Post on 17-Dec-2015
transcript
a technology for manufacturinghollow seamless articles
a technology for manufacturing hollow seamless articles
Dissolving the bubbles
If melt is in diffusion equilibrium with atmosphere gas in the bubble tend to flow outwards because
of pressure difference ΔP until radius r of the bubble diminishes to zero .
PiPi
ΔP = Pi - Patm = 2T/rΔP = Pi - Patm = 2T/r
PatmPatm
Example of Gas Permeable Polymers:Example of Gas Permeable Polymers:
Silicone Rubber: high flexibility of the silicon-oxygen chain in siloxane provides “openings” which are freevolume and permit gas diffusion, see Zhang and Cloud (2006).
Silicone Rubber: high flexibility of the silicon-oxygen chain in siloxane provides “openings” which are freevolume and permit gas diffusion, see Zhang and Cloud (2006).
Gas Permeation of Polymers, Barrer
1
10
100
1000
10000
100000
1000000
LDPE Silicone PEG est.
N2
O2
CO2
H2O
What are micro-pellets?Small regular oval shaped
plastic granules with a diameter between 500-
600µm.
Produced from the same base material as powder, i.e.
Qenos 711UV etc.
Differ from powder by way of the manufacturing process
and particle size distribution.
Process comparison
Customer
Dust Collector
Blower
Bag
PE pellets Cyclone
Sieves
GrindingHead
OversizeParticles
Powder
85-105oC
Source: Practical Guide to Rotational Mouldingby R Crawford & M Kearns
POWDERPELLETS andMICRO-PELLETS
Source: Gala Industries
Bag
Centrifugal Dryer
Extruder
PE Powder
Die Plate
PDVCutter
Process Water
Process WaterPump
WaterBath
190-210oC
Particle size distribution comparison.
0
10
20
30
40
50
60
70
0 50 106 150 212 250 425 500 600 710 850 1000
Particle Size, Micron
% B
y W
eig
ht
Powder MicroPellets
Ave = 300-350 µm
Ave = 550 µm
IMPROVED ECONOMICS AND MORE OPTIONS FOR THE MOULDER
What are the benefits of micro pellets?Manufacturing Process
Consistent quality and sizeLess contaminationDust free during mould filling
Shape and Particle Size DistributionPotential for faster cook timesPotential for lower peak internal air temperatureGreater bulk density (0.51kg/m3 cf. 0.34 kg/m3)Improved flow (10 sec cf. 32 sec)Potential for improved mechanical propertiesImproved filling and definition of difficult to fill mould areasMoulded parts with more uniform wall thicknessMaintained / improved surface finish
Other Cheaper raw material
Micro Pellet Tank Trial
20
25
30
35
40
45
50C
ycle
Tim
e (m
ins)
Cook Time (min) Cool Time (min)
Cool Time (min) 17 16 16 17
Cook Time (min) 28 24 25 24
Powder Tank - 1 Tank - 2 Tank - 3
Meet requirements of tank standard impact testing with no ductile or brittlefailures using a 9.06kg drop dart @ 1.4m.
Oven machine, Tank Size = 2,250L, Shot Weight = 55kgs, Wall thickness = ~5mm, Colour = Merino.
> 12%
Rotomolding PPAs:Rotomolding PPAs: Silica Fume (SF): "Free-Flow" Agent.
PEG+SF: Densification & Processing Aid (D&PA).
PEG + Carboxylic Acids (CA): Advanced D&PA.
Novel Processing Additives: PEG + CA + SF.
Silica Fume (SF): "Free-Flow" Agent.
PEG+SF: Densification & Processing Aid (D&PA).
PEG + Carboxylic Acids (CA): Advanced D&PA.
Novel Processing Additives: PEG + CA + SF.
Extrusion PPAs:Extrusion PPAs: Silica Fume (SF): Thickening Agent.
PEG+SF+Anti-Oxydants: Processing Aid (PA).
PEG + Carboxylic Acids (CA): Advanced PA.
Novel Processing Additives: PEG + CA + SF.
Silica Fume (SF): Thickening Agent.
PEG+SF+Anti-Oxydants: Processing Aid (PA).
PEG + Carboxylic Acids (CA): Advanced PA.
Novel Processing Additives: PEG + CA + SF.