Rotational Moulding Conference Workshop - Question 1

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

Transcript of Rotational Moulding Conference Workshop - Question 1

Page 1: Rotational Moulding Conference Workshop - Question 1

Rotomould WorkshopProblem 1 Why are material specifications important to the rotomoulder

Materials, by Ian Hansen, Rotoconsult

Page 2: Rotational Moulding Conference Workshop - Question 1

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?

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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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Do you review the variation in material properties? Can this affect you?

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

2.4

2.6

2.8

3

3.2

3.4

3.6Melt Flow Index -10%

+10%MFI

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Melt Flow Rate ASTM D1238 or ISO 1133

As MFI increases, polymer flow properties increaseAs 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

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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

2021222324252627282930

Dry Flow

Do you review the variation in material properties? Can this affect you?

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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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Powder Quality important to fill tight corners and threads

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Image Source: www.aptis.be/

Examples of different flow characteristics

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Particle 1Ideal

Particle 2Very good

Particle 3Poor

Imag

e So

urce

: TP

Pict

ure®

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.

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Powder with tails Powder without tails

A BWhich powder is better quality?

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Powder without tails

BWhich powder is better quality?

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For those who do not have a microscope handy…measure quality with Dry Flow funnelWhich powder is better quality?

A•Dry Flow 22sec

B•Dry Flow 25sec

C•Dry Flow 29sec

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For those who do not have a microscope handy…measure quality with Dry Flow funnelWhich 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

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Ian Hansen Consult