PAGE 1 OF 19
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`BOREALIS EXHIBIT 1013
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`PAGE 1 OF 19
`
`BOREALIS EXHIBIT 1013
`
`

`
`I’0IVllI'0IWIe|lB
`
`The Definitive User’s Guide and Databook
`
`Clive qaaier
`
`Te resa C a I afu 1'.
`
`(007)
`
`Plastics Design Library
`
`PAGE 2 OF 19
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`

`
`IEPR 23 a Will
`
`‘\*\C_i_P_....-/’
`
`Copyright © 1998, Plastics Design Library. All rights reserved.
`ISBN 1-884207-58-8
`
`Library of Congress Card Number 97-076233
` ..
`
`Published in the United States of America, Norwich, NY by Plastics Design Library a division of
`William Andrew Inc.
`
`Information in this document is subject to change without notice and does not represent a
`commitment on the part of Plastics Design Library. No part of this document may be reproduced or
`transmitted in any form or by any means, electronic or mechanical, includingiphotocopying,
`recording, or any information retrieval and storage system, for any purpose without the written
`permission of Plastics Design Library.
`
`Comments, criticisms and suggestions are invited, and should be forwarded to
`Plastics Design Library.
`
`Plastics Design Library and its logo are trademarks of William Andrew Inc.
`
`Please Note: Although the information in this volume has been obtained from sources believed to
`be reliable, no warranty, expressed or implied, can be made as to its completeness or accuracy.
`Design processing methods and equipment, environment and others variables effect actual part and
`mechanical performance. Inasmuch as the manufacturers, suppliers and Plastics Design Library
`have no control over those variables or the use to which others may put the material and, therefore,
`cannot assume responsibility for loss or damages suffered through reliance on any information
`contained in this volume. No warranty is given or implied as to application and to whether there is
`an infringement of patents is the sole responsibility of the user. The information provided should
`assist in material selection and not serve as a substitute for careful testing of prototype parts in
`typical operating environments before beginning commercial production.
`
`Manufactured in the United States of America.
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`Plastics Design Library, 13 Eaton Avenue, Norwich, NY 13815 Tel: 607/337-5080 Fax: 607/337-5090
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`PAGE 3 OF 19
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`

`
`34
`
`bilization in experimental studies and had lower
`volatility and extractibility. It was not absorbed by
`fibers present in the formulation and did not inter-
`act with pigments during fiber spinning. [885]
`
`3.4.5
`
`Screeners
`
`Pigments added to a formulation to provide opac-
`ity or translucence, such as carbon black, titanium
`dioxide. and zinc oxide, act as UV screeners by
`absorbing or reflecting ultraviolet
`light. Carbon
`black absorbs ultraviolet and visible light through-
`out the entire spectrum and may also act as a free
`radical scavenger. It can be used at concentrations
`as low as 1 — 2%. The stabilization of resins con-
`taining carbon black can be enhanced by addition
`of antioxidants or HALS. Titanium dioxide (rutile)
`reflects light and is elfective at high loadings.
`Some pigments can act as synergists with com-
`pounds such as phosphites and nickel-organic salts
`to improve embrittlement time for polypropylene
`by over 60%. [822, 878]
`
`3.4.6 Evaluation of UV stability
`
`The most accurate test of UV stability is use of the
`material in its intended end-use environment over a
`period of time. Due to the long—term nature of out-
`door weathering tests, accelerated testing using arti-
`ficial light sources (xenon are lamp, sunshine car-
`bon arc lamp, mercury arc lamp, fluorescent sun
`lamp) is common. Filtered xenon most accurately
`reproduces the spectral energy distribution of sun-
`light, while light sources with significant emission
`below 290 nm can produce different results than
`those obtained with long-term, outdoor weathering.
`Accelerated exposure tests may underestimate the
`effectiveness of I-IALS due to the very high levels of
`UV radiation produced. [819, 821, 843, 885]
`
`3.4.7 Use of light stabilizers
`
`Use levels of light stabilizers range from 0.05-
`2.0%, depending on the type of stabilizer, part
`thiclcness, presence of other additives, type of resin,
`and application requirements. Benzophenones and
`hindered amines are widely used in polypropylene.
