Search

Polymer electrolyte membranes (PEMs) are potentially applicable in lithium-ion batteries with high safety, low cost and good performance. Here, to take advantages of ionic conductivity and selectivity of borate ester-functionalized small molecules as well as structural properties of polymer nanocomposite, a strategy of immobilizing as-synthesized polyethylene glycol-borate ester/lithium fluoride (B-PEG/LiF) in graphene oxide/poly(vinyl alcohol) (GO/PVA) to prepare a PEM is put forward. Chemical structure of the PEM is firstly characterized by 1H-, 11B- and 19F-nuclear magnetic resonance spectra, and Fourier transform infrared spectroscopy spectra, respectively, and then is further investigated under consideration of the interactions among PVA, B-PEG and LiF components. The immobilization of B-PEG/LiF in PVA-based structure is confirmed. As the interactions within electrolyte components can be further tuned by GO, ionic conductivity (~10–3 S·cm–1), lithium-ion transfer number (~0.49), and thermal (~273 °C)/electrochemical (>4 V) stabilities of the PEM can be obtained, and the feasibility of PEMs applied in a lithium-ion battery is also confirmed. It is believed that such PEM is a promising candidate as a new battery separator.

To provide ethylene-propylene random copolymer (PPR) with balanced mechanical properties, β-nucleating agent and CaCO3 nanoparticles are incorporated into PPR matrix by melt blending. It is found that crystallization rate and relative content of β-crystal increase with the addition of β-nucleating agent together with nanoparticles. Size of PPR spherulite is greatly reduced, and a specific morphology appears, in which α-crystal lamella is grown upon the β-nucleus. The results suggest that both β-nucleating agent and nano-CaCO3 have heterogeneous nucleation and synergistic effects on β-nucleation of PPR. Mechanical characterization shows that mechanical properties of PPR can be tuned by incorporation of β-nucleating agent and nano-CaCO3 particles. Under suitable compositions, low temperature impact strength and high temperature creep resistance of PPR, the bottlenecks of application of such material, can be simultaneously improved without sacrificing the Youngs’modulus and tensile strength.

To speed up curing of ethylene vinyl acetate (EVA) films as encapsulation materials for photovoltaic modules, a dual curing agent of benzoyl peroxide (BPO) and butylperoxy 2-ethylhexyl carbonate (TBEC) was introduced in this work. The experimental results indicated that for the weight ratio of BPO/TBEC of 0.6/2.4, over 80% gel content of EVA was yielded after curing at 130°C for 12 min. Compared with the case of single curing agent, the present one obviously operated at much lower temperature with faster rate. By carefully studying the influence of curing agent proportion and curing conditions on gel content of EVA films, as well as rheology and curing kinetics, the mechanism involved was analyzed and verified. The results are believed to be useful for developing new curing system of EVA encapsulation films with improved processability.

A ternary system based on blends of poly(vinylidene fluoride)(PVDF) and polycaprolactone (PCL) and made the multi-walled carbon nanotubes (MWNT) selective distribution in PCL phases via melt blending has been studied. The studies on conductivity of MWNT/PCL/PVDF composites with different proportions of PVDF and PCL showed that the conductivity was good in the mass ratio range of PVDF/PCL from 70/30 to 40/60 and that of other matching was poor. The scanning electron microscope (SEM) observation of the composites revealed co-continuous morphologies of PVDF and PCL were formed in composites under suitable proportion of PVDF to PCL. The interfacial tensions of PVDF and PCL melts was tested at mixing temperature of 200°C, the calculated wetting coefficient indicated that MWNT would selectively distribute in PCL phase owing to interfacial effects. Transmission electron microscope (TEM) observation further confirmed that co-continuous morphologies of PVDF and PCL could appear with the increase of PCL content, as indicated by MWNT selective localization in PCL.As the result, the desired structure of double percolation was built in MWNT/PCL/PVDF composites, which have much higher conductivity than that of PVDF or PCL composites with the same MWNT content. Through a strategy of selective localization of MWNT, PVDF based material with low percolation threshold (