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R & D REPORT DOW CHEMICAL U.S.A.
RESTRICTED: for ust within The Dow Chemical Company only.
OERARTMENT
Olefin Plastics
CRINUM8ER
74 1565
LABORATORY REPORT CODE
PCN-1-74-005
SATE ISSUED
March 15, 1974
LAB. NO. PROBLEM NO.
5 |4 |5 1 ,1 il ,1 ,0 ,0 ,6
Survey of Fillers and Reinforcements for Polyethylene
PAGES IN FULL REPORT
DESCRIPTIVE SUMMARY WITH CONCLUSIONS:
Summary:
(Include in this space references to data books, and to earlier related reports, parents and publications.)
Several fillers and reinforcements for polyethylene were discussed along with the properties of the filled resins. The fillers discussed include silica fillers, calcium carbonate, talc, fiberglass, asbestos fibers, ZnO, wood flour calcium sulfite, and calcium sulfate.
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Conclusions: 1. Due to the
large varieties
of fillers, and the variability of
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a particular filler (particle size, surface treatment, etc.) a filler ^
system needs to be evaluated with each resin to determine process-
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ability and end use properties.
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2. In general fillers impart the following properties to polyethylene:
a. Greater stiffness
"bTi .^Reduced mold shrinkage
c. Lower melt index and higher melt viscosity
dl.'. Decreased tensile and impact strength e. . Increased density f. Improved creep and heat distortion temperature '.AND
Discussion:
Fillers may be divided into three groups: low cost fillers (extenders), functional fillers, and reinforcements. An extender decreases the cost of a plastic material while a functional filler contributes a partic ular property to a plastic material such as improved electrical in sulation. A reinforcement such as glass fibers, asbestos fibers, car bon fibers, etc. are added to improve the strength and may increase the cost of a plastic material. In general a filler imparts the fol lowing properties to a plastic material:
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PCN-1-74-005
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ST0284385
a. Greater stiffness b. Reduced meld shrinkage c. Lower effective melt indexes d. Higher melt viscosity e. Decreased tensile strength f. Increased density g. Lowered impact resistance h. Improved creep i. Improved heat distortion temperature
Several commerical types of fillers have been used in poly ethylene2'3'4'5'6'7'^10'13
a. Silica fillers. Kaolin clays b. Calcium carbonates c. Talcs d. Fibers such as glass, asbestos, etc. e. Metal oxides, MgO, ZnO f. Wood flour g. Calcium sulfate and calcium sulfite.
Silica fillers such as Superfloss increase the stiffness of poly ethylene with the greatest increase in stiffness corresponding to the smallest particle size of the filler. The silica fillers also reduce the impact strength, tear resistance, reduces mold shrink age and degrade the electrical properties.2'5 Calcium carbonate increases the stiffness, lowers the tensile strength, lowers the impact resistance, lowers the tear resistance of films, reduces mold shrinkage and improves opacity.2'4'7 Talcs increase the stiffness, decrease impact strength by a smaller amount than silicas and calcium carbonate, increases melt tension, decreases tear resistance of film and reduces mold shrinkage. '4'7
The fiber materials, asbestos and glass give good mechanical properties to polyethylene. Asbestos imparts increased stiffness, lower tensile strength, and lower tear strength of films. Asbestos fibers, however, have been associated with lung cancer and the asbestos requires special handling equipment. Glass fibers reduce mold shrinkage, increase stiffness, improve heat resistance, and increase tensile strength.4'6 The impact strength of polyethylene filled with glass seems to depend on the resin used. Some resins show improved impact strength with glass while the impact strength of some resins remains unchanged, and still other resin 'exhibit reduced impact strength when filled with glass fibers.6'11 Fiber glass should be "sized" with a suitable coupling agent for good wetting and bonding of the polyethylene to the glass fiber. A typical "sizing" agent is an organic silane. Zinc oxide compounded into polyethylene has been reported to impart increased hardness and stiffness without affecting melt flow and toughness.6 Another investigator has shown that zinc oxide lowers the melt index, increases stiffness and increases melt tension.9 Wood flour in
PCN-1-74-005
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. concentration of 0 to 50% has been used to fill polyolefins. The wood flour is reported to improve impact resistance and humidity tolerance of polyolefins.^ An extruder with a vacuum part for moisture removal is necessary for compounding with wood flour. Wood flour normally has a high enough moisture content to produce severe foaming in the resin. Lion Fat and Oil Company (Japan) have patented the use of calcium sulfite and calcium sulfate as fillers for polyolefins. They report improved flexural and ten sile strengths and non-flammability with the use of these fillers.*3
In terms of cost per pound, the fillers listed above rank in cost from highest to lowest as follows:Zinc oxide>fiberglass> asbestos>silica>Kaolin clay>talcs>calcium carbonate. It is im portant to achieve good wetting of the filler by the polymer when compounding. The wetting is related to melt viscosity, processing pressure and processing temperature.^ In general, the processing
pressure and temperature of a filled polymer is higher than that of an unfilled polymer. To complicate matters, a particular filler may be obtained in different forms, particle sizes, surface treat ment, etc., and these differences will affect the properties and processability of the filled polymer. Therefore, any filler system needs to be evaluated on the particular resin in question to deter mine the proper means of processing and to check desired end use properties.