`A combination of stabilizers is used to obtain the
`desired stabilization; highly stabilized polypropyl-
`ene contains an ultraviolet absorber, a phosphite
`stabilizer, and a nickel quencher or hindered amine.
`[82l, 878, 822]
`Compatibility with the resin is more important
`in light stabilizers than in antioxidants, since they
`are used at higher concentrations. Higher concen-
`
`Additives
`
`trations of stabilizers can be dissolved at high
`temperatures than at low temperatures, so that sta-
`bilizers dissolved during resin processing may ex-
`hibit bloorning, migration of the stabilizer to the
`part surface, when the resin is cooled. Blooming
`and turbidity can occur if the stabilizer is incom-
`patible with the resin; compatibility of the gener-
`ally polar light stabilizers is more difficult
`to
`achieve with nonpolar resins such as polypropyl-
`ene. Diffusion of additives through the resin de-
`creases
`in resins with increased crystallinity,
`crosslinlcing, or orientation. Low molecular weight
`stabilizers can migrate in incompatible resins; mi-
`gration is considerably reduced with high mo-
`lecular weight stabilizers. [858]
`
`3.5 Nucleating agents
`
`Nucleating agents are added to polypropylene to
`improve processing characteristics and clarity and
`alter its mechanical properties. The addition of nu-
`cleating agents provides a large number of sites for
`the initiation of crystallization, so that spherulites
`formed are smaller and more numerous than in un-
`nucleated polypropylene (See Figure 2.2 in Chapter
`2: Morphology for a comparison of spherulite sizes
`in nucleated
`and unnucleated polypropylene).
`Spherulite crystallization around a nucleating agent
`is shown in Figure 3.1 1. [886, 693]
`Nucleation increases the crystallization tem-
`perature and the rate of crystallization; as a result,
`parts can be removed from the mold at higher tem-
`peratures, and molding cycle times are reduced.
`Crystallization is more complete in nucleated resins
`than in unnucleated resins, producing high levels of
`
`Figure 3.11 Micrograph of a spherullte of polypro-
`pylene termed In the presence at a nucleatlng agent.
`The nucleating agent is at the center of the spherullte.
`suggesting that the nucleating agent initiated crystal
`formation. The nucleatlng agent was sodium 2,2‘-
`rnethyIensbis(4.6-di-tert-butylphenyl) phosphate. [886]
`
`© Plastics Design Library
`
`PAGE 4 OF 19
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`

`
`crystallinity. Nucleated materials have higher tensile
`strength, stiffness, flexural moduli and heat deflec-
`tion temperatures than unnucleated materials, but
`impact strength is lower. The high levels of crystal-
`linity can result in reduced tolerance to radiation
`sterilization compared to unnucleated polypropyl-
`ene, and the effectiveness of hindered amine light
`stabilizers and other stabilizing additives can be re-
`duced. Because nucleated polypropylene shrinks
`more rapidly in the mold, shrinkage of the resin
`onto mold cores can occur if parts are not ejected
`fast enough. [696, 693, 67]
`Clarity is enhanced due to the increased cool-
`ing rate and the decreased spherulite size, which
`reduces the scattering of light as it passes through
`the material (See 2.3.4 haze for an explanation of
`haze
`in unnucleated polypropylene). Smaller
`spherulites can reduce warpage in some applica-
`tions and can provide a harder, more stain-resistant
`surface. [(596, 693]
`Nucleating agents used in polypropylene include
`carboxylic acid salts, benzyl sorbitols, and salts of
`organic phosphates. Carboxylic acid salts provide
`limited clarity enhancement but do enhance the me-
`chanical properties by an increase in the crystalliza-
`tion rate. Dibenzylidene sorbitols reduce crystal size
`dramatically, resulting in greatly improved clarity.
`Benzyl sorbitols can result in odor generation during
`processing which produces odor in the finished part.
