International Journal of Polymer Analysis and Characterization最新文献

A new class of quinolinyl phenol-based benzoxazines (QP-a, QP-cha, QP-2eha) were synthesized by using quinolinyl phenol [4-(6-chloro-4-phenylquinoline-2-yl)phenol] with three structurally distinct amines, namely aniline (a), cyclohexylamine (cha), and 2-ethylhexylamine (2eha) through Mannich condensation reaction using an appropriate solvent and reaction conditions. By using FTIR and ¹H-NMR spectroscopy methods, the molecular structures of the benzoxazines QP-a, QP-cha, and QP-2eha were identified. From the differential scanning calorimetry (DSC) analysis, the exothermic peak maximum of benzoxazine monomers viz., QP-a, QP-cha, QP-2eha were observed at 218, 202 and 187 °C respectively. The thermogram obtained from TGA studies the amount of char yield obtained for poly(QP-a), poly(QP-cha) and poly(QP-2eha) were found to be 45, 24, and 32%, respectively. The value of limiting oxygen index (LOI) for polybenzoxazines was calculated using the value of percentage char yield obtained from TGA studies infer that these benzoxazines exhibit good flame-retardant characteristics. Data from water contact angle studies ascertain that these samples possess good hydrophobic properties in the range of 129–138°. Results from corrosion studies infer that the mild steel specimens coated with these benzoxazines were found to be more stable and offer better surface protection against corrosion under the conditions studied.

Following the recent trends in polymer analysis, a novel fractionation method was developed using xylene as an alternative to trichlorobenzene (TCB) and offering a more exhaustive characterization of the chemical structure of high-density polyethylene (HDPE). The method is based on a linearized evaporative light scattering detector (LinELSD), which has a much better signal-to-noise for the solutions of HDPE in xylene, as compared with the traditional differential refractive index (DRI) and infrared (IR) detectors. The low viscosity of xylene opens the possibility to use the poly(styrene-co-divinylbenzene) (PS-DVB) columns not only for gel permeation chromatography (GPC) but also for temperature-rising elution fractionation (TREF). An immediate application is the simultaneous measurement of the wax fraction’s content and molecular weight (MW) in HDPE. Furthermore, there are strong indications that the thermogram profile corresponding to the isothermal extraction at 70 °C provides a fingerprint of the HDPE synthesis catalyst.

In the present study, the influence of shockwave impact on chitosan (CS) material samples is investigated. The shock tube is used to create the shock wave and the experiments are conducted for a shock Mach number of 1.6. CS material sample is exposed to the shock wave by fixing at the driven tube end flange and impacted to 30, 60 and 90 shock impulses. CS material after the impact was characterized for its structural changes by the Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and viscometer results. The FT-IR results of the treated sample indicate that the bond length is reduced as the functionality of amide increases by lowering the mass of the samples. Significant changes are observed for the CS samples exposed to 90 shock pulses. The degree of deacetylation is increased from 75% to 89%. XRD results indicate that the crystallite size is enhanced by 109% in the treated samples and significant morphological changes are noticed in the SEM images. The viscosity is decreased to 88% and the reduction in molecular weight by 92% indicates the shock-treated CS samples contain high water solubility. Results emphasized that the shock tube technique yields quick findings with favorable changes in the CS depolymerization reaction and demonstrated that it is an efficient, cost-effective and less time-consuming approach.

