An
amino curing agent containing silicon/titanium flame-retardant
elements (STCA) based on (3-aminopropyl)triethoxysilane (APTES) and
tetrabutyl titanate was successfully prepared. The thermal decomposition
and flame-retardant properties of a STCA-cured trifunctional epoxy
resin, which was facilely synthesized by 1,1,1-tris(4-hydroxyphenyl)ethane
and epichlorohydrin via a two-step method, were compared with those
of another amino curing agent containing silicon (SCA) based on APTES
and methyltrimethoxysilane. The structures of STCA and SCA were characterized
by Fourier transform infrared (FT-IR), 29Si NMR, and Raman
spectroscopies. The STCA-cured thermoset not only had good thermal
stability with an initial decomposition temperature of 344.8 °C
and a char yield of 52.7% at 800 °C but also exhibited the overall
improvement of flame-retardant properties. V-0 rating was achieved
using the UL-94 test, and the value of limiting oxygen index reached
33.8%. From the thermogravimetry–infrared test, the yield of
pyrolysis products of the STCA-cured thermoset was significantly decreased,
indicating the lower toxicity in contrast to the SCA-cured thermoset.
Flame-retardant performances were also investigated using the cone
calorimetry test, and the flame retardancy mechanism was studied using
scanning electron microscopy, FT-IR, and energy-dispersive spectrometry.
The results indicate that the introduction of silicon/titanium to
the system reveals the synergistic effects to promote the formation
of an intumescent, sufficient, and compact char layer during combustion,
which could effectively prevent heat, oxygen, and flame from penetrating
into the interior structure, and lead to the retardance of further
combustion.
Acrylic pressure-sensitive adhesive
(PSA) is widely used in transdermal
drug delivery systems, while the diffusion behavior of drug molecules
in PSA is of great importance. In this paper, PSAs with different
cross-link densities were prepared by adjusting the ratio of cross-linkers.
The effects of cross-link density and temperature on the diffusion
of drugs in PSA were investigated by Fourier transform infrared attenuated
total reflectance and molecular dynamics simulation. The consistency
between the experimental and simulation results demonstrated that
molecular dynamics simulation could be used to predict the diffusion
behavior of drugs in PSA. The results showed that free volume and
the wriggling of polymer chains are positively related to the diffusion
coefficient of drug molecules, while hydrogen bonds hinder drug diffusion.
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