Haroon A. M. Saeed

Effect of hot drawing on the structure and properties of novel polyamide 5,6 fibers

Polyamide 5,6 (PA 5,6) fibers were prepared using the melt-spinning method. The effects of draw ratio and temperature on the structure and properties of PA 5,6 fibers were investigated by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction, sonic velocity and tensile test measurements. DSC results revealed that the melting temperature showed no considerable variation, while the heat of fusion increased with increments with draw ratio and temperature. It was found that the crystallinity and crystal size of PA 5,6 fibers were directly proportional to the draw ratio and temperature and the orientation factor increases as expected upon drawing. The tenacity and Youngs modulus were found to be increased, while the elongation at break decreased with the draw ratio and temperature. The improvement in mechanical properties may be attributed to the increase of orientation along the fiber axis and the crystallinity.

Deep Eutectic Solvents (DESs) for the Isolation of Willow Lignin (Salix matsudana cv. Zhuliu)

Deep eutectic solvents (DESs) are a potentially high-value lignin extraction methodology. DESs prepared from choline chloride (ChCl) and three hydrogen-bond donors (HBD)—lactic acid (Lac), glycerol, and urea—were evaluated for isolation of willow (Salix matsudana cv. Zhuliu) lignin. DESs types, mole ratio of ChCl to HBD, extraction temperature, and time on the fractionated DES-lignin yield demonstrated that the optimal DES-lignin yield (91.8 wt % based on the initial lignin in willow) with high purity of 94.5% can be reached at a ChCl-to-Lac molar ratio of 1:10, extraction temperature of 120 °C, and time of 12 h. Fourier transform infrared spectroscopy (FT-IR) , 13C-NMR, and 31P-NMR showed that willow lignin extracted by ChCl-Lac was mainly composed of syringyl and guaiacyl units. Serendipitously, a majority of the glucan in willow was preserved after ChCl-Lac treatment.

Parameters characterizing the kinetics of the non-isothermal crystallization of polyamide 5,6 determined by differential scanning calorimetry

Abstract The non-isothermal crystallization behavior of polyamide 5,6 (PA56) was investigated by differential scanning calorimeter (DSC), and the non-isothermal crystallization kinetics were analyzed using the modified Avrami equation, the Ozawa model, and the method combining the Avrami and Ozawa equations. It was found that the Avrami method modified by Jeziorny could only describe the primary stage of non-isothermal crystallization kinetics of PA56, the Ozawa model failed to describe the non-isothermal crystallization of PA56, while the combined approach could successfully describe the non-isothermal crystallization process much more effectively. Kinetic parameters, such as the Avrami exponent, kinetic crystallization rate constant, relative degree of crystallinity, the crystallization enthalpy, and activation energy, were also determined for PA56.

Synthesis and characterization of A2 + B3 type hyperbranched aromatic-aliphatic polyester with carboxyl end groups

New types of carboxyl-terminated hyperbranched polyesters (HBPEs) with aromatic-aliphatic structure were synthesized by single step-melt polycondensation of adipic acid (as A2 monomer) and phloroglucinol (as B3 monomer) as a core via A2 + B3 approach, at three different monomer mole ratios (A2/B3 = 1: 1, 1.5: 1, 2: 1, respectively). FTIR spectroscopy indicated that the polymers contained hydroxyl groups, ester bonds, benzene ring, methyl and methylene groups, which were in agreement with the expected HBPEs. The HBPEs have inherent viscosities about 0.24 to 0.27 dL/g. The degree of branching of the HBPEs was estimated to be 0.45–0.49% by 1H-NMR and 13C-NMR measurements. The melting temperature of HBPE-1, HBPE-2 and HBPE-3 were 154, 155 and 160°C respectively measured by differential scanning calorimetry (DSC). The synthesized polymers were thermally stable; the thermogravimetric analysis (TGA) measurement revealed that HBPEs had 10% weight loss at 310°C in nitrogen.

Mechanical properties, moisture absorption, and dyeability of polyamide 5,6 fibers

Polyamide 5,6 (PA56) and polyamide 6 (PA6) fibers were spun by melt spinning process and drawn by a thermal drawing in order to improve their mechanical properties. The effects of drawing conditions on mechanical properties, moisture absorption, and dyeing behavior were investigated by means of tensile testing measurements, moisture absorption test, as well as color strength measurements. It was found that the tenacity and Young’s modulus were significantly increased, while the elongation at break decreased as the draw ratio (DR) and temperature increased due to the increase in molecular orientation along the fiber axis and the crystallinity. PA56 fibers showed a little lower mechanical properties and much higher moisture regain than PA6 fibers at different DRs. This can be attributed to the amide group content in the polymer backbone, which yields higher moisture regain in PA56 fibers than PA6 fibers. The dyeing behaviors of PA56 fiber, in terms of dyebath exhaustion, color strength, and wash fastness are similar as those of PA6. Those results indicated that PA56 is a competitive novel fiber for textile material.

