Polycarbonate cracking
Polycarbonate cracking
(OP)
Back in the 1970's when I first encountered Lexan polycarbonate, we used a lot of 1/8", 1/4" and 3/8" sheet to make machine guarding and enclosures. It was trmendously expensive then, but as I recall, virtually indestructable. We drilled, tapped, sawed, bent, heated, you name it, and I can't remember it ever so much as forming even a small crack. And I remember hitting it severely and repeatedly with a large hammer just trying to get it to crack. The stuff we get now cracks as soon as you look at it. The spec sheets for Tuffak and Lexan look similar as to impact and yield strength. Does anybody know what the story is with this material? I've called my distributor about different grades and he says the standard grade is the best. I know there are FRP types, but I don't think that's what we were getting 35 years ago.





RE: Polycarbonate cracking
Your polycarbonate is probably just fine initially but has been exposed to some unsuitable liquid. It may have been sprayed with some polish to clean it or been washed with detergent. Or some type of oil may have touched it. Look carefully at what is contacting your polycarbonate.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: Polycarbonate cracking
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: Polycarbonate cracking
RE: Polycarbonate cracking
I've done that too and it's pretty impressive. If you bend it first it explodes. Works on CDs too as they are made of polycarbonate.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: Polycarbonate cracking
RE: Polycarbonate cracking
We did that once at a semiconductor company. Our EPROM yields were abysmal, and a corporate-wide tiger team was formed to investigate and solve the problem. I'm happy to report that I was the one to find an obscure IBM Technical Journal article from 15 yrs prior that showed EPROM oxides had to be grown at no less than 1100°C, but someone in our fab had tweaked our process down to 1050°C, possibly to prolong the life of the furnace tube, but it caused us 100x more lost money in production yield hits than the savings in not replacing the furnace tube.
It was an incredibly tiny 5% temperature change, but it killed the yield by a factor of 100.
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Polycarbonate cracking
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: Polycarbonate cracking
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: Polycarbonate cracking
RE: Polycarbonate cracking
Part of the problem that Chris identifies is that some pointy haired 30 year old fresh out of business school fires all the burnt out old has beens that don't know the difference between an objective and a key success factor or a milepost or whatever they choose to label it this year.
Strange thing is those burnt out old has beens generally designed the processes these guys now think they know more about.
Don't get me wrong, there is a place for bright young recruits with lots of enthusiasm, but in this day and age, may need a lot more mentoring than they realise when they fire everyone capable of giving the mentoring.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Polycarbonate cracking
RE: Polycarbonate cracking
You might want to implement a moderate impact test during production to make sure they retain their impact resistance after drilling and forming.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry