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.

Ring-Opening Copolymerization of Biorenewable δ-Caprolactone with trans-Hexahydro-(4,5)-benzofuranone toward Closed-Loop Recyclable Copolyesters and Their Application as Pressure- Sensitive Adhesives

Copolymerization as an efficient strategy can provide an opportunity to create new closed-loop recyclable polymeric materials with tailored properties that are generally inaccessible to the individual homopolymers.In this contribution,the bulk ring-opening copolymerization of bio-renewable-caprolactone and trans-hexahydro-(4,5)-benzofuranone was achieved to produce closed-loop recyclable copolyesters by using an organobase/urea binary catalyst at room temperature.The obtained copolyesters exhibited composition-dependent thermal properties.Remarkably,the obtained copolyesters were able to depolymerize back to recover the corresponding monomers under mild conditions.

Conductive microsphere monolayers enabling highly conductive pressure-sensitive adhesive tapes for electromagnetic interference shielding

Conductive adhesive tape is one kind of electromagnetic interference(EMI)shielding materials for electronic packaging.However,the inferior conductivity of the pressure-sensitive adhesive(PSA)layer results in serious electromagnetic leakage at the conjunctions between the conductive tapes and target objects.Adding conductive fillers is a traditional method for highly conductive adhesive tapes.However,the content of conductive fillers is needed to reach the percolation threshold,which is usually as high as tens of percent.High-content fillers result in significant loss of adhesive property and high fabrication cost.Herein,we introduce a rational architecture of conductive microsphere monolayer(CMM)in the PSA layer.The CMM connects the top and bottom surfaces of the PSA layer and improves its conductivity in the z-direction.Importantly,low contents of conductive microspheres(≤5%(mass fraction,w))can achieve the target of conductivity improvement,but not result in the serious loss of the adhesive property.Therefore,the strategy of CMMs can balance the tradeoff between the conductivity and the adhesive property of conductive PSA tapes.Finally,we demonstrate the superior EMI shielding performance of as-made conductive adhesive tapes,indicating their potential applications as the advanced EMI shielding materials in the electronic packaging.