Flowability

Question 1

What are 2 driving forces of flowability

Answer 1

Gravitation force and mechanic agitation

Question 2

What are 2 restrictive forces of flowability

Answer 2

cohesiveness/ adhesiveness and friction

Question 3

What is adhesion

Answer 3

Attractive forces between two chemically different substances

Question 4

What is cohesion

Answer 4

attractive forces between 2 chemically similar substances

Question 5

What is the gravity equation

Answer 5

Force x acceleration

Question 6

What causes cohesion and adhesion

Answer 6

VDW forces, electrostatic interlocking and mechanical interlocking

Question 7

What factors affect VDW forces

Answer 7

the larger a particle, the stronger the VDW and the closer the particles, the stronger the VDW

Question 8

How are electrostatic forces produced between particles

Answer 8

friction between particles and between a surface and a particle creates static electricity thus oppositely charged particles attract

Question 9

What is mechanical interlocking

Answer 9

when particles interlock because of their shape, sharp edges and rough surfaces.

Question 10

What is friction

Answer 10

when with one particle moves against another or two are moving in opposing directions, stopping particle movement

Question 11

Factors the affect powder flow

Answer 11

size, larger particles flow better
Density, denser particles flow better
Shape, rounder particles flow better
Surface texture, smoother surfaces flow better

Question 12

What is the equation for specific surface area

Answer 12

= Total surface area/mass

Question 13

The effects of a large surface area

Answer 13

More bonding are; more cohesion; more resistance; less flowability

Question 14

Why is a spherical shape preferred to an edged shape with the same mass

Answer 14

has a smaller surface are and is unlikely to undergo mechanical interlocking thus reducing resistance

Question 15

What is bulk density

Answer 15

The density of powder with air when allowed to settle properly under gravity

Question 16

Bulk density equation

Answer 16

Bulk density = mass/bulk volume

Question 17

What is tapped density

Answer 17

The density of particles with minus air after mechanically tapping the powder

Question 18

Equation for tapped density

Answer 18

=mass/tapped volume

Question 19

What is true volume

Answer 19

true volume is the density of solid particles only, without air

Question 20

Equation for true volume

Answer 20

Bulk volume/ packing fraction

Question 21

What are the 4 ways of testing powder flow

Answer 21

Flow rate, density ratios, angle of repose and shear cell.

Question 22

What is flow rate

Answer 22

The amount of time taken for a specific amount of powder to empty out

Question 23

What are the two methods of calculating a flow rate

Answer 23

1) work put how long it takes a specific amount of powder to empty out
2)measure the amount of powder in a specific amount of time

Question 24

What is density ratio

Answer 24

Measure a change in volume after undergoing a set of parameters. E.g. tapping the container

Question 25

How is density ratio measured

Answer 25

As a ratio or cars compressibility as %. The smaller the value, the higher its flowability

Question 26

What is the angle of repose

Answer 26

The angle between the top of the slope downwards and horizontal

Question 27

How to calculate the angle of repose

Answer 27

Tan-1(H/R)
H=height
R=radius, 0.5x width

Question 28

What is Hausners ratio and how to calculate

Answer 28

A type of density ratio: tapped density/ bulk density

Question 29

How to calculate cars index %

Answer 29

(Tapped ratio- bulk ratio/tapped ratio) x100

Question 30

What is granulation

Answer 30

Making smaller grained larger using water