Title : Characterization of filler morphology and dispersion of silicone adhesive by scanning electron microscopy
Abstract:
Silicone adhesive has been used in assembly glass curtain walls for decades because of its excellent adhesion capacity for various substrates and high deformability. It is a filled elastomer with polydimethylsiloxane (PDMS) working as matrix and nano-CaCO3 or nano-SiO2 working as reinforcement filler. Due to the complexity of its composition, the mechanical behavior of silicone adhesive, such as hyperelasticity, viscosity, Mullins effect and degradation, is still under investigation. By now, the microstructure of silicone adhesive stays unclear, and the linkage between its macroscale properties and microscale structure evolution remains a challenge. To obtain an in-depth understanding of its mechanical behavior mechanism, constitutive modelling, engineering design and, furthermore, material modification, a detailed description of microstructure of silicone adhesive is required.
In this presentation, taking DOWSILTM 995 silicone structural sealant as an example, we will present typical microstructure of silicone adhesive obtained by scanning electron microscopy (SEM). By analyzing processed binary microscale images, filler morphology and dispersion will be discussed, where Gaussian mixed models are used to describe statistical features. The results show that the size of nano-CaCO3 filler particles mainly include two levels of 80nm and 120nm, approximately, and filler particles tend to form clusters with equivalent diameters ranging from hundreds of nanometers to several micrometers. The dispersion of filler is inhomogeneous according to Gaussian characteristics of skewness and kurtosis. The hierarchical structure of filler is then characterized by a fractal dimension of 1.5 calculated by box-counting method, which further confirms a heterogenous dispersion of filler and will be used in future study of constitutive modelling. The above-mentioned results give us a deeper insight into microstructure of silicone adhesive, which will enable us to better understand the mechanisms of its complex mechanical behaviors and to potentially modify target properties. The future research will focus on 3D characterization of in-situ loading conditions and aged conditions to study the evolution of microstructure of silicone adhesive under various circumstances.
Audience Take Away:
- Basic properties and applications of silicone adhesive in construction field
- A quantified characterization of hierarchical filler structure of silicone adhesive
- A better understanding of how microstructure affects the macroscale properties
- Methods to characterize and analyze similar filled polymers
