Today's KNOWLEDGE Share:Lubricant:

Today's KNOWLEDGE Share:

Lubricant:

Some molding compounds contain a so-called "external lubricant". It is essentially a second immiscible polymeric material with a much lower viscosity.

What happens when you mold such materials ?

In extrusion things are quite obvious. The hydrodynamic forces push the dispersed lubricant to the surface of the die where they can act as expected and promote slip of the major phase polymer.

In Injection Molding the combination of the Fountain flow, moving inner flow layers to the very edge, and the presence of a frozen skin, create a more complex situation.

The high shear layer where lubricant will accumulate is INSIDE the frozen skin ! While this can still help to reduce the pressure to fill, this situation will also induce a serious risk of blistering/delamination.

This delamination was well known for instance in the Xenoy grade made of PC/PBT. But other compounds, containing for instance a silicon based lubricant, will produce the same result, as reported by some of my customers.

So, keep in mind that the lubricant (possibly necessary at the outer surface of the molded part if the intention is to control friction coefficient) doesn't quite go where you'd hope to see it.

Note that this delamination can also occasionally be observed in pure HDPE if the molecular weight is high enough. In this case the low molecular tail (waxes) will accumulate at the frozen skin interface, promoting delamination.

Source:Vito Leo

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#injectionmolding #lubrication #plastics #polymerscience #medicaldevices #delamination #extrusion

Today's KNOWLEDGE Share:Failure Analysis of PC hub

Today's KNOWLEDGE Share:

Failure Analysis of PC hub

I recently completed a failure analysis on a polycarbonate hub used to secure a steel tube. A number of parts had cracked while undergoing engineering use testing in the laboratory. The fractographic examination, which included scanning electron microscopy (SEM), revealed fracture surface features that indicated that the parts failed though the application of stress at a high strain rate. It was concluded that the engineering testing produced rapid mechanical overload, in which the stresses exceeded the short-term strength of the material. Plastic materials, including polycarbonate, can undergo a ductile-to-brittle transition associated with high strain rate events.

The high strain rate failure mechanism was specifically identified in the SEM images by the presence of features known as river markings. They extended out from and bounded the crack origin. The crack origin area also displayed a relatively smooth texture, which was indicative of a brittle fracture mode. The cracking initiated with a design corner (yellow circle), which likely acted as a point of stress concentration.

Source:The Madison Group

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#failureanalysis #plastics #fractography #SEM #polymerscience #materialsscience #polycarbonate #plasticengineering #crack #stress #fracture

Today's KNOWLEDGE Share: TYPES OF FIBERS

Today's KNOWLEDGE Share:

TYPES OF FIBERS

The different fiber types that can be used as reinforcement phases in composite materials.

Today we would like to share with you the definitions and examples of the most common fibers used in the industry! 

Carbon fibers are long and thin strands of material with about 0.005-0.010 mm in diameter, composed mostly of carbon atoms (more than 90% content). The carbon atoms are bonded together in microscopic crystals that are more or less aligned parallel to the long axis of the fiber. The crystal alignment makes the fiber incredibly strong for its size. 

Glass fiber is a non-metallic material made from extremely fine fibers of glass. The base ingredients of glass fibers are forms of silica, mainly sand, limestone, stone ash and borax. It is also considered the oldest, and most familiar, performance fiber. 

Aramid (short for “aromatic polyamide”) fibers are synthetic fibers in which the fiber-forming substance is a long-chain synthetic polyamide that has at least 85% of the amide linkages attached directly to two aromatic rings. Its molecules are linked by strong hydrogen bonds that transfer mechanical stress very efficiently, making it possible to use chains of relatively low molecular weight. The most famous aramid fiber is DuPont's Kevlar. 

Polymer fibers are a subset of artificial fibers, which are based on synthetic chemicals rather than arising from natural materials by a purely physical process. Examples: PE fibers (Dyneema, Spectra), PP fibers (Innegra), PET fibers, polyester fibers and many others. Aramid fibers are also considered polymeric. 

Natural fibers are fibers that are produced by geological processes, or from the bodies of plants or animals. Examples: Hemp, jute, flax, kenaf, basalt, cotton,lyocell etc. 

Other fibers that we can mention: Boron fibers, metallic fibers (aluminum, titanium, steel) and ceramic oxide fibers. 

Now imagine the amount of possibilities when it comes to creating hybrid fabrics! 

Source:#managingcomposites #thenativelab

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#composites #fibers #fiberglass #carbonfiber #kevlar #lyocell #jute #flax #cotton #metallicfibers #dyneema #petfiber #basalt #hemp

Solvay Launches New High-heat Polymer for EV Battery Components

Solvay has announced the introduction of a new high-heat and flame-retardant grade in the company’s Xydar® liquid crystal polymers (LCP) portfolio, which is designed to meet critical safety demands in EV battery components.

Retains Insulation Upon Exposure to 400°C for 30 Minutes:

The new Xydar® LCP G-330 HH material addresses challenging thermal and insulation requirements and is targeted particularly at battery module plates of EV models operating with higher voltage systems.

