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To achieve a better balance between the refractive index and Abbe number, the thiol-functionalized polyhedral oligomeric silsesquioxane (POSS–SH) was incorporated as both nanoreinforcement and cros...

A time–temperature–transformation–viscosity (TTT-η) diagram can reflect changes in the physical states of a resin, which take on significance for the study of the curing process of polyurethane resin lenses. Coupling the differential scanning calorimetry (DSC) test, the curing kinetic parameters of 1,4-bis(isocyanatomethyl)cyclohexane (H6XDI)/2,3-bis((2-mercaptoethyl)thio)-1-propanethiol (BES) polyurethane system were obtained. By phenomenological modeling, the relationships between degree, temperature, and time were obtained. An isothermal DSC test was carried out at 423 K. Based on the DiBenedetto equation, the relationships between glass transition temperature, degree of cure, and time were obtained, and the glass transition temperature was thus correlated with temperature and time. The gelation time at different temperatures was measured by rotary rheometry, and the relationship between gelation time and gelation temperature was established. The time–temperature–transformation (TTT) diagram of H6XDI/BES system was constructed accordingly. Subsequently, a six-parameter double Arrhenius equation was used as the basis for the rheological study. The viscosity was examined during the curing process. The TTT-η diagram was obtained, which laid the theoretical foundation for the optimization and setting of processing parameters.

As a natural ore, Taichi stone brings potential market value and social value due to its health-care functions, such as releasing far-infrared and anti-ultraviolet (anti-UV) and anti-bacterial functions. In this study, Tachi masterbatch (containing 10% Tachi nanoparticles)/polyester (PET) functional composite fiber was prepared by electro-spinning. To study the effect of nanoparticle content on the composite fibers, five spinning solutions with different nanoparticle contents were mixed and electrospun. The spun fibers were then characterized by using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and far-infrared and UV testing devices, respectively. The result shows that when the Taichi nanoparticle content is 3%, the composite fiber membranes will have a better dispersion, the fiber is more uniform, and smaller fiber diameter can be obtained. Compared with the pure PET fiber, the composite fibers have an improved far-infrared radiation performance and anti-UV performance. The highest nanoparticle content of 7% composite fiber gives the best far-infrared radiation and anti-UV performance. The newly developed Taichi masterbatch/PET functional composite fibers have potential application for the development of multi-functional textiles and apparels in the future.

Curing of a thermoset polythiourethane system of a diisocyanate and a trithiol was studied by Fourier infrared (FTIR) spectroscopy, dynamic rheological measurements and scanning electron microscopy...

An optical polythiourethane thermosetting system based on a 4-mercaptomethyl-3,6-dithia-1,8-octanedithiol and a m-xylylenediisocyanate has been studied. The solid-state isothermal cure reaction was followed by FTIR spectroscopy in the temperature range of 80–120°C. Kinetic and thermodynamic parameters were calculated using normalized conversion curves.

A polythiourethane thermoset system based on a diisocyanate and a trithiol was investigated by dynamic rheological measurements. Strain sweep was performed to determine the linear elastic region of the thermosetting system. The changes of characteristic parameters including elastic modulus, viscous modulus, and complex viscosity were recorded in a heating ramp to trace the cross-linking and structural evolution during the curing process. Time sweep at constant temperatures was also performed to explore possible curing strategy at reduced temperatures. In addition, frequency sweep was conducted to confirm the temperature- and time-dependent viscoelastic properties of the thermoset system during the curing process. Both continuous heating and isothermal aging gave rise to solidification of the polythiourethane with similar critical structure, as evidenced by the critical values of relaxation exponent. A combination of isothermal aging and heating is expected to be a facile strategy for fabricating thermoset polythiourethane polymers at lower temperature or/and reduced curing time. A kinetic study was done to confirm the gelation characteristics of the polythiourethane system, and the activation energy was also calculated.

An optical polythiourethane based on m-xylylene diisocyanate (XDI) and 4-mercaptomethyl-3,6-dithia-1,8-octanedithiol (BES) has been studied. Triethylamine was adopted as a catalyst, and the solid-state isothermal cure reaction was carried out using FTIR spectroscopy, in the temperature range of 75°C-105°C. The -NCO absorption band of XDI was used to monitor the conversion of diisocyanate into polythiourethane. The reaction rate enhanced with an increase in the content of the catalyst, and the gel time determined by swelling test was shorter for the system with higher catalyst content. Kinetic parameters were calculated from the infrared spectrum data, and the results showed that the curing reaction of polythiourethane accords with first-order kinetic characteristics. The activation parameters obtained from the evaluation of kinetic data were △H∗=97.22 kJ mol−1, △S∗=−6.77 J K−1 mol−1, and Ea=100.23 kJ mol−1. The observed negative entropy of activation value supported the formation of a transition state in the cure reaction.

