Alternative manufacturing processes to create flexible polymers can involve the replacement of DEHP with another plasticizer, or the use of a polymer or other material that does not require the use of a plasticizer to achieve the same characteristics and performance.
In general, desirable performance criteria for flexible PVC include compatibility, processability and hardness. Compatibility with PVC and any other additives present (i.e., the ability to create a stable single phase compound) is a critical factor when considering alternative plasticizers. Known as processability, PVC resin, plasticizer(s), stabilizers and lubricants should blend together readily using common plastics processing methods. In addition, the alternative plasticizer should achieve the required level of flexibility (measured as hardness) at a cost that is comparable to that of DEHP-plasticized PVC.
In medical device applications there are additional performance criteria for the plasticized polymer. Important considerations include the tendency of plasticizers to migrate out of the polymer matrix, and the ability of the plasticized polymer to be sterilized by different methods. Additional concerns include:
- For sheet applications - tensile strength, cold flexibility (because solutions must be cold-storable) and clarity.
- For tubing applications - elastic recovery must be optimized to assure that tubing does not kink during use.
TURI conducted an assessment of various plasticizer and polymer alternatives associated with DEHP in its 2006 study for the Commonwealth, entitled "Five Chemicals Alternatives Assessment Study". As part of that study, several alternative plasticizers and polymers were identified. Alternative plasticizers include other phthalates (DINP, DIDP, DIHP, BBP, DBP, and BOP), di (2-ethylhexyl) terephthalate (DEHT), dibenzoates (DGD, DEGDB, and TEGDB), adipates (DEHA and polymeric adipates), phosphates (DEHPA and TCP), citrates (ATBC and BTHC), and sebacates (DEHS and DBS).
In addition to alternative plasticizers, alternative materials can be used. As with plasticizers, appropriate alternative materials differ depending on the application.
Alternatives for Consumer Products
DEHP has historically been used in a number of consumer products, ranging from toys to footwear to household products such as wall coverings and resilient flooring. However, the use of DEHP in these products has decreased in the past decade, largely due to increased consumer demand, as well as in response to international restrictions. DEHP has largely been eliminated from the footwear and toy industries in favor of other plasticizers or polymer matrices.
However, footwear products and toys manufactured in other parts of the world, in particular Asia, may still have DEHP and other phthalate plasticizers present.
Consumer products where DEHP may still be found include other flexible vinyl products such as rain gear, shower curtains, vinyl flooring and wall coverings. Of these, the most significant uses are in resilient flooring and in wall coverings.
TURI focused on resilient flooring as a priority use in its 2006 study. Resilient flooring uses include residential flooring as well as commercial and high-traffic industrial applications. TURI identified several plasticizer alternatives for resilient flooring, including di (2-ethylhexyl) terephthalate (DEHT), di isononyl phthalate (DINP), dipropylene glycol dibenzoate (DGD) and di (2-ethylhexyl) adipate (DEHA).
In general, these alternative plasticizers offer similar or improved technical/performance, cost, and environmental and human health benefits to DEHP. Use of alternative plasticizers often does, however, require modifications to processing equipment and practices and there has been little incentive for resilient flooring manufacturers to pursue alternatives except in higher priced products.
Alternative materials that do not require the use of plasticizers are also available for resilient flooring applications. Performance issues that must be considered when assessing alternative materials for resilient flooring include installation, cleaning and maintenance, cost, end of life and other environmental and human health concerns. The most promising alternatives identified by TURI include linoleum (made from linseed oil, wood flour, resin, jute and limestone), cork and polyolefin co-polymers with limestone. While linoleum and cork tend to be more appropriate for residential uses, the polyolefin co-polymer flooring is designed for large high-traffic commercial areas such as in health care facilities, ships, shopping centers and airports.
In general, each of these material alternatives exhibit equal or improved performance, cost and EH&S characteristics over DEHP plasticized vinyl flooring. As with alternative plasticizers, however, use of alternative materials for flooring is largely dictated by costs. With little external incentive to manufacture or use alternative materials the adoption rate of these alternatives has been slow, especially in the residential market. However, many health care facilities are moving towards alternative materials and polymer formulations for their resilient flooring needs. As the trend towards green building expands in the US, it is expected that the market for natural resilient flooring materials will also grow.
Vinyl wall coverings are used in both commercial and residential settings for decorative as well as protective purposes. According to industry representatives, the majority of US wall covering manufacturers do not use DEHP. DEHP is used by some international manufacturers, and therefore may still enter the US market in their products. Alternatives to DEHP are readily available. The two most widely recognized alternatives to DEHP for wall coverings are DEHA and DINP. These alternative plasticizers present similar or improved cost, and environmental and human health characteristics. While DINP also represents a potential direct replacement for DEHP from a technical/performance standpoint, DEHA presents some challenges with respect to PVC compatibility and emissions during processing and use.
