Friday, 24 March 2023

Polymer Selection Funnel Example - Vacuum Cleaner Canister and Canister Holding (Example Electronics Consumer Goods)

Hello and welcome to another polymer materials selection example using the Polymer Funnel methodology. In this post we discuss the selection of a vacuum cleaner housing. Figure 1 presents the four different stages of the material selection funnel and this overview serves us as a guideline.

Figure 1: Polymer Selection Funnel - overview of the four different funnel stages 

Global Electronics Consumer Goods Market

The global electronics consumer goods market has a predicted growth rate of around 6% CAGR till 2030 and can be split into four major segments: 

Household appliances are the largest segment. Leading polymers are Polyolefins (PE, PP), Polystyrene PS, Acrylonitrile butadiene styrene ABS, Polycarbonate PC, Polyvinyl Chloride PVC, Polyamide PA, and Poly(methyl methacrylate) PMMA. 

Polymer material selection for vacuum cleaner canister with canister holding

Figure 2 shows a bagless canister vacuum cleaner. The transparent canister is attached to the upper holding element allowing for easy removal and cleaning. Task is to select the optimal material for the canister and the holding element. 

Figure 2: Example of a vacuum cleaner with transparent canister and canister holding

Funnel stage 1: Material selection factors

In Funnel stage 1 we assess the canister and holding requirements:

  • Good Surface Quality & Paintability and high surface gloss

  • Scratch Resistance

  • Colorability for housing parts

  • High flowability, 

  • Dimensional stability, 

  • Good heat resistance

  • Thin wall capability (reduction of material usage and part weight ->> easy handling)

  • Impact behavior

  • Recyclability

The canister itself needs to be transparent, allowing to check the dust filling level. The holding element requires no transparency. 

Table 1 summarizes the important requirement information with quantitative and qualitative values (requirement worksheet).

Table 1: Requirement worksheet for the vacuum cleaner parts.

Funnel stage 2: Decision on thermoplastic or thermoset

In Funnel stage 2 we decide between the thermoplastic and thermoset material route. Transparency and flowability can be fulfilled by both classes, however thin wall stability with good impact behavior and recyclability is better achieved by thermoplastics. Therefore, a first material screening is done and grades for both parts are summarized in Table 2. 

Table 2:  Overview preselected grades and their commercial suppliers.

Funnel stage 3: Selection discussion with worksheet (qualitative matrix analysis)

Now we reached the core element of the Polymer Selection Funnel: the selection discussion by using qualitative matrix analysis. In the first step we take the requirements from Table 1 and insert them on the top of the matrix table. This is followed by giving them a priority number (0= low priority; 5= high priority). After this we add the materials from Table 2 followed by a ranking of each material for each requirement (how good can this requirement be fulfilled? 5= perfect). Then we multiply each requirement priority number with the fulfillment number and add them up. In the end we have on the right side a ranking of the selected materials. In our case, for the canister holding part,  ABS (118HF) has the highest number (85), followed by ABS (LX-0951) with 81. for the transparent canister itself, transparent ABS reached 80 points and PMMA 76 points. They are close to each other and for Funnel stage 4, both can be tested. The same is valid for the canister holding part. ABS (118HF) and ABS (LX-0951) can be tested. 

Table 3: Qualitative matrix analysis for canister holding part
Table 3: Qualitative matrix analysis for the canister

Funnel stage 4: Testing, selection of material and vendor

We reached the final Funnel stage and started with material evaluations, followed by producing prototypes for functional tests. After completion of all tests, the final decision can be done. In our case, ABS (118HF) was selected for the canister holding part and transparent ABS (LX-0951) for the canister itself. 

Check out more polymer material selection examples: baby bottles and plumbing water pipes.

Thanks for reading and #findoutaboutplastics

Greetings Herwig

Herwig Juster

Interested to talk with me about your polymer material selection, sustainability, 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.












Tuesday, 21 March 2023

2 Component Injection Moulding: How TPS (SEBS) Can Stick to Polyamide or Polycarbonate Without Using Additional Adhesive?

Overmoulding PA and PC with PC - 2 component moulding

Hello and welcome to a new blog post in which we discuss how TPS can stick to Polyamide or Polycarbonate in 2 component injection moulding. 

During polymer material selection, one scenario can be that a solid plastic housing, made out of Polyamide, needs to have a sealing moulded on it. The selected sealing material is a styrene-ethylene-butylene-styrene (SEBS) from the thermoplastic elastomer class. A two-phase block copolymer with hard and soft segments forms the basis of SEBS. 

SEBS (Figure 1)  is used in different applications such as footwear, and seals which have low requirements towards chemicals and (heat) aging. Furthermore SEBS has excellent weatherability making it useful for many outdoor applications. It is also known for its ability to uptake oil and soften its Shore hardness. SEBS is non-polar leading to a harder adherence on polar polymers such as Polyamide. 

Figure 1: Structural formula of SEBS.

How can we increase the adherence of SEBS towards PA and PC?

