Virtually all injection moulding grades of nylon have a small amount of mould release built in by the manufacturer. Some do it at the reaction vestle stage to avoid a compounding process. They traditionally used things like about 0.1 or 0.2% of stearates and monoethanolamine, however there are more efficient chemicals available now. I am not at liberty to disclose them.
The main reasons nylons stick on a mould are shrinking onto a core as they are high shrinkage materials or flashing down a pin and creating a suction cap effect on the end of the pin. This flash can be so fine so as to be invisible to the naked eye.
Mould release can help the first but can actually make the second more severe.
In 30 years of close involvement with moulding nylons and detailed knowledge of the practices of hundreds of moulders who use nylon, I have only ever seen two or three occasions where extra mould release over the standard compound content was required, and that was over 20 years ago. These days there is always a grade that will release unless as Harry says, there is another problem like undercuts or flash.
There are grades of impact modified nylon 6 that can match most of the properties of ST801. They may exceed a few in some areas and fall short a bit on others, but overall pretty close if not identical. You need to examine your needs in detail then compare the properties compared to your requirements.
Of course you need to do your comparisons moisture conditioned to the environment of use.
re 6 vs 6.6 comparisons, once the impact modifiers are added, this has less relevance as the more effective modifiers alter all properties substantially and you need different amounts of the modifiers to modify 6 or 6.6 to the same impact, but essentially, 6 has a substantially lower melting point, is a little less crystaline, is a little tougher, has lower tensile compressive strengths and lower creep resistance. It absorbs a little more moisture and absorbs it a bit quicker and also absorbs other chemicals easier and faster, thus lowering it's resistance to them in some cases. As I say, impact modifier have an effect on this and mostly have a far greater influence on properties that most of the differences seen between straight 6 and 6.6, except for maybe temperature effects.
Regards
Pat
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