Jingxin Lei

Preparation of waterborne polyurethanes based on the organic solvent-free process

A green waterborne polyurethane (WPU) was prepared based on an organic solvent-free process, using sodium 2,4-diaminobenzenesulfonate (SDBS) as a chain extender. Water was only used to dissolve the solid reactants and reduce the viscosity, obtaining the homogenized reaction mixture. Characterization results showed that this green WPU presented similar mechanical properties and water resistance with conventional WPU whose synthesis process involved organic solvents. In addition, the use of SDBS eliminated the employment of catalysts and reduced the reaction time and temperature of the chain extension step, resulting in the conservation of energy.

Novel solid–solid phase change materials with biodegradable trihydroxy surfactants for thermal energy storage

Polyurethane polymers were synthesized as novel solid–solid phase change materials (SSPCMs) by bulk polyaddition in the absence of organic solvents, in which polyethylene glycol (PEG) was selected as the working phase change substance and Span 80 and Tween 80 were used as crosslinking agents for the first time. The chemical structures, crystalline properties, phase change properties and thermal stability of the synthesized SSPCMs were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). An accelerated thermal cycling test was carried out to reveal the thermal reliability of the synthesized SSPCMs. The XRD patterns showed that the synthesized SSPCMs have a completely crystalline structure and defective crystallization compared with the pristine PEG. The DSC results showed that the synthesized SSPCMs have suitable phase change temperatures of 37–48 °C and high latent heats in the range of 120–130 J g−1. TG results showed that the synthesized SSPCMs possess good thermal stability.

Preparation and Characterization of Thermoplastic Elastomer Based on Amino-terminated Polyamide-6 and Diisocyanate-terminated Polytetramethylene Glycol

ABSTRACT Polyamide thermoplastic elastomers are successfully synthesized by adding polycondensation of amino-terminated polyamide-6 (with a molecular weight of 1000 and 2000 g/mol) and diisocyanate-terminated polytetramethylene glycol (with molecular weight of 1500 and2500 g/mol) with dimethylacetamide as solvent at 140°C. The structures of oligomers and polyamide thermoplastic elastomers are characterized by Fourier transform infrared. The thermogravimetry analysis result shows that the product displays good thermostability. Differential scanning calorimetry curves of polyamide thermoplastic elastomers exhibit two melting temperatures indicating phase separation of polyamide thermoplastic elastomers. Besides, the polyamide thermoplastic elastomers display excellent mechanical properties of high tensile strength (33–61 MPa) and high elongation at break (384–1220%). GRAPHICAL ABSTRACT

Preparation and thermal properties of crosslinked polyurethane/lauric acid composites as novel form stable phase change materials with a low degree of supercooling

In this article, a series of crosslinked polyurethane/lauric acid composites was prepared as form stable phase change materials (FSPCMs) through a brief and solvent-free method. In the FSPCMs, lauric acid functioned as a phase change substance, and crosslinked polyurethane simultaneously functioned as a supporting material and phase change substance. Compared with traditional supporting materials in FSPCMs, the crosslinked polyurethane here obviously reduces the loss of latent heat from the supporting material and reduces the degree of supercooling of the obtained FSPCMs. The obtained FSPCMs were extensively studied by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), polarizing microscopy (POM), differential scanning calorimetry (DSC), thermal cycling tests and thermogravimetric analysis (TGA). The FTIR confirmed the chemical structure of the obtained FSPCMs. The XRD and POM results indicated that the FSPCMs exhibit comprehensive crystalline properties of polyurethane and lauric acid. DSC data showed that the FSPCMs have superior phase change properties with the phase change temperature and latent heat in the range of 26–38 °C and 90–131 J g−1. Moreover, low or no supercooling of the obtained FSPCMs was detected by DSC. The phase change temperature is suitable in the fields of solar energy saving and building engineering. Thermal cycling tests and thermogravimetric analysis (TGA) proved the good thermal reliability and stability of the obtained FSPCMs.

Prepatation and characterization of poly(ether-block-amide)/metal-salt antistatic composites

ABSTRACT Polyether diol and end-capped diisocyanates were first employed in a step-growth addition polymerization with amidogen terminated Polyamide-6 to synthesis segmented poly(ether-block-amide) (APEBA) with organized molecular chain structure. Colorless salts were mixed with the copolymers to develop solid polymer electrolyte (SPE). Chemical structures of composites were characterized by infrared-spectroscopic analysis (FTIR). Thermal behaviors were studied by differential scanning calorimetery (DSC) and thermo gravimetric analyzer (TGA). The APEBA elastomer showed excellent antistatic properties in decreasing the surface resistivity (Rs), which decreased to 107.78Ω cm−2 when the doping-salt content approaches 2.5 phr. Also, Rs exhibits humidity-independency and enduring-existence.

