Today's KNOWLEDGE Share: How Strong is Your Material?

-

Today's KNOWLEDGE Share:

How Strong is Your Material?

Do you know the true strength of your material? With plastics, that is a trick question.

 

Because of their molecular structure, thermoplastic materials have different properties compared to other materials, like metals.

·    The polymer molecules consist of very long chains – high molecular weight.

·    The individual polymer chains are entangled in each other.

·    The polymer chains are mobile and can slide past each other because they do not share chemical bonds with the other chains around them.

 

Because of this, plastics exhibit viscoelastic behavior, displaying aspects of both elastic and viscous performance. Attributed to their viscoelastic character, the properties of plastics, including tensile strength, will vary depending on the conditions of the stress loading. This means the “strength” of the material will vary over temperature, time under load, duration of dynamic loading, strain rate, and more.



 

Unfortunately, this is not captured on plastic material datasheets. For a particular grade of polycarbonate, the tensile strength as determined by standard tensile testing was determined to be 64 MPa, a good match with the datasheet value. However, this is not how the component manufactured from the polycarbonate will be stressed – it is expected to last longer in field use than the 90 seconds it took for the tensile test, and it will be under continuous static loading or dynamic loading depending on the specific application. Based upon realistic conditions, creep and fatigue tests were performed. The testing determined that the actual material strength was 20 MPa for 5 years under continuous loading and 31 MPa at 750,000 cycles, the expected service life. Obviously these are far less than the 64 MPa identified as the tensile strength.

 

Source:The Madison Group

Visit MY BLOG http://polymerguru.blogspot.com


#plastics #plasticsengineering #polycarbonate #failure #engineering #design #failureanalysis #fatigue #stess #creep #tensile #loading


Comments

Post a Comment

Popular posts from this blog

Today's KNOWLEDGE Share:PLA BOTTLE

-
Image
Today's KNOWLEDGE Share Ever wondered how we can reduce plastic pollution in India? The Mysuru-based Defence Food Research Laboratory (DFRL), affiliated with the DRDO, has launched an eco-friendly remedy with the introduction of biodegradable water bottles. Crafted from sustainable Polylactic acid (PLA) material, these bottles not only combat plastic waste but also contribute to reducing the overall carbon footprint. The best thing about this bottle is its all-encompassing sustainability approach – the bottle, cap, and label are all compostable. This innovation, derived from 100% bio-based and renewable sources, sets us on a path towards environmental conservation and fosters a greener and more sustainable future. Source:The Better India #polymers #bioplastics #pla   #compostable   #ecofriendly   #sustainability
Read more

Today's KNOWLEDGE Share:High and low shear rate changes in Rheology

-
Image
Today's KNOWLEDGE Share If a relatively high Mw grade flows from thin to thick, as shown in the picture, and if the time needed to fill the thick section is way shorter than the average polymer relaxation time, the polymer will not be able to reach its higher viscosity (corresponding to higher thickness/lower shear-rate). I am assuming here the polymer reached equilibrium low viscosity in the thin section, say for instance because it is much longer. Any pressure prediction not accounting for transient rheology would then overpredict the pressure to fill.Of course the diverging flow will further complicate the situation and mess with the molecular orientation created in the thin section, but to what extent ? Since this is more of a reasonable "conjecture", don't take this for granted, and discuss or share your opinion in the comments. There are hundreds of Rheology papers on the "4:1 contraction flow". Not sure I have ever seen any on the..."1:4 expansio
Read more

Today's KNOWLEDGE Share : biobased content of polycarbonate diols

-
Image
Today's KNOWLEDGE Share MCG increases biomass content of polycarbonate diols Mitsubishi Chemical Group (MCG) has introduced grades of its Benebiol biomass-based polycarbonate diols that have a higher biomass content. The product is primarily used in the manufacture of polyurethane resins for coatings in sectors such as automotive, furniture and outdoor products. It is also used in the production of artificial leather. Existing Benebiol grades had a bio-based content of 20-50%, but the new HSS and NLDS grades have a biomass content in excess of 80%. Some of its previous petroleum-derived grades have also been converted to biomass, as the NLS grades. This, the company said, allows it to offer bio-based grades of all its Benebiol products. The shift to biomass-based raw materials while maintaining high-quality functions will contribute to our customers’ efforts to achieve sustainable manufacturing. source:MCG/www.utech-polyurethane.com
Read more