Today's KNOWLEDGE Share : phthalonitrile resin

Today's KNOWLEDGE Share

Novel liquid phthalonitrile monomers towards high performance resin:

Phthalonitrile resins are one of the high temperature resistant polymers which can be potentially used for harsh environments in both military and domestic fields. The high melting points of the monomers led to short processing windows and made processing procedure challenging and energy intensive. To solve this problem, liquid phthalonitrile monomers containing flexible siloxane segments were designed and synthesized. The long bond length and large bond angle of Si-O-Si chain segments introduced flexibility into the monomers and effectively reduced the melting point to −35.9 °C. Meanwhile, the high bond energy preserved the thermal stability of the resulting cured resin. The high fluidity (viscosity of ∼ 2 Pa·s at 30 °C) allows the monomers to be processed at room temperature without additional heating. In addition, the monomers can be dissolved in common organic solvents, such as ethyl acetate and ethanol. The resins cured at 250 °C demonstrated good thermal and thermal oxygen stability. The weight loss of 5 % in argon and air at temperatures of 428.6 °C and 434.9 °C, respectively.

Furthermore, blending this liquid monomer blended with powdered monomers improved both the processibility of the high melting monomers and the overall temperature resistance of the cured resin. The resin showed a weight loss of 5 % in argon and air of 534.4 °C and 532.3 °C, respectively.

Conclusion:

Phthalonitrile monomers with melting points below room temperature were successfully synthesized by introducing siloxane segments. The flexible Si-O bond with high bond energy reduced the melting point while preserving thermal stability. The ideal fluidity at room temperature provides an appealing choice for phthalonitrile-based resins that precludes stringent processing requirements such as high temperature, complex equipment, and high energy consumption. 

source:Muyao Gao,, Tianhao Li and their team/Elsevier

Today's KNOWLEDGE Share : EU regrets lack of conclusion on global plastics agreement

Today's KNOWLEDGE Share

EU regrets lack of conclusion on global plastics agreement

After two years of negotiations, UN member states failed to reach an agreement.

The EU regrets that the 5th session of the Intergovernmental Negotiating Committee on the Global Plastics Treaty (INC-5) finished without a deal yesterday in Busan, South Korea.

After two years of negotiations and a week of talks in Busan, UN member states could not find an agreement on what would have been the first-ever global legally binding instrument to end plastic pollution. The session has now been suspended and negotiations will continue in 2025. 

Speaking on the result, Jessika Roswall, Commissioner for the Environment, Water Resilience and a Competitive Circular Economy said:

“I strongly regret that there is no agreement on a new global plastics treaty. If business as usual continues, plastic production will triple by 2060.

“The EU will remain firmly committed to finding a global solution. Our oceans, our environment and citizens around the globe need it.” 

The EU remains strongly in favour of such a global instrument and calls on the countries obstructing the deal to show more ambition when the preparations for a new negotiation process resume.

With plastics leaked into the environment forecasted to triple by 2060, half of all plastic waste still being landfilled and less than a fifth recycled, a decisive response to the global pollution crisis is needed.

Almost two-thirds of plastic waste in 2060 will be in the form of short-lived items such as packaging, low-cost products and textiles, according to the OECD.  

Lack of convergence around treaty objectives:

The negotiators sitting around the table could not unite around a text of a binding instrument with disagreements most notable on measures for the reduction of overall plastic production, the elimination of certain plastic products, chemicals of concern in products, improved design of plastics, extended producer responsibility and enhanced waste management.  

The main points of divergence were a possible target of reducing the production of primary plastic polymers, bans and restrictions of chemicals of concern in plastic products, as well as problematic and avoidable plastic products. It is on this that major oil-producing countries and the “High Ambition Coalition” countries which includes the EU, the UK, Canada, as well as many African, Latin American and Pacific countries could not find convergence.  

Even though no agreement was reached in Busan, the negotiating committee has made significant progress towards a deal by agreeing on a text that should serve as a basis for negotiations at the next meeting. An overwhelming majority of more than 100 countries shared the ambitions of the EU and the number of countries continues to grow. 

source:European Commission

Today's KNOWLEDGE Share : PEKK vs PEEK

Today's KNOWLEDGE Share

PEKK (Polyetherketoneketone) vs PEEK (Polyetheretherketone):

PEKK and PEEK are both in the Polyaryletherketone family of ultra-high performance polymers. 

Unlike PEEK, PEKK is a copolymer with a slower and highly tunable crystallization rate making it the preferred choice for additive manufacturing. Kepstan® PEKK can be printed directly in either the amorphous or semi-crystalline state, or printed amorphous and crystalline in a secondary process, offering the ultimate combination in performance and processing flexibility.

   

CHEMICAL COMPOSITION AND STRUCTURE

PEKK :

Structure: PEKK consists of ether (O) and ketone (C=O) linkages, with two ketone groups in the repeating unit. This structure provides high thermal stability and chemical resistance, making PEKK ideal for demanding environments.

