PPubMed31 Jan 2023Cited 35×

Mechanical and Shape Recovery Characterization of MWCNTs/HNTs-Reinforced Thermal-Responsive Shape-Memory Polymer Nanocomposites

Sivanagaraju Namathoti, Manikanta Ravindra Kumar Vakkalagadda, Marcelo Antunes

Abstract

'Marcelo Antunes'] Mechanical and shape recovery characteristics of thermal-responsive shape-memory polyurethane (SMPU) reinforced with two types of reinforcements, multiwalled carbon nanotubes (MWCNTs) and halloysite nanotubes (HNTs), were studied in the present research work. Three weight percentages of reinforcement (0, 0.5 and 1%) in the SMPU matrix were considered, and the required composite specimens were obtained through injection moulding. Tensile, flexural, impact and shape recovery behaviours were studied experimentally. Further, flexural tests were performed for multiple cycles to understand the specimens’ flexural strength variation after shape recovery. The concentration of both reinforcements (MWCNTs and HNTs) considered in the present study significantly improved mechanical properties and shape recovery.

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Adding small amounts of MWCNTs or HNTs to a shape‑memory polyurethane markedly boosts its strength and shape‑recovery performance, with HNTs giving higher flexural strength and MWCNTs enabling faster recovery.

What’s new

i.Mechanical (tensile, flexural, impact) and shape‑recovery characterization of SMPU reinforced with MWCNTs and HNTs using injection moulding
ii.First report of flexural behavior of these composites over multiple loading‑recovery cycles
iii.Demonstrated that HNTs provide higher flexural strength while MWCNTs enable faster shape recovery
iv.Provided DSC analysis showing increased glass transition temperature with reinforcement

How they did it

Nanocomposite filaments were prepared by twin‑screw extrusion of SMPU pellets with 0, 0.5 or 1 wt% MWCNTs or HNTs, then injection‑moulded into test specimens. Tensile, flexural (including three‑point bending over three cycles), impact, DSC and water‑bath shape‑recovery tests were performed according to ASTM standards.

What they found

Pure SMPU tensile strength 6.7 MPa; 0.5 wt% MWCNTs 13.6 MPa; 0.5 wt% HNTs 22.4 MPa; 1 wt% MWCNTs 23.5 MPa; 1 wt% HNTs 22.7 MPa
Highest flexural strength 63.5 MPa for 1 wt% HNT‑reinforced specimen
Flexural strength reduced up to 33.5 % after three cycles for 1 wt% MWCNT‑reinforced samples
Impact energy increased ~250 % when reinforcement rose from 0 to 0.5 wt%
Shape‑recovery time was shortest for MWCNT‑reinforced samples, especially at 1 wt%

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