Der beste Schaum kommt von der Statistik

Geschäumte Materialien sind allgegenwärtig – oft verwenden wir sie, ohne dass wir es merken. Schäume werden nicht nur eingesetzt, um Gewicht und somit auch Kosten zu sparen. Sie werden verwendet, um besondere Eigenschaften, wie zum Beispiel eine hohe Dämpfung, zu erreichen, was besonders bei einem Helm wichtig ist

Copper ions absorbed on acrylic-acid-grafted polystyrene enable direct bonding with tunable bonding strength and debonding on demand

Recycling adhesively bonded polymers is inconvenient due to its expensive separation and removal of adhesive residues. To tackle this problem, adhesive technologies are needed allowing debonding on demand and which do not contaminate the surface of the substrate. Direct bonding enabled by oxygen plasma treatment has already achieved substantial adhesion between flat substrates. However, debonding takes place by water, thus limiting the applications of this technology to water-free environments. The work presented in the following shows that this drawback can be overcome by grafting acrylic acid and adding copper(II) ions on the surface of polystyrene. In this process, the number of functional groups on the surface was significantly increased without increasing the surface roughness. The bonding strength between the substrates could be increased, and the process temperature could be lowered. Nevertheless, the samples could be debonded by exposure to EDTA solution under ultrasound. Hence, by combining acrylic acid grafting, variations in the bonding temperatures and the use of copper(II) ions, the bonding strength (5 N to >85 N) and the debonding time under the action of water can be tuned over large ranges (seconds to complete resistance)

Direct bonding and de‐bonding on demand of polystyrene and polyamide surfaces, treated with oxygen plasma

Smooth polystyrene (PS) and polyamide 12 (PA 12) surfaces were produced via an injection molding process followed by a smoothing process and subsequently treated with O2 plasma to increase the number of polar groups capable of hydrogen bond formation on the surface. The presence of related groups was evident from X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The sample topographies were investigated by atomic force microscopy (AFM). The plasma treatment allowed the joining of the substrates without adhesive by pressing the substrates together below or around the glass transition temperature. Notably, not only substrates of the same polymer but also PS and PA 12, which are incompatible, were joined with this method. The adhesion between the substrates was determined using a LUMifrac apparatus. The adhesion strength increased with increasing bonding temperature and when both substrates were plasma-treated, reaching adhesive strengths up to 5.5 ± 1.7 MPa. Remarkably, the joint substrates could be rapidly de-bonded on demand simply by treatment with water, and the separated substrates could be re-bonded by renewed plasma treatment

Basic study on the evaluation of thermoplastic polymers as hot-melt adhesives for mixed-substrate joining

A selection of 22 low-melting polymers was thermally and rheologically evaluated to be used as hot-melt adhesives in mixed-substrate joining samples. The choice of polymers was based on the published melting point. It was required to include a broad variety of different polymers backbones to study the influence of the different polymers comprehensively. A tool-box of widely applicable tests was developed to judge if a thermoplastic polymer is suitable for a hot-melt adhesive application. Melting temperature (onset, peak and offset temperature) and melting enthalpy were determined using standardized methods. Rheological methods were used to characterize the shear rate dependence and the flow behavior at the application temperature. The wetting behavior of the polymers was evaluated with contact angle measurements. The adhesive strength of the most promising candidates was analyzed using the Lumi Frac-adhesion method including the failure pattern

Improving the filament weld-strength of Fused Filament Fabrication products through improved interdiffusion

Fused Filament Fabrication (FFF) is a popular additive manufacturing technique where molten polymer filament is applied in a raster pattern, layer by layer, to obtain the work piece. A necessary consequence of this method is a pronounced mechanical anisotropy of the product; the interface between the filaments is weaker compared to the filament itself. The strength of this interface is governed by the reptation theory which postulates a more efficient interpenetration of polymeric surfaces with decreasing polymer viscosity. This relationship was utilized in this work to modify a polycarbonate-acrylonitrile butadiene styrene polymer blend to produce FFF work pieces with less mechanical anisotropy, independent of printer settings. The tensile strength ratio of the printed interface to bulk tensile strength could be increased from 41% to 95%. Though the absolute bulk tensile strength decreases slightly, this method presents an easy and effective way to address the mechanical problems inherent in the FFF-method

Modular und 3D-gedruckt

Der Hauptkostenträger bei der Herstellung von Kunststoffbauteilen im Spritzgussverfahren ist die Herstellung der Spritzgussform. Besonders bei komplexen Geometrien fallen hohe Kosten und Herstellzeiten für gefräste und erodierte Formen an. Aus diesem Grund können Investitionen in Spritzgussformen fast ausschliesslich mit hohen Stückzahlen begründet werden

Molekulares Kleben durch den Einsatz von Plasma und Metallionen

Konventionelle Polymerklebstoffe bieten permanente Verbindungen, die oft schwer zu lösen sind und Rückstände auf den Substraten hinterlassen. Mit der Schaffung einer reversiblen Verbindung zwischen Polymeren aufgrund intermolekularer Wechselwirkungen wurden Polystyrol und Polyamid 12 durch Sauerstoff-Niederdruckplasma, Acrylsäure-Pfropfung und Openair-Plasma modifiziert, um eine hohe Haftung und Debonding-on-Demand zu ermöglichen

Funktionalisierte Polymere : Klebstoffentwicklung

Der Begriff «Polymer Engineering» bezeichnet die Anwendung der Polymerwissenschaft auf praktische Probleme im Zusammenhang mit Eigenschaften und die Verwendung von Polymermaterialien in anspruchsvollen Umgebungen. Er soll eine ganzheitliche Betrachtungsweise implizieren, von der Synthese, Verarbeitung und Oberflächenbehandlung über Konstruktion, Werkzeugtechnik und Fertigung bis zur Wiederverwertung und Entsorgung