Materials.Business Weekly ⚙️
December 21, 2021
Quote of the week: “The greatest, truest essence of creative productivity is joy.” Pat Martino (1944 - 2020), US guitarist.
From The Editor's Corner
Junction points: Significant challenges
Meeting points: Perennial weak points
Since the beginning of humankind, engineers have spent our lives trying to join parts. We had to join immense structures like bridges to the road or smaller like joining atoms and molecules. We need to join stone to wood, wearables to the skin, or parts of space-borne equipment that must withstand vacuum and extreme temperatures. A few times, joining is done just by mechanical forces, putting the pieces in contact, like a “Lego,” but most of the time, we need a third part or material linking or connecting the components. Binders are diverse, natural and synthetic, polymeric, ceramic, metallic, composites, etc. Nature itself uses binders, and biomimetics is copying some of such possibilities. For example, the imitation of the Van der Waals adhesion mechanism of the gecko foot-hairs is reproduced by arrays of nanofilaments, such as carbon nanotubes, across the surfaces to be joined. Points of joining are heterogeneities and usually preferred points of corrosive attack. Also, they are weak points in the whole assembly most of the time. Stress concentration points also act as crevices and generate oxygen and other corrosive species concentration gradients. Humidity penetration often occurs, colonies of microorganisms can be established quickly, and conditions for corrosion starting are served. In addition, concerns related to sustainability threats and Circular Economy guidelines, such as dissemblance limitations and environmental impact of adhesives, are increasing. To avoid joining points is a wish, but it is often a must. But options are emerging, and additive manufacturing is beginning to provide solutions. Even so, binders have a long life as engineering materials.
Polymeric adhesives are an outstanding family of binders. A wide range of vinyl-based adhesives is the most demanded type because of applications like porous materials, paper, etc. Acrylic-base adhesives rank second because of their properties like fast setting time, high adhesion to difficult to bond substrates, waterborne, and heat resistance. Other common adhesives include polyurethane, epoxy, silicone, and styrenic blocks. Concerning the technology, adhesives are classified as water-based (e.g., cellulose ethers, polyvinyl alcohol, methylcellulose, carboxymethyl cellulose, and polyvinyl pyrrolidone), solvent-based (e.g., polychloroprene, polyurethane, acrylic, silicone, and elastomers), hot melt (formulated from a variety of thermoplastic polymers such as polyamide, polyolefin, polyurethane, and ethylene-vinyl acetate), pressure-sensitive (most of them made from acrylic monomers like 2-Ethylhexyl acrylate, n-butyl acrylate, and isooctyl acrylate), and reactive adhesives (usually based on modified polymers like polyurethane, polysulphide, silicone, or silyl terminated).
The construction industry is one of the more significant users of adhesives, with around 25 percent of the total worldwide consumption. Furthermore, the traditional user sectors are leather & footwear, and woodworking. Emerging users include medical, electronics, and aerospace. Paper & packaging is snowballing (significantly associated with the “New Normal”), but the energy and especially the automotive & transportation sectors are the fastest-growing applications fueling the adhesives market.
The global market value in 2016 was USD $ 34.300 million. In terms of volume, the global market garnered 11.700.140 tons of adhesives in 2020. According to a Compound Annual Growth Rate – CGAR or “rate of return,” calculated like five percent, estimations of the global market value in the current year are USD $ 45.900 million. The expected value by 2030 is around USD $ 77.500 million, corresponding to approximately 20 million tons of adhesives produced. A large proportion of this amount is due to the growing demand from the automobile industry. Around 15 kg of adhesives are used in an average car, which increases because lighter and safer designs have been achieved. 3M, ARKEMA, BASF, HB Fuller, Henkel, Sika, and Hexcel, are some of the top companies sharing this market.
