January 17, 2014
Question - Are any Epolene products NSF certified?
Answer – Yes, Epolene E-14 and Epolene E-14P are both certified by National Sanitation Foundation (NSF) for use under NSF/ANSI 14 for pipe in potable water service.
Question - What is the minimum ignition energy of a dust cloud in air and Kst (pressure and rate of pressure rise of combustible dusts) for Epolene powders?
Answer - Westlake has measured the explosive nature of dust from Epolene E-14EP which should have about the same tendency for the dust to explode as any polyethylene. The biggest factor on dust exploding is the actual particle size of the dust or powder. The Epolene E-14EP was tested as sold – that is 99.5% of the particles were smaller than 18 mesh. The average particle size as tested was in the 180 to 300 micron size (80 to 50 mesh). The results were:
Maximum Explosion Pressure (Pmax) : 5.4 bar
Max. Rate of Pressure Rise (dP/dt)max : 75 bar/s
Kst Value : 20 bar.m/s
The following table gives a general rating for dust explosions based on the Kst value:
Dust Explosion Class Kst (bar.m/s) Characteristics
St 0 0 No explosion
St 1 >0 and <=200 Weak explosion
St 2 >200 and <=300 Strong explosion
St 3 >300 Very strong explosion
Question – We have been using Epolene C-17 to raise the softening point of our paraffin blend. However, we notice that the viscosity is too high for our end use. How can we lower it?
Answer – I suggest you use Epolene N-21. It has a 121C softening point and a viscosity of 400 cps at 140C. The viscosity increase with Epolene N-21 will be much less but the contribution to softening point will remain high.
Question - We have tried Epolene E-43 in an adhesive formulation for automotive application under high heat conditions. While we are happy with the bonding properties, we don’t like the yellowing experienced at the high temperatures. However, could you suggest any other grade we might consider that gives good (or similar) bonding but without the yellowing at high temperatures?
Answer - Epolene E-25 which is a 25 acid number maleated PP with about the same viscosity as E-43. It is lighter yellow and appears to maintain its color better when heat aged. This may work in your application. Alternately, you could add TiO2 (or carbon black) to the mix to hide/mask the yellow color.
Question- I am looking for powdered or resin PE that can be cast and sintered, to be used for marking pen nibs using permanent ink. Do you make a product that would be suitable for this purpose?
Answer - One of the critical requirements for these materials seem to be the actual powder size and geometry. In terms of the sintering process, my understanding is that even with similar materials, the size and shape of the powder can exert a great influence on the process and properties, such as porosity, of the final product. We do offer powder material, and while it is not specially formulated and produced with sintering in mind, it may be suitable in this application. Epolene N type polymers are low molecular weight, low density PE polymers that are available as course powders. These may well be too soft for use as nibs. The Epolene C type polymers are also available as powders and have an MI range from 19 to 4,200 g/10min and are produced with powder size as a controlled property. Suitable C grades are listed below:
Epolene C-15P 4,200 MI
Epolene C-13P 190MI
Epolene C-16P 1,700 (chemically modified)
Epolene C-17P 19 MI
These Epolene powders may be useful for producing sintered nibs. (Contributed by Erik Dunham, subject matter expert.)
Question – I want to go from injection molding a thicker-walled plastic container to a thin-walled container. Is there an additive to help to preserve impact strength? There is no natural fiber / filler being used.
Answer - Usually to maintain properties when moving to thinner cross sections the MI of the material is lowered (which moves the material toward higher molecular weight) and the density of the material is raised a little which also increases the impact and tensile strength. The degree of change to these properties is controlled by the rate of flow into the mold cavity.