Journal of Polymer Research最新文献

Enhanced interfacial polarization is one of the most effective methods for efficient electromagnetic wave absorbing (EMA) performance. In this study, we propose a cladding morphology modulation strategy for preparing high-performance PPy/MWCNTs(PC) by controlling the polymerization cladding morphology of PPy through acid doping using an in-situ polymerization method. By constructing a 3D network structure with a rough surface, many interfaces and pore spaces are generated to increase the multiple reflections and scattering of electromagnetic wave energy, improve the interfacial polarization of the material, and enhance the polarization relaxation process. Meanwhile, the 3D conductive network generated by the cladding provides a channel for electron transfer between MWCNTs and PPy nanoparticles and PC nanorods, which improves the conductivity loss of the material and allows more electromagnetic wave to be dissipated in the form of thermal energy. With the doping acid of p-toluene sulfonic (TsOH), the EMA absorption performance of PC composites can reach a maximum reflection loss(({RL}_{min})) of -60.21 dB at the frequency of 8.24 GHz, and the best effective bandwidth (EAB_max) of 5.04 GHz for single thickness and 14.08 GHz for full-thickness (EAB_sun), providing excellent EMA performance.

Polylactic acid (PLA) shows high potential for various fields such as food packaging and biomedical applications due to its biodegradability and low toxicity. However, the shortcomings including brittleness and low thermal stability limit its real applications. In this study, we fabricated PLA/polyhydroxyalkanoate (PHA) compound to overcome the brittleness of PLA. Then we investigated the effects of cellulose, derived from paper waste, on the thermal and mechanical properties of PLA/PHA compounds. While cellulose negligibly affected the glass transition temperatures of PLA and PHA, the cold crystallization temperature of PLA was reduced and its degree of crystallization was increased, after the addition of cellulose. With the increase of cellulose contents, the reduced tensile strength, the increased elastic modulus, and the reduced elongation at break of the compounds were observed, attributing to the aggregation formation of cellulose. Heat deflection temperature of the compounds was raised after the addition of cellulose.

Natural fibers are eco-friendly material, they cause less pollution and minimal health hazards. Hybrid composites are those composites that uses two or more fibers as reinforcement. The lightweight property of the natural fibers is used in production of lighter composites which have lesser density compared to that of glass composites. Vetiver is known for its uses in construction field due to their desirable heat absorbing properties. Jute is mostly used in textile and carpet industries. In current market trends, natural fiber composites are experiencing a steady growth in construction industries and have potential to replace synthetic fiber composites in many applications in the coming future. The focus of the present research is on examining mechanical properties (impact, flexural, tensile, and hardness tests), and morphological (Scanning Electron Microscope- SEM) characterizes on vetiver -jute fiber hybrid composite. The composite materials are created using various layering patterns in varying proportion with epoxy resin and fiber. The Jute-Vetiver-Jute hybrid composites shown superior tensile strength (25.43 MPa), flexural strength (55.18 MPa), impact (26.48 J/m), and hardness (84 Shore D) than with both the neat and hybrid epoxy composites. It was noted that, comparing the stacking sequence, the sandwich type prepared composite shows better mechanical and morphological properties than the layer by layer composite preparation and results that emerged from the research have the potential to be utilised for the effective implementation of a different set of industrial applications.

The Coconut Shell Fillers (CSF) loaded with different wt% (10, 20, 30, 40, and 50) and reinforced with a single layer of Pine Apple Fibre Mat (PAFM) epoxy sandwich polymer composites were fabricated through closed mold hand layup techniques. The sandwich composite specimens were carried out the mechanical characterization and found the maximum tensile strength (42 ± 0.5 MPa), compressive strength (39 ± 0.5 MPa), flexural strength (133 ± 0.5 MPa), and Shore D Hardness (90 ± 0.5 SHN). Using X-ray diffraction (XRD) analysis of the CSF, the fillers’ cubic and tetragonal structures were discovered. The Field Emission Electron Microscope (FESEM) was revealed the surface morphology of the 30 wt% CSF loaded PAFM sandwich composite. The different elements present in the composite were identified through Energy Dispersive X-Ray Spectroscopy (EDX) such as O₂, Mg, Si, N, Ca, and Cl respectively. The melting point, energy absorption, and thermal degradations of the composite was found through Differential Scanning Calorimetric (DSC) and Thermogravimetric analysis (TGA). The energy absorbed by the composite was − 11.46 J/g at the peak temperature of 279.5ºC. The onset exothermic temperature is 256.9ºC and the end temperature is 285.5ºC. The newly fabricated CSF fillers loaded PAFM reinforced sandwich composite could be used in switchboard panels, door panels in bathrooms, modular kitchens, and interior cabins.

