International Journal of Polymer Analysis and Characterization最新文献

Quasi-static tensile tests are commonly used to determine the mechanical properties of fiber bundles. These tests are generally carried out at a low standard speed of 1 mm.min⁻¹, which is recommended for elementary fibers, although other moderate and high speeds are rarely used. In this study, tensile tests were carried out on coir and sisal fiber bundles from the coastal region of Cameroon using four different speeds: 1, 2, 5, and 10 mm.min⁻¹ to assess mechanical properties. Samples were prepared by attaching the two ends of each randomly selected fiber bundle to a paper frame to obtain a length of 30 mm. The results showed a significant effect of extension speed, indicating a decrease in tensile strength and Young’s modulus, and an increase in strain at break with increasing speed. These trends were correlated with the power functions. A strong dependence between fiber bundle diameter and tensile strength was also observed. Furthermore, statistical analysis based on the Weibull distribution highlighted the dispersion of mechanical properties, demonstrating a reduction in dispersion with increasing extension speed for coir fibers. These data can be used to develop specific standards for these natural fibers and contribute to the advancement of composites based on plant fibers.

The present effort reports on the synthesis of novel and recyclable polymer-based adsorbents based on polypyrrole (PPy) and polyethyleneimine (PEI) for the removal of cationic crystal violet (CV) dye from aqueous solutions. The characterization of the composites was determined by FTIR, XRD, FESEM, and XPS techniques. The effects of different variables on the adsorption of crystal violet dye were studied, including the pH, adsorbent doses, and contact time. The research findings show that the different oxidants used to prepare polypyrrole in PPy-PEI adsorbents play a vital role in CV dye adsorption. The PPy-PEI composite prepared by using the ammonium persulfate oxidant was found to exhibit the highest adsorption of 70.9% among the three different oxidants, namely, anhydrous ferric chloride, ferric chloride hexahydrate, and ammonium persulfate. The ideal adsorption conditions for the removal of CV dye were discovered using an adsorbent dosage of 0.3 g at pH 11, with a contact time of 180 min. Kinetic regression analysis indicated that the adsorption processes followed the pseudo-second order kinetic model and fit well with the Langmuir isotherm, with a maximum monolayer sorption capacity of 142.86 mg/g at a temperature of 27 °C. In addition, the regeneration of the PPy-PEI composite was accomplished with dye adsorption efficiency decreasing from 70.9% to 64.4% after three adsorption-desorption cycles. The present work suggests that the PPy-PEI composite is a promising adsorbent for removing cationic CV dye in aqueous solutions.

Recycled polypropylene (rPP) often contains a small amount of polyethylene (PE). Since polypropylene (PP) and PE are incompatible, the presence of PE compromises the performance of rPP materials and needs to be closely monitored. In our previous work, Raman and near-infrared (NIR) spectrometries were evaluated to monitor PE content in rPP with partial least square regression (PLSR) modeling. The NIR spectrometry exhibited a wider application range, but the accuracy of the prediction models might be further improved. In the current work, a different modeling method, principal component regression (PCR) was employed to analyze PE content in rPP with NIR spectrometry. Spectrum pretreatment methods, including multivariate scatter correction (MSC), standard normal variate transformation (SNV), smoothing, and first derivative, were investigated to improve the NIR spectrum quality. Forward and backward interval methods were used to optimize spectral range selection. The outcomes were compared with our previous PLSR modeling results. The highest accuracy in independent validation was achieved by a PCR model with an R² of 0.9991 and a root-mean-square error of prediction (RMSEP) of 0.1596 PE%. On the other hand, a PLSR model achieved the lowest RMSEP of 0.9712 PE% for a non-colored post-consumer rPP sample. The PCR models might be sensitive to interference and more suitable for post-industrial materials, which have a simpler chemical composition. The PLSR models might have better stability and be more suitable for complicated post-consumer samples. Both the PCR and PLSR models were successfully applied to a gray commercial rPP sample.

The selection and evaluation of the hyperelastic model of tread rubber material were of great value and significance to the clarification and application of the mechanical properties of tread rubber material. In this article, a non-contact tread rubber material rolling test bench was established. The improved digital image correlation method was used to calculate the strain rate distribution of the marked point under different test conditions. Combined with the stress distribution of the marked point, the rolling dynamic stress-strain characteristics of tread rubber material were obtained. Based on rubber material models under different tensile test modes, the parameter inversion identification of the hyperelastic model was completed, and the influence of the tensile test mode on the parameter inversion of the tread rubber hyperelastic model was revealed. A new method for selecting and evaluating the hyperelastic model of tread rubber material under rolling contact conditions was proposed. The selection criterion for the hyperelastic model of tread rubber material was developed under different rolling conditions. The experimental and analytical results show that the nonlinear degree of the constitutive relation of the hyperelastic model decreased with the increase in rolling speed. Compared with hyperelastic models under different tensile modes, the fitting error of the Yeoh model was less than 3%, and the overall fitting error of the Yeoh model was less than 2%. Therefore, the Yeoh model had better stability and accuracy and was more suitable for describing the rolling mechanical properties of tread rubber under rolling contact conditions.

