Primary properties mean size

Tensile properties of PVC filled with precipitated calcium carbonate particles having two different mean sizes were studied. The particles were porous agglomerates of spherical primary particles. 10-50 parts of the particles were mixed with 100 parts PVC and 3 parts lead stearate using a mixing roll. Tensile tests were carried out using dumbbell test specimens. 20 refs. 

A suitable model system is necessary to study the correlation between the texture properties (mean pore size) and transport characteristics (pore diffusion coefficient) of the primary pore system of catalyst supports. The model catalyst support should be characterized by (i) a monomodal pore structure with pore sizes in the range between 2 and 20 nm (typical... 

Hydrolysis is carried out in brick-lined, stirred tanks (n) into which steam is passed. The hydrolyzate does not have any pigment properties. The properties of the hy-drolyzate are strongly influenced by the particle size and degree of flocculation of the hydrolyzate (mean primary particle size of hydrolyzate is ca. 5 nm, and the particle size ofTi02 pigments is 200-300 nm). 

Alumina(s) from Nanotek Properties y-form [977], mainly y-form [978], BET specific surface area 47 mVg [978], mean particle size 36 nm [978], average primary particle size 33 nm [977], spherical particles [977]. 

The total mass of particulate matter per unit volume of air is perhaps the simplest integral property, and it is on this quantity that U.S. federal standards for particulate pollution have been based. Until recently there was a single primary (health related) standard of 50 g/m (annual geometric mean) and 150 /rg/m- (maximum 24-hr concentration not to be exceeded more than once per year), with an upper cutoff in panicle size of 10 /ttm (PMio). However, epidemiological studies indicate an association between adverse health effects, including enhanced mortality, and submicron aerosol concentrations in many U.S. cities (Pope cl al.. 1995). This has led to the establishment of an additional mass ba.sed standard for particles smaller than 2.5 /im (PMj.j) (U.S. EPA, 1996). There is also a separate health-based standard for lead, one component of the atmospheric aerosol. 

Cyclones are seldom used as the primary means of particulate collection, but often serve as first-stage air cleaning devices that are followed by other methods of particulate collection. Cyclone collection efficiency is probably more susceptible to changes in particulate characteristics than are other types of devices, therefore, care should be taken if used. Cyclone operation is dependant, generally, on physical parameters such as particle size, density, and velocity, as opposed to the chemical nature or properties of the material being collected. 

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