Jun-Feng Su

Investigation of the Self-Healing Behaviors of Microcapsules/Bitumen Composites by a Repetitive Direct Tension Test

The aim of this work was to evaluate the self-healing behaviors of bitumen using microcapsules containing rejuvenator by a modified fracture healing–refracture method through a repetitive tension test. Microcapsules had mean size values of 10, 20 and 30 μm with a same core/shell ratio of 1/1. Various microcapsules/bitumen samples were fabricated with microcapsule contents of 1.0, 3.0 and 5.0 wt. %, respectively. Tension strength values of microcapsules/bitumen samples were measured by a reparative fracture-healing process under different temperatures. It was found that these samples had tensile strength values larger than the data of pure bitumen samples under the same conditions after the four tensile fracture-healing cycles. Fracture morphology investigation and mechanism analysis indicated that the self-healing process was a process consisting of microcapsules being broken, penetrated and diffused. Moreover, the crack healing of bitumen can be considered as a viscosity driven process. The self-healing ability partly repaired the damage of bitumen during service life by comparing the properties of virgin and rejuvenated bitumen.

Preparation and physicochemical properties of microcapsules containing phase-change material with graphene/organic hybrid structure shells

Microcapsules containing phase-change materials (microPCMs) have received increasing attention in the field of latent thermal storage. The addition of graphene in the shells could be a promising approach to enhance the physicochemical properties of microPCMs because of its superior characteristics particularly the thermal conductivity. The aim of this study was to prepare and investigate the chemical microstructure and physicochemical properties of novel microPCMs with graphene/organic hybrid structure shells. Paraffin was used as a phase-change material, which was microencapsulated by graphene and methanol-modified melamine-formaldehyde (MMF) through an in situ polymerization. The mean size and shell thickness were analyzed. The scanning electron microscopy (SEM) results showed that the microPCMs were spherical particles and graphene enhanced the smoothness of the shell surface. The contents of graphene in the shells were analyzed using X-ray photoelectron spectroscopy (XPS); the microstructure of the shells was investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). It was found that the shells had a graphene/organic hybrid structure, which was formed though the electric charge absorption and long-molecular entanglement. At the same time, the mechanical properties of the microcapsules were improved because of the graphene addition. Thermogravimetric analysis (TGA) tests showed that the microPCMs had a higher degradation temperature of 295 °C. In addition, graphene greatly enhanced the thermal stability of the microPCMs. The phase-change properties of the microPCMs were studied by differential scanning calorimetry (DSC) and thermal cycling tests. The results indicated that the phase-change temperature was regulated by the graphene addition and that graphene reduced the thermal barrier of the polymer shell material. The thermal conductivity of microPCMs with 1.0 wt% graphene was increased by about 100% compared to that of microPCMs without graphene. Moreover, the phase-change cycling tests implied that the microPCMs possessed a sensitivity response to heat because of the excellent thermal conductivity of graphene.

Reduced in vivo lung metastasis of a breast cancer cell line after treatment with Herceptin mAb conjugated to chemotherapeutic drugs

Anthracyclines and taxanes have remarkable anticancer efficacy, but have poor selectivity and high toxicity. Targeted delivery of chemotherapeutics has emerged as a strategy to achieve higher drug levels at the tumor site, to spare noncancerous tissue and potentially to use lower systemic drug doses, thus preventing side effects. In this study, we targeted the HER2 receptor using the monoclonal antibody (mAb) Herceptin (Trastuzumab) chemically conjugated to Doxorubicin or Taxol. In vitro, drug–Herceptin conjugates exhibited cytotoxicity comparable to equimolar concentrations of free drugs, with the benefit that the cytotoxicity of the conjugates was selective for cells expressing the HER2 target. In vivo, treatment of tumor-bearing mice with Taxol–Herceptin conjugates had a reduction of primary tumors comparable to equivalent doses of free drugs. However, Taxol–Herceptin conjugates significantly reduced metastasis compared with equivalent doses of free drugs. Thus, the data support the concept that conjugates might target metastasis better than primary tumors. This would offer a potential therapeutic approach for management of metastatic breast cancer.

Microstructure and Thermal Reliability of Microcapsules Containing Phase Change Material with Self-Assembled Graphene/Organic Nano-Hybrid Shells

In recent decades, microcapsules containing phase change materials (microPCMs) have been the center of much attention in the field of latent thermal energy storage. The aim of this work was to prepare and investigate the microstructure and thermal conductivity of microPCMs containing self-assembled graphene/organic hybrid shells. Paraffin was used as a phase change material, which was successfully microencapsulated by graphene and polymer forming hybrid composite shells. The physicochemical characters of microPCM samples were investigated including mean size, shell thickness, and chemical structure. Scanning electron microscope (SEM) results showed that the microPCMs were spherical particles and graphene enhanced the degree of smoothness of the shell surface. The existence of graphene in the shells was proved by using the methods of X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). It was found that graphene hybrid shells were constructed by forces of electric charge absorption and long-molecular entanglement. MicroPCMs with graphene had a higher degradation temperature of 300 °C. Graphene greatly enhanced the thermal stability of microPCMs. The thermal conductivity tests indicated that the phase change temperature of microPCMs was regulated by the graphene additive because of enhancement of the thermal barrier of the hybrid shells. Differential scanning calorimetry (DSC) tests proved that the latent thermal energy capability of microPCMs had been improved with a higher heat conduction rate. In addition, infrared thermograph observations implied that the microPCMs had a sensitivity response to heat during the phase change cycling process because of the excellent thermal conductivity of graphene.

