Wednesday, 30 December 2020

Plastic Part Marking – Overview Codes and Standards

 In this blog post, we have a closer look at the plastic part marking standards and their differences.

I made a short presentation about this topic which you can watch here:



Why Part Marking Codes?

Identification of plastics products is easier with a part marking system. This allows for better decision making for:

  •        handling plastic products,
  •        better waste recovery
  •        more efficient disposal.

Overview of Marking Standards

There are three main standards; however there are additional ones for each of the polymers.

ISO 11469:2016: Generic identification and marking of plastics products

Example: acrylonitrile-butadiene-styrene polymer “>ABS<”

ASTM D7611: Resin Identification Codes (RICs) consisting out of a equilateral triangle, Resin Identification Number, and abbreviated term for polymeric material.

Example:

ISO 1043, ISO 1629 (rubber), ISO 18064 (TPE): Plastics – Symbols and abbreviated terms:

Part 1: Basic polymers and their special characteristics

Part 2: Fillers and reinforcing materials

Part 3: Plasticizers

Part 4: Flame Retardants

Example:


Summary of standards:

 



Thanks for reading and #findoutaboutplastics

Herwig

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

Sunday, 27 December 2020

Find Out About Plastics Blog – The Top 10 Most Watched Posts in 2020

 


The eventful year 2020 is drawing to a close and in this post I present you the top 10 most watched blog posts of 2020.

Starting from highest to lowest rank:

1.  Design Properties for Engineers: Weldline Strength of High Performance Polymers

2.   The Secret of High Performance Polymers: Why They Can Handle High Heat and Harsh Chemicals?

3.     Design Properties for Engineers: Chemical Resistance of High Performance Polymers

4.   EMI Shielding for EVs: Thermoplastic Compounds vs. Coatings – What is Better?

5.  What is the Difference Between an Industrial Designer and a Design Engineer? incl.Polymer Part Design Checklist [Guest Post]

6.     Plastic Part Failure – Part 1: Reasons

7.  Microplastics: What Should We Know About Them and How Are They Impacting Our Life?

8.  Design Properties for Engineers: Coefficient of Linear Thermal Expansion (CLTE) of High Performance Polymers

9.     Plastic Part Failure – Part 2: The Antidote

10. Strategic Sales and Marketing in Plastics Industry: My 2x3 Matrix Approach


Outlook

In 2021, I will continue to present posts which evolve around 4 main categories:

- Polymer material selection

- High performance polymers

- Design properties for engineers

- Rule of Thumbs in polymer engineering

Furthermore, I invite you all to leave topics you would like to read about in 2021 in the comment box below or leave me a short message here.

Last but not least, I would like to thank all readers of my posts!!!

I hope to welcome you next year again.

Thank you and #findoutaboutplastics,

Greetings,

Herwig Juster

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


Tuesday, 22 December 2020

Rule of Thumb for Polymer Processing: The Importance of Melt Uniformity in Injection Moulding

 



In this rule of thumb, we discuss the importance of melt uniformity in injection moulding.

In a previous rule of thumb, we showed that there is a 20% variation in viscosity due to the intrinsic polymer structure (here thefull post). Additionally, non-molten plastic pellets and non-uniformity of melt can cause several more problems in the final part.

Here are some of the problems related to improperly molten resin pellets:

1. Decrease in part performance and increase in part failures

2. Increase of part warpage issues

3. Shot-by-shot filling not uniform, combined with short shots

4. Decrease in weld-line strength

5. Black specs caused by material degradation (dead spots)

20% of part failure can be related to processing. However, the biggest causes for part failure are poor specification and materialmisselection [1].

How to improve melt uniformity?

There are several ways to improve the melt uniformity in injection moulding: changing the injection moulding screw, the use of in-situ monitoring devices such as ultrasonic-based systems, and the processing conditions itself (temperatures, pressures).