`Pigments, such as phthaloxyanine blue and green and
`phthalyl blue, and mineral fillers such as talc can also
`act as nucleating agents, although tale is not as efi?ec-
`tive. [693, 886, 779, 696]
`Applications of nucleated polypropylene in-
`clude food bottles and packaging, automobile parts,
`medical syringes, and houseware containers. [855]
`
`3.6 Flame retardants
`
`Many plastics are inherently flammable due to
`their origins in petroleum manufacturing. Polypro-
`pylene ignites when in contact with a flame and
`burns with a faintly luminous flame even after the
`ignition source is removed. Melting occurs due to
`the high heat of the flame, producing burning
`drips. For applications in the construction, auto-
`motive, appliances, and electronics
`industries,
`polypropylene must be stabilized by the use of
`flame retardants. [825, 820, 326]
`Polypropylene is one of the most difficult
`plastics to make flame retardant. High levels of
`flame retardants are required in the polypropylene
`
`35
`
`formulation to meet standards for applications
`such as in the electronics industry; 25% flame
`retardant is required in polypropylene compared to
`10-20% for styrenics or engineering thermoplas-
`tics. These high levels of flame retardant increase
`brittleness and impair the mechanical performance
`of the material. Flame retardants can also reduce
`processability and can interfere with the action of
`other additives, such as hindered amine light sta-
`bilizers. [834, 836, 837]
`
`3.6.1
`
`Fire
`
`in
`Combustion is a highly exothermic reaction,
`which hydrocarbons are oxidized to carbon diox-
`ide and water. Combustion is a gas-phase reaction
`— polypropylene or its decomposition products
`must become gaseous for a fire to begin. Fire in a
`candle occurs when melting wax (composed of
`hydrocarbons) migrates up the wick through cap-
`illary action and is pyrolyzed at 600—800°C
`(11D0—1500°F) to gaseous hydrocarbon decompo-
`sition products (Figure 3.12). Pyrolysis is the de-
`composition of a material by heat alone (in the ab-
`sence of oxygen). Some of the gaseous hydro-
`carbons are converted to soot; smoke consists of
`suspended soot particles. Reaction with carbon di-
`oxide and water in the luminescent region pro-
`duces carbon monoxide. Most of the gaseous hy-
`drocarbons react with oxygen at the exterior of the
`flame to produce heat, which melts more wax and
`begins the cycle again. [768, 828, 662, 896]
`A fully developed, damaging fire results when
`
`Gas reaction zone
`
`.
`
`Oxygen diffusing into
`the reaction zone
`
`Luminous flame zone
`
`Icandescent soot
`particles
`
`Pyrolysis zone
`
`Surface pw°'y5i5
`Melt
`
`Figure 3.12 A candle flame. Mailing wax migrates up
`the wick and pyrolyzes at the suriace of the wick to form
`gaseous hydrocarbon decomposition products. Some at
`the gaseous hydrocarbons form soot in the incandes-
`oenl region of the llarne: gases can also react with water
`and carbon dioxide in air. forming carbon monoxide in
`the luminous tlarne zone. Most gases react with oxygen
`at the exterior of the flame to produce heat. [896]
`
`© Plastics Design Library
`
`Additives
`
`PAGE 5 OF 19
`
`

`
`39
`
`achieved in polypropylene with 230% of a cyclo-
`aliphatic chlorine and 213% antimony oxide. A
`V-2 rating (530 s flame duration, 560 s afterglow,
`cotton ignition) can be achieved with 5—10% bro-
`minated cycloaliphatic imides, ammonium fluoro-
`borates, or chlorinated polyolefins, with an antim-
`ony oxide synergist. [822]
`
`3.7 Colorants
`
`Color is used in almost all plastic applications.
`Color can improve the aesthetic appeal of a prod-
`uct — qualities such as “warm”, “soft”, “bright”,
`or “pleasant” are determined primarily by color.
`Product color influences consumer perception and
`can determine how well
`the product sells, and
`color changes may be necessary over time as con-
`sumer preferences change. A variety of colors are
`available for use in plastics, in addition to special
`effect colorants
`that produce metallic effects,
`pearlescence, fluorescence, and phosphorescence.
