Weight-average Particle Size Research Articles

Temperature adjusting performance of thermoregulated woven fabric finished with phase-change microcapsule in low-temperature environment

This study deals with the temperature adjusting performance of thermoregulated woven fabric based on phase-change microcapsules in low-temperature environment. Phase-change microcapsules containing n-octadecane (MicroC18) with melamine–urea–formaldehyde as shell were synthesized by an in situ polymerization using styrene maleic anhydride copolymer as emulsifying agent. Surface morphology, chemical structure, and thermal properties of MicroC18 were, respectively, characterized using field emission scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and thermal gravimetric analysis. The results indicate that a series of microcapsules with spherical shapes were fabricated with about 20.6-μm weight-average particle size. Latent heat is about 188.2 J/g and encapsulation efficiency of n-octadecane (C18) is 85.2%. Phase-change microcapsule composite fabric was prepared through foaming method with plain weave, twill weave, and satin weave as substrates. Thermal insulation property, low-temperature resistance, air permeability, and mechanical property of the finished fabric were investigated. The results show that the cooling rate of finished fabric is significantly slower, and low-temperature resistance time increases. Finished satin fabric has the best thermal resistance performance. The air permeability of finished fabrics is lightly reduced, and final elongation in warp and weft are increased by 16.5% and 15.2%, respectively.

Morphology and Crystallization Behavior of PTT Blends with PTW

Poly (trimethylene terephthalate) (PTT)/Poly (ethylene-butylacrylate-glyciyl methacrylate) (PTW) blends have been prepared in composition by weight 95/5, 90/10, 80/20 and 70/30 using the twin screw extruder approach. Their morphologies, crystallization behavior and mechanical properties were investigated. Scanning electron microscopy observation shows the uniform dispersion of PTW in PTT matrix with weight-average particle size from 0.98 to 3.64μm when the PTW content increases from 5wt% to 30wt% in the blends. The presence of the PTW increased the crystallinity of PTT matrix in PTT/PTW blends. A nucleation activity of the PTW appears in PTT/PTW blends.

Optimization of the new technology for manufacturing γ-polyoxymethylene

A new technology of manufacturing γ-polyoxymethylene (γ-POM) by the polymerization 1,3,5-trioxane in the presence of a boron trifluoride etherate aprotic catalytic agent and a methylal telogen in the medium of the non-ozone-depleting solvent toluene, with an yield exceeding the yield of γ-POM manufactured by the existing industrial technology by 30% is developed. Regression equations for the yield and weight-average particle size of γ-POM synthesized in the toluene medium were derived by means of the optimal experimental design technique. The equations were used to optimize parameters of the synthesis and obtain γ-POM with the weight-average particle size of 15 μm and the highest possible yield.

Optimization of process parameters of γ-polyoxymethylene synthesis

Two procedures for γ-polyoxymethylene production are considered: the existing commercial procedure and high-efficiency perspective procedure, differing in the chain-transfer agents and catalysts used. Mathematical models of the dependences of the yield and weight-average particle size of γ-polyoxymethylene on the synthesis process parameters for the commercial and perspective technologies are constructed using the method of optimum experiment design. The mathematical models were used for determining the optimum synthesis parameters allowing preparation of γ-polyoxymethylene with the weight-average particle size d ≤ 14 μm in maximal yields.

Synthesis of organoboron nanoparticles

Organoboron nanoparticles (C2B10H4) n with weight-average sizes of 8.3, 10.6, and 15.3 nm are synthesized from carborane C2B10H12 by high-temperature pyrolysis of its vapor. The dependence of the weight-average particle size on the temperature and initial carborane vapor pressure of the synthesis is obtained.

Reaction and stabilizing mechanism of the cross-type macromonomers in the dispersion polymerization of styrene

The cross-type (C-VUM) and linear-type (L-VUM) bifunctional vinyl urethane macromonomers and polystyrene (PS) using these macromonomers were synthesized in the dispersion polymerization in ethanol, and the reaction and stabilizing mechanism of the macromonomers was proposed. The structural verification of the macromonomers and PS was studied using 1H NMR. The weight-average particle size of C-PS (PS prepared with C-VUM) and L-PS (PS prepared with L-VUM) decreased from 4.41 to 1.36 μm and from 3.56 to 1.52 μm, whereas the average-molecular weight of those increased from 34,100 to 100,500 g/mol and from 32,200 to 71,800 g/mol, respectively. The XPS result showed that the C-PS was anchored with a larger amount of PEG than that of the L-PS on the particle surface. Thus, the reaction and stabilizing mechanism of the macromonomers for the formation of PS particles is proposed as the following. The particle surface of the C-PS is surrounded by a large amount of tail shaped macromonomers leading to higher molecular weights and smaller particle sizes. On the other hand, the particle surface of the L-PS is comprised of relatively small amounts of loop shaped macromonomers inducing lower molecular weights and larger particles of L-PS than C-PS.

Polypropylene–rubber blends: 4. The effect of the rubber particle size on the fracture behaviour at low and high test speed

The effect of the rubber particle size and rubber content on the fracture behaviour of polypropylene–EPR blends was studied at low and high test speeds. The particle size was varied by changing the molecular weight of the EPR phase, and ranged from about 0.5 to around 4.0 μm. The fracture behaviour was determined as a function of temperature by the notched Izod impact test (high test speed) and by a tensile test on notched Izod bars at 1 mm/s (low test speed). At high test speed the brittle–ductile transition temperature ( T bd) increases with increasing particle size. At low test speed the T bd decreases slightly with increasing particle size. The weight average particle size gave a better correlation with the notched Izod results than the number average particle size. This suggests that the larger particles initiate the fracture more easily.

Electron Microscopy of Synthetic Latices

A study has been made by electron microscopy of the size and size distribution of 22 synthetic latices. Included are GR-S latices Types II, III, and V, polystyrene latices, and several latices of special character. Details are given on sample preparation, measurement, application of corrections, calculation of number, volume to surface, and molecular weight average diameters, as well as the number and weight average distributions. The weight average particle size range covered was 730 to 3920A. The smallest sizes were shown by Type II latices, followed in order by Type III, polystyrene, Type V, and some of the special latices. The latices were all nonhomogeneous in size and showed size distributions both on a number and weight basis which in some instances contained single and in some cases double maxima.