A number of alternative materials to DEHP-plasticized vinyl wall coverings have been developed. These range from polymers, to polymer/natural fiber (e.g., wood or cellulose) blends, to inorganic based textiles. The majority of alternative materials exhibit similar or improved performance, cost, and environmental and human health characteristics. However most of the alternatives are not currently available in similar color and pattern choices, which may limit their acceptance in certain applications. As with resilient flooring however, there is a move toward alternative materials for wall coverings used in health care facilities as well as in residential and commercial applications, largely in association with the increased emphasis on green building in the US.
Alternatives for Medical Devices
PVC is widely used as a plastic in medical sheet and tubing type devices. Studies suggest that as much as 25% of all plastics used in hospital environments are PVC-based. These devices include bags used to store a variety of medical solutions and tubing used in the transfer of those solutions to the patient.
The most commonly used alternative plasticizers in medical device applications include trioctyl trimellitate (TOTM), DEHA and butyryl trihexyl citrate (BTHC). In addition, a newer plasticizer currently approved in the EU for food applications, di isononyl cyclohexane-1,2-dicarboxylate (DINCH) is being evaluated for use in medical devices in the US.
In general each of these plasticizer alternatives may provide equal or improved performance, cost and environmental and human health characteristics over DEHP. Adoption of alternatives is happening across the health care industry, though rather slowly. In part this is due to the relative lack of information about the health effects of the alternatives and their metabolites and the industry's need to protect the health of its patients.
Materials that are either inherently flexible, or that fulfill the function of the DEHP/PVC material without being plasticized are also available. One of the key concerns for these materials is their shelf life in a medical setting - that is their ability to retain flexible characteristics without leaching harmful chemicals.
Materials that have been found to be appropriate alternatives to DEHP/PVC for medical bag devices include:
- Ethylene vinyl acetate (EVA), a copolymer used in medical film applications such as for parenteral and enteral solutions, and for custom mixing of pharmaceuticals.
- Polyolefins such as polyethylene and polypropylene - stable and inert polymers which are widely used in medical device applications due to their flexibility, transparency and toughness.
- Glass, which was historically used for solution storage purposes, though is now less commonly used due to handling concerns and cost.
Materials used in medical tubing applications must be able to be formed in a variety of configurations, have thin inner walls, be durable and strong with low coefficients of friction, be highly resistant to chemicals and to temperature variations, be inert and be weldable to other components of the medical device. Appropriate alternative medical tubing materials include EVA, polyolefins and glass, as well as:
- Silicone, a naturally translucent, odorless and tasteless synthetic rubber.
Thermoplastic polyurethane (TPU), formed by reacting alcohols
with a diisocyanate or polymeric isocyanate.
In general, these materials exhibit equal or improved performance and environmental and human health characteristics over DEHP/PVC. The cost of the alternative materials tends to be greater than that of the DEHP/PVC. In addition, gas permeability of EVA and polyolefins and manufacturability of silicone and TPU are worse than DEHP/PVC. There is an environmental and human health concern associated with the manufacture of TPU, potentially making it less favorable as an alternative from that perspective.
Danish Environmental Protection Agency "Environmental and Health Assessment of Alternatives to Phthalates and to flexible PVC" 2003; Toxics Use Reduction Institute "Five Chemicals Alternatives Assessment Study" 2006 -- see: http://www.turi.org/industry/research/five_chemicals_study
EU Marketing and Use Directive 76/769/EEC; Fischer "Floorward thinking" Environmental Health Perspectives 1999; Hileman "Panel Ranks Risks of Common Phthalate: Additional research underscores concerns about DEHP that were first expressed in 2000 report" Chemical & Engineering News 2005; Marshall "Letter to TURI from OMNOVA Solutions Inc" 2007; Toxics Use Reduction Institute "Five Chemicals Alternatives Assessment Study" 2006 -- see: http://www.turi.org/industry/research/five_chemicals_study
Rossi "Neonatal Exposure to DEHP and Opportunities for Prevention" 2002; Schaefer "Personal communication with Marketing Manager Specialty Plasticizers BASF Corporation" 2006; Tickner "The Use of Di-2-Ethylhexyl Phthalate in PVC Medical Devices: Exposure, Toxicity and Alternatives" 2000; Toxics Use Reduction Institute "Five Chemicals Alternatives Assessment Study" 2006 -- see: http://www.turi.org/industry/research/five_chemicals_study