Evaluating and Modeling the Internal Diffusion Behaviors of Microencapsulated Rejuvenator in Aged Bitumen by FTIR-ATR Tests

Microencapsulated rejuvenator has been attracted much attention for self-healing bitumen. The diffusion coefficient is one of the key parameters to estimate the feasibility of rejuvenator to age bitumen. The objective of this research was to evaluate diffusion behaviors of microencapsulated rejuvenator in aged bitumen by a FTIR-ATR method. Various microcapsule samples were mixed in bitumen to form thin films. The core material of microcapsules used as rejuvenator was diphenylsilane (DPS), its fairly specific absorption band at 843 cm−1 was selected as a marker band to calculate the diffusion coefficient (D). The microstructure parameters, including contents, mean size and mean shell thickness of microcapsules, were considered to understand the diffusion behaviors under different temperatures (20, 30, 40 and 50 °C) in bitumen. The results showed that a larger mean size of microcapsules did not greatly affect the D values under the same temperature. In contrast, a higher mean shell thickness decreased the D values because of the decrement of damage probability of microcapsules under the same content. With the same microcapsule sample in bitumen, the D values presented a trend of linear increase when the content of microcapsules was increased. All these results indicated that the microstructure affected the diffusion behaviors based on the concentration of released rejuvenator. A preliminary model of diffusion behaviors of microencapsulated rejuvenator in bitumen was given based on the Arrhenius equation considering the microstructure of microcapsules, the amount of released rejuvenator and the age degree of bitumen. This model may be a guide to the construction and application of self-healing bitumen using microcapsules.

Soy Protein Isolate/Poly (Vinyl Alcohol) Films with IPN Structure by Crosslinkage of Ferulic Acid

Blend films from nature soy protein isolates (SPI) and synthetical poly (vinyl alcohol) (PVA) were successfully fabricated by crosslinkage of ferulic acid (FA) based on a solution-casting method. Structure analysis results indicated that FA had chemical reactions with both SPI and PVA, a three-dimensional interpenetrated polymer networks (IPN) had formed between SPI and PVA. The miscibility of SPI/PVA blends had improved by crosslinkage of FA. Moreover, the transparency of films had enhanced with the increasing of FA contents, which proved the INP structure of SPI/PVA blends could be adjusted by cross-linking degree. This method supplies a highlight potential usage of SPI as environmental-friendly packaging films.

Fabrication and Characterization of Novel Electrothermal Self-Healing Microcapsules with Graphene/Polymer Hybrid Shells for Bitumenious Material

Self-healing bituminous material has been a hot research topic in self-healing materials, and this smart self-healing approach is a promising a revolution in pavement material technology. Bitumen has a self-healing naturality relating to temperature, healing time, and aging degree. To date, heat induction and microencapsulation rejuvenator are two feasible approaches, which have been put into real applications. However, both methods have disadvantages limiting their practical results and efficiency. It will be an ideal method combining the advantages and avoiding the disadvantages of the above two methods at the same time. The aim of this work was to synthesize and characterize electrothermal self-healing microcapsules containing bituminous rejuvenator with graphene/organic nanohybrid structure shells. The microcapsules owned electric conductivity capability because of the advent of graphene, and realized the self-healing through the two approaches of heat induction and rejuvenation. The microcapsule shells were fabricated using a strength hexamethoxymethylmelamine (HMMM) resin and graphene by two-step hybrid polymerization. Experimental tests were carried out to character the morphology, integrity, and shell structure. It was found that the electric charge balance determined the graphene/HMMM microstructure. The graphene content in shells could not be greatly increased under an electrostatic balance in emulsion. X-ray photoelectron spectroscopy (XPS), Energy dispersive spectrometer (EDS), Transmission electron microscope (TEM) and Atomic force microscopy (AFM) results indicated that the graphene had deposited on shells. TGA/DTG tests implied that the thermal decomposition temperature of microcapsules with graphene had increased to about 350 °C. The thermal conductivity of microcapsules had been sharply increased to about 8.0 W/m2·K with 2.0 wt % graphene in shells. At the same time, electrical resistivity of microcapsules/bitumen samples had a decrease with more graphene in bitumen.