Research shows 'BPA-free' bottles live up to manufacturers' claims

The alarm caused by bisphenol A (BPA) presence in reusable plastic bottles resulted in a recent industry change, producing products made with supposed BPA-free materials.

Prompted by requests and concern from consumers, University of Cincinnati (UC) researchers wanted to see if these alternatives--including products made with stainless steel and coated aluminum--were truly giving the consumer an option free of BPA.

In a study reported in the July 8, 2011 advance online edition of the journal Chemosphere, Scott Belcher, PhD, associate professor in the pharmacology and cell biophysics department, and colleagues found that stainless steel- and/or co-polyester lined-aluminum bottles did not release BPA; however, aluminum bottles lined with epoxy-based resins still resulted in BPA contamination of liquids.

"BPA is an ever-present, high-volume industrial chemical that is an estrogen and an environmental endocrine disrupting chemical," explains Belcher, adding that it has been shown in experimental models to negatively impact the heart and reproductive system and enhance the growth of certain tumors.

"It is used extensively in the production of consumer goods, polycarbonate plastics, in epoxy resins that are used to coat metallic food and beverage cans and in other products," he continues. "There is great concern regarding the possible harmful effects from exposures that result from BPA leaching into foods and beverages from packaging or storage containers.

"The objective of this study was to independently assess whether BPA contamination of water was occurring from different types of reusable drinking bottles marketed as alternatives to BPA-containing polycarbonate plastics."

Belcher says that all reusable bottles used in the study were obtained from retail sources and were constructed from polycarbonate, co-polyester, stainless steel, aluminum with co-polyester lining or aluminum with epoxy resin lining.

The bottles, divided into test groups based on their material or lining, and collection vials were washed and rinsed using a standardized protocol to ensure that they were free of non-experimental contaminants. The interior of each bottle was scrubbed with a soft nylon bristle brush for approximately 30 seconds with a cleaner.

Belcher says bottles were then rinsed six times with BPA-free water, two of those times with high-performance liquid chromatography (HPLT)-grade water used to identify, quantify and purify the individual components of the water, and then air dried.

"Briefly, 100 milliliters of HPLC-grade water was added to each bottle on the first day and was kept in the bottle for five days at room temperature," he says.

Three replicate experiments were performed for each bottle. The water was then rotated using a cell culture roller bottle system to ensure even contact of the water and the bottles' surface.

The effect of hot water on BPA leaching from the epoxy resin-lined bottles was measured by the addition of 100 milliliters of HPLC-grade water heated to 100 degrees on the first day.

Following the transfer of boiling water, the bottles were kept at room temperature with rotation for 24 hours during which water samples cooled to room temperature.

"Results once again showed that, at room temperature, detectable concentrations of BPA migrated from polycarbonate bottles. This confirmed our lab's previous study," says Belcher. "However, under the same conditions, BPA migration from aluminum bottles lined with epoxy-based resins was variable depending on the manufacturer. The discount store branded bottles tested released much more BPA."

He says boiling water significantly increased BPA migration from the epoxy-lined bottles. No detectable contamination was observed in water stored in bottles made from co-polyester plastic, uncoated stainless steel or aluminum lined with EcoCare™.

"The results from this study show that when used according to manufacturers' recommendations, reusable water bottles constructed from 'BPA-free' alternative materials are suitable for consumption of beverages without the fear of BPA contamination," Belcher says. "BPA does, however, migrate into water stored in polycarbonate plastic and metal bottles coated with epoxy-resins, especially when heated to high temperatures.

"Consumers should not think that just because a bottle isn't polycarbonate plastic that it is safe from the dangers of BPA, but while there are no standards for claims of 'BPA-free,' it appears that 'BPA-free' labels used to market co-polyester-based water bottle alternatives actually reflect a lack of BPA contamination in liquids stored in those containers," he continues.

"While consumers have been skeptical of manufacturers' claims, these studies confirm that these specific products do offer a BPA-free alternative to polycarbonate or epoxy lined bottles and that companies have responded to their consumers' desires for BPA-free products."