“As automakers are moving from 400V to 800V on next-generation electric vehicles, new regulations in Europe, China, the United States and other countries are increasing the demand on battery components to withstand temperatures from 300°C to 1000°C for an extended window of up to 15 minutes,” states Brian Baleno, head of marketing, Transportation at Solvay Materials. “Appropriate materials are expected to retain a level of electrical insulation protection that will provide sufficient time for passengers to exit the vehicle in a thermal runaway event. Our new Xydar® LCP grade combines this high safety potential with exceptional processability."

Xydar® LCP G-330 HH is a glass-filled LCP for injection molding capable of retaining its electrical insulation upon exposure to 400°C for 30 minutes. Xydar® LCP is an inherently flame-retardant polymer, without the use of halogen or bromine additives. In addition, it offers exceptional flowability and helps battery designers achieve thinner parts than possible with incumbent battery module insulation materials, such as polycarbonates or aerogels. It has been successfully tested with plates molded in typical dimensions of 100 x 150 x 0.5 mm.

Extends Portfolio of Battery Solutions:

Xydar® LCP has a proven fit in many electrical and electronic as well as coating applications. Besides automotive lighting components, sensors, solenoids and connectors, advanced examples in e-mobility include thin-wall slot liners used in the rotor design of an electric drive traction motor.

Xydar® LCP G-330 HH extends the portfolio of Solvay’s battery solutions, which also includes Solef® PVDF for binders and separators, Ryton® PPS for coolant line connectors and vents, and Amodel® PPA for connectors and busbars.

Source: Solvay/Omnexus.specialchem.com

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#solvay #lcp #polymers #evbattery #insulation #electrical #electronics #materialsscience

Today's KNOWLEDGE Share:Waste Metals

Today's KNOWLEDGE Share:

Waste Metals

Half of all the metals used today have a lifespan of fewer than 10 years.

As a society, we use around 61 different metals.However, more than half of them will end in a landfill or in a recycling yard within ten years.This speaks to the enormous amount of wastage that we accrue as a civilization.

Billions of tonnes of metals are mined each year, which accounts for 8 % of all greenhouse gas emissions. Now, if we could save the metals that we discard, it could bring down both mining and greenhouse gas emissions.

The results are from an industrial ecology group at Yale University.

The only notable exception to this list is gold, which continues to be maintained and reused for centuries.Perhaps we should start mandating metal recycling and make it profitable to extract waste metals from landfills.

Source:http://ow.ly/7iNj50JmBGh

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#metals #wastemanagement #landfills #gold #mining #co2emissions

Today's KNOWLEDGE Share:Earthquake Effect on Spherical Storage Tanks

Today's KNOWLEDGE Share:

Earthquake Effect on Spherical Storage Tanks:

A major earthquake of magnitude 9 (Richter scale) hits eastern Japan at 14:46, a leak on a LPG pipe is detected at 15 h 35 in a refinery located within a large petrochemical complex in the bay of Tokyo . At 15 h 48, the leak ignites and spreads to the adjacent spherical tanks stocking liquefied butane and butylene.
The rapid development of the fire causes the fall of most tanks (broken foot support) and a cascade of BLEVE (BOILING LIQUID EXPANDING VAPOUR EXPLOSIONS).

The initial leak of LPG, by crushing of a pipe, resulted from the collapse of an overhanging sphere filled with water for a hydraulic test after the 1st aftershock of the main earthquake.
The main earthquake weakened the supporting structure by cracking the crosspieces, and then led to the failure of the support legs during the 1st aftershock of magnitude 7.2 at 3.15 pm.

What Went Wrong???
The design of the structure adapted to the seismic risk for a gas (LPG) load did not take into account the overload due to the filling of the tank with water.
In addition, the automatic safety shutdown of the gas transport pipeline triggered by the seismometers was inoperative on this part of the pipeline, as the automatic cut-off valve was shunted open following earlier problems with the pneumatic control.(big mistake).The temporary procedure of manually closing this valve pending repair could not be implemented due to a large LPG pool.
As a result, the fire was uncontrollable.

What We Learned From This Accident?
-Reduction of the duration of the water presence in the spheres in hydraulic tests (judged abnormally long during the accident) ;
-In the new sphere design, additional loads from water, especially seismic loads, should be taken into account.
-Systematic isolation and draining of a gas pipeline close to the spheres under hydraulic test.
-Increasing the flexibility of new on site gas transport pipelines to accommodate large multidirectional displacements during major earthquakes.
- Emergency shut-off valves are critical equipment, their faults should be repaired in a short time.

Source:https://lnkd.in/dNpCnuw4/ Technical Engineering Portal
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#LPG #sphericaltanks #fire #earthquake #seismicloads #oil #chemical #propane #butane #butylene #Bleve #gas #refinery #petrochemical #engineering #safety #design #pipeline
#development #transport