`[8‘71, 821, 824]
`Colorants used in plastics are pigments or
`dyes. Dyes are organic compounds that are soluble
`in the plastic, forming a molecular solution. They
`produce bright, intense colors and are transparent
`and easy to disperse and process. They can have
`poor thermal and UV stability, however, and are
`mainly used in applications with low processing
`temperatures and low UV stability requirements,
`such as
`toys. Dyes are not compatible with
`polyolefins, having a tendency to bleed and plate
`out, but
`they have been used in oriented or
`crosslinked polypropylene. [826, 871]
`Pigments are generally insoluble in the plastic;
`color results from the dispersion of fine particles
`(-0.0l—l um) throughout the resin. They produce
`opacity or translucence in the final product. Pig-
`ments can be organic or inorganic compounds, and
`they are available in a variety of forms -— dry
`powders, color concentrates, liquids, and precol—
`ored resins. [32], 826]
`
`3.7 .1 Optical effects of pigments
`Pigments and dyes produce color in a resin from
`selective absorption of visible light (wavelength
`range from -380 nm (violet) to 760 (red)). The
`perceived color is the color of the light transmitted
`through the colorant and not the light that was ab-
`sorbed. Complementary colors are seen by the eye:
`light absorption at 490-560 nm (green) will be -
`perceived as a red color. (Complementary colors
`
`Figure 3.15 The UL 94 vertical burn test. A speci-
`men suspended verticalty over absorbent cotton is ig-
`nited by a bunssn burner. Duration of the flame and at-
`tergiow is measured. and any generation of flaming
`drips that ignite the cotton is noted. Each of five samples
`are ignited for 10 seconds; rating criteria include V-0, V-
`1. V-2. V-5, and HB levels. [888]
`
`rial under specified conditions, in order to predict its
`performance in an actual fire. Many applications re-
`quire specific performance levels in particular tests.
`The most common test is the UL 94 in electrical
`
`devices, in which burning times resulting from vari-
`ous ignition orientations are measured. The purpose
`of the test is to ensure that a spark or electrical short
`will not result in a fire. In the UL 94 V test (Figure
`
`3.15), a specimen is suspended vertically over a
`bunsen burner and surgical cotton. The results rate
`the specimen at different
`levels based on thick-
`nesses; a V-0 rating, the highest, corresponds to a
`flame duration of 0-5 seconds, an afterglow of 0-25
`seconds, and no flaming drips that ignite the ab-
`sorbent cotton. [828, 662]
`In the limiting oxygen index (L01) test, the
`minimum concentration of oxygen necessary for
`candle-lilce bunting of 23 minutes is measured. It
`is primarily used for product development. Nu-
`merical data are obtained, and the LOI is generally
`directly proportional to the concentration of flame
`retardants. A higher L01 indicates that more oxy-
`gen is needed to support combustion. Air contains
`--21% oxygen, so a rating lower than this will usu-
`ally support combustion under normal atmospheric
`conditions. [662, 328]
`Combinations of flame retardants are gener-
`ally used to achieve the required level of fire inhi-
`bition. A V-0 or V-1 (530 s flame duration, 560 s
`afterglow, no cotton ignition)
`rating can be
`
`(9 Plastics Design Library
`
`PAGE 6 OF 19
`
`

`
`40
`
`are red-green, blue-orange, violet-yellow). The
`human eye can detect color differences of about 1
`nm in wavelength. Absorption at all wavelengths
`of visible light will produce a black color, while
`no absorption will appear colorless. [766, 590]
`Because dyes are in solution, color is pro-
`duced only from light absorption, and the material
`is transparent. A dispersion of pigment particles in
`a resin can also reflect or scatter fight. If the re-
`fractive index of the pigment particle is different
`from that of the spherulites in the plastic micro-
`structure, light will be reflected, and the particle
`dispersion will scatter light in all directions. Light
`reflection and scattering produces opacity in an
`originally transparent resin. Resins can be colored
`and ‘opaque if light was absorbed only at particular
`wavelengths, or white and opaque if all light was
`reflected (no absorption). The color shade is af-
`fected by particle size of the pigment. Ultramarine
`blue pigments are nonreflective due to a refractive
`index similar to that of the plastic. [859]
`
`.
