problem4_rotationalmoulding_workshop_question4
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Rotomould WorkshopProblem 4 What is the cause of ‘Orange peel’ in stone effect colours
Materials, by Ian Hansen, Rotoconsult
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“Orange Peel” [OP] defined
Ian Hansen Consult1: STUDY OF ORANGE PEEL PHENOMENA IN ROTATIONAL MOLDING, E. Soos Takacs, M. Emami, D. D’Agostin and J. Vlachopoulos, Department of Chemical Engineering, McMaster University, Canada
The term “orange peel” describes an inside surface defect that is characterized by irregular grooves and pitting—much like the topography of the outer skin of an orange.1
“Orange Peel” [OP] effect
Ian Hansen Consult
Rough internal surface. Seen in varying levels from mild to severe Found thru whole batch of parts of a batch of powder
Source : Orange Peel in Rotomoulded Parts; Bloys Rijkmans – ICO Polymers – ARMA Rotomould Conference 2009 Sydney
Intermittent Difficult to predict Occurs Natural &
Colour Not well
understood
“Orange Peel” [OP] effect in Colours
Ian Hansen Consult
Example of same base polymer, “same” green colour, same Particle Size – but different pigment formulation, in 50/50 blend of 2 batches.
Pigment can act as a nucleating agent and affect the crystallization process.1
Density has stronger effect on OP than MI - Differential shrinkage
Particles RAISED Particles
SUNKEN
1. The effect of colour compounding on crystal grow
th during rotomoulding
M.P.M
cCourt, M
ark P.Kearns, G
.M.M
cNally, Polym
er Processing Research C
entre, Queen's U
niversity Belfast,
and R.J.C
rawford, U
niversity of Waikato
Source : Test This : Materials Guide – Ian Hansen – ARMA Rotomould, Penang 2011
ianhansenconsult.com
Crystal Structure affected by pigment
Homogeneous crystal structure. Some air bubbles are observed.
Dissimilar crystal structure. Indicating two different materials. This was a mixture of Batch 1 and Batch 2
Homogeneous crystal structure. Change in crystal size. Some air bubbles are observed.
Batch 1 Batch 2
Batch 1 +2 50/50
Source : Test This : Materials Guide – Ian Hansen – ARMA Rotomould, Penang 2011
Cause of “Orange Peel” effect in Stone Effect
Ian Hansen Consult
1. Small DENSITY differences of coloured polymer particles shrink differently. Different colours, are different
pigments, are different densities Independent of degree of cure or
additive depletion.
Cause of “Orange Peel” effect in Stone Effect
Ian Hansen Consult
2. Effect of Pigment Different colours create different crystal
structure. Dry blending of colours results in more severe
OP 3. Effect of Particle Size
Higher % coarse particles increases ease at which you can observe OP – but PS is not the cause.
Ian Hansen Consult
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