In this article, maleic anhydride (MA) was used to graft-modify chitosan (CS) to obtain maleic anhydride-modified chitosan (MCS). Composite films with different ratios were prepared by melt blending-extrusion pelletizing-blown film using Poly (butylene adipate-co-terephthalate) (PBAT) as the substrate and CS or MCS as the filler. These films can be utilized in a variety of ways, such as food packaging, agricultural mulching film, and more. The composite films were characterized and tested by a Fourier transform infrared (FTIR) spectrometer, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), scanning electron microscope (SEM), and electronic universal testing machine, and the effects of different fillers and filler contents on the properties of the composite films were investigated. The results showed that the thermal stability of the composite films decreased slightly with the increase in filler ratio, the melt crystallization temperature increased and then decreased, and the tensile strength and elongation at break of the composite films decreased. Compared with unmodified CS, MCS had better dispersion and compatibility when blended with PBAT, and the interaction between MCS and PBAT was greater than that of CS. The optimal filler amount of MCS was 6% for the combination of film material cost and performance considerations.

This investigation explores the water intake characteristics of hybrid composite samples composed of Wood Dust as organic filler (WD), Prosopis Juliflora as fiber (PJF), and epoxy as matrix. The specimens underwent immersion in both distilled and seawater environments for a duration of 240 hours. The composite samples, with compositions of 10WD + 30PJF + 60 PF, 20WD + 20PJF + 60 PF, and 30WD + 10PJF + 60 PF, were subjected to moisture content measurements at different intervals. Mechanical properties were tested following ASTM standards for both dry and wet conditions. Results indicate that seawater immersion leads to higher moisture absorption compared to distilled (condensed) water, with the fiber (PJF)-rich composite (30PJF +10WD + 60 PF) exhibiting the greatest water absorption. The water absorption pattern exhibited by the hybrid composite of WD/PJF/PF does not adhere to a Fickian behavior. Tensile, flexural, and impact properties were evaluated, with the (10WD + 30PJF + 60 PF) specimen showcasing superior performance in dry conditions, boasting a tensile character of 51 MPa, flexural (bending) strength of 60 MPa, and impact value of 1.4 KJ/m². However, its strength diminishes upon exposure to distilled water and seawater. SEM analysis of fractured surfaces from seawater-exposed specimens provides additional insights. In conclusion, this study sheds light on the influence of immersion on moisture absorption and mechanical properties, emphasizing the prevalence of non-Fickian behavior and the varying performance of different compositions, with the (10WD + 30PJF + 60 PF) composition demonstrating remarkable strength under dry conditions.

Polyacrylonitrile (PAN) fiber modification can promote the stabilization efficiency and mechanical properties of the subsequent carbon fibers; however, it could cause damage to the fibers to some extent. In this article, the effects of NaIO₄ treatment on the chemical and physical properties of PAN fibers were investigated. After NaIO₄ modification, the cyclization reaction has partially occurred, owing to the FTIR revealed that the C≡N peak was weakened, but the C=N stretching vibration peak, the –N = C=O stretching vibration peak, the C=O stretching vibration absorption peak, and the short sequence conjugate C=N characteristic peak were enhanced simultaneously, indicating a successful cyclization and dehydrogenation reaction. Moreover, owing to more oxygen-containing functional groups successfully attached to the PAN fibers and the cyclization reaction taking place, the initial temperature, peak temperature, and heat release of cyclization decreased, which means a more efficient and safer stabilization process. X-ray diffraction (XRD) showed that the (100) crystal plane microcrystal size was the smallest at 40 °C of the modification temperature, whereas the (002) crystal plane microcrystal size was the largest at 60 °C. The modified stabilized PAN fibers presented lower crystallinity and a more aromatic structure compared with untreated fibers. Raman spectra revealed a significant increase in the intensity of the G peak after NaIO₄ modification; the R-value decreased from 1.65 to 1.43, demonstrating a transformation of the sp³ hybrid carbon structure into a more graphite-like sp² hybrid C=C structure. Meanwhile, scanning electron microscopy (SEM) images disclosed additional grooves and cracks on the fiber surface after modification.