Influence of Long-Term Storage on Shape Memory Performance and Mechanical Behavior of Pre-stretched Commercial Poly(methyl methacrylate) (PMMA)

Abstract

In this paper, we experimentally investigate the influence of storage at 40 • C on the shape memory performance and mechanical behavior of a pre-stretched commercial poly(methyl methacrylate) (PMMA). This is to simulate the scenario in many applications. Although this is a very important topic in engineering practice, it has rarely been touched upon so far. The shape memory performance is characterized in terms of the shape fixity ratio (after up to one year of storage) and shape recovery ratio (upon heating to previous programming temperature). Programming in the mode of uniaxial tension is carried out at a temperature within the glass transition range to one of four prescribed programming strains (namely 10%, 20%, 40% and 80%). Also investigated is the residual strain after heating for shape recovery. The characterization of the mechanical behavior of programmed samples after storage for up to three months is via cyclic uniaxial tensile test. It is concluded that from an engineering application point view, for this particular PMMA, programming should be done at higher temperatures (i.e., above its T g of 110 • C) in order to not only achieve reliable and better shape memory performance, but also minimize the influence of storage on the shape memory performance and mechanical behavior of the programmed material. This finding provides a useful guide for engineering applications of shape memory polymers, in particular based on the multiple-shape memory effect, temperature memory effect, and/or low temperature programming.2 of 12 applications [34][35][36][37][38][39][40], activation of the SME may not be carried out right after programming, but after a period of storage. As such, we need to consider the influence of aging at around room temperature after programming [41], which is a topic that has been less explored so far [42,43], but that is utterly important from an engineering application point of view.The purpose of this paper is to experimentally investigate the influence of storage at 40 • C on the shape memory performance and mechanical behavior of a commercial poly(methyl methacrylate) (PMMA), which is a typical engineering polymer, used in many applications, including optical lens [44,45] and plastic screw. This particular PMMA has been verified to have excellent heating-responsive SME in our previous studies (e.g., in [46,47]), and unlike some moisture/water-responsive SMPs (e.g., the polyurethane reported in [48]), it appears to be non-sensitive to moisture in air. PMMA and polycarbonates (PC) are typical amorphous polymer, and their SME was reported over 20 years ago [49,50]. Both experimental investigation and simulation on the SME of amorphous polymers (without chemical cross-linking, but via physical cross-linking) have been well documented in the literature (e.g., in [41,51-53]). Different programming temperatures (all within the glass transition range) and programming strains (up to 80%, in the mode of uniaxial tension) are applied in this study, as they have been identified to be influential para...

On-Demand Tailoring between Brittle and Ductile of Poly(methyl methacrylate) (PMMA) via High Temperature Stretching

“…In the second step, the programmed polymer is heated to high temperatures (above its T g ), so the polymer returns its original shape (also called permanent shape) from the temporary shape. As reported in [ 28 ], after aging at 40 °C for up to one year, the PMMA samples programmed via high temperature (within the glass transition range and slightly above) uniaxial stretching to up to 80% strain are still able to almost fully recover their original shape upon heating.…”

“…According to [ 26 ], most polymers have the heating/chemo-responsive SME. Excellent heating responsive SME based on the glass transition has been reported in typical amorphous polymers, such as PMMA and polycarbonate (PC) [ 27 , 28 ].…”

“…Above mentioned high temperature stretching for brittle-ductile transition is actually the first step of the shape memory cycle. For polymers with excellent SME (such as PMMA and PC [ 27 , 28 ]), after one complete shape memory cycle, not only the shape, but also other thermo-mechanical properties, are largely recovered.…”

Thermodynamic and Kinetic Characteristics of Combustion of Discrete Polymethyl Methacrylate Plates with Different Spacings in Concave Building Facades

“…Polymethyl methacrylate (PMMA) is widely used as a building roof and a curtain wall for natural lighting, which can reduce building energy consumption by 33–78% [ 1 , 2 ]. Moreover, the thermal conductivity of PMMA is much lower than that of glass, leading to the better thermal insulation properties.…”

Effects of Overlap Length on Flammability and Fire Hazard of Vertical Polymethyl Methacrylate (PMMA) Plate Array

“…In recent years, polymethyl methacrylate (PMMA, also referred to as organic glass) has been widely used in industry and buildings due to its advantages, such as better transparency, chemical stability, mechanical properties, weather resistance, easy dyeing, and processing property, as well as graceful appearance. A great number of papers focus on the mechanical and environmental properties of PMMA [1,2]. However, there are relatively fewer studies concerning flammability and fire hazard, especially flame spread characteristics.…”