Today's KNOWLEDGE Share: The Injection Molder’s Most Important Job

Today's KNOWLEDGE Share:

The Injection Molder’s Most Important Job

What is the most important job of the injection molder? Ask people in the plastics industry, and you will get a variety of answers.

·  Produce parts to the part drawing dimensions.

·  Keep the supply chain fed with parts.

·  Produce parts at low cost.

·  Parts with acceptable cosmetic appearance.

As significant as these functions are, I believe the most important and fundamental role of the injection molder is to protect the integrity of the plastic material. A particular resin was chosen for a part for a reason – because it satisfied the requirements of the application. The injection molding process can have deleterious effects on the properties of the molded part material – mechanical, thermal, chemical, electrical, environmental, and physical.

Injection molding is a very complicated manufacturing process. Some plastics industry leaders suggest forming plastic parts through injection molding is the most difficult of all manufacturing processes, regardless of material.

Think about the complexity of this process. There are so many factors to take into consideration in taking a number of individual solid plastic pellets of comparatively high molecular weight, homogenizing them, getting them to a viscosity low enough to flow through thin runners and gates, and then converting them into a solid of entangled polymer chains. This is not easy. So many things can go wrong when injection molding plastics. In the course of performing thousands of failure analyses, I have seen countless instances where the molder did not sufficiently take care of the resin, which led to premature product failure. Some of the things I have seen go wrong include:

·  Contamination

·  Voids

·  Molecular Degradation

·  Skin Effects / Delamination

·  Poor Fusion / Poorly Fused Knit Lines

·  Under-crystallization

Have I missed any that you have seen?

Remember this: the molder should focus on taking care of the material through processing, regardless whether they are a contract molder or a captive molder.

Source:Jeffrey A. Jansen | The Madison Group

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#plastics #plasticsengineering #polymers #manufacturing #materialsscience #injectionmolding #failureanalysis 

Today's KNOWLEDGE Share: Types of HYDROGEN:

 Today's KNOWLEDGE Share:

Types of HYDROGEN:
Low carbon hydrogen from water electrolysis using renewable power:green

Low carbon #hydrogen from water electrolysis using nuclear power: pink

Low carbon hydrogen from natural gas using reforming with #CCS: blue

Low carbon hydrogen from coal #gasification with CCS: purple

Low carbon hydrogen from #naturalgas pyrolysis and solid carbon production: turquoise

Visit MY BLOG https://lnkd.in/fcSeK9e
#hydrogeneconomy #hydrogen #greenhydrogen #bluehydrogen

Wearable patch can painlessly deliver drugs through the skin

Using ultrasonic waves that propel drug molecules into the skin, the patch could be used to treat a variety of skin conditions.

The skin is an appealing route for drug delivery because it allows drugs to go directly to the site where they’re needed, which could be useful for wound healing, pain relief, or other medical and cosmetic applications. However, delivering drugs through the skin is difficult because the tough outer layer of the skin prevents most small molecules from passing through it.

In hopes of making it easier to deliver drugs through the skin, MIT researchers have developed a wearable patch that applies painless ultrasonic waves to the skin, creating tiny channels that drugs can pass through. This approach could lend itself to delivery of treatments for a variety of skin conditions, and could also be adapted to deliver hormones, muscle relaxants, and other drugs, the researchers say.

“The ease-of-use and high-repeatability offered by this system provides a game-changing alternative to patients and consumers suffering from skin conditions and premature skin aging,” says Canan Dagdeviren, an associate professor in MIT’s Media Lab and the senior author of the study. “Delivering drugs this way could offer less systemic toxicity and is more local, comfortable, and controllable.”

MIT research assistants Chia-Chen Yu and Aastha Shah are the lead authors of the paper, which appears in Advanced Materials, as part of the journal’s “Rising Stars” series, which showcases the outstanding work of researchers in the early stages of their independent careers.

A boost from sound waves

The researchers began this project as an exploration of alternative ways to deliver drugs. Most drugs are delivered orally or intravenously, but the skin is a route that could offer much more targeted drug delivery for certain applications.

“The main benefit with skin is that you bypass the whole gastrointestinal tract. With oral delivery, you have to deliver a much larger dose in order to account for the loss that you would have in the gastric system,”

Ultrasound exposure has been shown to enhance the skin’s permeability to small-molecule drugs, but most of the existing techniques for performing this kind of drug delivery require bulky equipment. The MIT team wanted to come up with a way to perform this kind of transdermal drug delivery with a lightweight, wearable patch, which could make it easier to use for a variety of applications.