Research on Natural Fiber Reinforced Composites (NFRCs) is growing at an exponential rate due to their eco-friendliness and high potential to replace synthetic and traditional materials in a variety of applications. These materials are not only environmentally friendly, but also have other qualities including greater strength, lightweight, inexpensive, and biodegradable. In this research, five distinct composites were made: two of them are non-hybrid Jute (20 J) and flax (20 F) fibres, while the other three composites were made with various weight proportions of fibres (15 J/5F, 10 J/10F, and 5 J/15F), which were hybridized into polyester resin using a hand lay-up approach. Experimentation was done to study the tensile, flexural, and impact strengths of the prepared composites. The interaction between the fibres and polyester resin was investigated using Scanning Electron Microscopy (SEM). The chemical compounds, fibre constituents, and bonds present in the hybrid composite were analyzed using Fourier Transform Infrared Spectroscopy (FTIR). A water absorption study is carried out to verify the hybrid composites for use in outdoor and indoor environments. The results demonstrated that flax and hybrid composites made with high flax weight content have superior tensile, flexural, and impact strength when compared to jute composites. In contrast, jute and hybrid composites with high jute weight content absorb more water than flax fibres because jute fibres contain less cellulose content than flax. Applications for these composite materials include automotive, packaging, infrastructure, and indoor and outdoor use.

Intrinsic moisture permeability of bio-based polymer cellulose diacetate (CDA) is not sufficient for some requirements. Herein, isophorone diisocyanate (IPDI) modified polyethylene glycol (IPEG200) was served as a reactive plasticizer to enhance the water vapor permeability (WVP) of CDA films without plasticizer migration problems. The performances of CDA films were further improved by adding hydrophilic nanometer Al₂O₃ fillers. Fourier transform infrared spectroscopy (FTIR) was used to the synthesis processes of the prepolymers and their reaction with CDA chains. The crosslinking reaction was indicated by monitoring the gel content. When IPEG200 is 9.66 phr and Al₂O₃ filler is 5 phr, the WVP is raised to 8.9 × 10⁻¹³ g·cm/cm²·s·Pa, which is much higher than CDA’s. WVP 14.2 × 10⁻¹³ g·cm/cm²·s·Pa of CDA film can be obtained by adding 60 phr PEG600 and 25 phr Al₂O₃ when using IPEG200 as the compatibilizer. This study provides a simple, feasible, low-cost method for preparing high moisture permeable film by reactive plasticizers.

This experimental study investigates the impact of different silicon-to-alumina (Si/Al) ratios on geopolymers synthesized from metakaolin. Various ratios of Si/Al (1:1, 1.5:1, 2:1, 3:1, 4:1, and 5:1) were employed, nano-silica was the source material to alter the Si ratio. Microstructure and strength were analysed using SEM, XRD, NMR, and compressive strength testing Geopolymerization, a sustainable material synthesis process, was investigated using FTIR spectroscopy and computational modeling. The dissolution rates of aluminum and silicon molecules, as well as the formation of N-A-S-H gel, were studied. Results revealed that a Si/Al ratio of 2:1 significantly enhanced the dissolution of silicon and aluminum, leading to the formation of Si-O-T bonds and superior compressive strength. Computational analysis confirmed that the mechanical performance was primarily attributed to the formation of N-A-S-H gel, rather than zeolitic nuclei or silicate derivatives. These findings provide valuable insights for the application of geopolymerization in valorizing mine tailings, which often exhibit high Si/Al ratios.

