Lifen Su

Preparation and study on thermal conductive composites of chlorinated polyethylene rubber reinforced by boron nitride particles

The composites of chlorinated polyethylene rubber (CM) filled with boron nitride (BN) were prepared and examined systematically. Scanning electron microscopy (SEM) was used to observe microscopic morphology of composites. Mechanical properties of composites were analyzed by a rubber process analyzer (RPA) and dynamic mechanical thermal analyzer (DMTA). Thermal conductivity as well as thermo stability of composites was improved by adding BN particles into the CM rubber. It was found that BN particles can reinforce the rubber matrix while they also break down the network of polymer chains and ruin the physical properties of the rubber matrix. During the dynamic compressing process, BN particles can transfer heat from the matrix and alleviate the heat build-up phenomenon. The BN/CM composites (volume content CBN=18%) with thermal conductivity 1.179 W/(m·K) and good flexibility (Elongation at break=320%) were prepared, which may be used as thermal interface materials in a dynamic compressing process.

Three-Dimensional Simulation of the Shrinkage Behavior of Injection-Molded Poly Lactic Acid (PLA): Effects of Temperature, Shear Rate and Part Thickness

The effects of injection temperature, shear and part thickness on the linear shrinkage of injection-molded poly (lactic acid) (PLA) were intensively analyzed using the Autodesk Moldflow software. The obtained results showed that both melt temperature and shear rate had obvious effects on the linear shrinkage of PLA, i.e., the linear shrinkage of PLA increases significantly with the increase of melt temperature and shear rate. In addition, the shrinkage of high-crystallinity PLA was remarkably larger than that of low-crystallinity PLA, and thin-walled parts was larger than thick-walled ones in shrinkage.

Preparation of pH-sensitive amphiphilic block star polymers, their self-assembling characteristics and release behavior on encapsulated molecules

Poly(ethylene glycol) (PEG), a polymer with excellent biocompatibility, was widely used to form nanoparticles for drug delivery applications. In this paper, based on PEG, a series of pH-sensitive amphiphilic block star polymers of poly(ethylene glycol)-block-poly(ethoxy ethyl glycidyl ether) (PEG-b-PEEGE) with different hydrophobic length were synthesized by living anionic ring-opening polymerization method. The products were characterized using 1H NMR and gel permeation chromatography. These copolymers could self-assemble in aqueous solution to form micellar structure with controlled morphologies. Transmission electron microscopy showed that the nanoparticles are spherical or rodlike with different hydrophilic mass fractions. The pH response of polymeric aggregates from PEG-b-PEEGE was detected by fluorescence probe technique at different pH. A pH-dependent release behavior was observed and pH-responsiveness of PEG-b-PEEGE was affected by the hydrophobic block length. These results demonstrated that star-shaped polymers (PEG-b-PEEGE) are attractive candidates as anticancer drug delivery carriers.

Preparation of the Yellow-Colored Aluminum Pigments with Double-Layer Structure Using a Crosslinked Copolymeric Dye

Colorization for fabricating aluminum pigments has broad application prospects in recent years. In this study, yellow-colored aluminum pigments with the double-layer structure Al@SiO2@PFMV were prepared using a sol-gel method. A crosslinked copolymeric dye (PFMV) was firstly synthesized by radical polymerization using vinyl triethoxysilane (VTES) and a small molecular dye (FGMAC) as monomers. Then, colored aluminum pigments were prepared by hydrolysis and condensation of the copolymers on the surface of aluminum pigments. SEM, AFM, FTIR, and XPS were used to characterize the surface morphology and chemical structure of the colored aluminum pigments. It was found that the colored aluminum pigments have a heterogeneous and smooth surface layer. The anticorrosion results showed that the colored aluminum pigments had better chemical stability with significantly improving corrosion resistance compared to raw aluminum pigments and Al@SiO2 with the single-layer coating. Chromatism analysis indicated that the lightness of Al@SiO2@PFMV pigments decreased slightly and the color changed from silver-gray to yellow.

Preparation and Mechanical and Thermal Properties of Chlorinated Polyethylene Reinforced Polypropylene Foam

The foamed polypropylene (PP) with excellent mechanical and thermal insulating properties was reinforced by blending chlorinated polyethylene (CPE), followed by compression molding foaming in cross-link. The effects of CPE on the foaming behavior, thermal and mechanical properties of the foamed PP were studied by the measurements of density, thermal conductivity, Vicat softening temperature, tensile strength, impact strength and SEM. The results showed that the foamed PP got the best properties when the weight ratio of CPE/ PP was 20wt%. The density of the obtained foamed PP was as low as 0.37 g/cm3, the impact strength was 16.5 kJ/m2, the tensile strength was 17.7 MPa, the thermal conductivity was 0.035 W/(m·K), and the Vicat softening temperature was 112 °C.

