ARMA Rotational Moulding Workshop June 2016 Questions and Answers

1. Rotomould Workshop
Problem 1
Why are material specifications important to the rotomoulder
Materials, by Ian Hansen, Rotoconsult

2. Do you have specifications from your powder
supplier?
 Dry Flow Is it the ARMO funnel?
 Particle Size
 Bulk Density
If you don’t have copy, why not?

3. MATERIAL
 Melt Flow Index (MFI)
POWDER
 Dry Flow
 Bulk Density
 Particle Size
Do you receive a COA for each different batch
of powder delivered ?
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4. Do you review the variation in material
properties? Can this affect you?
2.4
2.6
2.8
3
3.2
3.4
3.6
13226
13233
13240
13246
13253
13255
13258
13262
13270
13271
13273
13274
13319
13430
13438
13454
13462
13466
13478
13489
13490
13491
13492
13493
13499
14001
14002
14005
14006
14008
14009
14009
14010
14022
14031
14032
14033
14035
Melt Flow Index -10%
+10%
MFI
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5. Melt Flow Rate ASTM D1238 or ISO 1133
As MFI increases, polymer flow properties increase
As MFI decreases, polymer flow properties decrease
Melt Flow Increase
Melt Flow Rate, sometimes referred to as Melt Flow Index, is a measure of the viscosity or
flowability of the plastic once melted. This provides a value – the Melt Flow Index (MFI) –
which gives a relative indication of the ease of flow of a polymer melt.
Melt Flow Decrease
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Source : ARMA Materials Properties Guide

6. 20
22
24
26
28
30
13226
13233
13240
13246
13253
13255
13258
13262
13270
13271
13273
13274
13319
13430
13438
13454
13462
13466
13478
13489
13490
13491
13492
13493
13499
14001
14002
14005
14006
14008
14009
14009
14010
14022
14031
14032
14033
14035
Dry Flow
Do you review the variation in material
properties? Can this affect you?
www.ianhansenconsult.com

7. Powder Quality important to fill tight corners
and threads
 Dry flow is the measure of how a powder will tumble and flow in the mould
during the rotational moulding process.
 The dry flow affects the heat transfer in the powder pool and how the powder
distributes itself over the mould surface.
 Dry flow depends mostly on the Particle Shape, and to a lesser extent Particle
Size.
 Particles that have been ground poorly will have ‘tails’ and tend to be ‘fluffy’.
 These two characteristics will give the powder poor flow properties - possible
leading to uneven wall thickness, bridging across narrow recesses and a high
void content within the moulded product
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8. Powder Quality important to fill tight corners
and threads
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Image Source: www.aptis.be/
Examples of different flow characteristics

9. 9www.ianhansenconsult.com
Particle 1
Ideal
Particle 2
Very good
Particle 3
Poor
ImageSource:TPPicture®
 The most desirable particle is thought to be cubic in shape with generously
rounded corners, without tails.
 WHY? The rate at which powder melts is a function of the shape of powder
particles.

10. Powder with tails Powder without tails
Which powder is better quality?
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11. Powder without tails
Which powder is better quality?
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12. For those who do not have a
microscope handy…
measure quality with Dry Flow funnel
Which powder is better quality?
A
• Dry Flow
22sec
B
• Dry Flow
25sec
C
• Dry Flow
29sec
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13. For those who do not have a
microscope handy…
measure quality with Dry Flow funnel
Which powder is better quality?
A
• Dry Flow
22sec
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In most cases standard powder with
faster dry flow is usually better ‘quality’
than slower dry flow
If you receive a Certificate of Analysis [COA] with
each powder batch delivered, you can quickly &
easily compare ‘quality’ by reviewing the Dry
Flow time on the COA

14. Ian Hansen Consult