There is a chemical trick one can apply: grafting maleic anhydride (= acid anhydride of maleic acid) onto the ethylene butadiene mid-blocks allows for better connection. The functional groups enable an adherence to polar PA or PC. 2 component overmoulding applications can be done and no additional usage of adhesives is needed.

Thanks for reading!


Herwig Juster

Interested to talk with me about your polymer material selection, sustainability, 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.




Monday, 6 March 2023

Rule of Thumb - Residence Time and Temperature Profile of Engineering Polymers

Hello and welcome to a new Rule of Thumb post. Today we discuss the importance of melt temperature and residence time of engineering polymers. Here the link to the residence time of high performance polymers. 

Melt temperature - injection moulding 

In general, melt temperature and residence time of the polymer melt are strongly linked and have a high impact on reaching the mechanical properties of your part. It is best to follow the recommendation of the material supplier for the optimal melt temperature. For example, if you decrease the melt temperature 10 Kelvin, starting from the recommended optimum value, tensile strength and elongation can drop 25 %. Reason are unmolten particles which enter the final part during moulding and cause a drop in mechanical properties.  On the other side, a 10 Kelvin increased melt temperature is not as critical as the lower temperature profile. The final part still will have 95% of the mechanical properties. The polymer melt can handle short increases in temperature which in turn leads to a better flow profile too. 

Residence time of engineering polymers - injection moulding 

Next to the temperature is the residence time. The biggest impact on the residence time has the size of your plasticizing unit and its optimal selection. If you have a high metering stroke, residence time is low. If you have only a small metering stroke, residence time will be up and you have to check if you are not above the maximum residence time of the polymer. It can encounter this by using an increasing temperature profile on your plasticizing unit. Figure 1 shows the maximum residence levels of different engineering polymers. POM and TPE can have high residence times (up to 30 minutes) and Polyesters (PET, PBT, PC) should not be much above 6 minutes in total residence time (including hot runners if applicable). 

Figure 1: residence time (minutes) of most used engineering polymers. 

I created also calculation tools which allows you to estimate the residence time for injection moulding and extrusion - here the link

Thanks for reading and #findoutaboutplastics


Herwig Juster

Interested to talk with me about your polymer material selection, sustainability, 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.


[1] Kunststoff Taschenbuch - Hanser

[2] Serie Kunststoffpraxis Teil 12: Verweilzeit und Temperaturprofil - Plastverarbeiter 

Wednesday, 1 March 2023

Long Fiber Plastic Processing - How to Not Make Long Fibers Short (Rule of Thumb Series)

Hello and welcome to this blog post which is part of our Rule of Thumb series. Today we discuss the processing of long glass fiber plastic compounds using injection moulding. 

Long glass fiber (LFT) plastics 

LFT compounds have a fiber length between 9 mm and 12 mm and most are produced via pultrusion technique. Aim in processing is to keep the fiber length as long as possible since it is needed to build up a 3D-network consisting out of entanglements. Having an entangled system allows for high impact and strength properties as well as increased thermal performance of the final part. 

How to not make Long Fibers short - processing recommendations

In general we have to avoid excessive fiber breakage during all phases of injection moulding in order to have a long enough fiber length to form an entangled three dimensional network. 

1. Injection moulding setup: the feed hopper must be large with a slope angle of 45°; the hopper flanges do not need to be cooled and it is enough to have the same temperature as the feeding section of the barrel. A general three section screw can be used (screw diameter above 35 mm), however if possible use a longer feeding zone (> 60% of total length; compression and metering section 20 % length). Regarding the compression ratio, 2:1 or 2.5:1 is recommended. Avoid the use of mixing and shear elements along the screw sections. There are long-fiber screws available and they dramatically improve fiber length. Figure 1 compares the fiber length reduction over the different screw sections of a long-fiber screw and a standard 3 section screw. 

Figure 1: Glass fiber length reduction of a long-fiber screw and a standard screw [3]

2. Processing temperatures: in terms of processing temperature it is advantageous to have a temperature above the melting temperature before the compression section, together with the avoidance of shear heating. Avoid shut-off valves since they induce fiber breakage. Reduction of shear can be achieved by using a flat or reverse barrel temperature profile. Aim to ease melting in the compressing section. 

3. Plasticizing unit: keep the screw speed rotation in a low to medium range (< 100 RPM) together with low back pressure (0 to 10 bars). 

4. Injection moulds: reduction of glass fiber breaking is achieved by using large gate sizes (>80% of wall thickness). Proper venting of the tool will support weld line quality of the final part. Hot runner system can be used, however shut-off valves are not recommended.

5. Recycling: using post industrial waste or post consumer waste is possible up to 10 weight %. 

Additionally, most LFT parts I have seen had a fiber length between 2-3.5 mm and it was efficient enough to have 1.5 mm in average length for good strength properties. With 1.5 mm already ~80% of the strength was reached and after that it leveled off into a plateau with increased fiber length.

Key properties of LFT compounds can be found here and more Rule of Thumb posts here.

Thanks for reading and #findoutaboutplastics


Herwig Juster

Interested to talk with me about your polymer material selection, sustainability, 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.




[3] K. Kikikawa History of development of injection molding machine technologies and future perspectives