Synthesis and immobilization of polystyreneb-polyvinyltriethoxysilane micelles

Diblock copolymers polystyrene-block-polyvinyltriethoxysilane (PS-b-PVTES) were synthesized via atom transfer radical polymerization (ATRP), which self-assembled into spherical micelles in solvent of THF-methanol mixtures. The self-assembled micelles were immobilized by cross-linking reaction of VTES in a shell layer of micelles. The chemical structures of block copolymers and morphology of micelles were characterized in detail. It was found that the size of immobilized micelles was strongly affected by the copolymer concentration, composition of mixture solvent, and block ratios.

Melt Crystallization Behavior of Injection-Molded High-Density Polyethylene Based Upon a Solidification Kinetic Analysis

Abstract Rheological characterization and an in-situ temperature measurement were carried out to investigate the solidification behavior and crystallization kinetics of injection-molded (IM) high-density polyethylene (HDPE) samples. The temperature profiles obtained via the enthalpy transformation method (ETM) were also used to disclose the effect of cooling rate on the solidification kinetics during the IM process. A four parameter model (FPM) was developed in the present work, based on a three-parameter model (TPM) we proposed previously, with the FPM shown to have an obviously better fitting effect. It was seen that heat transfer at locations χ ≤ 0.5 was primarily dominated by a thermal conduction mechanism, which was unlike the situation when χ > 0.5, with χ being the fractional distance from the mold surface to the center. The results of the present study are suggested to be of significance to further research on the correlation between microstructures and properties of IM products.

An evaluation of the melt crystallisation behaviour of injection-moulded high-density polyethylene (HDPE) based on a solidification kinetics analysis

ABSTRACT Dynamical rheology, transient temperature measurement, and two-dimensional wide angle X-ray diffraction were performed in this work to investigate the effects of the solidification behaviour and crystallisation kinetics on the gradient structure formation of the injection-moulded high-density polyethylene (HDPE) samples across the thickness. The temperature profiles obtained via enthalpy transformation method were used to elucidate the effect of cooling rates on the solidification kinetics during the injection moulding process. A four-parameter model was proposed for the first time, based on the ‘three-parameter model’ of our previous research, and the former one is shown to have a better fitting effect. Heat transfer at locations χ ≤ 0.5 from the mould surface was found to be primarily dominated by a thermal conduction mechanism, unlike the situation when χ > 0.5. The degree of orientation of the HDPE samples was closely associated with the shear distributions and temperature fields.

Effect of Microstructure on Thermal Conductivity of Polymer Composites

Thermal conductivity (TC) of polymer composites is strongly depended on thermal conductive fillers as well as heat conduction pathways formed by these fillers. In this work, we examined effects of morphology, size and arrangement of fillers on TC of polymer composites by using energy-conserving dissipative particle dynamic (e-DPD) simulation. Theoretically, we explored effects of ideal and “pseudo” thermal conductive pathways on composites’ TC and investigated heat conduction of filler particles with cubic-center and lamellar morphology. To confirm orientation and size effects of lamellar filler particles on composites’ TC, we prepared a series of Boron Nitride/Silicon rubber composites (BN/SiR). Being same with those observed in e-DPD simulation, orientation could efficiently improve TC of BN/SiR composites. The TC of composites with filled diameters about 10 micrometer of BN flats is 11 times higher than that of SiR matrix. Our researching results show that heat conduction pathways are essential to transportation of heat flux in polymer composites and even “pseudo” pathways by disconnected filler particles along temperature gradient can accelerate heat conduction.

Study on Crystallization Kinetics of Dynamically-Vulcanized PP/EPDM Blends

Two types of β nucleating agents (β-NAs), aryl dicarboxylic acid amide (TMB-5) and diphenyl phthalate diamine (NT-C), were adopted to modify the polypropylene (PP)/ethylene propylene diene monomer (EPDM) blends, which were prepared by dynamic-vulcanization technology. Wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) were used to study the crystallization kinetics of PP. Our results showed that the addition of β-NAs can considerably increase the crystallization temperature, and significantly decrease the spherulite size of β-PP (L 300 ). The Jeziorny analysis showed there were ~82% and ~89% of relative crystallinity generated from the primary crystallization in the composites containing TMB-5 and NT-C, respectively. The crystallization half time (t 0.5 ) showed that NT-C improved the overall crystallization rate more effectively than TMB-5. In addition, the peaks of the relative crystallization rate curves were shifted towards higher temperature by 14 and 9℃ with the addition of TMB-5 and NT-C, respectively.