Synthesis, characterization, and self-assembly behaviors of a biodegradable and anti-clotting poly(EDTA-diol-co-butylene adipate glycol urethanes)

Anti-clotting EDTA-diol was successfully synthesized by an esterification reaction between EDTA-2Na and poly(ethylene glycol). Novel anti-clotting and biodegradable multi-block polyurethanes were then prepared by EDTA-diol and biodegradable poly(1,4-butylene adipate glycol) (PBA) as the soft chain, and 1,4-butanediol (BDO) and hexamethylene diisocyanate (HDI) as the hard chain, respectively. The effect of the EDTA-diol content in the soft chain of the prepared polyurethanes on mechanical properties, thermal stability, hydrophilicity, and anticoagulant ability was largely investigated by tensile tests, thermogravimetric analysis, contact angle and water absorption measurements, and hemolytic measurement. Self-assembly behaviors of the resulting polyurethanes were also evaluated by fluorescence spectroscopy and transmission electron microscopy. The prepared polyurethanes have large potential applications in the fields of biomedical materials such as tissue engineering and drug carriers.

The Relation Between Particle Structure and the Peel Strength of Vinyl Acetate/Acrylate Core-Shell Latexes Laminating Adhesives

The cross-linkable laminating adhesives (LAs) based on core-shell vinyl acetate/acrylate latexes were synthesized through multistage emulsion polymerization. The effects of core copolymer Tg, core/shell weight ratio, cross-linking structure and molecular structure on the peel strength of LAs were studied. It was found that peel strength increases with the decrease of core/shell weight ratio and core copolymer Tg. And cross-linking structure could improve adhesion properties of LAs evidently. Moreover, the molecular structure of core-shell latexes has a significant influence on adhesion properties of LAs. The peel strength of sample 14-H could reach 3.4 N/15 mm even under 60°C by particle structure design.

Real-time tracking the Li + -ion transition behavior and dynamics in solid Poly(vinyl alcohol)/LiClO 4 electrolytes

To delicately track the Li-ion transport in SPEs under an external electric field (EF) is a big challenge, considering the limitation of most spectroscopic methods to monitor the real-time conformational changes and track the dynamic process. Herein, real-time Li-ion transition behavior and transport dynamics in typical poly(vinyl alcohol)/LiClO4 electrolytes under an external EF have been studied by combining time-resolved Fourier transform infrared (FTIR) with two-dimensional correlation FTIR spectroscopy. Results show that no migration of Li-ions has been detected when the time scale of the EF loading is at nanosecond (less than 200 ns). However, for the first time, Li-ions have been found to significantly transfer along the EF direction as the time scale enhances to microsecond order of magnitude and the migration period is less than 10 microseconds. The Li+ migration in the SPEs under an EF is a complicated process including quasi-periodic dissociation and coordination effects between Li-ion carriers and polymeric chains.

Preparation, characterization and properties of poly(lactic acid)/poly(1,4-butylene adipate) blends for biodegradable packaging materials

Poly(lactic acid) (PLA)/poly(1,4-butylene adipate) (PBA) blends with different PBA content were directly prepared via melt blending as potential biodegradable packaging materials. PBA with 1000 g/mol number average molecular weight was served as plasticizer to improve PLA properties. The morphological, thermal and mechanical properties of the blends were extensively investigated by scanning electron microscope (SEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile and impact tests and thermogravimetry (TG). The results show that the degree of crystallinity of PLA increased with increasing PBA content. The addition of PBA (20 wt%) result in the positive effect on the elongation at break and toughness, which increased from 7.9% to 74.4% and from 3.9 kJ/m2 to 12.6 kJ/m2, respectively. Meanwhile, the migration tests indicate that PBA exhibits excellent lower migration ratio compared with citrate esters.

Resistivity optimization and properties of silver nanoparticles-filled alcohol-soluble conductive coating based on acrylic resin:

An alcohol-soluble acrylic resin used to improve the dispersity of modified silver nanoparticles (AgNPs) was successfully synthesized. The structure of acrylic resin was designated according to the elements and groups on the surface of modified AgNPs. The content of γ-(2,3-epoxypropoxy)propytrimethoxysilane (KH-560) and conductive filler, temperature, mechanical properties, anticorrosion, and so on were investigated in order to optimize the electrical conductivity and dispersion of modified AgNPs in coating. Surface chemical structure of modified AgNPs was characterized by X-ray photoelectron spectroscopy. Morphology of conductive coating was characterized by scanning electron microscopy. Groups in modified AgNPs and acrylic resin were characterized by Fourier transform infrared spectroscopy. And surface resistivity of conductive coating was characterized by digital multimeter techniques. The optimum surface resistivity of the acquired AgNPs conductive coating could be up to 0.01 ohm/sq, reaching the level of electromagnetic interference shielding. Moreover, the conductive coating possesses good property of anti-chemical and weather corrosion resistance.