Papers by Author: Jun Feng Su

Abstract: Microencapsulated phase change materials (microPCMs) contain paraffin was fabricated by in-situ polymerization using methanol-modified melamine-formaldehyde (MMF) as shell material. The shell of microPCMs was sooth and compact with global shape, its thickness was not greatly affected by the core/shell ratio and emulsion stirring rate. More shell material in microPCMs could enhance the thermal stability and provide higher compact condition for core material. After a 100-times thermal cycling treatment, the microPCMs contain paraffin also nearly did not change the phase change behaviors of PCM. With the increasing of weight contents of microPCMs in gypsum board, the thermal conductivity (λ) values of composites had decreased. The simulation of temperature tests proved that the microPCMs/gypsum composite could store the time-dependent and intermittent solar energy, which did not necessarily meet the energy needs for space heating at all times.

Abstract: The aim of this work was to fabricate novel microPCMs containing dodecanol by an in-situ polymerization using methanol-modified melamine-formaldehyde (MMF) prepolymer as shell material and investigate the interface morphologies of microPCMs/epoxy composites treated by a simulant thermal process with a 10 times repeated temperature variation. A series of microPCMs were fabricated by 1000-3000 r·min^-1 emulsion speed with the PCM contents of 40-70%. Micro-cracks and gaps occurred after a thermal treatment in the interface of microPCMs and epoxy matrix obviously. The internal stress generated by the expansion or shrinking of the microPCMs was the main factor leading to the interface morphology changes and damaged of composites.

Abstract: The objective of this work was to investigate the color stability in air under photo-oxidative degradation influencing consumer acceptance and biodegradation behaviors in soil of soy protein isolate (SPI)/poly (vinyl alcohol) (PVA) blend packaging films during 30 days. The results showed that PVA could dilute the yellow color and make the SPI-based films less darkness in application and the transparency of SPI/PVA films at various stages of degradation was improved. Aerobic biodegradation of films in soil proved that the PVA compound interacting with protein imposed negative effects on biodegradation of blend films prolonging their decomposing time. The SPI/PVA blend films decomposed into small fragments of less complex molecules along with surface completely digested after 30 days.

Abstract: Polyurethane microcapsules containing phase change materials (microPCMs) of n-octadecane applied in building materials were successfully synthesized by an interfacial polymerization in aqueous styrene-maleic anhydride (SMA) dispersion with diethylene triamine (DETA) as a chain extender reacting with toluene-2, 4-diisocyanate (TDI). FTIR and SEM morphologies results confirmed that the shell of microcapsules was polyurethane. Thermal stability and heat absorption simulation were investigated by TGA, DSC and an environmental simulation apparatus. TGA data showed that the decomposition of the microcapsules began at approximately 339oC at 2oC/min of increasing temperature and 320oC under 20% humidity, respectively. Shell structure was affected by environmental changes including temperature and humidity. The microcapsules will be compact and service longer time in practical application under gentle environmental changes. Also, the thermal absorption characterization was performed on a self-made design to improve the understanding of the thermal properties of dried microcapsules in practical application.

Abstract: The aim of the present work was to fabricate heat energy storage microcapsules, which could be used in indoor-wall materials as environmental temperature-controller. Melamine formaldehyde resin (MF) double-shell structure microcapsules were fabricated and the mechanical properties of shell were investigated. The average diameter of microcapsules was in the range of 5-10 μm, and the globular surface was smooth and compact. The mechanical properties of shell were evaluated through observing the surface morphological structure change after pressure by means of scanning electron microscopy (SEM). The results showed that a yield point was found both on single and double shell, and when the press was beyond the point the microcapsules showed plastic behavior. In addition, the mechanical intensity of double-shell microcapsules was better than that of single shell. Analysis of DSC indicated that the phase change temperature was not affected by the double –shell structure.

Abstract: The aim of the present work was to investigate the moisture sensitivity of soy protein isolate (SPI) films blending with poly (vinyl alcohol) (PVA) plasticized by glycerol. Water vapor permeability (WVP) was measured based on the contents of PVA and glycerol in films. WVP values of various SPI/PVA films with/without glycerol were in the range of 8.25 and 10.9 g mm/m2 h kPa. The results showed that WVP values decreased with the increasing content of PVA. Moreover, XRD tests confirmed that the glycerol would insert into the macromolecular blending structure and destroy the crystalline of blends, and the crosslinkage between glycerol molecules and SPI reduced the interstitial spaces in protein matrix, thus allowing for decreasing diffusion rate of water molecules through the films.