Paving continuous heat dissipation pathways for quantum dots in polymer with orangeinspired radially aligned UHMWPE fibers

Thermal management of nanoscale quantum dots(QDs)in light-emitting devices is a long-lasting challenge.The existing heat transfer reinforcement solutions for QDs-polymer composite mainly rely on thermal-conductive fillers.However,this strategy failed to deliver the QDs’heat generation across a long distance,and the accumulated heat still causes considerable temperature rise of QDs-polymer composite,which eventually menaces the performance and reliability of lightemitting devices.Inspired by the radially aligned fruit fibers in oranges,we proposed to eliminate this heat dissipation challenge by establishing long-range ordered heat transfer pathways within the QDs-polymer composite.Ultrahigh molecular weight polyethylene fibers(UPEF)were radially aligned throughout the polymer matrix,thus facilitating massive efficient heat dissipation of the QDs.Under a UPEF filling fraction of 24.46 vol%,the in-plane thermal conductivity of QDs-radially aligned UPEF composite(QDs-RAPE)could reach 10.45 W m^(−1) K^(−1),which is the highest value of QDs-polymer composite reported so far.As a proof of concept,the QDs’working temperature can be reduced by 342.5℃ when illuminated by a highly concentrated laser diode(LD)under driving current of 1000 mA,thus improving their optical performance.This work may pave a new way for next generation high-power QDs lighting applications.

Statistical Tensile Strength for High Strain Rate of Aramid and UHMWPE Fibers

Dynamic tensile impact properties of aramid (Technora) and UHMWPE (DC851) fiber bundles were studied at two high strain rates by means of reflecting type Split Hopkinson Bar, and stress-strain curves of fiber yarns at different strain rates were obtained. Experimental results show that the initial elastic modulus, failure strength and unstable strain of aramid fiber yarns are strain rate insensitive, whereas the initial elastic modulus and unstable strain of UHMWPE fiber yarns are strain rate sensitive. A fiber-bundle statistical constitutive equation was used to describe the tensile behavior of aramid and UHMWPE fiber bundles at high strain rates. The good consistency between the simulated results and experimental data indicates that the modified double Weibull function can represent the tensile strength distribution of aramid and UHMWPE fibers and the method of extracting Weibull parameters from fiber bundles stress-strain data is valid.

Residual Characteristic of High-Velocity Steel Fragments Penetrating UHMWPE FRP Laminates

The mechanical performance of ultra-high molecular weight polyethylene fiber (UHMWPE) and its composites were proposed. Penetrated properties of different thicknesses UHMWPE FRP laminates (URP) impacted by 3.3g cubic high velocity fragments were studied. According to the ballistic experimental results and theoretical analysis, the linear relation between ballistic limit vBL and area density AD was confirmed. The relative parameters of showing experientially residual velocity vr were expressed by the function of AD. In the end, versatile experiential expression between vr and AD was found. Prediction of vr and vBL using obtained expressions under the above stated condition of impacting URP was consistent with the experimentaled results. Consequently, the two experiential relations can be used to predict the residual velocity and ballistic limit of cubic high velocity fragments impacting URP. The residual characteristic of high-velocity steel fragments penetrating UHMWPE FRP laminates can be more exactly forecasted by the two derived experiential formulas.

Adjusting the interfacial adhesion via surface modification to prepare high-performance fibers

Ultra-high molecular weight polyethylene(UHMWPE)fiber is a new kind of high-performance fiber.Due to its excellent physical and chemical characteristics,it is widely used in various fields.However,the surface UHMWPE fiber is smooth and demonstrates no-polar groups.The weak interfacial adhesion between fiber and resin seri-ously restricts the applications of UHMWPE fiber.Therefore,the surface modification treatments of UHMWPE fiber are used to improve the interfacial adhesion strength.The modified method by adding nanomaterials elu-cidates the easy fabrication,advanced equipment and proper technology.Thus,the progress of UHMWPE nanocomposite fibers prepared via adding various nanofillers are reviewed.Meanwhile,the effects of other various methods on surface modification are also reviewed.This work advances the various design strategies about nano technologies on improving interfacial adhesion performance via treatment methodologies.

Structure and Properties of Gel-spun Ultra-high Molecular Weight Polyethylene Fibers with High Gel Solution Concentration

The gel-spun ultra-high molecular weight polyethylene （UHMWPE） fibers were prepared at the industrial production line with different gel solution concentrations of 15 wt%, 18 wt% and 24 wt%. The difference in ultimate structure and mechanical properties of UHMWPE fibers for different gel solution concentrations were analyzed by tensile testing, differential scanning calorimetry （DSC）, wide angle X-ray diffraction （WAXD） and small angle X-ray scattering （SAXS）. With the increase of gel solution concentration, the ultimate mechanical properties of UHMWPE fibers were decreased and the crystallization and orientation of UHMWPE fibers became inferior. Besides, both the average shish length （ （Lshsh） ） and shish misorientation （B0） of UHMWPE fibers were decreased with the increase of gel solution concentration. In addition, the appropriate increase of spinning temperature led to the further optimization of the ultimate structure and mechanical properties of UHMWPE fibers.

Synthesis of Granular Hydroxy‑Functionalized Ultra‑high‑molecular‑weight Polyethylene and Its Fiber Properties

Granular hydroxyl-functionalized UHMWPE was successfully prepared through copolymerization of ethylene and 10-undecen-1-ol protected by tri-iso-butylaluminum using a titanium complex.[tBuNSiMe_(2)(2,7-tBu2Flu)]TiMe_(2) was activated in hexane by silica-supported modified-methylaluminoxane.Without any additional pretreatments,the obtained polymer powders were transformed into fibers through a gel-spinning and heat drawing process.When compared to fibers generated from the equivalent unfunctionalized UHMWPE or the commercial HUMWPE,both creep resistance and hydrophilic properties were improved in the hydroxy-functionalized UHMWPE fibers without losing tensile strength.