Provided by University of Cincinnati (news : web)

Understanding how glasses 'relax' provides some relief for manufacturers

 Researchers at the National Institute of Standards and Technology and Wesleyan University have used computer simulations to gain basic insights into a fundamental problem in material science related to glass-forming materials, offering a precise mathematical and physical description of the way temperature affects the rate of flow in this broad class of materials -- a long-standing goal.

Manufacturers who design new materials often struggle to understand viscous liquids at a molecular scale. Many substances including polymers and biological materials change upon cooling from a watery state at elevated temperatures to a tar-like consistency at intermediate temperatures, then become a solid "glass" similar to hard candy at lower temperatures. Scientists have long sought a molecular-level description of this theoretically mysterious, yet common, "glass transition" process as an alternative to expensive and time-consuming trial-and-error material discovery methods. Such a description might permit the better design of plastics and containers that could lengthen the shelf life of food and drugs.

A fundamental question is why many materials behave differently when temperature changes. In some "fragile" glass-forming materials, a modest variation in temperature can make the material change from highly fluid to extremely viscous, while in "strong" fluids this change in viscosity is much more gradual. This effect influences how long a manufacturer has to work with a material as it cools. "For decades, material scientists have heavily relied on empirical rules of thumb to characterize these materials," says NIST theoretician Jack Douglas. "But if you want to design a material that does precisely what you want, you need a molecular understanding of the underlying physical processes involved."

According to Douglas, the increasingly viscous nature of glass-forming liquids is related to molecules that move together in long strings around other atoms that are almost frozen in their motion. The growth of these snake-like structures leads to an increase in the viscosity of the liquid: the lower the temperature, the longer the chains, and the more viscous the fluid. The team found that the rate at which these spontaneously organizing snake-like strings grow in size as the material cools is quantitatively related mathematically to the fluid fragility -- confirming intuitive arguments made nearly half a century ago by physicists G. Adams and J.H. Gibbs, but now bolstering them with a firm computational underpinning.

Douglas and his collaborator Francis Starr of Wesleyan University achieved a large variation of fluid fragility through use of a computer model, which mimics a polymer fluid that includes tiny nanometer-sized particles. Portraying the addition of various amounts of nanoparticles and varying their interaction with the polymers, Starr says, gave the team a sort of "knob to tweak" to reveal how the fluidity changed with temperature and how the motion of the clusters was quantitatively related to changes in the fluid's properties. This tuning of cooperative motion in glass-forming liquids and fragility should be crucial in material design. Douglas says.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by National Institute of Standards and Technology (NIST).

Journal Reference:

Francis Starr, Jack Douglas. Modifying Fragility and Collective Motion in Polymer Melts with Nanoparticles. Physical Review Letters, 2011; 106 (11) DOI: 10.1103/PhysRevLett.106.115702

Laser printing speeds parts on demand to manufacturers

Pull into the auto repair shop with a smashed bumper, and there's no wait while they order a replacement. Instead, the technician downloads specifications from the manufacturer's database. You both watch as a laser beam probing a container of liquid plastic material almost magically builds a new bumper inch by inch.

The scenario may sound like science fiction, but advances in polymer materials are moving the technology for 3-D printing" of prosthetic limbs, hearing aids, designer furniture, surgical tools and other products out of the designer's studio and into the marketplace. That's the topic of an article in the current edition of Chemical & Engineering News, ACS' weekly news magazine.

In the article, Alexander H. Tullo, C&EN senior editor, explains that the technology –– termed stereolithography, laser sintering, rapid prototyping, and additive manufacturing –– has been in limited use for decades to produce models of new products and for other design-shop applications. With polymer manufacturers developing new raw materials for the process, this so-called "additive manufacturing" technology is now moving into a new phase –– making actual products. The market has been expanding at an average annual rate of 26 percent, and exceeded $1 billion in 2009.

More information: "Parts on Demand" This story is available at http://pubs.acs.or … 917bus1.html

Provided by American Chemical Society (news : web)