(Press-News.org)
What makes some plastics stick to metal without any glue? Osaka Metropolitan University scientists peered into the invisible adhesive zone that forms between certain plastics and metals — one atom at a time — to uncover how chemistry and molecular structure determine whether such bonds bend or break.
Their insights clarify metal–plastic bonding mechanisms and offer guidelines for designing durable, lightweight, and more sustainable hybrid materials for use in transportation.
Combining the strength of metal with the lightness and flexibility of plastic, polymer–metal hybrid structures are emerging as key elements for building lighter, more fuel-efficient vehicles. The technology relies on bonding metals with plastics directly, without adhesives. The success of these hybrids, however, hinges on how well the two materials stick together.
“The molecular-level mechanisms that determine how strongly these materials bond at the interface have remained unclear,” said Takuya Kuwahara, lecturer at Osaka Metropolitan University’s Graduate School of Engineering and lead author of this study.
Zeroing in on the bond, the team used all-atom molecular dynamics simulations to investigate how polyamides (PAs), in this case nylon, adhere to alumina surfaces. The researchers tested two types of PAs, which differ in rigidity: PA6, which has a flexible aliphatic backbone; and PAMXD6, which contains rigid aromatic rings.
They studied them on both hydroxylated (OH-terminated) and non-hydroxylated (non-terminated) alumina surfaces. “Terminated” here refers to how the outermost layer of a material ends: in this case with a functional OH-group or no functional group.
To track molecular behavior at the interface, the researchers first categorized polymer chain segments.
“Surface-adsorbed segments were classified as ‘trains,’ non-adsorbed segments existing between two trains as ‘loops,’ and non-adsorbed end segments connected to the PA interior as ‘tails,’” Kuwahara explained.
The polymer–alumina interface underwent yielding when subjected to tensile strain. In this context, ‘yielding’ refers to the onset of irreversible atomic rearrangements, where the interface is permanently deformed and atoms can no longer return to their original positions even after the stress is taken away. The researchers analyzed the mechanical response of the polymer–metal interface before and after yielding to evaluate the strength, durability, and reliability of materials at the point where they meet, revealing the strength of the bond.
The simulation results showed that adhesion strength depends on both polymer chemistry and surface termination.
“In the elastic regime, or before the interface yields, the tensile stress is determined by PA chemistry,” Kuwahara said. “After yielding, however, the alumina surface termination becomes critical.”
Before yielding, the aromatic PAMXD6 is stiffer and resists stretching better than PA6. After yielding, the behavior changes depending on the surface: on hydroxylated surfaces, PAMXD6 detaches, or desorbs, whereas PA6 reorganizes, transforming loops into stretched tails without fully detaching. On non-hydroxylated surfaces, both polymers remain firmly attached through trains and loops.
The findings not only clarify why some metal–plastic pairs bond better than others, but also offer practical design guidelines for selecting surface treatments and polymer types. These insights facilitate theoretical, mechanism-based materials design, reducing reliance on trial-and-error experimentation.
“By understanding how molecular structure and surface chemistry interact, we can design stronger, lighter joints that help reduce vehicle weight and energy use,” Kuwahara said. “Ultimately, this work moves us closer to achieving sustainable, carbon-neutral transportation.”
###
Established in Osaka as one of the largest public universities in Japan, Osaka Metropolitan University is committed to shaping the future of society through the “Convergence of Knowledge” and the promotion of world-class research. For more research news, visit https://www.omu.ac.jp/en/ and follow us on social media: X, Facebook, Instagram, LinkedIn.
END
A new study reveals that the impact humans are having on the Amazon rainforest is so profound it is even changing the evolutionary history and functionality of the forests.
As the world gathers at COP30 to discuss climate in the world’s largest rainforest, the focus is often on the carbon that these forests either store or sequester.
However, tropical forests are much more than just carbon: they are among the biggest reservoirs of biodiversity on the planet. For example, the Amazon holds up to 16,000 species of tree alone, with a single hectare frequently holding more than 300 species. In comparison, the UK has just 32 species of ...
