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Stress relaxation study of fillers for directly compressed tablets.

Rehula M, Adamek R, Spacek V - Powder Technol (2012)

Bottom Line: This method records the decrease in pressing power in a tablet at its constant height.Mannitol had higher plasticity and lactose monohydrate on the contrary reduced plasticity.No similar interpretation of moduli calculated on the basis of three exponential equations has been realized yet.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmaceutical Technology, Faculty of Pharmacy in Hradec Králové, Charles University in Prague, Czech Republic.

ABSTRACT
It is possible to assess viscoelastic properties of materials by means of the stress relaxation test. This method records the decrease in pressing power in a tablet at its constant height. The cited method was used to evaluate the time-dependent deformation for six various materials: microcrystalline cellulose, cellulose powder, hydroxypropyl methylcellulose, mannitol, lactose monohydrate, and hydrogen phosphate monohydrate. The decrease in pressing powering of a tablet during a 180 s period was described mathematically by the parameters of three exponential equations, where the whole course of the stress relaxation is divided into three individual processes (instant elastic deformation, retarded elastic deformation and permanent plastic deformation). Three values of the moduli of plasticity and elasticity were calculated for each compound. The values of elastic parameters ATi have a strong relationship with bulk density. The plastic parameters PTi represent particle tendency to form bonds. The values of plasticity in the third process PT3 ranged from 400 to 600 MPas. Mannitol had higher plasticity and lactose monohydrate on the contrary reduced plasticity. A linear relation exists between AT3 and PT3 for the third process. No similar interpretation of moduli calculated on the basis of three exponential equations has been realized yet.

No MeSH data available.


The relationship between parameter AT2 and bulk density.
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f0025: The relationship between parameter AT2 and bulk density.

Mentions: Lum and Duncan-Hewitt [12] described the second process as a retarded elastic response. Particles try to recover its original volume but with a lower rate. The free space in tablets is filled and the particle–particle interactions occur more intensively than in the first process. This second process runs approximately for 25 s. The elastic parameters AT2 are lower than AT1. The value of the parameter A1 increased exponentially with a decrease of tapped density. However, MAN is an exception (Fig. 4). No significant difference was found (p = 0.102) for relaxation constants T2, except DHCP (p = 0.011).


Stress relaxation study of fillers for directly compressed tablets.

Rehula M, Adamek R, Spacek V - Powder Technol (2012)

The relationship between parameter AT2 and bulk density.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4020615&req=5

f0025: The relationship between parameter AT2 and bulk density.
Mentions: Lum and Duncan-Hewitt [12] described the second process as a retarded elastic response. Particles try to recover its original volume but with a lower rate. The free space in tablets is filled and the particle–particle interactions occur more intensively than in the first process. This second process runs approximately for 25 s. The elastic parameters AT2 are lower than AT1. The value of the parameter A1 increased exponentially with a decrease of tapped density. However, MAN is an exception (Fig. 4). No significant difference was found (p = 0.102) for relaxation constants T2, except DHCP (p = 0.011).

Bottom Line: This method records the decrease in pressing power in a tablet at its constant height.Mannitol had higher plasticity and lactose monohydrate on the contrary reduced plasticity.No similar interpretation of moduli calculated on the basis of three exponential equations has been realized yet.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmaceutical Technology, Faculty of Pharmacy in Hradec Králové, Charles University in Prague, Czech Republic.

ABSTRACT
It is possible to assess viscoelastic properties of materials by means of the stress relaxation test. This method records the decrease in pressing power in a tablet at its constant height. The cited method was used to evaluate the time-dependent deformation for six various materials: microcrystalline cellulose, cellulose powder, hydroxypropyl methylcellulose, mannitol, lactose monohydrate, and hydrogen phosphate monohydrate. The decrease in pressing powering of a tablet during a 180 s period was described mathematically by the parameters of three exponential equations, where the whole course of the stress relaxation is divided into three individual processes (instant elastic deformation, retarded elastic deformation and permanent plastic deformation). Three values of the moduli of plasticity and elasticity were calculated for each compound. The values of elastic parameters ATi have a strong relationship with bulk density. The plastic parameters PTi represent particle tendency to form bonds. The values of plasticity in the third process PT3 ranged from 400 to 600 MPas. Mannitol had higher plasticity and lactose monohydrate on the contrary reduced plasticity. A linear relation exists between AT3 and PT3 for the third process. No similar interpretation of moduli calculated on the basis of three exponential equations has been realized yet.

No MeSH data available.