A small amount of ultrahigh molecular
weight polyethylene (UHMWPE)
was added to a PE matrix that was then processed into a pipe by a
self-designed rotation extrusion system. The results showed that during
the rotation extrusion of the PE pipe, the polymer melts helically
moved forward in an off-axis direction to induce molecular orientation
and shish-kebab alignment deviate from the axial direction. However,
because of sufficient relaxation of oriented molecules at high temperature,
numerous spherulites arose in the pure PE pipe. With the addition
of UHMWPE, the flow character of the PE matrix was tailored so the
molecular relaxation was suppressed and the flow effect on formation
of shish-kebab was amplified, bringing about denser shish-kebabs off
the axial direction in the PE pipe. As a result, a PE pipe with excellent
resistance to slow crack growth was prepared.
Flexible
and stretchable strain sensors are crucial components
for wearable electronics that can detect and quantify the stimuli
from the environment and thus realize the rapid feedback and control
of smart devices. However, reconciliation of the conflict between
resourceful design of conductive networks and large-scale production
in the industry still faces a huge challenge. Herein, we present a
new flow-manipulated strategy to prepare a wearable strain sensor
featuring a helically intersected conductive network, which exhibited
easy integration, multidimensional sensibility, and robust mechanical
properties. From visualization of simulation and verification of experimental
results, the helically intersected conductive network formed in an
elastomer ring can simultaneously reflect the static and dynamic mechanical
responses with a tunable gauge factor (10.41–31.12), wide linear
region (0–40o), mechanical robustness (σs = ∼7 MPa, ε = ∼1400%), and rapid response
time (∼300 ms). We further constructed a control system based
on smart rings and demonstrated its application in controlling industrial
robotic arms and remote-controlled cars. Looking ahead, this kind
of a smart ring will be more widely used in space and underwater exploration,
intelligent robotics, and human–machine interface technologies.
Polypropylene (PP) pipe is extraordinarily important in modern construction and transportation engineering owing its predominant advantages over metal such as good dimensional stability, low cost, and light weight. However, low toughness and hoop strength always stand in the way of the wide application. In this study, two kinds of β-nucleating agents (NAs) (WBG-II and NAB-83) were added in isotactic polypropylene and thereafter, the crystalline composition, morphology, and alignment were investigated under the combination effects of rotation extrusion and NA. The experimental results showed that both NAB-83 and WBG-II could promote numerous β crystals, but dot-like NAB-83 could only induce randomly distributed isotropic spherulites. On the contrary, by adjusting the temperature gradient along the extrusion to rotation section, WBG-II first dissolved into PP melts and then self-assembled into fiberlike nuclei before the formation of PP crystals. Compared to homogeneous crystallization, fibrous WBG-II nuclei lowered the energy barrier for PP crystals; therefore, epitaxial β lamellae grew on these fibrous NAs and stacked into β-form hybrid shish kebabs. Meanwhile, the alignment of these highly oriented structures deflected from the axis driven by the helical movement caused by die rotation. Consequently, PP pipe with outstanding hoop tensile performance as well as excellent toughness was prepared. J. VINYL ADDIT. TECHNOL., 25: E195-E202, 2019.
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