General purpose is no purpose and why screw design matters

Let us focus on the change of injection moulding screw. Most moulding machines have a three section screw consisting out of solid conveying, compression, and metering zone. It is commonly referred to as General Purpose (GP) screw. And there it starts the challenge. Often people say that the general purpose screw is a no-purpose screw. Following the pellet melting model of a GP screw, it can happen that not all pellets are melted up. This can cause solid-bed break ups, which in turn decrease the overall mixing quality. Furthermore, material degradation and black specs can occur.

However, there are alternatives and all the major injection moulding machine manufacturers put a lot of focus and resources into developing improved screws. A well-known example is the barrier-screw, which allows the formation of a more homogeneous melt. Also, there is no need of having mixing elements anymore. Barrier screws are double flighted screws and they allow the pinpointing of the location where melting is completed. The aim is to separate the melt from the solid polymer by using a smaller diameter on one of the screw flights. Allover, plasticizing is easier; however it is not suitable for all polymers.

In conclusion, using special screws in injection moulding operations can lead to a reduction of melt temperatures, reduction of backpressure, removal of coloring problems due to non-melted pellets, reduction of screw cleaning operations and reduction of cycle times. Due to the aforementioned advantages, specialized screws pay off already within several months.

Thanks and #findoutaboutplastics,

Greetings and happy Christmas holidays,

Herwig

 If you liked this post, please share and like!


Check out my other rule of thumb posts: 





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://www.findoutaboutplastics.com/2020/11/plastic-part-failure-part-1-reasons.html

[2] Saechtling-Kunststoff-Taschenbuch, Volume 30, Hanser, 2007

[3] https://www.ptonline.com/articles/improve-quality-productivity-with-advanced-screw-design

[4] https://www.ptonline.com/articles/the-melting-precision-of-barrier-screws

[5] https://www.findoutaboutplastics.com/2016/06/polymer-injection-moulding.html


Thursday, 17 December 2020

Polymer Material Selection for Electric Vehicles (xEVs) - Introduction to New Online Course

 


Electrification of vehicles, in particular of private cars, gained momentum in 2020. All major car makers are rolling out their electric vehicle programs. In 2020, the European average CO2 emission target for new fleet cars will be 95 g CO2/km. From 2012 to 2019, the reduction target was 130 g CO2/km. The main driver for this is the regulation (EC) 443/2009.

Electric Vehicles (EVs) offer several advantages such as emission free driving, sourcing of energy in a renewable way, less car parts and reduced maintenance, together with decreased noise polution. This is the overall macro level.

Looking at the micro level, EVs face some roadblocks. One of them being materials. Currently, it is challenging to find the optimal polymers for electric car applications. There are 100 base polymer families which result in 20,000 grades offered by over 500 different suppliers. This is even for a polymer expert a challenge. 


Furthermore, 45% of plasticpart failures are linked to material misselection and poor specification. This was found out in the study of Mr. Wright [1].

Allover, this cannot remain unsolved. Thus I took this as a motivation to create a new online course to provide support in the polymer material selection for EV applications.

New online course

Polymer Material Selection for Electric Vehicles is the name of my new online course, which can be found on Thinkific.

In 42 lessons, split over seven modules I will show you: 

- Why proper material selection is important (Module 1)



- How electric cars work and the main EV architectures (Module 2)


- What are the polymer material requirements, technologies and applications (Module 3)


- The use of commodity polymers, engineering polymers, and high performance polymers for EV applications (Module 4-6)



- How to compare different materials and applications (Module 7)


During the training, we discuss suitable materials from all major material suppliers. This supports you to cut down on the time for finding suitable polymer compounds for evaluation. Time is crucial and development lead time of projects becomes shorter and shorter.

How can I get started?

There is a free preview of different modules available upon registration on the Thinkific platform. This allows you to become familiar with the training system. You can also watch the introduction videos of the different modules.

Altogether, this training course helps you to sort out through the plastics grade jungle and choose the optimal polymer compound for your application.

Let’s do it! - start your training now! 

