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OUTLINE 1. 2. 3. 4. Introduction Raw Materials Manufacturing Process Issues and Solutions 1. 2. 3. 4.
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Pearlescent Pigments for Plastic Applications OUTLINE 1. 2. 3.
4. Introduction Raw Materials Manufacturing Process
Issues and Solutions 1. 2. 3. 4. 3 INTRODUCTION Forty years ago,
anything made of plastic was considered "cheap. However with the
development of high quality plastics this is not true today.
Plastics are used in thousands of products ranging from computers,
automobile parts and important medical equipment, to toys,
cookware, sports equipment, and even clothes. Plastic Products
Packaging: Products: Personal care products
Electronics Automotive Household Films Toys Sports Packaging:
Personal care products Food Household Sanitary Toys 5 Plastic
Applications Plastics Raw Materials
PE LDPE / MDPE / HDPE / LLDPE PVChard PVC / soft PVC PP Homo
Polymer / Copolymer EVA ABS semi transparent ABS/transparent ABS
TPU PS HIPS / GPPS TPE PC PEEK PA PA6 / PA66 / PA46 PPS PBT PI PET
PMMA POM Plastic Properties Density Transparency Gloss Elongation
Flexibility
Impact Melt Flow Deflection temperature Molding Temperature Acid
and alkali resistance Flammability Electronic properties
MANUFACTURING FLOW Pearl Forming Colorant Master batch Pumping
tablet
Color paste Forming Extrusion Molding Extrusion is the most common
processes used to form plastics. A heated plastic compound is
forced continuously through a forming die made in the desired
shape, like squeezing toothpaste from a tube, producing a long,
usually narrow, continuous product. The formed plastic cools under
blown air or in a water bath and hardens on a moving belt. Rods,
tubes, pipes and toys such as Slinkys. Sheet and thin films (such
as food wraps) are extruded then coiled or cut to desired lengths.
Extrusion Molding Machine parameters for best results with
pearlescent pigments Masterbatches or compounds are usually used to
color the molten mass with effect pigments. For a satisfactory
result in plastic extrusion with effect pigments, a balanced ratio
must be maintained between the mixture energy and pigments which
are as undamaged as possible. Excessive shear from mixing sections
or inappropriate screws or filters destroy effect pigments and
dramatically decrease the pearl luster effect. The orientation of
the pigments is a requirement for an even effect. This has to be
ensured in the process through a corresponding engineering and
design of the machinery. Injection Molding Injection moulding Is
the second most widely used process to form plastics. The plastic
compound, heated to a semi fluid state which is injected into a
mould under great pressure and cools and hardens quickly. The mould
is opened and the part is released. This process can be repeated as
many times as necessary and is particularly suited to mass
production methods. Injection moulding is used for a wide variety
of plastic products, from small cups and toys to large objects
weighing or more. Injection Molding For best results with
pearlescent pigments
In injection molding, flow processes in the molten mass cause the
orientation of pigment platelets. By a technically well engineered
tool construction the Effect pigments can orientate perfectly and
showing nearly no flowline or welding effects. Another point to
optimize the effect appearance is the position of the injection
gate. Circular, centralized and edge minimized forms are perfectly
suited for Effect pigments. In cases, where this is not possible we
recommend, using our Diamond Effect pigment series in a low
concentration. It shows a strong sparkling effect and decreases the
optical perception of irregularities. Blow Molding Blow molding is
where gas pressure is used to form hollow objects, such as the soda
pop bottles, in a direct or indirect method. For direct
blow-molding, a partially shaped, heated plastic form is inserted
into a mold. Air is blown into the form, forcing it to expand to
the shape of the mold. For indirect blow-moulding, a plastic sheet
or special shape is heated then clamped between a die and a cover.
Air is forced between the plastic and the cover and presses the
material into the shape of the die. In this process Effect pigments
develop their full optical effect. Blow Molding For best results
with pearlescent pigments
Effect pigments are excellently suited to the extrusion blow
moldingprocess, since the extrusion process guarantees that
platelet-shapedeffect pigments are aligned evenly to the surface so
they can developtheir full optical effect. Co-extrusion is an
efficient option for combining high coverage and good effects.