PEAK :

Often confused with PEKK, PEAK is a general term referring to various types of polyetherketones. It includes polymers with similar structures but slight variations in the arrangement of ether and ketone groups, encompassing both PEKK and PEEK among others.

THERMAL PROPERTIES

PEKK:

PEKK boasts a higher glass transition temperature (Tg) and melting point compared to PEEK.

Tg typically ranges between 160°C to 165°C.

Melting point is around 340°C.

PEEK:

Tg is around 143°C.

Melting point is approximately 343°C.

MECHANICAL PROPERTIES

PEKK:

The additional ketone group in PEKK increases rigidity, resulting in higher mechanical strength and stiffness.

It offers better wear resistance and a lower coefficient of friction, which is advantageous for high-stress applications.

PEEK:

PEEK provides an excellent balance of toughness, stiffness, and strength.

It is slightly more flexible than PEKK, which can be beneficial for applications requiring a degree of ductility.

CHEMICAL RESISTANCE

PEKK:

The more rigid structure of PEKK grants it superior chemical resistance.

It excels in resisting a wide range of chemicals, including acids, bases, and organic solvents.

PEEK:

PEEK is highly resistant to many chemicals, though slightly less so compared to PEKK.

Its chemical resistance is still exceptional, making it a reliable choice for harsh environments.

PROCESSING AND APPLICATIONS

PEKK:

PEKK can be processed using similar methods as PEEK, such as injection molding, extrusion, and 3D printing.

It is commonly used in aerospace, automotive, and medical applications where high performance is required under extreme conditions.

PEEK:

PEEK is widely used across various industries, including aerospace, automotive, electrical, and medical devices.

It is easier to process than PEKK due to its slightly lower melting point and greater flexibility.

Additive Manufacturing and Injection Molding

Both PEKK and PEEK have significant implications for additive manufacturing (3D printing) and injection molding.Their high-performance properties allow for the production of complex, precision parts that can withstand extreme conditions.

source::addmangroup/arkema

Today's KNOWLEDGE Share : Pros of 3D Printing

Today's KNOWLEDGE Share

What are the Pros of 3D Printing?

1. Flexible Design

3D printing allows for the design and print of more complex designs than traditional manufacturing processes. More traditional processes have design restrictions which no longer apply with the use of 3D printing.

2. Rapid Prototyping

3D printing can manufacture parts within hours, which speeds up the prototyping process.This allows for each stage to complete faster.When compared to machining prototypes,3D printing is inexpensive and quicker at creating parts as the part can be finished in hours,allowing for each design modification to be completed at a much more efficient rate.

3. Print on Demand

Print on demand is another advantage as it doesn’t need a lot of space to stock inventory, unlike traditional manufacturing processes.This saves space and costs as there is no need to print in bulk unless required.

3D design files are all stored in a virtual library as they are printed using a 3D model as either a CAD/STL file.

4. Strong and Lightweight Parts

The main 3D printing material used is plastic, although some metals can also be used for 3D printing.Plastics offer advantages as they are lighter than their metal equivalents.This is particularly important in industries such as automotive and aerospace.

5. Fast Design and Production

Depending on a part’s design and complexity,3D printing can print objects within hours, which is much faster than moulded or machined parts.It is not only the manufacture of the part that can offer time savings through 3D printing but also the design process can be very quick by creating STL or CAD files ready to be printed.

6. Minimising Waste

The production of parts only requires the materials needed for the part itself, with little or no wastage as compared to alternative methods which are cut from large chunks of non-recyclable materials.Not only does the process save on resources.

7. Cost Effective

As a single step manufacturing process,3D printing saves time and therefore costs associated with using different machines for manufacture. 3D printers can also be set up and left to get on with the job,meaning that there is no need for operators to be present the entire time.

8. Ease of Access

3D printers are becoming more and more accessible with more local service providers offering outsourcing services for manufacturing work.This saves time and doesn’t require expensive transport costs compared to more traditional manufacturing processes produced abroad in countries such as China.

9. Environmentally Friendly

As this technology reduces the amount of material wastage used this process is inherently environmentally friendly.The environmental benefits are extended when you consider factors such as improved fuel efficiency from using 3D printed parts.

10. Advanced Healthcare

3D printing is being used in the medical sector to help save lives by printing organs for the human body such as livers,kidneys and hearts.

source:twi-global.com/EOS M290

Today's KNOWLEDGE Share : Enhanced flexural properties of aramid fiber/epoxy composites by graphene oxide

Today's KNOWLEDGE Share

Enhanced flexural properties of aramid fiber/epoxy composites by graphene oxide:

The reinforcing effect of graphene oxide (GO) in enhancing the flexural strength and flex modulus of aramid fiber (AF)/epoxy composites were investigated with GO-AFs at a weight fraction of 0.1-0.7%. The flexural strength and flexural modulus of the composite reached 87.16 MPa and 1054.7 MPa,respectively, which were about 21.19% and 40.86% higher than those of the pure epoxy resin. In addition, the flexural properties and interfacial shear strength (IFSS) of composite reinforced by GO-AFs were much higher than the composites reinforced by AFs due to GO improved the interfacial bonding between the fiber& matrix.