Additionaly, I made an introduction video which you can watch here:

Thanks and #findoutaboutplastics

Greetings,

Herwig Juster 

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] David Wright, Failure of Plastics and Rubber, 2001, Rapra Technology Ltd.


Sunday, 13 December 2020

Rule of Thumb for Polymer Material Selection: Key Properties of Long Fiber Thermoplastics (LFTs)

 

Rule of Thumb for Polymer Material Selection: Key Properties of Long Fiber Thermoplastics (LFTs)

In this blog post, I present to you another helpful rule of thumb for plastics part design and materialselection.

Long fiber thermoplastics (LFT) – an overview

The pellet size of LFT is between 9 mm and 12 mm. The use of low shear injection moulding enables a 3D network out of long fibers in the part. LFTs are suitable for up-engineering lower cost plastics in order to replace higher cost engineering polymers. Moreover, LFTs are materials for metal replacement and replacement of underperforming polymers.

In the picture above, unfilled Polyamide, 50% short glass fiber PA 6.6 and 50% long glass fiber PA 6.6 are compared to each other with key properties such as HDT, strength, impact, and creep. Long glass fiber PA is outperforming short and unfilled PA in several areas.

When looking at the properties in detail, three of them stick out:

Stiffness: using long fibers will increase the modulus of ductile polymers. Depending on the fiber type (glass, carbon, and natural), different increases are achieved. Furthermore, short term temperature performance will be increased too which is reflected in the higher HDT (heat deflection temperature).  

Strength: increased strength is the result of higher aspect ratio due to longer fiber length. This in turn leads to a higher resistance towards deformation and creep. Fatigue endurance is improved too.  

Toughness: the long fiber network allows transferring impact energy more efficiently between polymer matrices and fibers. Energy dissipation is all over the part and not restricted to an isolated area.  

Additionally, LFTs increase the cyclical fatigue endurance due to the dissipation of stress energy over an extensive part area. The longer fibers decrease crack formation and propagation lowering the overall part failure. 

In addition, properties of LFT are highly process dependent meaning that without taking the process into account no reliable statements about properties are possible. There is always the risk to mill down the fibers when exposed to high screw rotations. Several studies have shown the fiber breakage due to moulding. For creating the 3D network, fiber lengths between min. 1 -5 mm are essential.

Thanks and #findoutaboutplastics

Greetings, 

Herwig

If you liked this post, please share and like!

Check out my other rule of thumb posts: 




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://www.plasticomp.com/long-fiber-benefits/

[2] https://www.solvay.com/en/brands/xencor-long-fiber-thermoplastics/properties

Wednesday, 9 December 2020

Design Properties for Engineers: Water and Moisture Absorption of High Performance Polymers


Design Properties for Engineers: Water and Moisture Absorption of High Performance Polymers


In this blog post, we discuss the water and moisture of high performance polymers.

Important for material selection is the behavior of polymer compounds when they are exposed to water (part immersion) or humid environment. Contact of plastics with water and humidity is possible; however water can diffuse into the plastic and change its physical and dimensional properties. This is depending on the contact time and geometry of the plastic part.

Depending on the polymer, water remains on the surface or it diffuses into the polymer. Diffusion lowers the inter-molecular binding forces and in turn increases the chain mobility. As a consequence, mechanical strength is reduced. Furthermore, electrical and other physical properties are reduced too. Also, dimensional changes occur. Polymers which show a strong volume change (high diffusion rate) are called hygroscopic.

The good message is that most of those processes are physical nature and are reversible by applying a proper drying process. However, when polymers are often exposed to water vapor, the risk of hydrolysis (=chemical reaction in which water molecules rupture one or more chemical bonds and can lead to chain breakage) is much higher compared to normal water exposure.

Measurement standards

Classification of water and moisture uptake is done by using ISO 62 (water absorption 24 hours, 23°C) and/or ASTM D570.

