Featured Research

from universities, journals, and other organizations

Understanding Plastic "Sharkskin": Results May Pave Way For Eliminating Problems In Low-Cost Plastics

Date:
March 8, 2001
Source:
American Institute Of Physics -- Inside Science News Service
Summary:
Plastics may be on the verge of a widespread advance, if researchers can surmount a "fishy" problem. A new technique, called "metallocene catalysis polymerization," enables researchers to manufacture cheap versions of expensive, engineering-grade plastics.

Hilton Head Island, SC (February 20, 2001) -- Plastics may be on the verge of a widespread advance, if researchers can surmount a "fishy" problem. A new technique, called "metallocene catalysis polymerization," enables researchers to manufacture cheap versions of expensive, engineering-grade plastics. For example, it can make a version of the common plastic polyethylene so strong that it can stop bullets. However, the new technique often produces an undesired effect, known as "sharkskin," in which the manufactured plastic has a rough surface containing a repeated pattern of ridges. Despite the best attempts of researchers to make smooth materials, sharkskin remains a problem.

Related Articles


Now, polymer physicists at the National Institute of Science and Technology have made new insights into the causes--and solutions--for sharkskin. They reported their findings at last week's meeting of the Society of Rheology in Hilton Head Island, South Carolina. These insights may help manufacturers to control--and eventually eliminate--the problem. Studied since the World War II, sharkskin is actually a problem in many plastic manufacturing techniques. Plastics are made of polymers, long, spaghetti-like chains of molecules made of organic material, which are based on carbon, oxygen, and hydrogen atoms. Workers make many plastic products in a process similar to pushing pasta through a pasta maker: they force molten polymer mixtures through small holes in a die. For many polymer mixtures, sharkskin forms, marring the desired appearance and texture of the plastic.

Several fixes for sharkskin exist, but none are entirely satisfactory for industry. Sharkskin can be prevented by pushing the polymer slowly through a die, but this is too inefficient for companies wishing to make plastics quickly. It can be prevented by manufacturing the plastic through highly controlled conditions, but this is expensive and impractical for mass-production. Manufacturers often use anti-sharkskin additives, but until now it was unclear why they work.

Kalman Migler and his colleagues have performed new experiments that investigate how sharkskin forms--and how it can be prevented. Sending polyethylene through a transparent sapphire tube, Migler and colleagues used a high-speed video microscope to watch what happens to polyethylene as it forms sharkskin. With these direct observations, researchers have seen that the polymer undergoes extreme stretching as it passes through the exit hole of the tube, causing the material to rupture. The polymer splits into two parts, one consisting of the surface of the polymer, and the other consisting of its buried, inner core. The surface of the polymer actually passes slowly, as it sticks to the wall of the tube, but the polymer core passes through quickly. The surface of the polymer accumulates near the wall of the tube and then peels off. Migler and colleagues conclude that this peeling-off of the surface polymer creates the ridges. This picture supports a 25-year-old theory, advanced by Frederic Cogswell, then at ICI (a leading manufacturer of paints and other specialized materials), but very difficult to test directly until now.

In addition, the researchers directly observed why one particular anti-sharkskin additive is good at preventing sharkskin. The additive, known as a fluoropolymer, was mixed with the polyethylene as the combination traveled through the sapphire tube. (A fluoropolymer is a polymer in which some of the hydrogen atoms are replaced by fluorine atoms.) In their observations, the researchers found that the polyethylene slips over the fluoropolymer, rather than sticking at the walls. This dramatically reduces the extreme stretching at the exit, thus inhibiting the formation of sharkskin.

"This is a long-standing and very interesting problem," says Mort Denn, professor of chemical engineering at the City University of New York and editor of the Journal of Rheology. "Kalman is doing nice work, as are others."


Story Source:

The above story is based on materials provided by American Institute Of Physics -- Inside Science News Service. Note: Materials may be edited for content and length.


Cite This Page:

American Institute Of Physics -- Inside Science News Service. "Understanding Plastic "Sharkskin": Results May Pave Way For Eliminating Problems In Low-Cost Plastics." ScienceDaily. ScienceDaily, 8 March 2001. <www.sciencedaily.com/releases/2001/02/010226071948.htm>.
American Institute Of Physics -- Inside Science News Service. (2001, March 8). Understanding Plastic "Sharkskin": Results May Pave Way For Eliminating Problems In Low-Cost Plastics. ScienceDaily. Retrieved December 18, 2014 from www.sciencedaily.com/releases/2001/02/010226071948.htm
American Institute Of Physics -- Inside Science News Service. "Understanding Plastic "Sharkskin": Results May Pave Way For Eliminating Problems In Low-Cost Plastics." ScienceDaily. www.sciencedaily.com/releases/2001/02/010226071948.htm (accessed December 18, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Thursday, December 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

3D Printed Cookies Just in Time for Christmas

3D Printed Cookies Just in Time for Christmas

Reuters - Innovations Video Online (Dec. 18, 2014) A tech company in Spain have combined technology with cuisine to develop the 'Foodini', a 3D printer designed to print the perfect cookie for Santa. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com
How Sony Hopes To Make Any Glasses 'Smart'

How Sony Hopes To Make Any Glasses 'Smart'

Newsy (Dec. 17, 2014) Sony's glasses module attaches to the temples of various eye- and sunglasses to add a display and wireless connectivity. Video provided by Newsy
Powered by NewsLook.com
Los Angeles Police To Receive 7,000 Body Cameras

Los Angeles Police To Receive 7,000 Body Cameras

Newsy (Dec. 17, 2014) Los Angeles Mayor Eric Garcetti announced the cameras will be distributed starting Jan. 1. Video provided by Newsy
Powered by NewsLook.com
Jaguar Unveils 360 Virtual Windshield Making Car Pillars Appear Transparent

Jaguar Unveils 360 Virtual Windshield Making Car Pillars Appear Transparent

Buzz60 (Dec. 17, 2014) Jaguar unveils a virtual 360 degree windshield that may be the most futuristic automotive development yet. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins