Plasticizers add flexibility to harder plastics, but may also migrate from these materials, raising health concerns about human exposure via medical devices or children's toys. Scientists are working with the widely used plasticizers known as phthalates and have locked down these compounds, preventing them from migrating. The research may lead to improved versions of hard plastics that don't leach their ingredients.
The research team from the Institute of Polymer Science and Technology in Madrid, Spain, worked with DEHP (Di(2-ethylhexyl) phthalate). They first added a compound incorporating a sulfur group to DEHP and then mixed this decorated phthalate with polyvinyl chloride (PVC). The sulfur bumped a chlorine atom aside, double-bonding the phthalate to the PVC backbone. The scientists then tested the material by putting it in a solvent that typically prompts migration of phthalates. "In our case it is impossible to get it out," says Reinecke, the research leader. They detected no trace of free phthalates even after five hours of soaking; usually after three hours, he says, all of the phthalate would be released.