ST0284386
RJB
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References
ST0284387
1 Hunt, R. E., Plastics Technology, pp. 33-43, November 1969.
2 Bostwick, R., and R. H. Carey, Industrial and Engineering Chemistry, pp. 848, 849, 42, No. 5 May 1950.
3 Furter, W. F., The Canadian Journal of Chemical Engineering, pp. 77-81, April 1964.
4 Beam, R. J., Texas Polyolefin Research Databook #13472, 13741 and 16188.
5 Bylsma, H. R. and F. J. DiCeglie, Saran Development Lab CRI Report # SD54-5426-1 (1958).
6 Conwell, Y, and D. S. STotz, Modern Plastics, pp. 82-84, October 1969.
7 Modern Plastics Encyclopedia, pp. 222-255, Vol. 48, 1971-1972.
8 U. S. Patent 3,462,389 issued to Hercules (1969).
9 Beam, R. J., Texas Polyolefin Research CRI Report TPR-1215-4, (1971).
10 Kliff, Edward J., Extender and Filler Pigments, pp. 254-272. Kline Publishing Company, New Jersey 1967.
11 Murphy, T. P., "Reinforced and Filled Thermoplastic"., Industrial and Engineering Chemistry, pp. 41-49, Vol. 58, No. 5, May 1966.
12 Modern Plastics, pp. 50-52, January 1974.
13 Susuki, Rinnosuki, et. al.. Lion Fat and Oil Company, Ltd., German patent 2,117,077.
PCN-1-74-005
-5Table I Effects of Fillers on Resin Properties9 Base Resin: 06067 (HDPE)
ST0284388
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FILLER
12 7-25
5S& Aluminum Silicate 7.1*9
5$ Zinc Oxide
5.73
536 Talc
5.82
10$ Talc
5.15
5$ Aluminum
5-95
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DENSITY RIGIDITY gm/cm3 psi x 10'
8.7 0.9641* 8.1* O.9887
17.5 I6.9
9-5 0.9812
17.5
9-0 O.9876
I8.5
9.1* 1.0174
20.6
9.0 0-9884
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ST028439I
PCN-1-74-005
Table V4 Talc Filled 06067 (HDPE)
-9-
Property
Melt Index Tensile Yield % Elongation Rigidity Density I10
0% 51
7.25 3225 4745
115 1.75 x 104
0.9644 62.76
5.82 -
1.85 x 104 0.9876 52.67
10%
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20.6 x 104 1.0174 48.52
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R. C. Schumann R. C. Aslakson J. D. Striebel B. W. Heinemeyer R. M. Nowak W. L. Bressler M. C. McGaugh G. E. Waples G. W. Knight K. C. Finster E. R. Eastman G. D. Tiner Z. L. Champion J. T. Hill H. R. Colvin G. L. Xidwell C. A. Royalty L. L. Devillier J. L. Hermann A. B. Baker L. E. Tallman B. L. Crim R. A. Maugans J J Hood M. K. Mitchell G. J. Easterling R. L. Beam R. R. Turley
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ST028U93