Features at a glance
- Resolves particle sizes in complex mixtures
- Simple, rapid operation, stable
- No calibration necessary, exact derivations
- Suitable for a wide range of sizes and densities
- Variety of operating modes
- External and internal gradient
- LINE or HOST start methods
- Successive sample injections allowed
- Stationary or scanning detector
- variable rotation speed
- Quantitative determination of weight distributions
- Optimize experimental conditions in advance
- Customizable analysis and reports
- Continuous monitoring of temperature
No other type of instrument can resolve several peaks in the difficult range around 1 micron.
The DCP incorporates a custom electronic drive system with high efficiency while operating quietly on your bench top. An integral strobe light is synchronized to the drive circuit for checking hydrodynamic stability of the sample. A sensor is used to monitor temperature in the disk. The BI-DCP offers the largest range of speeds, 500 to 15,000 rpm, which allows an even greater range of particle size measurements. A scanning detector head reduces measurement time.
Benefits of Use
An instrument is an investment in the present as well as in the future. The BI-DCP is truly cost-effective because it enables users to:
- Resolve complex particle size distributions to improve rheological and structural properties.
- Monitor incoming raw materials to reduce rework.
- Fingerprint finished products to minimize lot-to-lot variations.
- Increase cost effectiveness by reducing process and scale-up time.
- Optimize material properties to enhance product performance.
- Study particle size fundamentals to develop new products and processes.
Particles scatter and for some, absorb light. A beam of LED light is used, and the following relationships describe the basic principles for the DCP. This analysis relies on a simplified form of light scattering, namely turbidity. Whereas static and dynamic light scattering rely on quantification of scattered light to calculate particle size, turbidity only requires that you be able to measure the light lost due to scattering and/or absorption, essentially via a reduction in transmittance.
- It = I0 exp (-Qext * C * L) where I0 = incident intensity and It is transmitted intensity
- Qext = Extinction efficiency = f(dp, np/nf, λ)
- c = Mass concentration
- L = Path length (width of fluid segment in disc)
- Light is either absorbed or scattered, the sum of which is called extinction.
- Extinction is a strong function of particle size. Significant optical corrections are necessary for dp ≤ 5 μm
- Sensitive, but less quantitative for high density materials such as metal oxides where Qext is not easy to calculate accurately.
The key equation for diameter of the particle is:
Note that the relationship between time and particle size squared is inversely proportional.
t = time
ƞL = viscosity of the liquid
RD = radius of the detector
RI = radius to the meniscus
ρp = density of the particle
ρL = density of the liquid
The final particle size distribution obtained from the BI-DCP depends on hydrodynamics to the extent that this dictates the time required for a band of particles to pass the detector. The optical correction becomes more difficult when materials with complex refractive indices are considered, such as metal and metal oxide particles. These sorts of samples are better suited to X-Ray detection. Higher atomic mass nanomaterials tend to have higher densities, and thus sediment more rapidly. This is common with metal and metal oxide particles.
Read our article comparing our two disc centrifuges for more information.
The versatile BI-DCP offers high resolution results to particle sizing problems where the particles are dispersed in a liquid and cover the size range from 0.01 to 30 microns. This range is useful for a variety of materials and many applications:
- Polystyrene, PVC, other polymers
- Carbon blacks
- Metal oxides, refractories
- Ink particulates, alumina, titania
- Pharmaceuticles, cosmetics, foods
- Coatings, paints
- Minerals, silicas
- Clays, ceramics
A Case History:
The Bl-DCP’s value was demonstrated in a coatings application involving an emulsion polymerized latex. The performance of the coating varied from batch-to-batch with each latex produced, and was not within he desired specifications. So, the unacceptable product was discarded or stored for use in less exacting applications. This resulted in increased handling charges, storage/disposal problems and greatly reduced profitability. Using the Bl-DCP, the problem was traced to variations in the particle size distribution of the latex produced in a typical large production reactor. The detection of variations in particle size distributions and the subsequent corrections, resulted in much tighter controls over the end product. This in turn resulted in a completely usable product that eliminated storage/disposal problems and brought the company higher profit margins.
|Analysis||Size range of 0.01 to 30 µm maximum; 0.05 to 10 µm typical for low density particles, 0.01 to 2 µm for high density particles; wide variety of materials dispersed in water and other solvents|
|Data System||Windows computer with printer. Real time graphics and data display, high resolution color (SVGA). Menu driven data analysis and management system, with single copy license and software distribution copy.|
|Drive System||Microprocessor controlled digitally driven electronic motor. Digital readout for setting and montoring speed. Speed ocntinously variable from 500 to 15,000 rpm. Speed accuracy and stability better than + 0.01%. Temperature sensor and digital readout. Dual purpose integral strobe.|
|Disc Cavity||Polymethylmethacrylate with stainless steel hub. Dynamically balanced over range of roatational speeds. Spin fluid volume from 10 to 40 mL.|
|Power Requirements||100/115 VAC, 220/240 VAC, 50/60 Hz, 1,000 Watts|
|Dimensions||260 x 500 x 550 mm (HWD)|
A policy of continual improvement may lead to specification changes