HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
<<  <  Page 3/3
Dave Palmer
User Rank
Platinum
Re: Commonplace Chemicals
Dave Palmer   2/3/2012 11:50:24 AM
NO RATINGS
@Alex: When it comes to environmental stress cracking, there is not necessarily any advantage to making the plastic thicker or thinner.  The key variables are stress and chemical exposure.  If by making the plastic thicker, you can reduce the stress below the threshold, then it might be a solution.  But often the threshold stress is so low that this is impractical.  And if the internal stresses in the material are high enough, it doesn't matter what you do with the external stress.

Here is a good introduction to residual stress in plastics.  At some risk of oversimplification, thin-wall sections are more likely to have flow-induced residual stresses, while thick-wall sections are more likely to have thermal-induced residual stresses.  But either way, molded-in stresses can be significant.

Alexander Wolfe
User Rank
Blogger
Commonplace Chemicals
Alexander Wolfe   2/3/2012 11:16:41 AM
NO RATINGS
I never realized the commonplace chemicals like oil and grease were precursors to stress cracking in plastics. Good to know. Also didn't realize there's some built-in prestress. It seems that, in consumer systems, the plastic always ends up cracking at some point. Is that because thin(ner) plastics are always prone to cracking (and on the other side of the design equation, making them thick enough to be more crack resistant doesn't comport with weight and cost requirements. Or are the thicker plastics just as stress-crack prone?)

<<  <  Page 3/3


Partner Zone
Latest Analysis
Thanksgiving is a time for family. A time for togetherness. A time for… tech?
The promise of the Internet of Things (IoT) is that devices, gadgets, and appliances we use every day will be able to communicate with one another. This potential is not limited to household items or smartphones, but also things we find in our yard and garden, as evidenced by a recent challenge from the element14 design community.
Researchers have developed a new flexible fabric that integrates both movement and sensors, introducing new potential for technology-embedded clothing and soft robots.
Made by Monkeys highlights products that somehow slipped by the QC cops.
If you didn't realize that PowerPoint presentations are inherently hilarious, you have to see Don McMillan take one apart. McMillan -- aka the Technically Funny Comic -- worked for 10 years as an engineer before he switched to stand-up comedy.
More:Blogs|News
Design News Webinar Series
11/19/2014 11:00 a.m. California / 2:00 p.m. New York
11/6/2014 11:00 a.m. California / 2:00 p.m. New York
10/7/2014 8:00 a.m. California / 11:00 a.m. New York
12/11/2014 8:00 a.m. California / 11:00 a.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Dec 1 - 5, An Introduction to Embedded Software Architecture and Design
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Last Archived Class
Sponsored by Littelfuse
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service