Group Members: Kristy Bulkley

Properties of PVC Plastics………………………………………………………………1-2

Processing Considerations………………………………………………………………...3

Migration of PVC Additives from Plastic……………………………………………....4-7

Health and Environmental Concerns…………………………..……………………..…8-9

Alternatives for PVC That Produce Safe Children’s Toys……...……………………10-11

References………………………………………………………………………………..12

Plastics are manufactured from organic materials such as hydrogen, carbon, and nitrogen. Plastics are produced when hydrocarbons are broken down into smaller molecules with a catalyst. During this process the temperature and pressures are controlled. The molecules are formed to produce monomer chains. Polymers are then produced from the chemical bonding of the monomers to form chains.

When plastics emerge from reactors they do not have the desired properties they need, and are considered a raw material. To make plastic a more desirable material additives are included to give the polymer specific properties. Additives are incorporated into polymers to improve their basic mechanical, physical or chemical properties. PVC used in the production of toys incorporates plasticizers that allow the polymer to become soft and pliable.

DEHP (Di-Ethylhexyl Phthalate) and DINP (Di-Isononyl Phthalate) are plasticizers that are used to manufacture children’s plastic toys and are shown below:

The properties of a plasticized polymeric material are a result of the interaction between the polymer and the plasticizer. PVC is comparable to glassy polymers at room temperature having a high modulus, or stiffness. In the production of children’s plastic toys the polymer is blended with a plasticizer to reduce the glass transition temperature and improve its thermal stability ⁹.

By lowering the glass transition temperature the modulus of the polymer is reduced. The glass transition temperature for PVC is 85 degrees Celsius. The high modulus (glassy) plateau region to the low modulus (rubbery) plateau region takes place at lower temperatures as the percentage of plasicizer increases.

The T_g of the polymer is a function of the plasticizer concentration and the T_g and is estimated by the wood equation as shown below:

Where: k: adjustable parameter

W_i: weight fraction of component i

The component 1 (T_g1) is for the dilute solution that is present. The T_g for a polymer composition mixture is computed using the following equation:

The reduction in the polymer is called the plasticizer efficiency when considering plasticization. The glassy to rubbery transition to occur over a broad temperature range when high efficiency is present. The difficulty with high efficiency plasticizers is that they diffuse out of the polymer due to their low miscibility with the polymer. This causes migration of phthalates over time from plastic when pressure is applied ⁹.

PVC is classified as a thermoplastic, a polymer in which the molecules are held together by weak secondary bonding forces that soften upon exposure to heat and revert back to their original form when returned to room temperature. This characteristic of PVC allows toys to be formed by rotational molding and injection molding.

Rotational molding consists of a mold mounted on a machine that rotates simultaneously on two axes. Solid or liquid resin is placed in the mold and heat is applied. The rotation distributes the plastic into a uniform coating on the inside of the mold until the plastic cools and sets. This process allows a hollow object to be produced ⁸.

Injection molding consists of putting the plastic into a hopper, which feeds it to a heating chamber. A plunger pushes plastic through the heating chamber where the material is softened into a fluid state. At the end of the chamber resin is forced into a closed mold. The plastic is allowed to cool into its solid state, the mold is then opened and the finished product is ejected ⁸.

To produce PVC a plasticizer is needed to ensure that plastic will be soft and flexible. Additives such as DEHP (Di-Ethylhexyl Phthalate), and DINP (Di-Isononyl Phthalate) are used in the production of children’s plastic toys. Additives leach from plastic due to weak Van Der Waals forces that are present. Metal salts such as lead and cadmium are added as stabilizers to PVC to add resistance from heat and light. Chemical dusts from lead and cadmium have been found on the surface of plastic toys. Exposure to these toxic chemicals can cause medical problems ranging from cancer to reproductive problems ¹².

Phthalates migrate when stresses such as bending or chewing are applied to plastic. PVC is an amorphous substance that exhibits a disordered state. Strong chemical bonds are not present and the phthalates are easily released when stress is applied. Research has been conducted by CSTEE (Scientific Committee on Toxicity, Ecotoxicity and the Environment) concerning the release rates of phthalates. Human volunteers applied stress to children’s plastic toys that contained PVC. Their saliva samples were then studied and analyzed to determine the amount of phthalates present ⁶.