Adhesives in corrosive environments
Beyond the limitations of the joining regions as the “defects” in the structure mentioned before, sometimes an adhesive is exposed to a harsh environment (extreme temperatures and pressures, but also the presence of aggressive chemical agents and solvents). And its deterioration happens. The actual effect of the adhesive on the integrity of the object depends on the specific situation, and “each case is a case.” Most of the time, adhesive acts as an insulator, breaking potential electric circuits and avoiding the establishment of galvanic pairs and other possible electrochemical corrosion cells. In other situations, conductive adhesives are relevant, but the risk of corrosion cells increases; however, such a situation could be helpful in cases including cathodic protection, where electrical continuity is essential. As polymeric materials, many times adhesives are managed as anticorrosive options. Research and new developments concerning anticorrosive properties of fillers, coatings, paints, and polymers, in general, are also valid for adhesives. Curiously, one of the first natural adhesives widely used at least one thousand years ago is Gum Arabic, which is currently receiving attention as an environmentally sustainable alternative corrosion inhibitor. Some of the exciting innovations concerning anticorrosive adhesives developed during the last decades include:
- Adhesive specially developed for fixing automotive panels. A product combining two modified epoxy resins (bisphenol modified with a butadiene-acrylonitrile-(meth)acrylic acid copolymer and a urethane modified epoxy resin), and a curing agent, doped with aluminum orthophosphate as a corrosion inhibitor.
- Applique system with anti-corrosion adhesive for aeronautical uses. The backing of a thin polymer film and a pressure-sensitive adhesive containing corrosion inhibiting additives, acting as a primer layer beneath appliqués. Consequently, the environmental benefits because the elimination of toxic chromate primers and the cost benefits by eliminating a treatment step.
- Adhesion of metal and polymer with anticorrosive properties. This is an invention concerning an adhesive comprising a polymeric mixture of poly(arylene sulfide) and a small amount of tertiary nitrogen heterocyclic polymer (N-vinylimidazole-N-vinylpyrrolidone). Such a product achieves good polymer-metal adhesion and anticorrosion properties.
In addition, more recent results related to ongoing research also deliver exciting knowledge about the new possibilities with adhesives in front of the corrosion risks. As usual, adhesives and coatings are often combined, and developments coincide. Some of the recently published papers talking about the subject are:
- Bioinspired ultrathin coatings. There was studied the anticorrosive behavior of catechol-containing poly(alkyl methacrylate)s copolymers spin-coated on several metallic substrates as a transparent and dense layer of ca. 5 nm thickness. In the end, a highly protective ability was observed due to the synergic effect between the bonding capacity of the catechol and the defect-free layers formed in the presence of hydrophobic alkyl chains.
- Resin-based adhesive with superhydrophobic SiO2 nanoparticles. Was prepared a cationic resin containing hydrophobic silica nanoparticles and corrosion inhibitors and then applied in one step, by cathodic electrophoresis, onto the surface to be protected. The results demonstrated outstanding mechanical durability, superior anti-corrosive behavior, and self-healing performance.
- Epoxy-based adhesive with silica nanoparticles. Concurring with the above study, the behavior of an epoxy resin mixed with silica gel was investigated. In this case, the product was applied with a one-step spray. Again, here there was obtained a compound with good properties like outstanding water repellency, good mechanical robustness, good adhesion-to-substrate, self-healing behavior, and remarkable corrosion resistance.
- Development of a new sustainable phosphonated methacrylate. Has been synthesized a new polymer, namely dimethyl(methacryloyloxy)methyl phosphonate, followed by selective hydrolysis of the ester group with sodium bromide. The obtained product can be copolymerized with methyl methacrylate and blended with polyvinylidene difluoride. In the end, good adhesion and good anticorrosive properties have been reported.
- Galvanic corrosion protection bond-riveted joints. The corrosion resistance of AA50083-carbon fiber-epoxy laminates with bond-riveted bonds has been improved by reinforcing the polymeric matrix with polyaniline. Significantly, mechanical and anticorrosive properties around the rivets were substantially improved.
- Non-isocyanate polyurethanes - NIPUs. Here, we can refer to a review paper devoted to underlining the importance of non-isocyanate polyurethanes, which are based on the polyaddition of poly(cyclic carbonate)s to polyamines, as a more sustainable option to polyurethane. Polyurethanes have been used for adhering parts in many industrial applications, particularly where large surfaces must have adhered. But the toxicity of its isocyanate-based starting material is a relevant disadvantage—the current development of NIPUs at a lab-scale wait for further steps towards proper industrial applications.
