Flexural Modulus, MPa
Flexural Modulus, MPa
(OP)
A number associated with the flexibilty or stiffness of a material.The lower the number the more flexible, the higher the less flexible, my question is
Dose this number affect the shrinkage of plastic materials,
I.E the higher the number the more shrinkage you get??
Have just sampled two new plastic resins with the FM# higher than the regular resin that i use and both have shown more shrinkage, than the regular resin.
Any thoughts on this. All 3 materials share the same MFI and density etc the only differance is the FM# regular material is 1150 new materials are 1400 and 1450.
Dose this number affect the shrinkage of plastic materials,
I.E the higher the number the more shrinkage you get??
Have just sampled two new plastic resins with the FM# higher than the regular resin that i use and both have shown more shrinkage, than the regular resin.
Any thoughts on this. All 3 materials share the same MFI and density etc the only differance is the FM# regular material is 1150 new materials are 1400 and 1450.






RE: Flexural Modulus, MPa
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Flexural Modulus, MPa
However, if the polymer is the identical chemical type, and is a semi crystalline material, the degree of crystallinity effects both flex mod and shrinkage, but only to a minor degree.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Flexural Modulus, MPa
the part size being 1.3250 +/-0.003. With the regular material i get a mean of 1.3239 but with the other materials i get a mean of 1.3204 and 1.3212 which the parts out of spec, but going back to the regular material the size returns to spec.
All three materials are PP and identical in every way except for the flex mod number.
The degree of crystallinity affects both flex mod and shrinkage, ok, is this something that can be tested to determine its effects and if so how?
RE: Flexural Modulus, MPa
The moulding conditions and the amount of time after moulding can both effect crystalinity as can post treatments like annealing or thermal cycling due to use or other processes.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Flexural Modulus, MPa
I think you are not quite understanding structure-property relationships. Materials have certain structures that provide certain properties. The crystallinity of the material is the structure; the modulus, shrinkage, melt flow rating, etc. are the properties. Crystallinty can be measured directly using x-ray diffraction, which is almost prohibitively expensive. It can be assessed indirectly using many other techniques, like density, strength, modulus, DMA, etc.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Flexural Modulus, MPa
The problems I see here are that quietone is trying to draw conclusions from very small changes in properties and is trying to hold very tight tolerances.
As you say, x-ray diffraction is well beyond the means of almost everyone, and other methods can be lost in the smokescreen of cause and effect, however a change crystalinity will effect the properties in question in the manner described.
Whether or not quietone really is being supplied with exactly the same compound every time, or whether there are other variables is in my opinion the real question at this stage.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Flexural Modulus, MPa
RE: Flexural Modulus, MPa
Thanks for the help folks I'll let you know the outcome.
Regards
Quiteone