The Effect of POSS Type on the Shape Memory Properties of Epoxy-Based Nanocomposites.

Avraham I Bram,Irina Gouzman,Asaf Bolker,Ronen Verker,Noam Eliaz

doi:10.3390/molecules25184203

Abstract

Thermally activated shape memory polymers (SMPs) can memorize a temporary shape at low temperature and return to their permanent shape at higher temperature. These materials can be used for light and compact space deployment mechanisms. The control of transition temperature and thermomechanical properties of epoxy-based SMPs can be done using functionalized polyhedral oligomeric silsesquioxane (POSS) additives, which are also known to improve the durability to atomic oxygen in the space environment. In this study, the influence of varying amounts of two types of POSS added to epoxy-based SMPs on the shape memory effect (SME) were studied. The first type contained amine groups, whereas the second type contained epoxide groups. The curing conditions were defined using differential scanning calorimetry and glass transition temperature (Tg) measurements. Thermomechanical and SME properties were characterized using dynamic mechanical analysis. It was found that SMPs containing amine-based POSS show higher Tg, better shape fixity and faster recovery speed, while SMPs containing epoxide-based POSS have higher crosslinking density and show superior thermomechanical properties above Tg. This work demonstrates how the Tg and SME of SMPs can be controlled by the type and amount of POSS in an epoxy-based SMP nanocomposite for future space applications.

Highlights

The volume and mass budgets of spacecraft are limited
The crosslinking density of the epoxide functional groups (EP)–EPOSS increased samples have higher crosslinking densities than pristine epoxy, their degree of curing was significantly as more EP–polyhedral oligomeric silsesquioxane (POSS) was added to the system, from 3 × 10−6 mol/cm3 for pristine epoxy lower compared to pristine epoxy (Figure 3)
Despite amine functional groups (AM)–EPOSS exhibiting a much−6lower degree of curing than significantly as more EP0409 glycidyl POSS (EP–POSS) was added to the system, from 3 × 10 mol/cm3 for pristine epoxy to pristine epoxy, the crosslinking density of these samples hardly changed as was added to the

Summary

Introduction

The volume and mass budgets of spacecraft are limited. Spacecraft have to be equipped with lightweight, compact, reliable built-in mechanisms for the deployment of antennas, radiators, solar arrays, optical systems, and more. The demand for lighter and smaller deployment systems increased recently due to the growing interest in the so-called “new space” nanosatellites [1]. A class of materials that can be used for lighter and smaller deployment mechanisms is based on shape memory polymers (SMPs) [2,3,4]. SMPs are stimuli-responsive materials that, after being deformed, have the ability to return to their pre-deformed shape by external stimuli, such as light, chemoresponsivity, electric current, electromagnetism, and temperature [5,6,7]. The SMP is comprised of a chemical network that consists of molecular switching segments, i.e., “soft segments” and “hard segments”

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