Monday, 20 September 2021

Design Properties for Engineers: UL RTI vs HDT of Commodity, Engineering and High Performance Polymers

In this blog post, we compare the long-term thermal properties (based on UL RTI 746B) to the short-term properties (based on the Heat Deflection Temperature, HDT @ 1.8 MPa).

The figure below shows the comparison of the long-term and short-term thermal data. This allows designers to immediately assess the suitability of a selected polymer in terms of continuous heat exposure as well as short-term heat impact. Furthermore, alternative polymers can be selected too.

UL RTI vs. HDT (1.8 MPa):Long-Term vs. Short-Term Thermal Properties of Thermoplastics


I made a YT video which shades light into this topic in more detail:



Thank you for reading and #findoutaboutplastics

Greetings

Herwig Juster

#materialselection #polymerengineering #plasticsdesign

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] UL Prospector – 746B

Monday, 13 September 2021

Rule of Thumb for Plastics Injection Moulding: Weld Line vs Meld Line

 In this rule of thumb post, we discuss the difference between a weld line and a meld line in polymer injection moulding as well as how we can apply effective troubleshooting.

In short: the angle at which the converging polymer flow front meets in the tool again determines the difference between weld line and meld line.

A weld line is formed if the angle is less than 135°.  A meld line is formed if the angle is greater than 135° and the polymer molecules are more uniform compared to the orientation formed after a weld line. This is demonstrated in the picture below.

It is important to understand the flow fronts and the flow angle for achieving proper weld lines. Such an understanding allows the use of multiple submarine gates rather than fan gates to be used. Prediction of weld lines prior to the tool being cut allows the optimization of the part design and gate location which in turn reduces tool development time. Consideration of material, filler and pigmentation is important and this is why discussion with the technical team at your material supplier at the early stages are useful.

Rule of Thumb: Weld Line vs Meld Line


Troubleshooting of weld and meld lines

Weld and meld lines can cause a decrease in mechanical properties and are often clearly visible on the surface. An effective way of troubleshooting them is to move them in a non-functional / non-visible area. This can be achieved by changing the gate position or part thickness. Furthermore the allover quality can be improved by increasing the melt and mould temperature. This facilitates a better interfusion of the flow fronts. Also injection speed can help as well as an optimization of the runner system design.



Thank you for reading and #findoutaoutplastics

Greetings,

Herwig Juster

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] https://knowledge.autodesk.com/support/moldflow-insight/learn-explore/caas/CloudHelp/cloudhelp/2017/ENU/MoldflowInsight/files/GUID-099634AE-DB7A-41BA-B70C-5A23FB013B06-htm.html

Tuesday, 7 September 2021

Design Properties for Engineers – Comparison Property Data of Polyphthalamides (PPAs)

 Hello and welcome to a new post. In this post I provide you engineering comparison data of the 5 most used PPA base polymers and their glass-fiber reinforced compounds. Semi-aromatic polyamides are used when the aliphatic counterparts reach their limits due to high temperature and/or mechanical loads.

The five base polymers of PPA are:

-PA 6T/6.6

-PA 6T/6I/6.6

-PA 6T/6I

-PA 6T/DT

-PA 10T/X

The data are shown in property vs. density plots and we are comparing the semi-aromatic polyamides to aliphatic polymers.  

Background

Semi-aromatic polyamides have an amide linkage together with an aromatic ring. The aromatic content is most of times derived from 2-methylpentanediamine (DT), terephthalic acid (TPA) and/or isophthalic acid (IPA). In general, the aromatic structure helps to increase the glass transition temperature, which in turn increases the thermal and chemical resistance. Furthermore, reduction in water uptake is achieved. More details can be found in this post.

The following properties are presented in the below infographic (PPA reinforced with 50% glass fibers):

-Glass transition temperature

-Melt temperature

-Tensile strength (dry as moulded; conditioned)

-Tensile modulus (dry as moulded; conditioned)

-Heat Deflection Temperature (HDT; 1.8 MPa)

-Izod notched impact strength




Design Properties for Engineers – Comparison Property Data of Polyphthalamides (PPAs)

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] D. Kemmish: Practical Guide to High Performance Engineering Plastics, Smithers

[2] D. Glasscock: High Performance Polyamides Fulfill Demanding Requirements for Automotive Thermal Management Components, DuPont Engineering Polymers

[3] Eurotec: Tecomid High Performance Compounds

[4] Saechtling Kunststoff Taschenbuch, Hanser