Polymer Material Selection: Pre-Selection of Thermoplastics

Hello and welcome to this post. Today I will discuss with you a practical approach on how to pre-select thermoplastics for your application.

In a past post I touched on some rules of thumb for making an educated guess on plastics material selection and in this post we will add another approach into our plastic selection toolbox.

Thermoplastics can be divided into amorphous and semi-crystalline morphology. Amorphous polymers are transparent or translucent, whereas semi-crystalline polymers are opaque. If you need a transparent part, then selecting an amorphous polymer is the path forward. Flexible polymers with a Young’s Modulus of < 1500 MPa are always semi-crystalline. Amorphous polymers can only be used below their glass transition temperature (Tg) and therefore have always a stiff behavior up to their Tg. If you need flexible and transparent polymers, amorphous Polyamide can be an option when working with additives (clarifiers) helping to make a semi-crystalline transparent. 

Maximum use temperature and Young’s modulus

In the table below are amorphous and semi-crystalline resins shown, together with the Young’s modulus and maximum use temperature as selection criteria. All the values are for orientation and further investigation for proper material selection needs to be done (for example, mechanical properties over different temperatures). Detailed data can be found in the Technical Data Sheets (TDS) of material suppliers or in material databases. Also on my blog, I have several engineering data in particular for high performance polymers listed.

Polymer material selection: pre-selection of thermoplastics by using maximum use temperature and Young's modulus

Thanks for reading and #findoutaboutplastics,

Herwig

#polymerMaterialSelection #herwigjuster

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

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Literature:

[1] M. Bonnet: Kunststofftechnik: Grundlagen, Verarbeitung, Werkstoffauswahl und Fallbeispiele

Why Plastic Parts Fail & How to Prevent Failure [Infographic]

 

Why Plastic Parts Fail & How to Prevent Failure [Infographic] by Herwig Juster

Thank you for reading and #findoutaboutplastics

Greetings,

Herwig

 #polymerMaterialSelection #herwigjuster

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

My YouTube channel

Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course

Enroll here for watching the free parts of the course

Polymer Processing – Resin Moisture After Drying (Support Table)

 Hello and welcome to this blog post on resin drying before processing them. In this post I provide you with a drying table of the most used polymers which can support you in your processing operations.

A word on resin drying

If material is not properly prepared for processing operations such as injection moulding, the moisture will break down the polymer in the barrel at the processing temperatures. In general, this is referred to as hydrolysis.

This can occur for many different polymers, including:

-Polyamides (all types)

-Polyesters (PET, PBT)

-Polycarbonate

-Polysulfones

-Polyurethanes

 

There are five keys to remember which ensure good drying of resins [1]:

1. Pellet / regrind incoming moisture level

2. Air temperature

3. Dewpoint/ Desiccant

4. Residence time

5. Air flow

In this video below here, I discuss the topic of material drying and troubleshooting of moisture streaks in detail:

 

The table below shows the different maximum moisture levels after resin drying to ensure proper processing.

 

Table: maximum moisture content after resin drying of most used polymers

Analyzing the moisture level after drying can be done over a Carl Fischer titration (lab equipment needed) or over the Tomasetti’s Volatile Indicator (TVI). The TVI represent a more practical approach since you need only a hot plate and a glass plate to place the pellets after drying. The temperature of the hot plate is increased till the pellets melt and then it is important to check if there are bubbles. The bubbles are an indicator for moisture and there can be few bubbles (0.02-0.03% moisture), numerous bubbles (0.05-0.1% moisture), or many large bubbles (moisture above 0.1%) or no bubbles at all (dry material). If you do not have a hot plat you can also use the heater band of the injection moudling machine. 

Thank you for reading and #findoutaboutplastics

Greetings,

Herwig

 #polymerprocessing #herwigjuster

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

My YouTube channel

Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course

Enroll here for watching the free parts of the course

Literature:

[1] GE Plastics – Moulding Guide

[2] Saechtling Kunststoff Taschenbuch, Hanser-Fachbuch

Composting Biodegradable Polymers – Helpful Standards

Hello and welcome to this blog post on biodegradable plastics and their related standards. In one of my last blog posts we discussed the difference between the standards EN16785-1 (bio-based content) and ASTM D6866/EN 16640 (bio-based carbon content). Today we have a closer look at ASTM D6868, ASTM D 6400, EN 13 432, ISO 17 088 and what it means for composting biodegradable polymers.

In general, biopolymers can be biodegradable or non-biodegradable as well as made from renewable sources or from fossil-based resources. This is shown in Figure 1 below.

Figure 1: Overview classification of biopolymers [1].

Standards for composting of biodegradable polymers

Apart from the estimation of the bio content, clarification of compostability after usage of the product is the next key topic for biodegradable plastics.

In Table 1, the most important ASTM / EN standards are shown to help you guide through the jungle of standards.

For example, ASTM D6868 standard is used for labeling of products that consist out of biodegradable plastics and polymers together with paper and other carriers intended for aerobically composition in municipal or industrial facilities. The products also include packaging applications. Performance of the materials in terms of compostability or biodegradability is not covered by this standard, only labelling.

Table 1: standards for composting of biodegradable polymers.

Update: ISO 17088 has been revised in 2012 and more recently in 2021.

Thanks for reading and #findoutaboutplastics

Greetings,

Herwig

#biopolymers #herwigjuster

 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

My YouTube channel

Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course

Enroll here for watching the free parts of the course

Literature:

[1] https://bpiworld.org/page-190424

[2] https://www.astm.org/Standards/D6868.htm

[3] https://bpiworld.org/page-190422

[4] https://docs.european-bioplastics.org/publications/bp/EUBP_BP_En_13432.pdf

[5] https://www.iso.org/standard/43373.html

Rule of Thumb in Plastics Design: Selection of Maximum Short-Term Operating Temperature

 Hello and welcome to a new rule of thumb blog post. Today we discuss how to select the maximum short-term operating temperature for your plastic part.

In general, it is acceptable to use a temperature which is between 7°C to 12°C below the Heat Deflection Temperature (HDT) of the finished resin as the maximum short-term operating temperature.

HDT tells us the short-term heat resistance of the selected material, which shows a certain amount of deformation under the load of 0.455 MPa or 1.82 MPa (tensile bar). Therefore, using the HDT minus some degrees in temperature is a good practical way to estimate the maximum short-term use temperature.

Greetings and #findoutaboutplastics

Herwig

#RuleofThumb #HerwigJuster

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

My YouTube channel

Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course

Enroll here for watching the free parts of the course

Literature:

[1] Designing with Plastics, A practical guide for engineers, Design news, 11.20.06