Routine screening is limited to only a few cancer types. New research indicates that routine liquid biopsy testing (multi-cancer early detection testing) could substantially reduce late-stage cancer diagnoses, allowing patients to receive treatment at earlier cancer stages, which are more likely to respond to interventions. The findings are published by Wiley online in CANCER, a peer-reviewed journal of the American Cancer Society.
Currently, routine screening is only recommended for four types of cancer, leaving approximately 70% of new cancer cases to be detected only after symptoms appear, often at an advanced stage when survival ...
Chronic fatigue syndrome leaves patients exhausted and struggling with brain fog — and it typically gets worse after mental or physical exercise, a phenomenon called post-exertional malaise. Now scientists investigating shortness of breath in chronic fatigue patients have discovered that they are highly likely to experience dysfunctional breathing, which could be caused by dysautonomia, abnormal control of innervation to blood vessels and muscles. Targeting treatments towards these breathing problems ...
New Zealand — particularly the South Island/Te Waipounamu — is one of the most seismically active regions in the world. For this reason, the country has acknowledged the importance of building awareness and preparedness.
In this kind of disaster communication, emotions — whether conscious or not — play a crucial role. Caroline Rowe, researcher at the Centre for Sustainability Research, University of Otago, New Zealand, explored this dimension, showing how risk communication can balance fear and anxiety with positive emotions such as fascination and confidence, using vivid imagery, ...
“People tend to joke about mood swings, saying ‘my mood swings throughout the day, I’m already a bit bipolar,’ or joke with each other saying ‘everything is bipolar.’ And it’s not quite like that, as bipolar disorder has a biological component.”
This is one of the statements featured in a short trailer on YouTube about bipolar disorder. The video is connected to the play Oxímoro, entre Solstícios e Equinócios (Oxymoron, Between Solstices and Equinoxes) by Marionet, a Portuguese theatre company that brings scientific research topics to the stage.
The play was developed through an in-depth collaboration with doctors, ...
A major study has found that people with eczema are able to bathe either daily or weekly, without any impact to their symptoms.
The findings of the new study, which are published in the British Journal of Dermatology, are great news for people living with eczema, as it will mean they will have the freedom to choose how often to bathe without fear it will worsen their symptoms.
People with eczema often have questions about how best to bathe including how often to have a bath or shower. The ‘Eczema Bathing study’, was prioritised and developed by people living with eczema, in partnership with researchers from ...
Children's access to NHS dentists and rates of tooth decay remain very poor despite improvements from national government interventions, oral health experts say.
Analysis of the latest government data by the Child of the North initiative gives cause for cautious optimism, they say, but the schemes need to be scaled up and strengthened to meet the needs of young people across the country.
The latest update, titled Improving Children’s Oral Health Update: Integrated Health and Education Solutions, is the seventh to be released ...
The risk of dying is six times higher among patients who become short of breath after being admitted to hospital, according to research published today (Monday) in ERJ Open Research [1]. Patients who were in pain were not more likely to die.
The study of nearly 10,000 people suggests that asking patients if they are feeling short of breath could help doctors and nurses to focus care on those who need it most.
The study is the first of its kind and was led by Associate Professor Robert Banzett from Beth Israel Deaconess Medical Center, Harvard Medical School, ...
Existing evidence does not clearly link paracetamol (acetaminophen) use during pregnancy with autism or ADHD in children, finds an in-depth evidence review published by The BMJ today, in direct response to recent announcements around the safety of using paracetamol in pregnancy.
The researchers say confidence in the findings of existing evidence reviews and studies on this topic is low to critically low, and suggest that any apparent effect seen in previous studies may be driven by shared genetic and environmental factors within families.
Regulatory bodies, clinicians, pregnant women, parents, and those affected by autism and ADHD should be informed ...
Nov. 9, 2025--In the United States, one in every 250 people has inherited a genetic variant that leads to dangerously high cholesterol levels from birth.
If high cholesterol isn’t lowered early, people with this genetic condition, called familial hypercholesterolemia (FH), have a high risk of having a heart attack or stroke as early as their 30s or 40s. But only about 1 in 10 of people living with FH (1.5 million Americans) is aware of their condition.
A new modeling study conducted by researchers at Columbia and Harvard Universities finds ...
