The structural differences between linear SMPU and flex-linked SMPUs can be observed in Fig.
The stretching vibrational mode of the carbonyl group is also affected by dipole-dipole interactions between SMPU chains.
g]) of a soft segment of SMPU was low (under -60[degrees]C) and difficult to detect by DSC, so instead the melting temperature ([T.
Crosslink density of SMPU determined by swelling experiments.
The intrinsic viscosity of SMPU dissolved in DMAC was investigated, under the theory that polymer chains in the crosslinked structure could drag each other more than in linear PU and thus increase solution viscosity.
The highest maximum stress of the previous flex-linked SMPU (with structure as shown in Fig.
From this figure, flexibly linked SMPU (C1-5 and C2-5) is c1early different from linear SMPU (C1-1 and C2-1), and the former exhibits behavior close to natural rubber in overall shape except that it is able to sustain higher stress and strain.
In previous research, crosslinking of SMPU generally resulted in increased maximum stress with a sacrifice in strain, but the adoption of flexible spacers and lateral linking along the SMPU chain both elevated maximum stress and improved the strain response [19, 20].
A cyclic shape memory test was used to compare shape recovery and shape retention of variously linked SMPU in the range [T.
The shape retention experiment was conducted at very low temperature (-- 20[degrees]C), and tested the tendency of a SMPU to retain its shape against a shape recovering force.