In tissue engineering bioresorbable polymers are commonly used to mimetize a damaged tissue characteristics. In spite of that, we did not find a comparative study of the response of the same cell to dense, porous, and fibrous biomaterials. The present work aimed to study the in vitro of pure polymers [poly (ε-caprolactone) (PCL) and poly (hydroxybutyrate-co-hydroxyvalerate) (PHBV)] and their 75:25 blend in dense, porous, and fibrous forms in Vero cells, a fibroblast cell line. The biomaterials were characterized morphologically by scanning electron microscopy (SEM). The MTT assay was used for analysis of possible cytotoxicity. Vero cells were cultured on biomaterials for 120 h and submitted to SEM, morphological and cytochemical analyses. The dyes used were crystal violet (morphology), toluidine blue at pH 4.0 (for nucleic acids and glycosaminoglycans) and 2.5 (for glycosaminoglycans only), periodic acid-Schiff reactive (for neutral sugars), xylidine ponceau at pH 2.5 (for total proteins), and picrosirius/hematoxylin (for selective collagen analysis). The biomaterials studied were not considered citocytotoxic. The cells were able to adhere to and proliferate on the substrates. The cytochemical data indicate that the cells have high functional activity, with high protein synthesis on the scaffolds but do not accumulate acid or neutral sugars. The cells on the fibrous polymers appear to be more elongated, following the shape of the fibers. Regarding the scaffold form (porous or fibrous), the in vitro data do not show great superiority of one type to the other. Then, all the polymers tested are suitable for tissue engineering.

Poly(butylene succinate) (PBS), poly(hexamethylene succinate) (PHS) and three kinds of poly(butylene succinate-co-hexamethylene succinate)s (P(BS-co-HS)s) were enzymatically hydrolyzed by Fusarium solani cutinase. The results showed that the characteristics of the enzymatic hydrolysis of these polyesters were mainly affected by crystallinity, thermal properties and the BS/HS ratio. The enzymatic hydrolysis rates of the polyesters are as follows: P(BS-co-HS52) ≈ P(BS-co-HS71) > PHS > P(BS-co-HS32) > PBS. Furthermore, with increasing HS content, both the degree of crystallinity (X_c) and melting temperature (T_m) of the polyesters first decreased and then increased. P(BS-co-HS52) and P(BS-co-HS71) had the lowest X_c and the lowest T_m, thus had the highest hydrolysis rate; this shows that the hydrolysis rate is affected by X_c and T_m. The results also showed that BS/HS ratio could affect the physical properties and degradability of polyesters. Thus, it is possible to prepare polyesters with various physical properties and degradability for different applications by adjusting BS/HS ratio. The crystalline and amorphous regions of the polyesters were both hydrolyzed, during which parts of the crystalline regions were converted into the amorphous regions. Finally, we found that the crystal structure and thermal stability of the polyesters were not affected by the enzymatic hydrolysis.

Cardanol/phenol-based foaming resol resins were prepared successfully by reacting formaldehyde with cardanol/phenol. Phenolic foams were fabricated with the above foaming resol resin and certain foaming agents. Two kinds of resol resins were characterized with Fourier transform infrared spectroscopy, rheological analysis and Scanning electron microscope. Meanwhile, the nonisothermal curing reactions of these resol resins were studied in detail using a dynamic Differential scanning calorimetry technique at a series of heating rates. The global activation energies of the reactions were determined with the Ozawa methods. The results indicated that the peak temperatures of the exothermic reactions and global activation energies of cardanol-based foaming resol resin were higher than those of phenol-based foaming resol resin, which indicated that the more complex molecular structure of cardanol-based foaming resol resin has a negative effect on the curing speed of resin.