Cellulose nanofibrils (CNFs) and dodecenyl succinic anhydride (DDSA) were used to prepare modified cellulose nanofibrils (D-CNFs). D-CNFs are partially wettable and can be used as ideal Pickering emulsion stabilizers. Moreover, the stability of D-CNFs in emulsion is better than that of CNFs. When the concentration of D-CNFs increased to 3.0wt%, the fluidity of the emulsion decreased significantly. Typically, the best performance was exhibited when D-CNFs were added at a concentration of 1.2wt%. Emulsions were more stable in alkaline environments when compared to low pH values. The droplet size of the emulsions increased significantly due to the addition of ions. However, in terms of macroscopic stability (CI), the emulsions could remain without delamination for 7 days when the NaCl concentration is not higher than 50mM. The results showed that D-CNFs can be used to prepare Pickering emulsions and have a good development prospect.

Graphical Abstract

This study employed the template method to fabricate microneedle (MN) arrays from hydroxyethyl methacrylate (HEMA) hydrogel: a high-drug-load pyramid-shaped microneedle array (MN-A) and a low-pain volcano-shaped microneedle array (MN-B). In addition, a pen-tip-shaped microneedle array (MN-C) was developed on the basis of the characteristics of the aforementioned two types of arrays. The results indicated that HEMA hydrogel, when photopolymerized under a fixed ultraviolet A (365 nm) intensity of 25 mW/cm² for 15 min, achieved optimal polymerization, with its elongation, moisture content, oxygen permeability, and maximum load-bearing capacity being 80%, 55.1%, 22.8 barrer, and 96.5 gf/cm², respectively. In addition, when the three microneedle arrays were fabricated from HEMA hydrogel under the aforementioned optimal process parameters, they exhibited penetration diameters of less than 500 μm and penetration depths of 300–600 μm in pig ear piercing experiments. Among the three microneedle arrays, the MN-A array exhibited the highest drug load and effective penetration depth, whereas the MN-B array exhibited the smallest wound area, thereby effectively reducing tingling sensation. The MN-C array, which was an improvement over the MN-A and MN-B arrays, not only exhibited the highest penetration stress (3.9 mN) but also retained the high drug load and low tingling sensation characteristics of the other two arrays. These findings suggest that microneedles produced from HEMA hydrogel by using the template method not only possess excellent mechanical stability and skin penetration capabilities but also have high potential for use in applications related to dermatology and cosmetology.

In the present framework, we aimed to elaborate intumescent composites polyurethane/ organically treated montmorillonite (PU/ OMMT) foams by the use of local “Bentonite” called “Maghnite”. These composites were elaborated via an in situ polymerization. The first stage relates to the organic treatment of the montmorillonite (MMT) using an alkylammonium (hexadecylamine C₁₆H₃₅N) in order to increase the interfoliate distance, resulting in an organically compatible modified montmorillonite (OMMT). The second one is reserved to the optimization of the polyurethane (PU) formulation. Composite’s foams (PU/ OMMT) are formulated via the free expansion process. Moreover, the physicochemical characterization of the developed foams was carried out. Characterization of the obtained foams have been done by various methods such as: FTIR, DSC, TGA, XRD, SEM, Charpy test, and normalized flammability test (UL 94 HB). FTIR analysis confirms the PU formation and the incorporation of the organically treated montmorillonite (OMMT) into the polyurethane (PU) via the in-situ polymerization. Add to that, it is assigned by the XRD analysis that the interfoliate distance has been increased from 11.63°A to 27.96°A using the hexadecylamine and the PU/ OMMT composite foams present a mixture of intercalated and exfoliated structure. The SEM images prove that the addition of 5 wt % of OMMT has resulted in similar cell size compared to the pristine PU formulation (about 100 µm). DSC and TGA analysis proved the good thermal stability of PU foams and confirmed that the PU/ OMMT composite foam is the most stable one. Regarding the fire behavior, the obtained foams are in accordance with the normalized flammability test. The strength and tenacity test revealed improved mechanical properties in comparison to those not treated.