The subjects were exposed to the phthalates by oral intake through chewing on the plastic toys for 3 hours, the time that a child 6-12 months old chews on plastic toys. After the study was conducted the phthalates in the saliva were compared to the amount that could be present before harmful side effects occurred. Table 1. shows the critical effects, no observed adverse effect level, maximum emission rates and intake dose for phthalates.

When the no observed effect level is exceeded, chronic illness may result. The results from the study conclude that levels of DINP and DEHP present do not reach levels that cause chronic illness. The daily intake doses for phthalates that subjects were exposed to were below the no observed effect level. The maximum emission rate of the chemicals represents the amount of phthalates that diffuse out of the surface of the plastic ⁶.

The levels the volunteers were exposed to do not cause chronic illness, however harmful medical problems can still result. The harmful levels children are exposed to on a daily basis are not as crucial as long-term exposure to toxic chemicals. Medical problems may result for children in the future as a result of exposure to chemicals during their developmental stage.

When metal salts are mixed with PVC plastic to resist exposure to heat and stress, the salts clump and migrate from the plastic. The hazards that result from exposure to lead and cadmium and the potential health risks in children’s products were studied by CPSC (U.S. Consumer Product Safety Commission). The studies were conducted on toys that are readily available from retailers. The laboratory data was obtained from wiping a product with filter paper that was moistened with distilled water, and from hydrochloric acid extraction. The filter paper was wiped across the product 30 times and placed in nitric acid, which detected the amount of lead or cadmium present. Hydrochloric acid was used to represent the situation when a child is actually chewing or sucking on the product and not just touching it. Extraction was performed on the product three times over a period of 6 hours, and the levels of lead and cadmium were detected ².

The toxicity of lead and cadmium are of concern due to health factors. Lead causes abnormal mental development and cadmium causes kidney damage. The CPSC determined that chronic levels of cadmium should not exceed 9.2 m g/day for a 1-year-old, 13.5 m g/day for a 3-year-old, and 20.2 m g/day for a 6-year-old. Toxic levels of lead should not exceed 15 m g per day for children ².

The levels detected in the study appear high, however they do not exceed the levels for chronic illness. Children can be exposed to lead and cadmium by merely coming into contact with plastics. The products do not need to be chewed or sucked on for levels of the toxic chemical to migrate to children’s bodies. The levels may not cause chronic illness, but there is no safe level of exposure to hazardous chemicals for children. Long term exposure to lead and cadmium is more of a concern than the amount a child is exposed to on a daily basis. Children’s lives are irreplaceable therefore, no levels of lead and cadmium should be acceptable in products intended for children.

Children are exposed to levels of toxic chemicals in PVC on a daily basis. Most soft and pliable children’s toys are made with PVC. Children can come in contact with chemicals in plastic toys through chewing, inhalation, licking, and hand to mouth transfer. Children’s plastic toys contain 40-50% phthalate composition by weight, which increases the health risks associated with ingestion of the chemicals.

Exposure to phthalates can cause tumors, organ damage and abnormalities in children. Children’s bodies are more susceptible to health hazards because their bodies are still in the developmental stage. The liver of a young child does not metabolize as efficiently as an adult. The critical effects resulting from exposure are based on ingestion per pound of body weight. Maximum intake levels for children are much lower than that of an adult. Therefore, children are at a higher risk of developing a chronic illness due to exposure.

Extensive use of PVC in products did not occur until the 1960’s. The accumulation of phthalates to a chronic level does not occur for 30 or 40 years. Therefore, a complete understanding of phthalate exposure will not occur until the year 2000 to 2020. Current chronic levels for exposure may be inaccurate, and may be higher then the recommended standard values for toxicity.

Lead and cadmium are known carcinogens that cause severe medical problems. The cumulative nature of lead toxicity is the major determinant in the development of health hazards. The daily intake of lead is not as essential as the duration of exposure and the amount ingested over time. At low blood levels lead causes changes in neural functions and brain development. The chemicals interfere with nerve signals and disrupt normal functioning. Lead and cadmium can alter gene expression and gene-regulated protein synthesis ².

PVC is the largest use of chlorine and is harmful to the environment. PVC is made from chlorine, and therefore can not be burned or disposed of without creating problems for the environment. PVC is composed of heavy metals and chemical additives. When PVC is disposed in landfills, the chemicals are slowly released, causing damage to water supplies. When PVC is produced or incinerated, chlorine reacts with other chemicals and toxic compounds such as dioxins are released.