Graphene possesses many remarkable properties, including high Young’s modulus (1100 GPa),superior fracture strength (125 GPa),large surface area (2630 m2/g).Due to these excellent properties, graphene and its derivatives, in particular grapheneoxide (GO) ,have found interesting applications in nanocomposites.GO has been demonstrated as an ideal reinforcement of the fiber-matrix.Research work on polymer nanocomposites.It showed that incorporation of nanoscale fillers graphene,with low content into polymers can obtain good enhancements in mechanical and physical properties. directly added GO into epoxy resin,the results showed that the mechanical properties of GO/epoxy composite were improved effectively. Among them,the maximum flexural modulus and flexural strength reached 2.94 GPa and 130.46 MPa,which are about 10.11% and 14.67% higher than those of the pure epoxy resin,found that GO utilization is an effective approach for improving the flex properties of carbon fiber reinforced polymer composites.The enhancement can be attributed to the existence of GO,providing fiber with increased roughness and polarity, resulting in strong mechanical interlocking between the fiber and matrix.

In this work,GO modified the AF surface firstly, then enhanced the epoxy matrix with GO-AFs. Based on the mechanical interlock mechanism mentioned above to systematically examine the role of GO in improving the flexural properties and IFSS of the AF/epoxy composite.

Although pure aramid fibers can be used to reinforce epoxy resin, significantly improved flex strength, flex modulus and IFSS can be obtained by introducing GO to modify aramid fibers.

1.The flexural strength and flexural modulus of the GO-AFs/epoxy composite containing 0.1 wt% GO-AFs are 87.16 MPa and 1054.7 MPa,which are about 21.19% and 40.86% higher than those of the pure epoxy resin.

2.The flexural strength and flexural modulus of the AFs/epoxy composite containing 0.7 wt% AFs are 81.59 MPa and 816.51 MPa, respectively, which are about 13.54% and 9.05% higher than pure epoxy resin.

3.The IFSS value of GO-AFs/epoxy composite reaches 8.29 MPa, which is higher than that of untreated AF by 36.8%.

4. GO is an excellent potential modifier to modify AFs.

source: Yinqiu Wu ,Bolin Tang &team

Today's KNOWLEDGE Share : Acrylic (PMMA) vs. Polycarbonate (PC) :

Today's KNOWLEDGE Share 

Acrylic (PMMA) vs. Polycarbonate (PC) :

Acrylic offers greater tensile strength than polycarbonate, typically around 80 MPa, compared to polycarbonate at 60-70 MPa. That means it can stretch a bit more before breaking.

Similarly, acrylic wins the battle for flexural strength at 115 MPa vs. 90 MPa for polycarbonate, set a heavy object on unsupported sheets of each and PC will give way first (but not by much).

Both polymers are quite impact resistant, but where acrylic comes in around 17 times that of glass, polycarbonate boasts a whopping 250x increase.

However, polycarbonate is more prone to scratching than acrylic, but as many eyeglass wearers know, coatings are available to avoid this common problem.

There's little difference in transparency between acrylic and polycarbonate (92% light transmission for acrylic vs. 88% for PC). Glass straddles the two at 90% transparency.

Leave these two polymers outside for a few years, however, and you’ll have no problem determining which is polycarbonate, since it will have taken on a yellowish hue; acrylic is much more resistant to sun and UV-light. That said, stabilizers are available for its UV-challenged issues.

Put those same plastic parts in a hot oven and just the opposite will occur. Where acrylic has a maximum service temperature of 100 °C (212 °F), polycarbonate is good to 150 °C (300 °F).

Fire is a different matter. Polycarbonate has low flammability and tends to self-extinguish while acrylic burns slowly and releases carbon monoxide, so it is not recommended where flames may be present.

Chemical resistance is another important attribute. Polycarbonate is generally the winner here since it better withstands acids and alkalis and can be cleaned with ammonia-based products. Not so with acrylic. Both polymers, however, fare poorly around solvents (which are often used to join machined acrylic and polycarbonate parts)

source:www.protolabs.com

Today's KNOWLEDGE Share : High shear layers in Injection molding process

Today's KNOWLEDGE Share

A local temperature increase in excess of 100°C is absolutely a realistic number for the thin high shear layers in Injection Molding.

Because this high T will last often less than a second (filltimes are short, the cold steel mold is extremely close), such high melt T will not necessarily result in a very visible quality loss, like discoloration.

This high shear-heating also happens in your barrel if you push RPM and backpressure up. However, testing for melt T plunging a thermocouple on the purged melt will hardly measure a significant change in average temperature, because the very hot layer is extremely thin (small overall volume fraction).

Despite the small volume involved in possible degradation, significant issues may arise, like VOC (volatile organic compounds) degassing, which will mess with your process and parts.

The message is : be aware that due to the low thermal conducivity of plastics, heating will be very localized (adiabatic) and will be difficult to evidence with typical observation/testing, while already creating issues.

Vito leo