The Effects of Gas Composition on the Atmospheric Pressure Plasma Jet Modification of Polyethylene Films

Polyethylene （PE） films are treated using an atmospheric pressure plasma jet （APPJ） with He or He/O2 gas for different periods of time. The influence of gas type on the plasma polymer interactions is studied. The surface contact angle of the PE film can be effectively lowered to 58° after 20 s of He/O2 plasma treatment and then remains almost unchanged for longer treatment durations, while, for He plasma treatment, the film surface contact angle drops gradually to 47° when the time reaches 120 s. Atomic force microscopy （AFM） results show that the root mean square （RMS） roughness was significantly higher for the He/O2 plasma treated samples than for the He plasma treated counterparts, and the surface topography of the He/O2 plasma treated PE films displays evenly distributed dome-shaped small protuberances. Chemical composition analysis reveals that the He plasma treated samples have a higher oxygen content but a clearly lower percentage of COO than the comparable He/O2 treated samples, suggesting that differences exist in the mode of incorporating oxygen between the two gas condition plasma treatments. Electron spin resonance （ESR） results show that the free radical concentrations of the He plasma treated samples were clearly higher than those of the He/O2 plasma treated ones with other conditions unchanged.

Boosting daytime radiative cooling performance with nanoporous polyethylene film

Radiative cooling without energy consumption and environmental pollution holds great promise as the next-generation cooling technology.To date,daytime radiative cooling performance is still slightly low,especially in humid areas.In this work,we demonstrated that nanoporous polyethylene(Nano PE)film can improve solar reflectivity from 96%to 99%,thus boosting radiative cooling performance.Moreover,the experimental results in humid areas indicate that Nano PE films can improve radiative cooling performance by∼76%in a clear day and 120%in a day with few clouds.Additionally,compared with ordinary PE films,thin Nano PE films have significantly higher weather fastness and mechanical strength.More importantly,nano PE films can scatter part of visible light,thus suppressing the generation of light pollution in practical applications.Lastly,the modeling results reveal that with Nano PE films,more than 95%of China’s areas can achieve daytime cooling performance.Our work can boost the development of radiative cooling technology with a very low cost.

Surface Modification of Polyethylene by Heparin for Improvement of Antithrombogenicity

The purpose of this paper was to enhance blood compatibility of polyethylene （PE） film. PE film pretreated by argon plasma was subjected to ultraviolet （UV） -induced graft polymerization with Acrylic acid（AAc） （AAc-grafted PE films, PE-g-PAAc） without photo-initiator, then heparin was covalently immobilized on the PE surface （PE-g-HPAAc）. The surface properties and microstructure of PE-g-PAAc and PE-g-HPAAc were studied by static contact angle measurement, atomic force microscope （AFM）, X-ray photoelectron spectroscopy （XPS） and Attenuated total reflectance Fourier transfer infrared spectroscopy （ATR-FTIR）. It was confirmed that AAc and heparin were successfully immobilized onto the surface of PE film. Results of platelet adhesion experiments indicated that the antithrombogenicity of the modified PE film was remarkably improved.

Annealing of Oriented PP/PE Double-layer Film within the Melting Range of PE:the Role of Partial Melting and Self-nucleation

Due to the mechanical stability of the PP layer,the oriented PP/PE double-layer film with a row-nucleated crystalline structure can be annealed at a higher temperature than the PE monolayer film.In this work,the effects of annealing temperature within the melting range of PE on the crystalline structure and properties of PP/PE double-layer films were studied.When the annealing temperature is between 100 and 130℃,below the melting point of PE,the crystallinity,the long period,lateral dimension and orientation of the lamellae in the PE layer increase with the annealing temperature due to the melting of thin lamellae and the self-nucleated effect of partially-melted melts during annealing.With the annealing temperature further increasing to 138℃,near the melting ending point of PE,since the lamellae melt completely and the melt memory becomes weak during annealing,some spherulite structures are formed in the annealed sample,resulting in a decrease of orientation.In contrast,the annealing only causes the appearance of a low-temperature endothermic plateau in the PP layer.The improved size and orientation of lamellar structure in the PE layer increase the pore arrangement and porosity of the stretched PP/PE microporous membrane.This study successfully applies the self-nucleation effect of partially-melted polymer melt into the practical annealing process,which is helpful to guide the production of high-performance PP/PE/PP lithium batteries separator and the annealing process of other multilayer products.