Tuesday, 19 April 2022

Design Properties for Polymer Engineering: Dynamic Mechanical Analysis (DMA) of Reinforced Engineering Polymers

Hello and welcome to a new blog post in which we continue with the DMA data. Today we discuss  reinforced engineering polymers (pls. find here the DMA data of neat resin, and here of high performance polymers)Here you can find the collection of all my posts on design properties for plastics engineering - engineering and high performance polymers.

Reinforcement such as glass fibers can increase thermal and mechanical properties of amorphous and semi-crystalline thermoplastics. 

Example Polyamide 6 (PA 6): neat vs. reinforced polymer

Figure 1 [1] shows an unreinforced Polyamide 6 which has a glass transition temperature of 65°C and a heat deflection temperature (HDT) of 65°C at 1.82 MPa. It can be shown that the modulus declines from 2.81 GPa (pre- Tg) to 0.56 GPa (post-Tg), resulting in a decrease of 80%. 

In the next step we add 14% glass fiber as reinforcements. This amount of glass fibers increases the HDT from 65°C to 200°C at 1.82 MPa. Also, modulus is almost doubled and the decline from pre- to post-Tg is 55% (from 4.46 GPa to 1.98 GPa).

In the last step we add 33% glass fiber reinforcements. In this final case, HDT can be slightly increased to 210°C at 1.82 MPa. However, modulus can be increased to 7.87 GPa and the decline is now below 50% (from 7.87 GPa to 3.99 GPa). 

Figure 1: DMA results of an unreinforced Polyamide 6 and glass fiber reinforced Polyamide 6.

DMA of reinforced engineering polymers (PBT, PA, PC and POK)

Figure 2 shows the elastic modulus of glass fiber reinforced PBT-GF30 (Valox® 420; SABIC), PC-GF20 (Lexan® 3412; SABIC), PA 6-GF30 (Ultramid® B3EG6; BASF), and POK-GF30 (RIAMAXX® HR; RIA-Polymers). 

PBT-GF30 and PA 6-GF30 have a similar elastic modulus behavior over the temperature range. Polyketone with glass fiber reinforcement is superior at lower temperatures, however above room temperature the behavior is similar to Polycarbonate. At higher temperatures (above 150°C), Polyketone is similar to reinforced PA 6 and PBT. 

Figure 2: Elastic modulus of glass fiber reinforced PBT-GF30 (Valox 420; SABIC), PC-GF20 (Lexan 3412; SABIC), PA6-GF30 (Ultramid B3EG6; BASF), and POK-GF30 (RIAMAXX® HR; RIA-Polymers).

All in all, DMA data allow you to decide if the selected material is suitable to fulfill the requirements of your application.

Thanks for reading and #findoutaboutplastics

Greetings, 
Herwig

Interested to talk with me about your plastic 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.
New to my Find Out About Plastics Blog – check out the start here section

Literature: 
[1] https://www.findoutaboutplastics.com/2020/10/rule-of-thumb-for-plastic-part-design.html
[2] M. Sepe: Dynamic Mechanical Analysis for Plastics Engineering, Elsevier
[3] https://www.findoutaboutplastics.com/2020/07/design-properties-for-engineers-dynamic.html
[4] https://www.findoutaboutplastics.com/2018/12/dynamic-mechanical-analysis-dma-as.html

Sunday, 10 April 2022

Carbonated PET Bottles - Saving Material by Optimization Calculation

PET bottle - Learn how to optimize the wall thickness

Hello and welcome to a new post. Today I will discuss with you how to optimize the wall thickness of well- known PET bottles by using safety factors and the stress equations.

What are some requirements for carbonated bottles?

In general, PET drink containers need to contain the pressure of dissolved C02 safely, easy processing via moulding / blow moulding, transparent or translucent, and must be recyclable. PET bottles are the cheapest solution to fulfill the aforementioned requirements. Next best alternative would be PLA which has the lowest embodied energy [1]. 

What equations do we need?

Figure 1 shows the internal pressure situation of a carbonated drink bottle. Tensile stresses along the walls are created  due to the internal pressure p inside the bottle. There are two stresses, the circumferential stress (𝛔c = pr/t) and the axial stress (𝛔a = pr/2t). t is the wall thickness and r is the radius of the bottle. Based on those, we can derive the must-have wall thickness so that the stresses are not leading to bottle failure: t= S [(pr)/(𝛔y)]. S is representing a safety factor and 𝛔y is the yield strength of the wall material. 

Figure 1: internal pressure situation of a carbonated drink bottle. 


Example: wall optimization of carbonated  PET bottle

In literature it can be found that the working pressure of a standard soda PET bottle is 0.5 MPa and has a diameter of 2r = 64 mm. As a safety factor we take 2.5. 70 MPa is the tensile strength of PET at room temperature. 

How thick do we need to make the walls to handle the pressure safely?

We start with our equation from before: t= S [(pr)/(𝛔y)]

t= 2.5 [(0.5x0.032)/(70)] = 0.00057 m = 0.57 mm

The required wall thickness t is 0.57 mm. After consuming your next soda drink in a PET bottle, you can check the wall thickness and see if the bottle already uses as little PET as possible. 

In another post I show how to select the optimal polymer material for an injection / blow moulded water bottle.

Thanks for reading and #findoutaboutplastics

Greetings, 

Herwig Juster

Interested to talk with me about your plastic 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.
New to my Find Out About Plastics Blog – check out the start here section

Literature:

[1] Michael Ashby: Materials and the Environment. Eco-informed Material Choice


Thursday, 7 April 2022

Design Properties for Polymer Engineering: Dynamic Mechanical Analysis (DMA) of Unfilled Engineering Polymers

Hello and welcome to a new post. Today I present to you dynamic mechanical analysis (DMA) data of most used unfilled engineering polymers. 

In a previous post we discussed the storage modulus vs. temperature behavior of different high performance amorphous and semicrystalline polymers. Also how DMA can be used as a polymer material selection tool. Here you can find the collection of all my posts on design properties for plastics engineering - engineering and high performance polymers.

In general, the DMA is a thermo-analytical method that estimates the viscoelastic properties of a given material over the course of different temperatures. It steps away from a single point view toward a multipoint data view which is beneficial for polymer material selection tasks.

Figure 1 shows the elastic modulus of ABS, POM, PBT, and PA 6.6 and Figure 2 shows it for PMMA, POK, PC, and mPPE. 

Figure 1: Elastic modulus of ABS, POM, PBT, and PA 6.6 (all unfilled)

Figure 2: Elastic modulus of PMMA, POK,PC, and mPPE (all unfilled)


Thanks for reading and #findoutaboutplastics

Greetings, 

Herwig

Interested to talk with me about your plastic 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.
New to my Find Out About Plastics Blog – check out the start here section

Literature: 

[1] M. Sepe: Dynamic Mechanical Analysis for Plastics Engineering, Elsevier

[2] https://www.findoutaboutplastics.com/2020/07/design-properties-for-engineers-dynamic.html

[3] https://www.findoutaboutplastics.com/2018/12/dynamic-mechanical-analysis-dma-as.html