The device that they designed consists of a patch embedded with several disc-shaped piezoelectric transducers, which can convert electric currents into mechanical energy. Each disc is embedded in a polymeric cavity that contains the drug molecules dissolved in a liquid solution. When an electric current is applied to the piezoelectric elements, they generate pressure waves in the fluid, creating bubbles that burst against the skin. These bursting bubbles produce microjets of fluid that can penetrate through the skin’s tough outer layer, the stratum corneum.

“This works open the door to using vibrations to enhance drug delivery. There are several parameters that result in generation of different kinds of waveform patterns. Both mechanical and biological aspects of drug delivery can be improved by this new toolset.

Source:MIT NEWS OFFICE

Today's KNOWLEDGE Share:Yellowing of Polycarbonate

Today's KNOWLEDGE Share:

Yellowing of Polycarbonate

Because of the molecular structure of polycarbonate, the polymer is susceptible to yellowing through a variety of degradation mechanisms. Discoloration of polycarbonate can occur through oxidation, either during processing or as a result of elevated temperature exposure in air. Yellowing can also take place through sterilization, such as autoclaving, radiation, or ethylene oxide. Further, polycarbonate is highly susceptible to yellowing through ultraviolet radiation (UV) exposure.

When polycarbonate is exposed to ultraviolet radiation as sunlight, yellowing can take place rapidly. This discoloration is principally a surface phenomenon, approximately 25 micrometers deep, due to the penetration depth of the UV radiation into the polycarbonate.

 

Yellowing within polycarbonate occurs as a result of the formation of degradation breakdown products that absorb in the yellow range of the visible light spectrum. This includes substituted ortho-quinones, quinone methides, phenones and phenone derivatives, and bisphenol-A derivatives. Analytical techniques, including gas chromatography-mass spectroscopy (GC-MS) and Fourier transform infrared spectroscopy (FTIR), have been used to study the degradation mechanisms and characterize the breakdown products. 

 

The yellowing of the polycarbonate is accentuated by the high level of transparency, which results in a strong yellow hue.

The effects of UV exposure, as well as oxidation and hydrolytic degradation, can be assessed through accelerated aging followed by color evaluation and physical/mechanical testing. Contact me to see how this can benefit you.

Souce:The Madison Group

Visit MY BLOG http://polymerguru.blogspot.com

#plastics #failureanalysis #uv #degradation #discoloration #yellowing #polycarbonate #testing #ftir #phenone

Today's KNOWLEDGE Share:Lightning damages the fuselage of a Boeing 787-9!

Today's KNOWLEDGE Share:

Lightning damages the fuselage of a Boeing 787-9! 

An American Airlines Boeing 787 Dreamliner needs repairs after a lightning strike significantly damaged its fuselage. The incident happened Monday, February 20th, when N839AA, a 787-9, was traveling from Tokyo to Dallas/Fort Worth. The aircraft is reportedly being worked on to be restored back to operational condition! 

Despite a strong and thick fuselage, the 787 reportedly has a known issue with lightning strikes. In 2019, Boeing reduced lightning protection in the wings of some 787s to reduce costs and speed up deliveries, but the company reportedly said that safety was not compromised. In May, a Jetstar 787 was grounded after sustaining extensive damage from a lightning strike.

Source: Simpleflying/ #managingcomposites #thenativelab

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#aerospace # #aircraft #airlines #boeing #safety #composites #boeing787

Today's KNOWLEDGE Share: Shear Rate

Today's KNOWLEDGE Share:

Shear Rate

Sorry to disappoint some of you, but there is NO such a thing as Maximum admissible Shear Rate for a material in Injection Molding.

 

30+ years back, Colin Austin (Moldflow founder) wanted to put a recommendation in the code documentation and, having no clear answers from suppliers ,he decided to list some values that were loosely based on a wild guess exercise. Actually an estimated typical shear rate (at some standard T) for a critical Shear Stress equal to an arbitrary fraction (abt 10%) of a Stress at break in the solid state. How wild is that ??

Shear rate does not destroy a polymer.

If chains break, that is due to Shear Stress, not shear rate. If they degrade thermally, it is the result of accumulated shear-heating along the flow. In both cases, shear rates alone CANNOT resolve the risk of damaging the material.

At low temperature (high viscosity hence higher stress) a lower shear rate can be more dangerous than a higher rate at a higher temperature (lower viscosity so potentially much lower stress).

So if you want to say something about the injection rate being too fast, check the stresses or the melt temperature increase. A high shear rate will be a warning signal, at best.

Source:VITO LEO

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#plastics #injectionmolding #shear #stress #melt #viscosity #temperature