`
`3.7.2
`
`Pigment characteristics
`
`Pigments must be adequately dispersed in the resin
`for optimum light scattering; specks and uneven
`coloration can result from incomplete dispersion.
`Primary pigment particles tend to agglomerate;
`these must be broken up and distributed homoge-
`neously throughout the polymer during processing,
`usually by viscous forces or milling. The presence
`of agglomerated pigment particles in the final part
`can result in brittleness and part breakage, and
`large particle sizes
`can dramatically decrease
`Gardner impact strength — the large pigment par-
`ticles act as stress concentrators that reduce the
`energy required for crack initiation. Higher shear
`forces can produce pigments with smaller particle
`sizes. [87l, 825. 840, 820]
`Pigments
`should be compatible with the
`polymer; poor compatibility can be a cause of part
`failure. Some pigments are partially soluble in the
`resin and can migrate through the polymer to the
`surface, where they rub off. Pigments must also be
`compatible with any other additives present in the
`formulation. Slip or antistatic agents can cause
`migration of some colorants. [819]
`Most pigments exhibit good light stability, but
`fading, color changes, or degradation can occur,
`especially in the presence of both sunlight and
`humidity. Some colorants, such as FD&C lakes
`(FDA-approved), can fade even under fluorescent
`
`lights. Surface treatments can improve weathering '
`resistance. [819]
`High temperatures during processing can
`damage or destroy the pigment, causing changes in
`shade or loss of color. Thermal sensitivity is re-
`lated to both temperature and duration of exposure
`— long cycles in injection molding or rotational
`molding can have a more adverse effect than high-
`speed extrusion. [87]]
`Some pigments can act as nucleating agents,
`altering the mechanical properties and improving
`the clarity of the resin. In studies with colored
`filaments, phthalyl blue was found to be an effec-
`tive nucleator; titanium dioxide (rutile) and carbon
`black (furnace black) were less eflective. [779]
`
`3.7.3
`Inorganic pigments
`The most common inorganic pigments include
`oxides, sulfides, chromates and other complexes
`based on heavy metals such as cadmium, zinc. ti-
`tanium, lead, and molybdenum. They are generally
`more thermally stable than organic pigments and
`are more opaque and resistant
`to migration,
`chemicals, and fading. They can cause wear on
`processing equipment such as extrusion machine
`screws and barrels. The use of heavy metals has
`been restricted due to OSHA regulations; alterna-
`tive formulations have been developed. but cost
`can be up to eight times that of heavy metal pig-
`ments, especially for bright colors. [825, 820, 87]]
`Sulfides — cadmium sulfoselenides (red and
`orange), cadmium sulfide (orange), cadmium/zinc
`sulfides (green to yellow). zinc sulfide (white), and
`ultramarines (blue and violet)" —— are generally
`thermally and light stable and migration and alkali
`resistant but are sensitive to acids. Cadmium com-
`pounds have a moderately high cost, and toxcity
`may be a problem due to the heavy metal content.
`Compounds with low or no selenium content are
`less resistant to weathering, since they can easily
`oxidize to sulfates. [826, 825]
`Ultramarines are sulfide-silicate complexes
`containing sodium and aluminum. They are trans-
`parent pigments with weak tinting strength (a
`measure of brightness) and are widely used in
`polypropylene and high density polyethylene. Ul-
`tramarine blue pigments are highly acid-sensitive
`and can fade in the presence of acidic catalyst
`residues. They exhibit poor UV stability; calcium
`carbonate
`(CaC0,)-filled grades
`have
`shown
`greater UV stability than talc-filled grades, due to
`the higher absorption capacity of talc and to the
`
`© Plastics Design Library
`
`PAGE 7 OF 19
`
`

`
`41
`
`primarily used in low density polyethylene garbage
`bags and iron blues in low cost applications. [826]
`
`3.7.4 Organic pigments
`Organic pigments are usually brighter, stronger, and
`more transparent than inorganic pigments but are
`not as light-resistant. They can be partially soluble
`in plastic, with a greater tendency to migrate. Azo
`pigments are the largest group of organic pigments;
`they contain one or more azo (—N-_-N-) chromopho-
`tic groups and form yellow, orange, and red pig-
`ments. Monoazo pigments. with only one chromo-
`phore, exhibit low thermal and light stability and
`have a tendency to bleed; they are not usually used
`in plastics. Polyazos, with more than one chromo-
`phore, do not tend to bleed and have better thermal
`stability
`and
`excellent
`chemical
`resistance.
