Peiying Guo

Effects of Crystallization Temperature and Blend Ratio on the Crystal Structure of Poly(butylene adipate) in the Poly(butylene adipate)/Poly(butylene succinate) Blends

The effects of crystallization temperature and blend ratio on the polymorphic crystal structures of poly(butylene adipate) (PBA) in poly(butylene succinate) (PBS)/poly(butylene adipate) (PBS/PBA) blends were studied by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD) and atomic force microscopy (AFM). It was revealed that the polymorphism of PBA can be regulated by the blend ratio even in a non-isothermal crystallization process. The results demonstrate that high temperature favors flat-on α crystals, while low temperature contributes to edge-on β crystals. It was also found that the effect of blend ratio on the crystallization mechanism of PBA is well coincident with that of the crystallization temperature. The increment of PBS content in the PBS/PBA blend gives rise to more β-form crystals of PBA. For those PBS/PBA blends with low PBA content, the interlamellar phase segregation of PBA makes its molecular chains so difficult to diffuse from one isolated microdomain to another that high crystallization temperature and sufficiently long crystallization time will be required if the PBA α-type crystals are targeted.

Effects of crystallization condition of poly(ethylene succinate) on the crystallization of poly(ethylene oxide) in their blends

The effects of the crystallization temperatures of poly(ethylene succinate) (PES) on the crystallization behavior of poly(ethylene oxide) (PEO) in their blends were investigated by means of differential scanning calorimetry, atomic force microscopy, and laser confocal fluorescent microscopy. It was found that confined and fractional crystallization of PEO takes place in the PES/PEO blends at all blend ratios if PES is crystallized at higher crystallization temperatures. And morphological observation gives a direct evidence of the different location distribution of PEO, resulting in the confined and fractional crystallization behavior.

Mechanical Properties and Wear Resistance of Sulfonated Graphene/Waterborne Polyurethane Composites Prepared by In Situ Method

In order to improve the dispensability of graphene oxide (GO) in waterborne polyurethane (WPU), sulfonated graphene (SGO) with superior dispersity was prepared by modifying graphene oxide with sodium 2-chloroethane sulfonate to introduce hydrophilic sulfonic groups into the structure. SGO/WPU composites were prepared using isophorone diisocyanate (IPDI), polytetramethylene ether glycol (PTMEG 2000), dimethylolpropionic acid (DMPA) and SGO as raw materials. The influence of SGO content on composite properties were investigated. The structure and morphology of SGO and SGO/WPU composites were characterized by infrared spectroscopy, X-ray diffractometry and transmission electron microscopy etc. Their mechanical properties and wear resistance were analyzed as well. The experimental results showed that SGO was successfully grafted onto polyurethane macromolecule by an in situ method and, with the introduction of sulfonic groups, the interfacial compatibility of GO and PU was improved significantly so that SGO evenly dispersed into WPU. The SGO that was grafted onto WPU macromolecules exhibited layered morphology with nanometers in the WPU matrix. With increasing SGO content, the tensile strength and the wear resistance of the film increased, but the addition of more than 0.8 wt % SGO yielded unfavorable results. When the added amount of SGO was 0.8 wt % of WPU, the tensile strength of the composite film was 46.53% higher than that of the blank group, and the wear resistance of the film was remarkably improved, which was due to a strong interaction between the SGO and WPU phases. Thus, the conclusion can be drawn that appropriate amount of SGO addition can enhance the mechanical properties of SGO/WPU composite film.

Improving moisture absorbent and transfer abilities by modifying superfine fiber synthetic leather base with collagen-chrome tannins