Properties of recycled poly (ethylene terephthalate) (PET)/hyperbranched polyester (HBPET) composite fibers

Hyperbranched polyester (HBPET) with aliphatic–aromatic structure was synthesized and extruded with recycled poly (ethylene terephthalate) (RPET) chips obtained from used water bottles, with ratio of 0.5% and 1 wt% of HBPET. Filament fibers from pure recycled PET (RPET-0) and (RPET-0.5 and RPET-1) composite were spun using a melt spinning process and drawn by a thermal drawing process to improve their mechanical properties. The effects of addition of HBPET on the properties of produced fibers as well as draw ratio are investigated by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD), universal tensile analysis, and sonic velocity. It was found that mechanical properties of the (RPET-0.5 and RPET-1) fibers were improved with respect to pure recycled PET (PET-0) fibers. Moreover, the crystallinity of composites fibers was also increased with an increasing of HBPET content. The improvement in mechanical properties may be due to the increase of orientation of fiber molecules along the fiber axis. Moreover, addition of HBPET serves as lubricant within recycled PET matrix which increased its mechanical properties.

Preparation of Polyamide 5,6 (PA56) Fibers and its Mechanical Properties

Polyamide 5,6 (PA56) fibers were successfully prepared by melt-spinning technique. PA56 fibers were subjected to hot drawing process at different draw ratio and temperature. The effect of the drawing conditions on their mechanical properties such as tenacity, tensile modulus and breaking elongation were investigated by means of tensile test measurements. The results revealed that the tenacity and tensile modulus were found to be increased, while the elongation at break decreased with the draw ratio. The improvements of the mechanical properties could be attributed to the enhanced of the molecular orientation along the fiber axis and an increase in crystallinity. On the other hand, the PA56 fibers mechanical properties do not show significant difference with the drawing temperatures.

Synthesis and Characterization of A2+B4 Hyperbranched Polyesters with Hydroxyl End Groups

Hydroxyl-terminated hyperbranched polyesters (HBPET) with aromatic-aliphatic structure were synthesized by melt polycondensation of isophthalic acid and pentaerythritol via A2+ B4 approach, at three different monomer mole ratios (A2/B4 =1:1, 1.5:1, 2:1, respectively). Fourier transform infrared (FTIR) spectroscopy indicated that the expected HBPET. The degree of branching of the HBPET was estimated to be between 0.39–0.45 by 1H-NMR and 13C-NMR measurement. The thermogravimetric analysis ( TGA ) measurement revealed that HBPET had a 10 % weight-loss at 350°C in N2.

Sudanese Dicots as Alternative Fiber Sources for Pulp and Papermaking

The suitability of the stems from two Sudanese dicotyledonous annual plants, namely castor bean (Ricinus communis) and Leptadenia pyrotechnica (L. pyrotechnica) were investigated for pulp and papermaking. Chemical compositions, elemental analysis, fi ber dimensions, paper physical properties and morphology revealed a relatively high α-cellulose content (46.2 and 44.3 %) and low lignin (19.7 and 21.7 %) in the stems of castor bean and L. pyrotechnica, respectively. The average fi ber length of castor bean and L. pyrotechnica is 0.80 and 0.70 mm with fi ber width of 16.30 μm and 18.20 μm, respectively, which makes them acceptable candidates. SodaAQ pulping of castor bean stem led to a higher pulp yield of 43.2 % at kappa number 18.2 compared to 40.3 % at kappa 20.3 for L. pyrotechnica. This yield is less than that obtained for wood plants and similar to that observed for annual plants. Paper handsheets produced from castor bean showed better mechanical properties than L. pyrotechnica. SEM images indicated that the produced papers were quite homogeneous, compact, closely packed, and well assembled.

Synthesis and characterization of aliphatic-aromatic hyperbranched polyesters with high organosolubility

Carboxyl-terminated, water soluble, hyperbranched polyesters (HBPET) with aliphatic-aromatic structure were synthesized at three different monomer mole ratios (A3/B3 = 1: 1, 2: 1, 1: 2, respectively) by melt polycondensation of aconitic acid and phloroglucinol via A3+ B3 approach. Fourier transform infrared (FTIR) spectroscopy indicated as that was expected HBPET, which showed excellent solubility in a variety of polar solvents such as N,N-dimethyl formamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), and tetrahydrofuran (THF). The weight-average molecular weight of HBPET ranged from 7792 to 9214 g mol−1 and their intrinsic viscosity were varied from 0.17 to 0.34 dL g−1. The degree of branching of the HBPET was estimated to be 0.44–0.49 by 1H and 13C NMR measurement. The thermogravimetric analysis (TGA) measurement revealed that HBPET was of 10% weight-loss at 340°C in N2.