DuPont Nylind 51 HSL

[brakemeister]

Has anybody had any experience with the use of regrind in molding Nylind 51 HSL glass fiber reinforced nylon. Specifically, I am looking for a percentage of regrind that can be used without shorting the glass fiber length.

 

[patprimmer]

Any regrind will shorten the glass fibre length. How much depends on previous processing conditions, regrinding conditions and how much you use.

At a wild guess, and short of washing out the polymer with a solvent and studying the glass residue under a microscope, I would think it was safe to estimate that the average glass fibre length in the regrind portion was reduced to half. Careless processing can also decrease the length of the glass in mouldings made with virgin resin.

How close are you to minimum tolerance on any property effected by fibre length.

Having said all the above, It is generally considered OK to use at least 10% regrind and up to 30% if the application is not especially critical and good techniques are used.

Regards

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[Demon3]

As always excellent advice from Pat. I wonder if there is anything he doesn't know!

Anyway, the glass fibre length is reduced dramatically on processing for the virgin material and the regrind. The fibres breakage is more or less exponential according to a study done by a friend on glass fibres in PP. What that means is that the long fibres in the virgin material are very delicate and get damaged fast on processing. Once damaged though they will not be damaged as fast when you use that regrind and put it in virgin material. So I would expect adding regrind to be less detrimental than you would expect. Also you will usually find advice about use of regrind on the site of the manufacturer.

Another good idea is adding some mica filled nylon to the glass fibre reinforced material. The mica particles have a plate form and gives good reinforcement in two directions. Glass fibres only reinforce in one direction (the flow direction) and that leads to warpage. Some mica will help reduce the warpage while maintaining mechanical properties.