Titanium Dioxide

The Advantage for
Plastic Films
Especially Suited for White Films

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Contents
HIGH OPACITY WITH TIO2................................................................................................................................................................................... 5Figure 1: Relationship Between TiO2 Content, Film Thickness and Opacity ���������������������������������������������������������������������������������������������������������������������������������������5
EASE OF PRODUCTION AND HIGH QUALITY WITH TIO2 MASTERBATCH 	�������������������������������������������������������������������������������������������������� 5Table 1: Pressure Development for Various Titanium Dioxide Products for Film Applications.................................................................................................5
Figure 2: Relationship Between TiO2 Dispersion in Masterbatch and Film Defects ����������������������������������������������������������������������������������������������������������������������6
COST EFFECTIVE SOLUTION WITH TIO2 MASTERBATCH	����������������������������������������������������������������������������������������������������������������������������� 6APPENDIX ONE: REFRACTIVE INDEX................................................................................................................................................................7Table 2: Indices of Refraction for Some White Pigments and Common Polymers ���������������������������������������������������������������������������������������������������������������������������7
Figure 3: Tinting Strength in Plasticized PVC �����������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������7Figure 4: Effect of Refractive Index on Opacity ������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������8Figure 5: Rutile TiO2 Provides More Scattering of Light ����������������������������������������������������������������������������������������������������������������������������������������������������������������������������������9Figure 6: Contrast Ratio Measurements for Films Containing Anatase and Rutile ������������������������������������������������������������������������������������������������������������������������9
APPENDIX TWO: PRESSURE BUILDUP AND IMPACT ON RATE	������������������������������������������������������������������������������������������������������������������� 10
APPENDIX THREE: TIO2 SURFACE CHEMISTRY IMPACT ON FILM PROCESSING	������������������������������������������������������������������������������������ 10Figure 7: Film Integrity and Lacing Rating Between Thermally Sensitive and Insensitive TiO2........................................................................................... 113

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Plastic films can be bent, molded, printed on and twisted into
different shapes and designs that are not easily achievable withother materials. Its versatility is only limited by the imaginationof the artist shaping and designing the film. Much like an artist,
plastic film fabricators require a canvas to paint their picture. The
most common and effective canvas is a white film, one that does
not allow light to shine through, i.e., high opacity. There are several
options to create the white plastic film. One technique is to add
a material in the film construction that can alter or attenuate thelight so that the light is scattered. Film producers most commonly
use rutile TiO2 to make a clear plastic film opaque(see Appendix 1 for more details).

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High Opacity with TiO2
Many film producers balance film thickness, TiO2 content,
and cost to find the most effective solution for film
opacity. Therefore, a model that calculates the optimal
TiO2 content for a chosen film thickness and target
opacity is highly valuable. Such a model would highlightthe effectiveness of TiO2 in producing a more opaque
backdrop versus increasing film thickness. The output ofa model which demonstrates the relationship between
TiO2 concentration, film thickness and opacity is shown in
Figure 1. A more detailed version of the model is available
from your masterbatch supplier.
Figure 1: Relationship Between TiO2 Content, Film
Thickness and Opacity
1.2
1.0

Opacity

0.8
0.6
0.4

1 mil film
2 mil film

0.2

4 mil film

Ease of Production and High Quality with TiO2Masterbatch

6 mil film

00510152025

Rutile TiO2 in Film (%)

Note: Opacity = Reflectance0 / Reflectance∞

Table 1: Pressure Development for Various Titanium
Dioxide Products for Film Applications
Gradebars/kg TiO2 per hr for 70% TiO2

Benchmark TiO2 for film

0.93

Typical TiO2 for film

2.89

Premium TiO2 for film

0.45

Data are calibrated for direct comparison—200 mesh screen usedfor filtration

30Film fabricators are not only looking to produce a highquality white film but also seek ease of production. Hence,
it is extremely important to be aware of processing
differences between TiO2 masterbatches. For example,
one of the main variables in producing a white film isthe rate at which the polymer melt exits the film die fora given film thickness. This rate is determined by theequipment design, melt pressure and polymer viscosity as
well as the TiO2 masterbatch (see Appendix 2 for details).
When specifying a grade of TiO2 for the masterbatch,
TiO2 dispersibility is key to achieving ideal film processing.
The maximum throughput of the film is related tothe extruder’s backpressure and its rate of increase.
Evaluations of various grades of TiO2 have demonstrated
that some grades can cause a more rapid pressure
increase (as measured by bars per hour) than others. The
pressure increase of various types of TiO2 based on theamount of pigment used is shown in Table 1.

