Compressive force Strength

Obviously, the discrepancy between the experimental data [238-241] and predictions of the theory [236,237] can be attributed to the difference of the coefficients of thermal expansion. The polymer exerts pressure on the filler, thereby masking the effect of the strength of adhesion on the modulus. The pressure on the filler may be sufficiently high. In [243] it was found, for example, that in PP, quartz particles experienced a compression force of about 100 MPa after cold drawing of the composite the force reduces to 50 MPa in the direction of drawing but at the same time increases to 300 MPa in the perpendicular direction. 

Compressive modulus of various PE foam boards, in different densities and open cell content, are measured and compared with different models. Contributory elements to compressive resistance are investigated. Agreement between test results and modelling improves significantly while only considering the struts strength parallel to compressive force. 7 refs. 

Figure 22 shows the tablet hardness profiles of the 25 mg strength. Tablet hardness slightly increased as the compression force increased and... 

System Drug polymer ratio Mean tablet mass (mg) Mean drug content (mg) Compressive force (kN) Tensile strength... 

Grain collapse. This is a problem which exists in some rockets where an appreciable pressure difference can develop between the forward and aft ends of the rocket. The latter is subjected to compressive forces which can squeeze it. A propellant of high tensile strength is therefore desirable. 

Fig. 7.25 An axisymmetric particle freely rotating in a simple shear field. The force F exerted hy one half of the particle on the other is zero when the main axis is perpendicular to the flow direction it reaches a maximum tensile strength at 45° and it drops to zero at 90°. Then at 135° it will reach maximum compression and return to zero at 180°. If the ellipsoid is at a certain angle to the direction of shear, the same phenomenon takes place, except that the tensile and compressive forces will he smaller and the particle will rotate and wobble. If the agglomerate is spherical it will smoothly rotate and a maximum tensile strength will be generated along an axis at 45° to the direction of shear.

Roll Force (kN) Gap Width (mm) Sieve Size (mm) Compression Force at 7 kPa Crushing Strength... 

In that frame, the use of a plane-plane rheometer has been evaluated. The purpose of the experiment carried out in the rheometer is not to mimic fire testing (this is not possible since the heating rate [slow ramp vs. quenching], heating source [convection vs. radiation], sample size, and boundaries effect are different) but to develop a test method that will permit the characterization of the char strength when exposed to pressure (in that case compression force). 

Table 13.12 Effects of punch design and compression force on tablet strength (MPa)...

There is significant evidence that strength varies according to compression force (.P < 0.001). High pressure always produces the greater strength. 

It is not possible to make any general statement about how much extra strength arises from the use of the higher compression force nor about the extent of the difference that arises from using (say) punch C instead of B. 

Riippi, M., Antikainen, O., Niskanen,T., and Yliruusi, J. (1998),The effect of compression force on surface structure, crushing strength, friability, and disintegration time of erythromycin acistrate tablets, Eur. J. Pharm. Biopharm., 46, 339-345. 

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