`Polypazos include disazo pigments; higher 1no~
`lecular weight disazo condensation products, with
`brighter colors and thermal and light stability; di-
`anisidine orange, with a brilliant color but poor light
`stability; and pyrazolone pigments, with good ther-
`mal stability and migration resistance and good
`light stability in red pigments. Metallized azos are
`prepared by precipitating from a metal salt or laking
`onto an absorptive surface. These red-maroon pig-
`ments have poor to good thermal stability. fair to
`good light stability, and good migration resistance.
`They include Lake Red C, Permanent Red 2B,
`Nickel azo yellow, Lithol Red, and Pigment Scarlet.
`[87], 820, 826]
`Nonazo pigments have varied structures, usu-
`ally polycyclic and sometimes complexed with met-
`als. Phthalocyanine blues and greens, most of which
`form complexes with copper, are highly stable to
`light, heat. and chemicals; they form highly trans-
`parent,
`intense colors with high tinting strength.
`Quinacridones (red, violet, orange) exhibit good
`light stability and excellent bleed and chemical re-
`sistance, but they are expensive and are best suited
`for plastics such as polystyrene and acrylic due to
`low thermal stability. Dioxazines (violet) are strong,
`high cost pigments with excellent light stability and
`limited heat stability. They are used in tinting other
`pigments and in low temperature applications in
`acrylic sheet, polyethylene and polyvinyl chloride.
`lsoindolinones (yellow, orange. red) are applicable
`to all plastics but are prima_ri.ly used in automotive
`applications due to their high cost. Other nonazo
`pigments include perylencs, flavanthrones, and an-
`tbraquinones. [$59. 826]
`
`greater amount of heavy metal residues (Fe, Cu,
`Mn), which catalyze oxidation. Addition of UV
`stabilizers increases the UV resistance of ultrama-
`rine blue; however, it is not usually recommended
`for outdoor applications of filled polypropylene.
`[826, 825, 838]
`titanium, antimony,
`Oxides of iron, barium,
`nickel, chromium, lead, and combinations of two
`or more metals are used in pigments. They have
`high thermal stability if the metal is present in its
`highest oxidation state (i.e. Fe” in Fe,,O3;
`iron
`oxide red). but oxidation can occur if the metal is
`present
`in a lower oxidation state (i.e. Fe” i
`(FeO)‘ - (Fe,O,),; iron oxide brown — oxidation
`from Fe” to Fe“). Iron oxide colors used in plas-
`tics are mainly red and brown; colors produced are
`relatively dull. They have excellent hiding power
`(a measure of opacity produced in the resin) and
`good alkali and light resistance. They are easy to
`disperse but require careful processing at high
`temperatures. Chromium oxides produce dull
`green colors with moderate opacity and low tinting
`strength. They are light and chemically resistant
`and have high thermal stability if not hydrated.
