Preparation and property of porous hydroxyapatite as an inorganic dispersant used in suspension polymerization

The porous hydroxyapatite(HAP)for suspen-sion polymerization dispersant was prepared using calcium carbonate and phosphoric acid as raw materials.The samples were characterized by scanning electron micro-scopy(SEM),X-ray diffraction(XRD)and BET nitrogen adsorption.The results show that the prepared HAP has a porous structure,low particle density,large specific surface area,uniform particle size and does not agglomerate easily between the particles.The preparation conditions for the HAP were optimized as follows:solid content of calcium carbonate aqueous suspension 90 g/L,concentration of phosphoric acid 1.0 mol/L,reaction/aging temperature 50℃,and aging time 3 h.The HAP prepared under optimal preparation conditions has 106.8 m^(2)·g 21 of specific surfacearea,whichisabout1.5–1.8timesasmuchasthatof JapaneseHAPorcommercialHAP.Itsapplicationresultin the suspension polymerization of styrene show that the porous HAP dispersant has high surface activity,excellent suspension dispersibility and stability and can markedly improve the quality of polystyrene beads.

Rheological Behavior of Polymer Melts and Concentrated SolutionsPart V: A New Molecular Theory of Non-linear Viscoelasticity for Polymeric Suspensions

A double-network model is established, which consists of the segments, E and A-constituent chains, the polymeric chains entangled with other ones by multi-entanglement and polymeric chains connected to a great number of destructible particles by multi-adsorption, based on which the E and A-constituent chains can be recreated and released dynamically. The distribution function of the end-to-end vector, the statistical distribution function of conformation for two kinds of chains in the multi-entanglement and multi-adsorption states and their number of polymeric chains are calculated by the combination of statistical mechanics and kinetics. Then the viscoelastic free energies of deformation for two kinds of the networks and suspensions are calculated by Boltzmann’s statistical theory. Also. elastic modulus and memory function for two kinds of the network and suspensions are derived. Consequently, a new molecular theory of the non-linear viscoelasticity for polymeric suspensions is proposed, and the constitutive equation and material function with yielding and thinning for the polymeric suspensions in different flow fields are derived from this theory.

Rheological Behaviors of Polymer Melts and Concentrated Solutions Part VI: Comparison of the Material Functions with Yielding and Thinning for Polymeric Suspensions with Their Experimental Values

The memory function and elastic modulus were introduced into the O-W-F type of constitutive equations with the Cauchy-Green and Finger tensors for simple fluid, and then the concrete constitutive equation and material function for polymeric suspensions in the difFerent flow fields were formulated : 1) Viscosity and first normal-stress difference coefficient in the shear flow field,2) Tensile viscosity at the uni-axial elongation flow field; and 3) Dynamic viscosity and modulus in the dynamic field. Then the dependence of the material function on the deformation rate and weight fraction of fillers was discussed, and the shear flow curves with four characteristic regions (1-low shear rate plateau region, II- apparent yielding region, III-intermediate rate plateau region,and IV-shear thinning region.) were explained theoretically. Finally, it was verified by a number of experimental values for the rheological suspensions and the viscoeIastic and mechanical behaviors can be predicted by the molecular theory of non-linear viscoelasticity for polymeric

Preparation and Performance of n-Dodecane Microencapsulated Phase Change Cold Storage Materials

Cold chain transportation is currently a hot research topic.Since the traditional refrigeration methods lead to the consumption of large amounts of energy,the search for new energy storage materials is a major trend.In the present contribution,n-dodecane/PMMA microencapsulated phase change materials were prepared by suspension polymerization for ice-temperature cold chain transportation and their preparation parameters were explored using the encapsulation ratio as optimization indicator.The results show that the n-dodecane-containing microcapsules have a maximum encapsulation ratio of 93.2%when using a core-to-wall ratio of 3:1,5%of emulsifier,30%of crosslinker,and 2000 rpm of emulsification speed.The phase transition temperature and enthalpy are-2℃and 195.9 kJ/kg,respectively.The microcapsules prepared with the optimized process parameters have good microscopic morphology,high energy storage efficiency,uniform particle size and good thermal stability,making them ideal materials for cold chain transportation.

Effect of Preparation Condition on Low-density PS Particle Size and Distribution

The preparation conditions were studied in order to obtain smaller, narrow size-distributed and low-density polystyrene (PS) micro-particles by suspension polymerization. The results show that some of preparation conditions, the shape and position of stirrers, and stirring rate etc., have important influence on the size and distribution of particles. The preparation conditions must be carefully designed and controlled in order to obtain high-quality PS beads. A bow-shaped stirrer is helpful to produce small-sized particles and narrow size distribution, and the upper edge of a stirrer should be set to the same level as the surface of mixture, and the stirring rate should be controlled in the range of 520-600 r/min.