High-Density (low-pressure) Polyethylene

Sheftel, VO. Indirect Food Additives and Polymers: Migration and Toxicology. Lewis 2000 pp.1144-1145

Structural Formula. [~CH₂CH₂~]_n
M = 70,000 to 80,000
Abbreviation. HDPE; LDPE.

Synonym. Ziegler HDPE.

Properties. Similar to LDPE but possess greater mechanical strength and elasticity. Color ranges from white to cream; its chemical stability is higher than that of LDPE.

Applications. Differences in the application of HDPE as compared to LDPE are determined by its greater rigidity and heat resistance. HDPE has a maximum continuous service temperature of 70°C but distorts at 60°C. It is resistant to moisture, gases, acids, bases, solvents, and fats/oils. It will build up static. HDPE is used for milk jugs, cleaning supply bottles, and trash bags.

Migration Data. The same substances may migrate from HDPE into water as from LDPE as well as traces of complex organometallic catalysts and solvents. Ziegler HDPE to be used in the food industry should be produced only with the use of isopropyl alcohol as a washing agent, migration of which from finished articles can reach 5.5 mg/l. No isopropyl alcohol is released after 16 to 19 washes.

The contents of catalyst (ash contents) can be reduced to a 0.002 to 0.003% minimum by washing. During prolonged (2 to 8 years) service of Ziegler HDPE water pipes, there is no increase in migration of chemical substances from them.² The oxidizability of aqueous extracts of this HDPE stabilized with P-24 phosphite, 2hydroxy-4-octyloxy benzophenone, and calcium stearate has proved to be higher than that of extracts of this HDPE with additions of N,N '-di-ß-naphthyl- p-phenylenediamine, gas channel black, and calcium stearate.³

In supersaturated extracts from this HDPE (stabilizers - amine compounds, gas black, calcium stearate, phenol, and benzophenone derivatives) a small amount of reducing agents and traces of amine compounds have been found. In the case of long-term (220 day) study, traces of stabilizer were found at the end of the experiment. In supersaturated aqueous extracts (10 cm^-1, 20 and 60°C) of unstabilized Ziegler HDPE, a very small amount of aluminum and traces of titanium and chlorides (0.3 to 0.7 mg/l) were found. Storage of Ziegler HDPE film for 8 months at room temperature had almost no effect on oxidizability or the concentration of chlorides and stabilizer in the extracts ⁴

Vanadium compounds do not migrate into water from Ziegler HDPE obtained on homogenic vanadium catalysts (1 cm 1; 80 and 20°C; 1, 3, and 10 days). Ziegler HDPE grades 22008-0.40 (injection-molding) and 21708-007 (extrusion) are recommended for use in contact with drinking water.⁵ No phenols or amine compounds were found in extracts (0.4 cm^-1; 20°C; 9 days) from "Hostalen GM-5010" (Norwegian company Haplest) which in addition to carbon black contains aromatic amines and phenol derivatives as stabilizers.⁶ Films, tubing, and injection-molded articles of gas-phase Ziegler HDPE can give water and simulant media a faint odor and taste up to rating of 1.5. Migration of Irganox 1010 and 1076, formaldehyde, and chromium was not found.⁷

Benzophenone-based ultraviolet absorbents (up to 0.5% of a composition) for commodities of HDPE showed a very slight tendency to migrate into aqueous, acid, or dilute alcoholic foods. Very high migration levels were noted for sunflower oil, fat-simulants HB 307 or 50% ethanol. Migration of 2-hydroxy-4-octoxy- benzophenone into fat-free foods was observed at the toxicologically insignificant level; nevertheless, the above ultraviolet sorbents should not be used for the ultraviolet stabilization of plastics designed for packaging fat-containing foods.⁸

Migration rates of radio-labeled antioxidants, Irganox-1010 and Irganox-1076, from HDPE were measured at temperature up to 135°C. Water, 8.0 and 95% aqueous solution of ethanol and corn oil were employed as food simulating liquids. The losses to foods were usually larger than those to water but below those to corn oil.⁹

Acute Toxicity. Mice fed 2.5 g of unstabilized Ziegler HDPE powder/kg BW and powder stabilized either with gas black, amine compounds and calcium stearate, or with benzophenone derivatives and calcium stearate in their diet, developed no changes in their general condition or BW gain. Histology of the visceral organs was insignificantly different from that in the controls.;

Short-term Toxicity. 1.25 to 100% Marlex-50 Ziegler HDPE was added to the diet of male and female rats. No manifestations of toxic action were observed. ⁵

Long-term Toxicity. Administration of extracts (10 cm^-1; 20 and 60°C; 10 days) from several Ziegler HDPE specimens with small quantities of chlorides, aluminum, and titanium ions to mice and rats over a period of 16 to 19 months caused slight transient changes in BW gain, STI, behavior, and relative weights of visceral organs. Histological examination revealed no changes attributed to the action of extracts.;

Regulations. U.S. FDA (1998) approved the use of HDPE as articles or components of articles intended for use in contact with food, subject to the provisions of 21 CFR part 177.1520.

References:

1. Braun, D. D., Hygienic evaluation of products made of medium-pressure polyethylene intended for use in the food industry, Gig. Sanit., 3, 36, 1973 (in Russian).

2. Sheftel, V. O. and Sinitsky, V. G., Attempt at the sanitary evaluation of the use of polyethylene pipes in rural water supply lines, Gig. Sanit., 3, 111, 1973 (in Russian).

3. Danishevsky, S. L. and Broitman, A. Ya., Study of mutagenic activity of chemicals on mammals, in Toxicology of High-Molecular-Mass Compounds and of Chemical Raw Material Used for Their Synthesis, S. L. Danishevsky, Khimiya, Moscow-Leningrad, 1966, 21 (in Russian).

4. Kalinin, B. Yu., Zimnitskaya, L. P., and Zalesskaya, V. M., Toxic properties of stabilized low-pressure polyethylene, in Toxicology and Hygiene of High-Molecular-Mass Compounds and of the Chemical Raw Material Used for Their Synthesis, Proc. 2^nd All-Union Conf., A. A. Letavet and S. L. Danishevsky, Eds., Khimiya, Leningrad, 1964, 110 (in Russian).

5. Michailets, 1. B., Sukhareva, L. V., and Yevsyukov, V. I., Hygienic characteristics of high-density polyethylene made with help of vanadium catalysts, in Environmental Protection in Plastics Production and Hygiene Aspects of Their Use, Plastpolymer, Leningrad, 1978, 99 (in Russian).

6. Sheftel, V. O., Hygiene Aspects of the Use of Polymeric Materials in the Water Supply, Thesis Diss., All-Union Research Institute of Hygiene and Toxicology of Pesticides, Polymers and Plastic Materials, Kiyv, 1977, 61 (in Russian).

7. Kalinin, B. Yu. and Sukhareva, L. V., New polymeric materials for use in the potable water supply, in Hygiene Aspects of the Use of Polymeric Materials, Proc. 3'd All-Union Meeting on New Methods of Hygiene Monitoring of the Use of Polymers in the Economy, K. 1. Stankevich, Ed., Kiyv, December 2-4, 1981, Kiyv, 1981, 181 (in Russian).

8. Uhde, W. J. and Woggon, H., New results of migration behavior of benzophenone-based UVG absorbents from polyolefins in foods, Nahrung, 2, 185, 1976.

9. Goydan, R., Schwope, A. D., Reid, R. C., and Cramer, G., High-temperature migration of antioxidants from polyolefins, Food Addit. Contam., 7, 323, 1990.