8:00 am – 11:30 am:
W7-Thermoplastic Materials and Foams: Frontiers-Room S320G

8:00 am – 9:00 am:
Thermoplastic Foam; 1930-2020

Shau-Tarng Lee
Thermoplastic foam began with polystyrene in 1930, then evolved into polyolefin foam to grow with extrusion technology to make useful products which benefit almost all aspects of our living. Its low density exhibits cushioning, insulation, thermoforming, and packaging properties. Its revenue was in the millions in the 60s. In 2016, it exceeds $40 billion. It’s a good plastics story. History reveals that challenges and setbacks were all over the place. The thermoplastic foam platform has simply become stronger. It makes our living much more advanced than ever. Looking forward, fast commoditization, environmental demand and new product expectation will never slow down. However, innovation and solution will push thermoplastic foam technology to the next level. Researchers in this field have wondered, can we create cells that are so small that light will not interfere with them? Could we thus create a foam that remains transparent, while providing insulation? Could we replace the window glass by such transparent and insulating foam some day? In an accidental discovery in our lab, Andrei Nicolae has produced transparent foam in PEI. Andrei subjected PEI specimens to a low-temperature carbon dioxide saturation process with a goal to drive the cell size in PEI foams to 20-50 nm range. In recent years, Humin Guo has written about this low-temperature saturation process in which he has achieved nano-cale cells, in 20-50 nm range, in a number of thermoplastics. Andrei was surprised to find that he could read through the foam he had created. This was in contrast to the white opaque foam normally produced, in PEI as well as in other thermoplastics, as the cells diffract the light to make the foam appear white. When he measured the density of this clear foam , he found the density had reduced to about 50% of the starting PEI polymer! A photo of the transparent foam is shown below. We have so far been unable to image this foam under SEM. In our previous work (see Humin Guo, et al) we have been able to image cells that are in the 20-50 nm range. In the PEI transparent foam, the cells are obviously too small to interact with light. We anticipate that the cells may be in the 1-10 nm range. Our efforts to capture structure of this unique material by other means are continuing.

9:00 am – 9:30 am:
Auxetic Foam Sensor with Silver Nanowire

Md Faisal Ahmed, Florida State University
This paper describes the fabrication and application of auxetic foam sensor using silver nanowire as the sensing element.

9:30 am – 10:00 am:
Poly(Vinylidene Fluoride)/ Graphene Nanoplatelets Composites with Microcellular Structure to Enhance Electromagnetic Shielding Properties

Biao Zhao, University of Toronto
It is well accepted that the microcellular structure can enhance electromagnetic interference shielding (EMI) properties due to the multiple reflection and scattering in the microcells. Moreover, the foams were proved to be the competitive materials owing to the savings of energy and raw materials. In this study, the poly(vinylidene fluoride)/ graphene nanoplatelets (PVDF/GnP) composite foams were successfully prepared through a facile home-made batching foaming avenue. The microcellular structure of PVDF/GnP foams can be tuned by the batching foaming temperature. We can notice that the void fraction of foams firstly increased and then decreased with increasing temperature. In addition, we also investigated the electrical conductivity and electromagnetic shielding properties of PVDF/GnP foams. The results revealed that the electrical conductivity and EMI properties can be effectively monitored, and the PVDF/GnP foam with low void fraction exhibited the high electrical conductivity and EMI properties. The optimal EMI values of PVDF/GnP foams with a thickness of 2.5 mm were 27.4 dB. An analysis of the shielding mechanism showed that the main contribution to the EMI shielding came from the absorption mechanism, and that the EMI shielding could be tuned by controlling the foams’ thickness. Thus, these PVDF/GnP foams could be considered as the high-efficiency EMI materials.

10:00 am – 10:30 am:
Enhancing Electromagnetic Shielding Performance of PVDF/MWCNT Composites Through Foaming

Chenyinxia Zuo, University of Toronto
The relationship between Electromagnetic interference shielding effectiveness and void fraction of foamed PVDF polymer-based composites with 1 wt% MWCNTs is investigated in this paper. The specimens are prepared through the film casting, compression molding, and batch foaming processes. The composite is advantageous to EMI shielding when the foaming technique is incorporated to reduce weight. It is found out that a 0.62 ~ 0.96 g/cm3 composite achieves an overall EMI SE of 10.5 ~ 25.4 dB in the frequency range of 26 ~ 40 GHz, since increased interfacial surface area from internal gas bubbles contributes to a rise in EMI shielding via absorption.

10:30 am – 11:00 am:
Piezoelectric Foams with High Thermal Stability and Flexibility

Zhe Liu, Florida State University
This paper discusses the fabrication and characterization of a hybrid piezoelectric foams that exhibit high thermal stability whiling maintaining good flexibility.