`[$59, 826]
`Titanium dioxide (TiO2) is a widely used white
`pigment
`that exhibits excellent brightness and
`opacity and good thermal stability. It represents
`>90% of the inorganic pigments used in plastics
`coloration and over 65% of all colorants used in the
`plastics industry. Titanium dioxides can accelerate
`surface photooxidation of the plastic if not surface-
`treated; the anatase form of TiO, has a greater ef-
`fect. Anatase is not as widely used as the rutile
`form, which also has better hiding power. Anatase is
`used when a bluer white, lower abrasiveness. or
`controlled chaulking is required. [825, 859]
`Lead chromates are yellow, bright pigments
`with very good migration resistance, moderate tint
`strength,
`and temperature stability to
`180°C
`(3S4°F). They are alkali-sensitive and,
`if not
`treated, darken when exposed to light. Molybdate
`orange, a combination of lead chromate, lead sul-
`fits, and lead molybdate,
`is an orange pigment
`with good light stability and acid resistance but
`poor alkali resistance. It can be combined with
`other pigments to make a red shade. [826]
`Iron blues, based on ferric ammonium ferro-
`cyanide, and chrome greens, a combination of iron
`blues, lead chromate, and lead sulfate, are not gen-
`erally used in polypropylene. Chrome greens are
`
`© Plastics Design Library
`
`PAGE 8 OF 19
`
`

`
`Carbon blacks are the most widely used black
`pigment. They are formed from incomplete com-
`bustion of natural gas (channel blacks) or or by re-
`duction of
`liquid hydrocarbons
`in refractory
`chambers (furnace blacks). They are composed of
`different
`functional groups
`(carboxyl, phenol,
`lactone, etc.) which increase dispersibility, and dif-
`ferent particle sizes; finer particle sizes result in
`deeper shades. Carbon blacks have some of the
`smallest particle sizes and highest surface areas of
`all pigments; furnace black particles are larger
`than those of channel blacks. Carbon blacks have
`
`high strength, but loose forms can cause severe
`dusting. [826, 859]
`
`3.7.5
`
`Special effect pigments.
`
`Some colorants produce special effects in the
`plastic, such as pearlescence or phosphorescence.
`The pigment must be well dispersed in the resin
`and must be carefully handled during processing.
`These pigments are most effective on transparent
`plastics; mechanical abuse and the presence of
`opaque fillers or pigments can reduce the effect
`desired. [826]
`A “granitc" appearance is produced by adding
`a foreground color, such as colored mica flakes
`(500—2000 pm) or large glitter flakes (26.4 mm;
`20.25 in.) to a background color. Pearlescent pig-
`ments produce pearly lusters and iridescence —
`the resin has a soft, silky andlor multicolor ap-
`pearance. Luster is produced by reflection of light
`by thin (<1 um) platelets oriented in parallel lay-
`ers. Length of the platelets is 10-40 tun. Any
`scattering of light by the plastic or other pigments
`will reduce the platelet reflection and the pearles-
`cence. Pearlescent pigments must be inert. Due to
`the orientation of the platelets, the appearance of
`the material can change with the angle of viewing.
`Pearlescent pigments include titanium dioxide-
`coated mica (muscovite). ferric oxide-coated mica,
`and bismuth oxychloride. The coatings vary in
`concentration from 10-60%; mica also provides
`mechanical support. Coated mica can resist several
`years of outdoor exposure. [8?2, 826]
`Metallic flakes are used to produce silvery
`lusters or gold bronze effects. Aluminum, copper
`and alloys of copper and zinc (bronze) are com-
`monly uscd. Flake particles are <1 pm in thick-
`ness and <50 ltm in length; smaller particles pro-
`duce greater opacity and a metallic sheen, while
`larger particles result in more brilliance and glitter.