Low water uptake

Among the high performance polymers, fluoropolymers such as PTFE and PVDF take up very low amounts of water. The same is valid for Polyphenylene Sulfide (PPS). Polysulfones (PSU, PESU, PPSU) take up a limited amount of water. Polyarylketones (PEEK, PEK, PEKEKK) absorb low amounts of water too.  Hydrolysis resistance of the aforementioned materials is outstanding. Water vapor sterilization is several times possible without compromising on the properties.

Hygroscopic high performance polymers

On the other hand, Polyimides are hydroscopic. They take up high amounts of water already in normal climate conditions (50% humidity in air). Direct contact with water results in even more water uptake (e.g. PBI: 14%). Hydrolysis resistance is lower compared to PEEK or PPS and as a result cracks are formed over time when exposed to water. If the plastic part is wet and will be rapidly heated (in case of high temperature applications), expansion of water turning into vapor can cause damage to the part.

A small water uptake of PAI is influencing the physical properties immediately: elongation increases more than 10% at 2% water uptake. Impact strength increases 20% compared to the starting point. Sometimes, changes due to water uptake can be an advantage too. There are lots of parts which need to be mounted and in such cases it is beneficial to have more elongation due to water uptake compared to a dry part.

Polyphthalamide (PPA), especially PA6T/6I and long chain PPA (PA9T and PA10T) show much lower water and moisture uptake compared to aliphatic polyamides. 

A word on moisture uptake and dimensional changes after moulding 

Moisture absorption begins in the moment the part leaves the mould (in particular for hygroscopic materials).

As moulded, the moisture content of the part is approximately equal to that of the pellets that went into the moulding machine. Let us assume that e.g. an aliphatic Polyamide such as PA 6.6 is properly dried before moulding, this would place the moisture content for a part produced from unfilled PA 6.6 below 0.20% (referred to as dry-as-moulded).

Water molecules force the polymer chains to increase and this leads to volumetric expansion. The part size increase can be equal to 0.5-0.6% in an unfilled PA 6.6 (at room temperature; higher temperatures results in higher changes). However, glass fiber reinforced compounds can reduce the dimensional changes down to 0.1%.

Thanks and #findoutaboutplastics

Greetings,

Herwig

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) - check out my new online course

Literature:

[1] Erwin Baur, Tim A. Osswald, Natalie Rudolph: Saechtling Kunststoff Taschenbuch, Hanser Munich 

[2] https://www.ptonline.com/articles/dimensional-stability-after-molding-part-4

 



Monday, 7 December 2020

Basics of Plastic Part Failure Evaluation in Injection Moulding

 In this Youtube video we cover the basics of part failure evaluation in injection moulding.


The video is divided into three parts: 1) Types of plastic part failure -Mechanical, thermal, chemical, environmental failures, combined with time 2) Areas of part failure in injection moulding -Premoulding, moulding, postmoulding, and Application (end-use) 3) Failure analysis in injection moulding In injection moulding, problems can occur in one of the four areas: - Raw materials - Additives involved in the material formulation - Injection moulding machine and tool in operation - Process control, settings, and monitoring Furthermore, there are two types of defects in injection moulding: - Moulding defects, occurring during injection moulding (short shots, air entrapment, etc) - Moulded part defects, which are identified after the part was moulded (jetting, weld lines, bubbles, etc). In conclusion, there are several root analysis tools which can be used to identify the problem and develop a solution to solve the moulding problem. Examples are the Pareto chart technique, the 5 Whys, the Fishbone diagram, and the Failure Mode and Effects Analysis (FMEA). Important is to have a systematic approach which helps to diagnose and solve part issues of the injection molding operation. Greetings and #findoutaboutplastics Herwig

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) - check out my new online course

Friday, 4 December 2020

Rule of Thumb for Plastic Parts: 4 Factors Impacting Plastic Part Performance

 


In this blog post, I present you another rule of thumb for your daily polymer engineering operations.

