Mick,
I have experienced no problems with extended dwell time using polypropylene
in direct AIM tooling although I normally purge a little prior to each shot
and I haven't performed any materials testing. When using materials such as
ABS, Nylon, glass filled nylon and PEEK it is necessary to purge some
material prior to injection in SL tools.
People who you might want to try include:
Russ Harris here at De Montfort University who has looked at shrinkage.
Joel Segal at Nottingham University who is looking at moulded material
properties.
Kent Dawson (still?) at Georgia Tech who has looked at moulded material
properties.
Regards
Neil
-----Original Message-----
From: Michael Priest [mailto:M.L.Priest@tesco.net]
Sent: 01 August 2001 00:05
To: rp-ml@ltk.hut.fi; Advantage Prototype Systems
Subject: Re: Thermal degradation of polymers?
Thanks for the advice. I have the results from the material manufacturer,
but I was wanting to know if anyone had carried out any independent research
in this area.
Mick Priest
Engineering Dept.
Warwickshire College
Leamington Spa
UK
-----Original Message-----
From: Advantage Prototype Systems <protoinfo@advproto.com>
To: Michael Priest <M.L.Priest@tesco.net>
Date: 30 July 2001 13:45
Subject: Re: Thermal degradation of polymers?
>Michael, Each polymer reacts differently. Polyethylene is one that has
>very little change after prolonged heating. There are some flame retardant
>materials that will degrade in minutes. The best thing to do is check
with
>the material supplier for there research.
>
>Mike Burg
>Advantage Prototype Systems.
>www.advproto.com
>
>----- Original Message -----
>From: Michael Priest <M.L.Priest@tesco.net>
>To: <rp-ml@ltk.hut.fi>
>Sent: Sunday, July 29, 2001 9:56 PM
>Subject: Re: Thermal degradation of polymers?
>
>
>> Hi all,
>>
>> Bearing in mind that rapid tooling mould cycle times are often longer
than
>> conventional tooling, a molten polymer will remain static in the barrel
of
>> an injection moulding machine for a greater length of time than in a
>> production environment. Has anyone established any links between the
>> prolonged heating of a molten semi-crystalline polymer in the machines
>> barrel and the mechanical properties or shrinkage that results in the
>> mouldings? I would assume that after a period of time the polymers
>molecules
>> would degrade and the properties and shrinkage of the moulding would be
>> affected. Any suggestions?
>>
>> Mick Priest
>>
>> Engineering Dept.
>> Warwickshire College
>> Leamington Spa
>> UK
>>
>>
>>
>>
>>
>> For more information about the rp-ml, see http://rapid.lpt.fi/rp-ml/
>>
>>
>
>
For more information about the rp-ml, see http://rapid.lpt.fi/rp-ml/
For more information about the rp-ml, see http://rapid.lpt.fi/rp-ml/
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