The superfine fiber synthetic leather base (SFSLB) is composed of the two components of nylon fibers and polyurethane. SFSLB has excellent performance, especially in terms of mechanical properties. However, compared with native leather, SFSLB has a hot feeling due to its poor moisture absorbent and transfer abilities. So our study proposed a method of grafting collagen-chrome tannins (C-CrT) on nylon fiber in the SFSLB for improving the moisture absorbent and transfer abilities. A three-step surface modification was developed, involving washing pretreatment, sulfuric acid hydrolysis and grafting of C-CrT on SFSLB. The dosage of sulfuric acid and chrome tannins, bath ratio, reaction temperature and the time for collagen permeation and chrome tannin cross-linking were optimized via single-factor experiments. Their efficiency was determined by measuring static water-vapor transmission rate (SWVT) and liquid wicking rate. The results showed that the dosage of sulfuric acid was 15% and chrome tannins was 5%, the bath ratio was 1500%, the reaction temperature was 60℃ and the time for collagen permeation and chrome tannin cross-linking was 3 hours. Under this condition, the SWVT of modified SFSLB was 986 g/m2 · 24 h, and the liquid wicking rate was 1.323 mm/s. Compared with untreated SFSLB, the SWVT and liquid wicking rate of modified SFSLB were improved by 90.35% and 344%, respectively. The static state contact angle, scanning electron microscopy and X-ray photoelectron spectroscopy were used for the determination of sample surface performance, morphology and chemical composition, and states before and after treatment, respectively.

Study on the improvement of water vapor permeability and moisture absorption of microfiber synthetic leather base by collagen

The microfiber synthetic leather base pretreated by sulfuric acid was modified by collagen in which the organic phosphine FP was used as a cross-linking agent, for the purpose of increasing the active groups and improving its properties. Compared with the pretreated base, it was found that the amino content in the modified base was two times and the carboxyl content was three times. The water vapor permeability of the modified base increased by 65% and the moisture absorption increased by 181%. It was further found that the tensile strength of the modified base was 19.06 N/mm2, the elongation at break was 54% and the tear strength was 112.34 N/mm. The test results of Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, thermogravimetric analysis and water contact angle showed that the collagen molecules had evenly cross-linked with fiber. The modified base microfiber dispersion was greatly increased, the hydrophility was enhanced and the relative average roughness was decreased. Moreover, modification by collagen also affected the thermal properties of the base.

Modification of PA/PU superfine non-woven fiber for “breath” property using collagen and vegetable tannins

Unfigured sea-island superfine fiber PA/PU non-woven (USFSLB) is used to mimic leather’s microstructure as the base of artificial leather. USFSLB has many characteristics and advantages resembling those of natural leather. However, compared with natural leather, the wearing comfort of artificial leather is inferior due to its poor moisture adsorption and permeability. In this work, a “two-step” method of chemical treatment is proposed, in which collagen/chromium-vegetable tannin (C-CrT) is immobilized on nylon fiber of USFSLB to improve its moisture adsorption and permeability (“breath” property). The two-step surface modification involved sulfuric acid hydrolysis and modifying the C-CrT on nylon fiber. Compared with the pristine USFSLB, the tensile strength, the elongation at break, the anti-static performance, the thickness, and the uniformity of C-CrT-treated USFSLB were improved at different levels. Importantly, the C-CrT-treated USFSLB showed excellent moisture adsorption and permeability, especially the liquid wicking rate (LWR) improved by 344%. The self-assembly mechanism of collagen/chromium-vegetable tannin (C-CrT) modified on nylon fibers was analyzed and discussed.

Properties of polymers as a nanoscale material for fibers in leather

Hyperbranched polymers, an innovative class of nano-polymers, could enhance the properties of fibers owning to their unique structures. In this study, the ester compound (HPAE) of 3-(bis(2-hydroxyethyl)amino)propionic acid and pentaerythritol was treated with undecylenic acid to obtain novel hyperbranched multiterminal alkenyl polymers (HPAE-UAs). The sizes of the HPAE-UAs could be controlled conveniently from 400 to 1300 nm by adjusting the capped fraction of the hydroxyl groups with undecylenic acids. The molecular structures of HPAE-UAs were characterized by means of FT-IR and 1H-NMR. Then, the effect of the HPAE-UAs on the structures, thermal, and mechanical properties of the wet blue leather were investigated. TEM and SEM demonstrated that the spacing between fibers was enlarged. The thermogravimetric analysis showed that the residual volume of leather could reach up to 30.3 % at about 500 °C. Furthermore, the shrinkage temperature increased to 89.4 °C. It was found that the HPAE-UAs used in leather could improve the thermal performance, physical and mechanical properties. All of these results indicate that HPAE-UAs can be used as a fatliquor with retanning in leather process.