There are several factors which impact plastic part performance. Altogether, we can divide them into four major categories [1]:

- Material and materialselection: 45% of cases related to part failure [2], are due to wrong material selection, together with insufficient specifications.

- Component design: there are 10 basic design rules [3] which serving as a helper when designing for injection moulded products:

1. Wall thickness as thin as possible

2. Continuous wall thickness to prevent accumulation of mass

3. Corners and edges with radius

4. Ribs designed for moulding: 40-60% of wall thickness for ribs

5. Avoid plane and even surfaces

6. Use draft angels 

7. Avoid undercut sections

8. No more accurate machining as necessary

9. Check for possibilities of function integration

10. Past performance of design can be guarantee of future results

- Part processing and assembly: depending on the processing technique involved, it is important to take proper care of the material (e.g. drying), mould (e.g. temperatures), machine conditions (e.g. temperatures).

- Service conditions of the part: this is linked to the first point “material”. If the requirements are well explored, then specifications are properly set which in turn allows optimal material selection. If e.g. the continuous service temperature is too high, reduction of mechanical properties may occur, together with material degradation.  

The four categories are schematically shown in the above figure.

In case of a plastic part failure, several factors combined lead to failure and it is rare that a single factor leads to part failure.

Therefore, keeping all four categories in mind during part design will reduce part failure and allow you to get the best performance out of your part.

Thanks for reading and #findoutaboutplastics

Greetings, 

Herwig 

If you liked this post, please share and like!

Check out my other rule of thumb posts: 




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) - check out my new online course

Literature:

[1] Jeffrey A. Jansen: Finding Fault, applianceDESIGN, 2006

[2] David Wright: Failure of Plastics and Rubber Products, Rapra, 2001

[3] https://www.findoutaboutplastics.com/2018/04/plastics-part-design-10-holy-design.html


Friday, 27 November 2020

Plastic Part Failure – Part 2: The Antidote

 


Welcome back to the second part of the blog post series “why plastic parts fail”.

Here you can jump to the first part and here to theYouTube video.

In part 1 of this series we discussed the types of plastic part failure such as environmental, thermal, chemical, mechanical failures, as well as time overarching all previous four types. Among the causes of failure we discussed the phenomenological and human related viewpoints [1].  We learned that among the phenomenological viewpoints, environmental stress cracking (ESC) is the major reason for plastic part failure. Among the human related failures, material misselection and poor specification are the main drives for failure.

Here, we focus on one of the most effective antidotes for battling plastic part failure.

Polymer Material Selection (PoMS) as a way to reduce failure

There are almost 100 generic “families” of plastics. Blending, alloying, and modifying with additives results in 1,000 sub-generic plastic types [3, 4]. The total number of grades is not known, however estimates range between 20,000 and 30,000 named grades covered by 500 suppliers [3]. When you add up the two factors “material misselection (45%)” and the diversity of plastics, you can see that it is a challenge, even for experienced people, to find the optimal polymer material for the application.

Successful plastic material selection includes the understanding of plastic material characteristics (amorphous vs. semi-crystalline thermoplastics), the specific material limitations, and failure modes. Furthermore, the application requirements such as mechanical, thermal, environmental, chemical, electrical and optical requirements need to be taken into account.

Furthermore, production factors (selection of the most efficient method of manufacture in relation to part size and geometry), together with economics (material cost vs. density, cycle times and part price) need to be considered too.

The Polymer Selection Funnel - A Systematic Approach

Enabling a systematic way for polymer material selection, I created the “Polymer Selection Funnel” framework.

The framework consists out of four funnel steps (Figure 1).


Figure 1: the four funnel steps for systemic polymer material selection and testing 

Let us discuss each phase briefly.

The information gathering phase:

In material selection, preparation is the be-all and end-all. In this phase it is important to collect as much information on environmental conditions (consider the trinity of thermal, chemicals and time, Figure 2), part cost estimations, agency approvals, industry specifications, just to name a few.


Figure 2: the environmental trinity

Funnel stage 1: Material selection factors

In this first stage we map out the true part functions and material requirements. After this we translate the requirements into material selection factors.

