V. Brunella

Iron-based reversible adhesives: Effect of particles size on mechanical properties

A hot melt adhesive – mainly used for bonding plastic component in automotive field – was modified with different iron-based particles to give it a reversible behaviour. Mechanical and physical properties of these reversible adhesives were experimentally assessed in the work. The modified adhesives, coupled with electromagnetic induction, are able to guarantee separation of the joints without any damage to the substrates for recycling, reuse or repairing of components. Single lap joint specimens were prepared using epoxy/glass fibres substrates and tests were carried out on neat and modified adhesive with 5% weight of iron and iron oxide. Three different Fe particles size were tested: 450 µm, 60 µm and 1–6 µm. The particles size of iron oxide was 50 nm. Separation was studied using single lap joint specimens under electro-magnetic induction. Experimental results showed that the maximum peak load decreases when the average particles sizes increase. The peak loads of the smallest particles were equal to the ones of the pristine adhesive. The elongation of the adhesives increases when the adhesive is modified with both iron and iron oxide particles. Finally, experimental tests on single lap joints coupled with electro-magnetic induction showed that separation of the substrates is possible using iron oxide particles. Electro-magnetic tests conducted on particles alone, helped to understand that bigger particles are able to overcome the melting temperature of the adhesive but hot-melt adhesives modified with these particles are not able to reach the melting. These tests showed that the number of particles into the adhesive matrix is very important for this kind of tests.

Impact response of adhesive reversible joints made of thermoplastic nanomodified adhesive

ABSTRACT The impact response of a reversible adhesive joint is experimentally assessed in this work. Joint reversibility is improved with a system that uses nanomodification of the thermoplastic adhesive used for bonding plastic components. This system, coupled with electromagnetic induction, is able to guarantee the separation of joints without any damage to the substrates. Drop dart tests at different impact velocities are carried out on neat and nanomodified bonded joints in order to compare the impact behavior before and after the introduction of nanoparticles. Experimental results show that the impact response, assessed in terms of peak load, absorbed energy, and flexural stiffness, can be affected by the introduction of nanoparticles. This work shows that adhesive nanomodified joints represent an effective and applicable solution for the reversible assembling of semi-structural components subjected to low-velocity impact loads.

Thermoplastic Adhesive for Automotive Applications

The objective of this study is to give a general overview on the thermoplastic adhesives used in the automotive sector. Some of the main applications in which the hot-melt adhesives (HMAs) are used in automotive industries are indicated, together with the adhesive characteristics that explain the reasons for their adoption. The chemical and mechanical behavior of these adhesives and the generally used experimental characterization methods are presented and opportunely criticized. In this study, some of the main properties of thermoplastic adhesives are reviewed together with the standard tests used for their characterization. For what concerns the structural performance, single lap joint test is used to determine the shear strength of the adhesive joint. Thermogravimetric analysis and Fourier transform infrared spectroscopy are used to characterize the chemical properties of the adhesive. This study clarifies what are the potentialities of a thermoplastic adhesive in car industries compared to other adhesives.