- Anti-corrosive graphene-modified polymers. One more review paper devoted to showing the current situation of polymeric matrixes reinforced with graphene nanoparticles as functional constituents of coatings and adhesives. Because of its hydrophobic properties and enhancement of the polymer's mechanical properties.
In conclusion, since the early days of humankind, the technique has brought to our hands a plethora of adhesives to solve the challenges of joining parts. Corrosion has been a common situation in joining areas most of the time. The “Century of Polymers,” or the 20th century, brought a jump on synthetic polymers and adhesives and helped solve some corrosion problems, among other things. Moreover, the future is promising for more and better adhesive options and options without joints. Adhesives are a powerful tool and an excellent challenge for Corrosionists, and their proper management and development is a duty.
Remember: Protection of materials and equipment is a profitable business!
Prof. Carlos Arroyave, Ph.D. Editor.
Materials Biz News
It has shown that there is a very strong demand for crude steel from a wide range of customers, "adds Kajsa Ryttberg-Wallgren, deputy head of the hydrogen business unit at H2 Green Steel - H2GS. The project aims to help Iberdrola "accelerate the commercialization of larger and more advanced electrolyzers and make green hydrogen more competitive," explains Aitor Moso, Director of Liberalized Trade at Iberdrola.
The first WIPO Global Awards will be presented in July 2022 to five SMEs, this is the initial category of awardees that will be followed by other groups, such as women and youth in the next years. Any SME from any of WIPO's 193 Member States can nominate themselves for the award until 14 March 2022. A panel of seven judges with expertise in IP, innovation, and entrepreneurship, and drawn from a variety of backgrounds, will evaluate candidates. The jury will then select the winners, who will participate in the award ceremony during the WIPO Council meetings scheduled from 15 to 22 July 2022.
As fears grow that global warming is exacerbating South Africa's vulnerability to drought, more desalination plants are likely to be installed along our coast. Coastal provinces such as the Western Cape and Eastern Cape have experienced severe drought in recent years and nearly 10 desalination plants have already been built. “Desalination plants use many pumps for different functions, each of which must be driven by an electric motor,” says Govender.
Networking & Knowledge Exchange
Henry Royce institute is sharing a hybrid workshop aimed at materials science researchers (from any discipline) who collect, store, analyze and share experimental data associated with their samples: e.g., optical images, SEM images, property measurements, etc. The workshop will share examples of best practices and current initiatives in the area and formulate a list of actions to enable better data management practices.
Date: Friday, January 14th of 2022.
Hours: 9:30 to 16:30 IST (GMT)
International Campus is sharing a virtual meeting to introduce participants to non-linear analyses of existing structures with embedded damage “concrete degradation and corrosion of reinforcing bars” and estimate safety indicators as damage changes. The common thread will be the "Holistic" approach to existing reinforced concrete.
Date: Thursday, January 18th to Saturday, January 25th of 2022.
Corrosion & Prevention 2021. In-person
Corrosion & Prevention “C&P” is the largest corrosion conference and exhibition in the Southern Hemisphere and is offering a four-day gathering of world experts on corrosion mitigation. This will be a premium networking event and a source for the latest information concerning corrosion mitigation.
Date: From Sunday, February 13th to Wednesday, February 16th of 2022.
Venue: 309 King St, Newcastle West, New South Wales, 2302, Australia.
December 21st Conference on application of remote inspection, automated monitoring & robotics technology (Link)
December 22nd Conference on materials selection & corrosion control (Link)
January 14th Data management for materials researchers. (Link)
January 18th Calculation methods for existing reinforced concrete structures and infrastructures are subject to corrosion degradation. (Link)
February 13th Corrosion & Prevention 2021. (Link)
May 29th The Electrochemical Society (ECS) 241st Meeting. (Link)
August 28th Digital innovations for improving safety in chemical plants. (Link)
August 28th EUROCORR 2022. (Link)
2021 Corrosion science symposium and advances in corrosion protection by organic coatings (Link)