The proliferation in substituting traditional petrochemical-based polymer with biobased polymer blends to achieve sustainable materials with outstanding physical, mechanical properties, and biodegradability has been investigated. To emanate biodegradable films with better mechanical properties, the biobased blend of poly (vinyl alcohol) (PVA) was formed with three different oil epoxies namely Castor Oil Epoxy (COE), Mustard Oil Epoxy (MOE), and Til Oil Epoxy (TOE) with varying weight ratios. To examine the changes in physical and mechanical properties, various tests were performed such as tensile test, Shore-D hardness test, and sealability. The permeability of the samples has been studied by the water vapor transmission rate test. Solubility tests in various solvents impart an idea about the workable environment of the samples. Among different PVA/COE blends, the PVA/COE 80/20 blend showed the highest tensile strength while the highest hardness and elongation at break percentage was observed in PVA/COE 60/40 blend. In the case of PVA/MOE blends, PVA/MOE 40/60 blend displayed the best results for hardness and tensile strength while PVA/MOE 30/70 blend possessed the highest value for percentage elongation at break. Lastly, PVA/TOE 30/70 blend exhibited the highest value for tensile strength and percentage elongation at break. PVA/MOE 20/80 sample performed best in a basic environment. In nutshell, PVA modification with epoxide oil can improve the mechanical and biodegradable properties owing to the enhanced crosslinking and hydrophobic association. Ultimately, it was found that PVA/COE 80/20 blend has the best properties to be used as a film forming material as it has performed better or shown comparable properties in most of the tests. The resultant films can be widely used in the packaging industry for packing foodstuffs like fruit, vegetables, dairy products, etc., and also for drink packaging (beverage packaging).

Pressing by ATR (Attenuate Total Reflection) accessory on the sample can cause reversible or irreversible material structure changes in the plastics. In the successive ATR- FT-IR spectra of the PP (polypropylene) film under constant compression, the shift of the baseline and the changes in the peak intensities can be observed, respectively. To interpret the changes in IR absorbances of the PP foil sample, a semi-empirical model is proposed by us. To separate the wavenumber-dependent and independent factors influencing the spectra, a spectrum pre-processing method consisting of baseline correction (rubber band correction) and SNV₁-Anti-SNV₂ transformation (SAS; SNV = standard normal variate) has been developed. With this spectrum pretreatment, the wavenumber-independent effect of the ATR sample holder on the IR spectrum can be compensated. As a result, the wavenumber-dependent effect can be uncovered. The feature of our spectrum pretreatment strategy to eliminate the wavenumber-independent effect is also supported by a mathematical deduction. The significant absorbance change induced by continuous clamping to PP foil has been confirmed by regression analysis. Correlation analysis among the spectral peaks shows strong correlations separately for both the primary and for the transformed spectra. Any peak combination of the primary spectra results in positive correlations. For the transformed spectra reflecting back only the wavenumber-dependent factor effect, the correlations between the peak intensities of the stretching and the bending vibrations are all negative. These negative correlations suggest that the compression applied in the ATR sample holder is give a rise to steric hindrance in deformation vibrations and affects the polarities of C-H valence bonds.

This research evaluates the influence of process parameters of the spark plasma sintering (SPS) technique on the densification and hardness properties of ECR/TiO₂/PI nanocomposite. Taguchi’s design of experiment was employed for designing the sintering process, while analysis of variance (ANOVA) was adopted to evaluate the contribution of the factor variables to the response variable of hardness and density. 10 wt% ECR-glass and 4 wt% TiO₂ were used as reinforcements in the polyimide matrix at varying pressure and temperature for the physical experiment. The sintered samples were examined using a scanning electron microscope, nanoindentation tests, and an Archimedes-based density tester. The optimization was performed on total 9 numbers of runs of experiments. The most desirable SPS processing parameters were recorded at 320 °C and a pressure of 30 MPa. Under this processing condition, a density of 1.49 g/cm³ (relative density of 98.7%), Vickers hardness, and nanoindentation hardness value of 33.46 HV and 361.30 MPa, respectively, were obtained. This research work suggests a facile way to produce high-performance PI nanocomposite for various engineering applications, such as mechanical load-bearing and insulation applications.

Nadic acid-based polyesters were prepared by polycondensation with different diols and different stoichiometry of the monomers. Due to the four stereocenters of the acid component, four diastereomers can form in the polyester. The use of different alcohols and influence on the formation of diastereomers in the polyester was investigated. Identification of the stereoisomers has been done with 1D and 2D NMR spectroscopy, which revealed an influence of the diol component on their formation. Further structural elucidation was done by MALDI mass spectrometry and size exclusion chromatography. Another big influence of the diols was found on the glass transition temperatures, which ranged from −30 °C to 40 °C.