Sunday, 11 April 2021

Design Properties for Engineers – Residence Times of High Performance Polymers (Injection Moulding)

Hello and welcome to a new post. Today we discuss the topic of melt residence times of high performance polymers in injection moulding.

In a previous blog post, I presented already a practical way to estimate the residence time and the online calculation tool can be found here.

Often comes the following question: I have calculated the residence time of the melt in my injection moulding machine. And now what should I do with this value? To what should this value be compared to?

One answer to this question is that generally, if your estimated shot size is between 30% and 60% of the plasticizing barrel capacity, the residence time will be in an acceptable range.

The other answer is that one needs to know the recommended and maximal residence time before thermal degradation of the resin takes place. These recommendations can be often found in the processing guides of the polymer manufacturers.

The figure below shows the recommended and maximal residence time of selected high performance polymers for injection moulding. 

Recommended and maximal residence time of selected high performance polymers for injection moulding


Thanks and #findoutaboutplastics

Greetings,

Herwig Juster

#ResidenceTime #Verweilzeit #InjectionMoulding

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Monday, 5 April 2021

Rule of Thumb for Polymer Material Selection: The Big 5 for Fast Decision Making

 

Rule of Thumb for polymer material selection: The Big 5 Polymers for Fast Decision Making

In nature, the big 5 are often referred to as lion, leopard, rhino, elephant and African buffalo. In polymer material selection, the big 5 allow you to make a quick estimation and decision on suitability for the planned application.

What are the big five for a quick assessment in polymer material selection and faster decision making?

This we discuss in today's post.  

Polypropylene (PP): is a commercial favorable solution with a good property balance up to 100°C. Limitations are in surface aesthetics, however if those are not critical, PP is a good choice.

Acrylonitrile Butadiene Styrene (ABS): it is an all-rounder and suitable for many applications and it is strong and relatively tough, combined with a low melting point. Furthermore, ABS has good processing properties and is in a reasonable price range.

Polycarbonate (PC): allows realization of applications which have higher temperature resistance as well as impact performance needs. PC is the next best candidate going from ABS.

Poly(methyl methacrylate) (PMMA):  offers a good overall aesthetics and transparency which makes it a good candidate for applications with the need of optimal appearance. Limitations of PMMA are for applications with higher impact needs (PMMA shows brittle behavior). PC will be tougher than PMMA, however the surface aesthetics might not fulfill the application needs. PS can be suitable for single use applications.

Polyamide (PA): aliphatic polyamides are the best for higher engineering demands. Polyamide 6.6 with glass fiber reinforcement is well established in several engineering applications, especially in automotive. If higher temperature resistance is needed (120-140°C), than aromatic polyamides (e.g. polyphthalamide (PPA)) are the choice of material.

In the table below we summarize the characteristics of engineering and commodity grades which additionally help during the selection process:

 

Characteristics of most common commodity plastics



Characteristics of the most common engineering plastics

Thanks for reading and #findoutaboutplastics

Greetings,

Herwig

Interested to talk with me about your plastic selection and part design needs - here you can contact me 
Interested in my monthly blog posts – then subscribe here and receive my high performance polymers knowledge matrix.
New to my Find Out About Plastics Blog – check out the start here section
Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course

Literature

[1] http://polymerdatabase.com/polymer%20classes/Thermoplastics.html

[2] https://www.ferriot.com/tips-tricks-traps-injection-molding-resin-selection/