3]2 (namely MOF– Co[Formula: see text] (M = Co), MOF– Ni[Formula: see text] (Ni), with methylamine ion as guest). The composition and morphology of composite films were characterized by XRD, IR, SEM, DSC and UV, respectively, while the dielectric characterizations of the composites including the dielectric permittivity, the dielectric loss, the breakdown field strength and the energy density were also performed. The composition–structure–property relationships were also investigated including the influence of MOF content and MOF category. With the introduction of MOFs, the dielectric constant of the polylactic acid substrate was improved slightly while the breakdown field strength can be improved in some systems. Interestingly, the Co(II)-containing formic acid MOF has advantages over other formic acid MOFs with similar structure for the enhancement of the dielectric constant and breakdown field strength. Also, in some composite films with methylamine ion guest MOF fillers and low-MOF content ( MOF– Co[Formula: see text] (1 vol.%) and MOF– Ni[Formula: see text] (1 vol.%)), the breakdown electric field enhanced significantly and further led to improved energy storage density which was about 43% higher than that of the polylactic acid matrix. The possible reason is that in these composites, the orientation of C–H bonds of MOFs seems more beneficial to the formation of hydrogen bonds between the carboxyl group of formic acid and the polylactic acid matrix. These relationships obtained from formic acid MOFs/polylactic acid composites are valuable to the design of high-performance polymer/MOF energy storage composites and may be a new perspective to the practical use of ferroelectric MOFs.

Fabrication of a novel chitosan/polyaspartic acid composite: A pH-tunable sorbent for efficient adsorption of heavy metal ions and dyes from water

Heavy metal ions and dyes pollutants have caused significant environmental pollution, posing a threat to human life and ecosystems. Herein, a novel pH-tunable composite adsorbent CS-PA integrated chitosan (CS) with polyaspartic acid (PA) was fabricated. The morphology and structure of CS-PA were characterized. The results indicated that PA was successfully introduced into CS, and the particle size of CS-PA was irregular and porous with a pore diameter of 10–100 μm. Adsorption experiments demonstrated that CS-PA was efficient in removing various charge properties of heavy metal ions and dyes: cationic [Cu(II) and methylene blue (MB)], anionic [Cr(VI) and congo red (CR)] species. Also, the sorption process in the experimental conditions fitted pseudo-second-order kinetic model and Langmuir isotherm. The maximum adsorption capacity of Cu(II), MB, Cr(VI), and CR were 133.33, 172.41, 138.89, and 178.57 mg/g, respectively, based on the Langmuir isotherm study. CS-PA has strong selective sorption ability for MB over Cu(II) under the acidic condition and CR over Cr(VI) at a weakly alkaline solution in their binary systems. Multiple attractions occurred in adsorbing Cu(II), MB, Cr(VI), and CR because of their diverse charge properties and structural characteristics. Finally, regeneration studies further demonstrate that <5 % in sorption efficiency on CS-PA after 5 cycles. Thus, this composite adsorbent is tunable, versatile and potentially applicable to wastewater treatment.

Hesperidin guided injured spinal cord neural regeneration with a combination of MWCNT-collagen-hyaluronic acid composite: In-vitro analysis

Restoring the lost bioelectrical signal transmission along with the appropriate microenvironment is one of the major clinical challenges in spinal cord regeneration. In the current research, we developed a polysaccharide-based protein composite Multiwalled Carbon Nanotubes (MWCNTs)/ Collagen (Col)/ Hyaluronic acid (HA) composite with Hesperidin (Hes) natural compound to investigate its combined therapeutic effect along with biocompatibility, antioxidant activity, and electrical conductivity. The multifunctional composites were characterized via FT-IR, XRD, SEM, HR-TEM, BET, C.V, and EIS techniques. The electrical conductivity and modulus of the MWCNT-Col-HA-Hes were 0.06 S/cm and 12.3 kPa, similar to the native spinal cord. The in-vitro Cytotoxicity, cell viability, antioxidant property, and cell migration ability of the prepared composites were investigated with a PC-12 cell line. In-vitro studies revealed that the multifunctional composites show higher cell viability, antioxidant, and cell migration properties than the control cells. Reduction of ROS level indicates that the Hes presence in the composite could reduce the cell stress by protecting it from oxidative damage and promoting cell migration towards the lesion site. The developed multifunctional composite can provide the antioxidant microenvironment with compatibility and mimic the native spinal cord by providing appropriate conductivity and mechanical strength for spinal cord tissue regeneration.

Plasma actuating modified multiwalled carbon nanotubes (MWCNTs) to strengthen interface of MWCNTs/Polylactic acid composites by constructing interlaminar stress-transfer bridge

A new stepwise hybrid manufacturing (HM) strategy based on plasma-actuating carbon nanotubes is proposed to enhance the interfacial properties of modified multiwalled carbon nanotubes (MMWCNTs)/polylactic acid (PLA) nanocomposites. Although the thermoelectric coupling field caused by plasma can partially destroy the MMWCNTs, it does not affect the functional groups on the MMWCNTs. Meanwhile, under the actuation of the thermoelectric coupling field, the MMWCNTs can react with the PLA matrix to form chemical bonds with a strong intermolecular force, thus forming a stress-transfer bridge between adjacent substrate layers and fully exerting the nanoscale “rib-reinforcing” effect of MMWCNTs to enhance the interlaminar interface. In addition, the proposed HM method can avoid the weakening of the interlaminar interface caused by the orientation of the nozzle and the restriction of MMWCNTs on the matrix activity indicated in conventional manufacturing methods. Experimental and molecular dynamics simulation results confirm the effectiveness of the proposed method in promoting the interfacial properties of MMWCNTs/PLA nanocomposites.

Supercritical CO2 solvent exchange and removal of water from dispersed cellulose nanofiber/polylactic acid composites without an alcohol exchange step

Supercritical CO2 solvent exchange and removal of water from dispersed cellulose nanofiber/polylactic acid composites without an alcohol exchange step