`Aluminum can be processed up to 3l0—340°C
`
`(60[}—650°F), with loadings from O.5—4%. It is
`usually treated to resist oxidation. Copper is sus-
`ceptible to oxidation beginning at »-120°C (250°F)
`and can tarnish, depending on the temperature and
`duration of exposure. Slow discoloration occurs in
`outdoor applications. [826, 872]
`Fluorescent pigments appear to glow in day-
`light; they absorb visible and ultraviolet light, then
`emit the light at longer wavelengths. A glow ap-
`pears when this light combines with the reflected
`color of the plastic. Phosphorescent pigments also
`emit light at longer wavelengths than it was ab-
`sorbed, but the yellow-green glow appears only in
`darkness. Phosphorescence is produced by the ad-
`dition of doped zinc sulfide. [826, 872]
`
`3.7.6 Colorant forms
`
`Colorant forms include dry color. color or pellet
`concentrates, liquid color. and precolored resin. A
`precolored resin contains the color already dis-
`persed in the resin; all other forms require disper-
`sion by the resin processor. The colorant form se-
`lected is dependent on factors such as volume
`requirements, handling provisions, regulatory con-
`cerns, labor and inventory costs, and equipment, in
`addition to performance requirements such as
`color strength development, color-matching toler-
`ances, and color consistency in long runs. [826]
`Dry colorants are powders composed of one or
`more pigments or dyes. They are supplied in pre-
`weighed packets and must be compounded and
`dispersed into the resin. Dry pigments are usually
`dispersed in polypropylene by batch blending; ad-
`dition of wetting agents helps the pigment adhere
`to the resin surface. Careful attention is required
`for consistent color from batch to batch, and accu-
`
`rate weighing ‘and blending are necessary for long-
`term, uniform color. Dry colorants are most often
`used for short runs, emergency situations, and the
`rotational molding of polyethylene. Dry colorants
`can be dusty and dirty during handling. Anti-
`dusting agents are available from suppliers, as well
`as closed packaging systems that hook up to
`pneumatic conveying equipment. [871. 821, 642]
`Dry colorants are the most economical color-
`ants. They provide the largest selection of colors
`and use a minimum of warehouse space. They are
`difficult to disperse, however, and dusting and
`cross-contamination problems discourage their
`use. Higher costs may result from problems with
`clean-up, color changes, scrap generation, and
`OSHA regulations concerning dust. [87l, 826]
`
`Additives
`
`© Plastics Design Library
`
`PAGE 9 OF 19
`
`

`
`Color concentrates are colorants dispersed in a
`resin carrier that is formulated for use with a par-
`ticular polymer family. In order to obtain a melt
`flow similar to that of the polymer,
`the carrier
`resin frequently has a lower melt flow than the
`polymer in order to compensate for the effects of
`pigments on melt flow. Low density polyethylene
`is frequently used as a carrier; however, for de-
`manding applications, polypropylene should’ be
`used to insure optimum processing and compati-
`bility. The form of the color concentrate can be
`matched to that of the polymer to be colored and
`includes pellets, beads, cubes, wafers, micro-
`beads, and chips. [82], 826, 642]
`Color concentrates can contain 10-80% color-
`
`ant, depending on the application requirements,
`the pigment used, and the compounding equip-
`ment, and are added to the polymer at a level of 1-
`10%. Concentrates can be blended either by batch
`blending or by automatic metering at the process-
`ing equipment. Letdown ratios of 100:1 to 10:1
`(polymer matrix:co1or concentrate) can be accu-
`rately metered with modern equipment, and other
`additives can be incorporated during pigment
`compounding. [82], 826]
`Color concentrates are the most popular form
`of colorant for in-house coloring. They are dust-
`free, easy flowing, and easy to meter. They require
`little warehouse space, and color changes are rela-
`tively easy. Newer concentrates include those de-
`signed for specific applications, such as injection-
`molded polypropylene battery cases, and concen-
`trates that can be used in a wide variety of poly-
`mers, simplifying inventory for plastics proces-
`sors. [826, 82]]
`Liquid color is composed of a pigment in a
`non-volatile liquid carrier. Liquid carriers include
`mineral oils and complex fatty acid derivatives and
`can contain surfactants for easier dispersibility and
`clean-up. A range of viscosities are available, from
`maple syrup to gel-like consistencies, and good
`
`43
`
`dispersion can frequently be obtained with high
`pigment loadings 00-80%); higher loadings are
`possible with liquid color than with color concen-
`trates. High pigment loadings can result in letdown
`ratios of greater than 100:]. Usually the highest
`loading possible is used, both for economy and to
`minimize the amount of carrier added to the ma-
`
`trix polymer. The carrier can affect polymer prop-
`erties and can lubricate the polymer, affecting pro-
`cess cycling and back pressure
`in injection
`molding. [82], 826]
`Liquid colorants are compatible with many
`plastics; however,
`they require special metering
`equipment and are most cost-effective for long
`runs. They are used in injection molding and ex-
`trusion and are usually pumped in below the hop-
`per at the throat. Consistent color levels can be
`obtained by electronically matching the metering
`speed of the pump with that o