Papers by Keyword: Temperature-Sensitivity

Abstract: A temperature-sensitive 2-hydroxy-3-allyloxy-propyl starch ehter (HAPS) was prepared by regulating the hydrophilic-lipophilic balance of etherified starch. Allyl glycidyl ether (AGE) was used as the hydrophobic reagent. ¹H-NMR was used to characterize the structure of products and determine the degree of substitution of etherified starch. UV-Vis and fluorescence spectroscopy methods were adopted to investigate the properties of HAPS aqueous solution. The results showed that the LCST of HAPS was reduced as the DS. When the cmc of HAPS decreases and DS increases, formation of micelles in an aqueous solution by self-assembly is possible.

Abstract: A series of novel cross-linked poly N-isopropylacrylamide (PNIPAM)/poly diallyl dimethyl ammonium chloride (PDMDAAC) semi-IPN hydrogels were synthesized through free radical solution polymerization in water at 30°C. FTIR was used to characterize the structure of resultant hydrogels. The pH and temperature sensitivity of hydrogels were systematicly studied, and the swelling properties of hydrogels were also explored. The results show that the semi-IPN hydrogels have both temperature and pH sensitivities. The hydrogels exhibit fast swelling rate and excellent stimuli-responsive behavior.

Abstract: The present study describes degradable and temperature/ionic-strength responsive polyurethane (PU) microspheres fabricated using toluene diisocyanate, polycaprolactone, polyethylene glycol, 2, 2-hydroxymethyl-2-propionic acid and triethylamine for drug delivery.^[1] We studied the properties of Temperature-sensitive, Ionic strength effects on SR, Swelling-deswelling reversibility, In vitro degradation, the result showed that: when the increase in temperature between 20°C and 50°C, as well as the ionic strength at certain temperature tended to decrease SR. The swelling kinetics was also investigated showing the presence of good ability to change reversibly at different temperature. The degradable studies using phosphate buffer solvent revealing polymeric matrix easily be tuned by varying polycaprolactam (PCL) composition, thus matching specific requirements.

Abstract: A semi-interpenetrating polymer network was fabricated from SMPU (Shape-Memory Polyureathan and PNIPAM (poly (N-isopropylacrylamide)) with the method of in-situ crosslinking polymerization. The temperature-sensitivity of the semi-IPN films was investigated and discussed. The morphology was achieved by extracting the SMPU phase. The influence of PNIPAM phase to the phase transition behavior of SMPU was studied with DSC, the results of which showing that the phase transition temperature is increased by PNIPAM. The introduction of PNIPAM also endows the semi-IPN films with a temperature-sensitive surface hydrophilicity, which was proved by water contact angle measurement at different temperatures. Finally, the water vapor permeability evaluation reveals the temperature-sensitive transportation property of the semi-IPN films, which is formed by the swelling and shrinking of PNIPAM phase according to the environmental temperature. These results shows that the semi-IPN material is a good candidate for the fabrication of intelligent breathable garments.

Abstract: A temperature-sensitive N-isopropylacrylamide (NIPAAm) grafted cotton fabric was prepared by the plasma-induced graft polymerization technique. The surface morphology of the grafted fabric was observed from field scanning electron microscopy (FSEM). Fourier transform infrared spectroscopy (FTIR) and DSC were used to characterize the structure and thermal property of the grafted fabric. The results showed that the PNIPAAm was grafted onto cotton fabrics. The DSC analysis results indicated that LCST value of the grafted fabric was around 32 °C. The water permeation flux of the grafted fabric varied dramatically with a slight change at temperature around the LCST, which showed that the grafted PNIPAAm could act effectively as a chemical valve to control the on-off behavior of cotton fabrics.

Abstract: Microporous membranes were prepared by immersion precipitation phase inversion method from the semi-interpenetrating polymer network (semi-IPN) of shape memory polyurethane (SMPU) and poly (N-isopropylacrylamide) (PNIPAM). The influence of material compostion and preparation procedure on the morphology of membranes such as pore structure and porosity was investigated by methods including Fourier-transform infrared (FT-IR) spectroscopy and scanning electronic microscopy (SEM). Both sponge-like structure and large-pore structure were found in the membranes. The introduction of PNIPAM content in the semi-IPN promotes the formation of large-pore structures and increases the porosity of membranes, due to the improvement of water diffusion into the casting solution. We also found that by increasing the temperature of coagulation bath and the concentration of DMF in the coagulation solution, the formation of large pores could be impeded, and membranes with more sponge-like structure could be prepared.

Abstract: In this paper, temperature-sensitive PET fabrics were prepared by Ar-plasma-induced simultaneous grafting Ploy-N-isopropylacrylamide (PNIPAAm) onto PET fabric. Fourier transform infrared spectroscopy (FTIR) was used to identify the structure of the grafted fabric. Then the surface morphology of the grafted fabric was observed from scanning electron microscopy (SEM) and AFM. The results show that the PNIPAAm was grafted onto PET fabrics, respectively. The grafted PET fabrics are characterized by differential scanning calorimetric analysis (DSC). The DSC analysis results indicated that LCST value of the grafted fabric was around 32°C. And the water permeability of the grafted sample showed a sharp change around 32°C. It was proved that grafted fabric was sensitive to temperature.

Abstract: This paper investigates the influence of thermal stress on FBG embedded in GFRP bar by the finite element analysis and the calibration test. The temperature sensitivity coefficient of smart FBG-GFRP analyzed by FEM is 17.42 pm/°C, which is about 1.65-fold of bare FBG’s namely 10.53 pm/°C. And the coefficient got by calibration test is 17.6 pm/°C. The result shows that the influence of thermal on FBG is very big, after encapsulated and before used in structure, the temperature sensitivity coefficient of FBG must be calibrated.

Abstract: The Fiber Bragg Grating (FBG) sensor’s temperature sensitivity which is influenced by the metal-coated material and thickness was presented. The accurate equation was gotten according to the elasticity and fiber sensor theory. As indicated by the experiment, the changeable curve of the temperature sensitivity between theory equation and experiment is identical. And the FBGs sensitivities can be improved to 3~20 times.

Abstract: It is known that the properties of asphalt-aggregate adhesion show great effect on the performance of asphalt pavement, while the temperature plays an important role in determining the fundamental properties of asphalt binder between single aggregate-aggregate contacts surfaces. The temperature sensitivity is considered to be very important on understanding the failures of asphalt pavement, especially on the asphalt-aggregate adhesion. Knowledge the temperature sensitivity of asphalt-aggregate adhesion is very important in asphalt mixture design. The purpose of this paper was to quantify the effect of temperature on the adhesion and cohesion of asphalt film between aggregate and asphalt. The adhesive/cohesive failure of asphalt film between single aggregate-aggregate contacts was investigated using dynamic mechanical analyzer under dynamic tension stress test with force-control mode, then fracture surface were analysis by a Polarizing Microscope. Contrastive experiments were conducted on SBS modified asphalt under different temperatures. Experimental results indicate that the area percentage of adhesive failure was decreased with the increase of test temperature. And the adhesive failure percentage is enhancing with the increase of loading max-stress level.