Strong pearl luster and other effects can be achieved with a thin
outer layer, while the desired opacity is created by the covering
inner layer. Blow Molding Phenomenon of Effect pigments and the
interesting FrostEffect. Due to the soft heating during the blow
molding process, its elasticity isnot very high. Effect pigments
are now elastic anyway due to theirinorganic composition. The
stretches form voids between the stretchedpolymer and the
unstretchable effect pigments.The larger the pigmentsand the higher
the stretching ratio, the more obviously the vacuoles are.Effect
pigments can be used at stretching ratios of up to 3:1. In
addition,1-level or 1.5-level processes are more suitable, because
the plastic isstill in a semi-viscous state. In general this void
effect is broadly used for the so-called frost effect in PET
bottles. This frost effect gives the surface an appearance like it
comes directly out of the fridge. Manufacturing Equipment
Twin-screw machine Single Screw Machine Injection molding machine
Blow Molding Machine Trombone Mixer Factors Affecting Pigment
Effects
Plastic resins transparency and gloss Brightness of the forming die
Product surface treatment Product size and structure Pearlescent
pigment quality Pearlescent pigment dispersion The extent of
damageof pearl during the manufacturing process Effect from
Enhancer and filler Pearl dosage COMMON ISSUES PEARLESCENT
PLASTIC
Color changing/ stability Black spots /pearly spots Flow lines Weld
lines Yellowing Poor pearlescent effects Crazes Bubbles Effect
Issue Analysis Formula Raw material Equipment
Pearlescent pigment Issue Investigation What is the raw material
used
Pearlescent Pigments dosage in Master Batch Dispersion used
Equipment Used Manufacturing reference such as pressure,
temperature, etc. Timing If the issue is regular Pearlescent
pigment coating is single layer or dual layer? The thickness of the
layer Pearl total dosage Final product structure and size Issue
Reasons and Solutions
Black Spots Solutions: Reduce pearl dosage in master batch Improve
dispersion Reduce grinding damage Clean the equipment Use
pre-dispersed pigments Use proper filtering Choose correct
pearlescent pigments Possible Reasons: Poor dispersion Damage
caused by grinding Impurities Accumulation Incorrect choice
ofpearlescent pigments Problems and Solutions
Yellowing Possible Reasons: Non-yellowing resistantpearlescent
pigments The yellow resistant coatinglayer is damaged
duringgrinding Chemical damage of the yellowresistant coating layer
Solutions: Choose proper yellowresistant pearlescentpigments Mix
the pearls properly, donot grind which destroys theyellowing
resistant coatinglayer Yellowing Is an reaction between Titanium
and Phenol antioxidant.
Occurs withouthumidity or lights. Is a Reversible chemical process.
The speed and strength of this reaction depends on the activity
ofPhenol group, such as BHT. Temperature affects its speed and
strength. When pearlescent pigments are used with polycarbonates
yellowingissues may occur Specially treated Yellow Resistant
pearlescent pigments arerecommended for polycarbonates Flow Lines
Solutions: Possible Reasons: Dispersion improvement
Poor master batch dispersion Equipment problems Waves created by
moisture Processing temperaturetoo low Mold temperature too low
Solutions: Dispersion improvement Adjust manufacturingreferences
such astemperature, speed andpressure Increase the processing
andmold temperature temperature Dry raw material Weld Lines
Possible Reasons: Solution: Mold structure
Pearlescent pigment andits dosage Solution: Weld lines are not
avoidable butcan reduced Improve the mold structure Cautions
Pearlescent pigments need to be dispersed first, except to mix
intodirectly with PVC power plastic Plastic pieces require wetting
with % adhesive first thenmixed in with pearlescent pigments.
Polyolefin. when it used with titanium power, reacts with
phenolsand may cause yellowing. PVC requires all transparent
ingredients with pearlescentpigments mixed in at the last step.
When Gold and Ironpearlescent pigments areused with PVC a lab test
is required PMMA, PC, PA: requiring drying first before use.
Exterior applications Only yellowing / weather resistant
productsare recommended.