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Figure 2: Relationship Between TiO2 Dispersion inMasterbatch and Film Defects

Specks (Number per 100 grams of film)

100806040200Acceptable

PreferredPremium
Ti-Pure™ Performance

Masterbatch Dispersion Quality

Cost Effective Solution with TiO2 Masterbatch

Highly dispersible TiO2 in the masterbatch is anotherimportant factor in producing a good quality plastic
film as well as ease of production. Numerous sourcesof defects, such as polymer gels, TiO2 dispersion
in the masterbatch, and contamination impact thefilm quality. A common quality evaluation for film is a
visual check to note the amount of defects within thefilm. These defects are referred to as “specks” andcan be visually counted per weight of film. Figure 2
shows the relationship between TiO2 dispersion in themasterbatch and film defects (number of specks).

6

It is no surprise that a cost-conscious film producer
would like to make thinner opaque films, or more film
area with the same weight of resin. For example, thiscan be achieved by increasing the take-off speed
which produces a thinner film using the same weightof resin; therefore, more film surface is produced. To
achieve this goal, the producer must optimize process
variables such as take-off speed, temperature andextruder RPM. But in order to keep the integrity andthe quality of the film intact, there can be limitations
to these process parameters. Some TiO2 grades aredesigned to minimize these limitations, dependent uponsurface chemistry, and give the film producers much
more flexibility to achieve a more cost effective solution
without sacrificing quality (see Appendix 3 for details
on how TiO2 choice impacts film production). In otherwords, selecting the right TiO2 masterbatch not only
reduces pressure buildup, improves quality and opacity
performance, but also provides greater flexibility in film
processing which can reduce cost.

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Appendix One: Refractive Index

such as polyvinyl chloride (PVC). The refractive index
difference for PVC and lithopone is approximately 0.16.
The refractive index difference for rutile TiO2 and PVC is
1.25. Therefore, any substitution of TiO2 with lithopone
will decrease the refractive index difference and reduce
opacity, as measured by tinting strength (shown inFigure 3).

The refractive index values listed in Table 2 highlightthat solids such as, calcium carbonate and lithopone,
dispersed in polyethylene offer a weak opacity option.
This is because the refractive index difference between
the polymer matrix and the dispersed solid is low. The
same result is observed in other polymer systems

Figure 3: Tinting Strength in Plasticized PVC
10080

Tinting Strength

There are many different materials that can be added
to a polymer to attenuate visible light. Inorganic solids
such as titanium dioxide, lithopone blends, zinc oxide,
zinc sulfide and others have been used in plastic films toachieve opacity. Opacity is achieved by scattering visible
light due to the difference in refractive indices between
the added solids and polymer matrix. Of course, the larger
the refractive index difference, the greater the scatteringof visible light and the more opaque the plastic film willappear. Therefore, the goal is to maximize the refractive
index difference between the polymer matrix and thesolid. It is clear that by using rutile TiO2, which has thehighest refractive index of commercially available white
pigments, one can achieve this goal.

604020100102030405060708090100

Rutile TiO2 in Blend (%)

Table 2: Indices of Refraction for Some White Pigments and Common Polymers
White Pigment

Reflective Index

Plastic

Reflective Index

Rutile TiO2

2.73

Polystyrene

1.60

Anatase TiO2

2.55

Polycarbonate

1.59

Antimony Oxide

2.09–2.29

SAN

1.56

Zinc Oxide

2.02

Polyethylene

1.50–1.54

Basic Carbonate, White Lead

1.94–2.09

Acrylic

1.49

Lithopone

1.64

Polyvinyl Chloride

1.48

Clay1.65

Magnesium Silicate

1.65

Barytes (BaSO4)

1.64

Calcium Carbonate (CaCO3)

1.63

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The unmatched power of titanium dioxide as an opacifying
agent when several inorganic solids are mixed into apolymeric system can be seen in Figure 4. This visual
representation demonstrates the theory of how thedifference in refractive index is crucial to obtaining
opacity in films.
Titanium dioxide provides opacity by restricting theamount of light passing through a film by either reflectingor scattering visible light. There are two crystalline formsof TiO2 that are used in plastic film applications, rutile andanatase. Rutile TiO2 has a higher refractive index due to amore dense crystalline form versus anatase, therefore it
provides a higher level of scattering. The difference in thescattering performance of the two crystalline structures
becomes more evident as the TiO2 content in the film
is increased. The advantage of rutile over anatase at aconstant film thickness and equal concentrations of TiO2
is shown in Figure 5.

