Stiffness applications

Bearings and sealing Ball bearings especially for high speed high stiffness applications No or low lubrication (vacuum pumps, dental drill handpieces) Under corrosive conditions (food ndustry chemistry metallurgy) high and low temperatures... 

It is often important for a PO material to have a spedfic, consistent impact resistance, preferably without reduced stiffness. Applications have driven the need for PP impact copolymers and rubber-modified PP, as wdl as for low-density PE made with metallocene catalyst reactor technology, all of which provide high toughness at various temperatures. But for practically all common POs, toughness can be inaeased via additions of impact modifiers by the compounder or processor. When considering the use of an impact-modified compound, a few questions should be reflerted on ... 

P(3) Composite materials manufactured from CSM reinforcements shall be limited to low stressed and low stiffness applications. 

An appreciable amount of work has been carried out on the use of PA in engineering applications such as automotive parts, precision engineering applications and high strength and stiffness applications such fan blades, gears, bearings and wind turbine blades. 

PBT, 30% carbon fibre filled Ultra-high strength and stiffness applications ... 

Ultra-high-strength and -stiffness applications Bearings, high-strength structures Connecting rods... 

UT 640 G (metal-like stiffness) - applicable for automotive (covers, grilles, and passenger compartment devices), industrial/mechanical (power tools, pump components, and products formerly manufactured from metal), lawn and garden (lawn mower components, trim equipment parts, tractor body shrouds). 

This type of coil was prepared from copper cladded printed circuit board material by applying photolithographic techniques. The p.c. board material is available with difierent copper thicknesses and with either a stiff or a flexible carrier. The flexible material offers the opportunity to adapt the planar coil to a curved three dimensional test object. In our turbine blade application this is a major advantage. The thickness of the copper layer was chosen to be 17 pm The period of the coil was 100 pm The coils were patterned by wet etching, A major advantage of this approach is the parallel processing with narrow tolerances, resulting in many identical Eddy current probes. An example of such a probe is shown in fig. 10. 

In the decoupled scheme the solution of the constitutive equation is obtained in a separate step from the flow equations. Therefore an iterative cycle is developed in which in each iterative loop the stress fields are computed after the velocity field. The viscous stress R (Equation (3.23)) is calculated by the variational recovery procedure described in Section 1.4. The elastic stress S is then computed using the working equation obtained by application of the Galerkin method to Equation (3.29). The elemental stiffness equation representing the described working equation is shown as Equation (3.32). 

It is used in gyroscopes, computer parts, and instruments where lightness, stiffness, and dimensional stability are required. The oxide has a very high melting point and is also used in nuclear work and ceramic applications. 

The combination of strong intermolecular forces and high chain stiffness accounts for the high melting points of polyamides through application of Eq.(4.5). 

Polypropylene polymers are typically modified with ethylene to obtain desirable properties for specific applications. Specifically, ethylene—propylene mbbers are introduced as a discrete phase in heterophasic copolymers to improve toughness and low temperature impact resistance (see Elastomers, ETHYLENE-PROPYLENE rubber). This is done by sequential polymerisation of homopolymer polypropylene and ethylene—propylene mbber in a multistage reactor process or by the extmsion compounding of ethylene—propylene mbber with a homopolymer. Addition of high density polyethylene, by polymerisation or compounding, is sometimes used to reduce stress whitening. In all cases, a superior balance of properties is obtained when the sise of the discrete mbber phase is approximately one micrometer. Examples of these polymers and their properties are shown in Table 2. Mineral fillers, such as talc or calcium carbonate, can be added to polypropylene to increase stiffness and high temperature properties, as shown in Table 3. 

Slides Of reflecting telescopes, aeroplanes, space capsules, bicycles (to illustrate applications of stiff but light materials). 

The ability to center tliis damper in applications where relatively heavy rotors are used has proven to be very advantageous. Tlie limited axial space present with most machinery does not hinder its applicability. Furthermore, the accuracy in predicting the stiffness and damping is anotlier desuable feamre tliat is irtissing witli conventional damper designs. 

Calendering processes, of great importance in the production of sheet materials from PVC compounds, are little used with polyethylene because of the difficulty in obtaining a smooth sheet. Commercial products have, however, been made by calendering low-density polymer containing a small amount of a peroxide such as benzoyl peroxide to give a stiff but crinkly sheet (Crinothene) which was suitable for lampshades and other decorative applications. 

The foams, marketed by Rohm as Rohacell, are stable at room temperature to hydrocarbons, ketones, chlorinated solvents and 10% sulphuric acid. They may be used under load at temperature up to 160°C. Uses quoted for these materials include bus engine covers, aircraft landing gear doors, radar domes, domes, ski cores and tennis racket cores. Their potential is in applications demanding a level of heat deformation resistance, solvent resistance and stiffness not exhibited by more well-known cellular polymers such as expanded polystyrene and the polyurethane foams. 

One unusual but nevertheless important application of SAN has been in the manufacture of polymer polyols used in the manufacture of flexible polyurethane foams. Proportions of up to 40% of the polyol may be used to increase stiffness as foam bulk densities are lowered (see Section 27.5.4). 

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