This can be done with the support of questions such as what load does the plastic part need to carry? Or/and will the part be exposed to chemicals?

At the end of stage 1 you have a clear picture on the material requirements which can be summarized in a work sheet as material selection factors.

Funnel stage 2: Thermoplastic vs. Thermoset

After translating the requirements into material selection factors, the first decision is made:

Which is the most suitable polymer chemistry to fulfill the listed requirements and selection factors?

In the funnel methodology, this stage is supported by a decision tree (Figure 2). It has two main paths: the thermoplastic and the thermoset path. The thermoplastic path is further split into making a decision about selection of amorphous or semi-crystalline polymers. In the end of this funnel stage, between two and three materials are obtained as input for the third funnel stage.


Figure 2: decision tree of funnel stage 2

Funnel Stage 3: selection discussion with worksheet

The third funnel stage represents a core element in the whole material selection funnel. It is a detailed selection discussion with a worksheet. I call it the decision matrix analysis and it ranks all of the pre-selected polymers. The decision matrix analysis consists of five steps. The base calculation principle is a scoring of each of the pre-selected materials for each of the material selection factors. In the end we add up all weighted scores for each material. The material with the highest score is most suitable for selection and further investigation in the fourth stage.

Figure 3: decision matrix analysis of funnel stage 3

Funnel stage 4: Testing, Material and Vendor Selection

In the last funnel stage, we would like to know in detail how the materials with the highest scores perform as a final part in a system of plastic parts or as a single plastic part alone.

For this, we can set up testing in the real (=laboratory and environmental) domain as well as in the virtual domain (processing simulation and mechanical analysis). In case of the real domain, prototyping needs to be done. There are several companies specializing in providing fast tooling and parts out of the selected materials for further tests.

In this phase, the material suppliers can be already involved. The costs of system validation are high and therefore the material from one supplier, maximal two may be evaluated.

After all the tests are done and the material has passed all tests, commercial conditions with the material supplier can be finalized and first small serial production can start.

Conclusions and Lessons for Polymer Material Selection

There are several different approaches on how to select polymeric materials for applications. On the basis of all material selection processes is a fundamental understanding between the nature of polymeric materials and traditional engineering materials such as metals.

Having a systematic approach for the polymer material selection reduces part failure. Furthermore, the time and effort of engineers and designers is limited and therefore knowledge transfer needs to be as efficient as possible. Here again, a systematic approach is useful for efficient communication within the project team and external partners such as material suppliers.

Another key element for efficient knowledge transfer is the, what I call the Polymer Product Pentagram (Figure 4): the optimal outcome occurs when part designer, material supplier, mould maker and injection moulder work together in a collaborative way.


Figure 4: overview of the Polymer Product Pentagram 


Learn more about PoMS and the Polymer Selection Funnel

If you have interest in learning the detailed execution of all the funnel steps for systematic polymer material selection, then have a look at my online course “Polymer Material Selection” on the platformThinkific.

In a few hours you will learn everything you need to select the optimal polymer material for your project, will save thousands of dollars by preventing part failure, and will have fun in the process.

There are also free chapters available to start the training immediately. This allows you to get a feeling if this course is interesting for you. 


Greetings and #findoutaboutplastics

Herwig Juster

If you liked this post, please share and like!

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) - check out my new online course

Literature:

[1] David Wright: Failure of Plastics and Rubber Products Causes Effects and Case Studies Involving Degradation, 2001, Rapra Technology Ltd.

[2] https://www.space.com/31732-space-shuttle-challenger-disaster-explained-infographic.html

[3] Jenny Cooper et.al. : Why Plastic Products Fail, Smithers Rapra Technology Ltd. 2010

[4] Ezrin Myer: Plastics Failure Guide - Cause and Prevention, 1996, Hanser

[5] https://www.findoutaboutplastics.com/2018/03/polymeric-material-selection-critical.html