Figure 4: Effect of Refractive Index on Opacity

RefectiveIndex

8Clay

Calcium Carbonate

Zinc Oxide

Anatase TiO2Rutile TiO2

1.65

1.63

2.022.55

2.73

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Another method of demonstrating the superior
efficiency of rutile TiO2 to scatter visible light is tomeasure contrast ratio of pigmented films. By placing
the films over black and white backgrounds, the ratio of
scattered visible light intensity is recorded. This is theresult of the scattering from the TiO2 in the film and thebackground. The background scattering occurs due tothe air between the film and background surface. As
shown in Figure 6, rutile has a higher contrast ratio infilms containing the same concentration of TiO2 and film
gauge. This advantage is even more apparent when thefilm background is removed.
Figure 5: Rutile TiO2 Provides More Scattering of Light

0.040
RutileFilm Scattering (m2/g)

0.035

Anatase

0.030
0.025
0.020
0.015
0.010
0.005
0.000
00.5

1.0

1.5

3.0

6.0

9.012TiO2 Content in Film (%)

Figure 6: Contrast Ratio Measurements for Films
Containing Anatase and Rutile
0.6
RutileAnataseContrast Ratio

0.5
0.4
0.3
0.2
0.10

With Back Scattering

Without Back Scattering

50 micron films with 2% TiO29Titanium Dioxide

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The evaluation is based on comparing films extruded at high temperature (above 280 °C) and increasing the takeoff speed to demonstrate the widening of operational parameters for cost savings.

Appendix Two: Pressure Buildup and Impact on Rate
The throughput of an extruder is defined by themechanical specifications such as the screw design andthe dimensions. The addition of TiO2 masterbatch into
the polymer melt for film production detracts from themaximum throughput by either affecting the viscosity
profile of the melt and/or by creating pressure within
the processing equipment. During the production ofa white film, pressure develops as the agglomeratesof undispersed TiO2 masterbatch are trapped. As thepressure increases, the RPM of the extruder must be
lowered to maintain good quality, therefore restricting
output and film yield.
The output of the metering section of a single screw
extruder is given by the following formula:
Output = 0.5pWHS—pWH3G/12µWherep = number of parallel flights
W = width of extruder screw channel
H = height of extruder screw channel
S = screw speed (rpm)G = pressure drop
µ = viscosity of polymer

The first term represents the drag flow—the flow due to the rotation ofthe screw. The second term is the pressure driven flow. In a well designed
screw, achievement of maximum rate is limited by those items which
effect viscosity, µ, and pressure, G.
10Appendix Three: TiO2 Surface Chemistry Impact onFilm Processing
The TiO2 surface chemistry can influence processingof a polymer melt. The design of the surface chemistry
can provide positive attributes for a film application. The
surface treatment of a TiO2 particle can cause defects
in a film when formulation and process parameters are
not adequately adjusted, especially at fast processing
speed or high temperature. Titanium Dioxide is classified
as either thermally sensitive or insensitive based on thesurface treatment. A thermally sensitive TiO2 causes thepolymer matrix integrity to degrade which will generatea weak spot in a film structure that can be aggravatedduring strenuous film processing. This degradation can be
subjectively quantified using a rating termed as “lacing”.
Films that are thermally robust are classified as a tenin the lacing scale (see Figure 7). Keep in mind that as
undesirable degradation of the polymer increases, thelacing rating decreases.

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Figure 7: Film Integrity and Lacing Rating Between Thermally Sensitive and Insensitive TiO2

TI TiO2
Thickness 100 μm

TS TiO2
Thickness 70 μm

TI TiO2
Thickness 70 μm

TS TiO2
Thickness 50 μm

TI TiO2
Thickness 50 μm

TS TiO2
Thickness 30 μm

TI TiO2
Thickness 30 μm

Film Integrity

TS TiO2
Thickness 100 μm

10Lacing Rating

86420100
Thermal Sensitive TiO2 (TS TiO2)

705030Thickness (µm)

Thermal Insensitive TiO2 (TI TiO2)

11The information set forth herein is furnishedfree of charge and based on technical datathat Chemours believes to be reliable. It isintended for use by persons having technicalskill, at their own risk. Because conditionsof use are outside our control, we makeno warranties, express or implied, andassume no liability in connection with any
use of this information. Nothing herein is tobe taken as license to operate under or arecommendation to infringe any patents.
For more information, visit www.titanium.chemours.com© 2018 The Chemours Company FC, LLC. Ti-Pure™ and any associated logos are trademarks or copyrights of The Chemours Company FC, LLC.
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