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| 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
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
Interested to talk with me about your plastic selection and part design needs - here you can contact me
Literature:
[1] GE Plastics – Moulding Guide
[2] Saechtling Kunststoff Taschenbuch, Hanser-Fachbuch
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. |
Thanks
for reading and #findoutaboutplastics
Greetings,
Herwig
#biopolymers
#herwigjuster
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
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
Literature:
[1]
Designing with Plastics, A practical guide for engineers, Design news, 11.20.06