There are many alternatives to PVC that do not pose a health risk to the public. Non-chlorinated plastic can be produced and manufactured without an unwanted financial burden on companies. Polypropylene and polyethylene can be used in the production of children’s toys without potential health risks. The prices of polypropylene and polyethylene are comparable to the price of polyvinyl chloride.

PVC toys can still be used in products for children, with no adverse health problems. The phthalates used to make PVC soft and pliable can be replaced with natural additives that produce the desired physical properties. Citrate esters are natural substances that are derived from renewable natural resources. The main raw material in citrate esters is citric acid, and it is made from the fermentation of corn and molasses. Citrate esters form a strong chemical bond with plastic, and can resist migration at higher pressures ¹¹.

The Scientific Committee on Toxicity, Ecotoxicity and the Environment (CSTEE) conducted a study comparing the release rates of citrate esters and DINP. In the experiment, 40mm thick disks of plastic were used and cleaned with a solvent to test extraction rates of DINP and O-Acetyltributyl Citrate (ATBC) ¹¹. The results are shown in Table 3 below:

Regardless of the amount of additive that is used in the production of PVC plastics, the loss of DINP is still significantly higher than that of ATBC. The results from the study concluded that phthalates such as DINP should be replaced with citrate esters. Citrate esters are a natural substance and exposure to citrates will not cause medical complications for children in the future.

It is often difficult to predict how harmful a chemical will be when information concerning long term exposure is not available. In today’s society, people are faced with many illnesses. It is almost impossible to evaluate medical problems that people are having and make a prediction as to what chemical or substance caused the illness.

Studies conducted by organizations concluded that levels of toxic chemicals are leaching from plastic, but that the levels are not high enough to cause concern. Most parents do not understand the technical aspect of migration and are easily influence by the media. If there are replacements for phthalates that can eliminate harmful side effects and still be comparable in price, it seems logical to eliminate the use of phthalates for products intended for children. Children are irreplaceable, and products manufactured for children should not contain any toxic chemicals, to avoid placing their lives in jeopardy.

1. "Calendering Poly(Vinyl Chloride): Theory and Experiments", J. Vlachopoulos and A.N. Hrymak, Polymer Engineering and Science, July, 1980, Vol. 20, No.11

2. "CPSC Staff Report on Lead and Cadmium in Children’s Polyvinyl Chloride (PVC) Products", US Consumer Product Safety Commission, November, 1997

3. "Dielectric Properties of Poly(Methyl-N-Propyl-Propiolactone)/Poly(Vinyl Chloride) Blends" Tariq M. Malik and Robert E. Prud’Homme, Polymer Engineering and Science, Mid-February, 1984, Vol. 24, No. 2

4. "Formulating PVC Plastisols With Low-Emulsifier Resins", Ashok C. Shah, Plastics Engineering, July 1984

5. "Fracture Behavior of Poly(Vinyl Chloride)/ Methyl Methacrylate/Butadiene/ Styrene Polymer Blends", Akira Takaki, Toshihiko Hasegawa, Polymer Engineering and Science, April 1994, Vol. 34, No.8

6. "Health and Consumer Protection", Scientific Committee on Toxicity, Ecotoxicity and the Environment, December 1999.

7. "Infant Toys Containing PVC and those without PVC" http://www.greenpeacecanada.org/toys/list.htm

8. "Plastic Resource, How Plastics are Made",

http://www.Plasticresource.com/plastic_101/manufacture/how_plastic_are_made.html

9. "Polymer Science and Technology", Joel R. Fried, Prentice Hall, 1995, pgs.(251-256)

10. "Soft PVC Toys, Plastic Food Wrap and Some Medical Devices – Dangerously Toxic",Charlie Cray, Central Oregon Green Pages, 1999.

11. "The Toxicological Characteristics and Risks of Certain Citrates and Adipates Used as a Substitute for Phthalates in PVC Products", Scientific Committee on Toxicity, Ecotoxicity and the Environment, September 1999.

12. "Toxic Toys: Which Toys Are Safe", Greenpeace Canada, 2000.

"What is PVC: Phthalate Plasticizers", http://www.turnertoys.com/pvc3Stabilizers.htm, November 1999.