The electrospinning of polyacrylonitrile (PAN) fibers from strain-hardening PAN solutions was studied. The strain-hardening PAN electrospinning solutions were prepared by adding ultrahigh-molecular-weight PAN (UHMWPAN) into medium-molecular-weight PAN (MMWPAN) solutions. The strain-hardening behavior of the solutions was evidenced by the CaBER extensional rheological tests. In electrospinning of PAN nanofibers, the solutions containing UHMWPAN were found to be stable when large electric field intensity was applied at a constant source-target distance, different from the case that a solution without UHMWPAN was used. PAN nanofibers with smaller diameter (270 nm compared with 496 nm for the nanofibers containing no UHMWPAN) could be electrospun from the strain-hardening solutions at larger electric field intensity and no beaded fibers were observed. The results of X-ray diffraction (XRD) and mechanical tests showed that the crystallinity, crystal orientation and mechanical performance of electrospun PAN nanofibers were improved with the increase of electric field intensity.

The spinnability in pre-gelled gel spinning of polyacrylonitrile (PAN) precursor fibers was investigated. The spinning solutions were aged at 25 °C for different times prior to fiber spinning. The pre-gelled spinning solution aged for 2.5 h was much more strain hardening than the ungelled one, which can increase the spinnability of the solution. The maximum take-up velocity of the first winding roller V 1m, which reflects the spinnability of the spinning solutions, was found to be largest when the aging time was 1.5 h. The spinnability increased with the increase of the air gap length and the lengthdiameter ratio L/D of the spinnerette. Once the L/D increased beyond 15, the spinnability hardly changed. The fibers spun from the spinning solution aged for 1.5 h had the best mechanical properties and favorable structure, showing that good spinnability favors the performance increase of resultant PAN precursor fibers.

Bovine serum albumin/poly(acrylic acid), BSA/PAA, nano-scaled particles were produced by noncovalent bonds induced self-assembly method at acid pH area. Proper conditions during preparation process, such as pH value, BSA/PAA weight ratio(WR), PAA molecular weight, were researched by studying the hydrodynamic diameter, polydispersity index, and ζ potential of the nanoparticles. Complex formation between BSA and PAA was studied by FT-IR, AFM, and TEM. BSA chains are supposed to be partly trapped in the nanoparticles core after interaction with PAA because of the electrostatic attractions and hydrogen bonds interactions between BSA and PAA, while the rest of the BSA chains should form the shell of the nanoparticles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The thermal-induced gel spinning of polyacrylonitrile/dimethyl sulfoxide/water solutions were performed. The structure and performance of the PAN precursor fibers were characterized by mechanical properties testing, swelling capacity testing, scanning electron microscopy, and X-ray diffraction. The effects of the water content, polymer concentration, coagulation bath temperature, and draw ratio on the cross-sectional morphology, structure, and tensile properties are reported. The results show that 2% water content is optimal due to dispersed small pores found in the fibers' cross section. With the coagulating bath temperature decreased, the large pores in fibers also decreased. Large pores almost disappeared up to −9°C. The mechanical properties of the PAN fibers increased with the enhancement of PAN concentration, while the decrease of the coagulating bath temperature or water content would induce the improvement of the fibers' mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The constant rotational rheological behaviors of PAN/DMSO solutions with two kinds of nonsolvent (water and ethanol) have been investigated, respectively, using a cone-plate rheometer. From viscosity measurements, the flow behavior was described within the shear rate range 0.1–1000 s−1. The PAN solutions show shear thinning at high shear rates. The viscosities of the solutions decreased with the rising of the temperature at low shear rate. H2O content has great influence on the viscosity of the solutions, depending on the hydration of H2O and PAN or desolvent effect, according to different H2O content. The role of ethanol compared with H2O was also researched and higher viscosity was found. Non-Newtonian index, structural viscosity index Δη, and flow activation energy of the PAN/DMSO/H2O systems were also studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The spinnability and polydispersity of polyacrylonitrile/dimethyl sulfoxide (PAN/DMSO)/H2O spinning solutions with conventional PAN molecular weight and comparative high PAN concentration have been investigated using a cone-plate rhe- ometer. It is observed from the measurements that, the viscosities of the solutions decreased with the rising of shear rate, and then stabilized to almost the same value, regardless of the PAN concentration. The chain orientation in the fiber formed under constant shear rate cannot be changed considerably even after long relaxation of more than 900s. For dynamic experiments, a steady increase of both G 0 and G 00 with escalating oscillation frequency was seen for all samples. Higher viscous-elastic mod- ulus at higher H2O content was found, too. It is also concluded from the log G 0 � log G 00 plot and the gel point that the PAN/DMSO/H2O system with regular PAN molecu- lar weight behaves very close to a mono-disperse system, thus very suitable for gel spinning and for preparation of high performance PAN precursor fiber. V C 2009 Wiley

The homogeneity of PAN/DMSO/H2O spinning dopes with conventional PAN molecular weight and comparative high PAN concentration have been investigated using rheology method. The rheological results show that G′ and G″ of these solutions increase with increasing oscillation frequency. At lower temperature and higher H2O content, higher viscous modulus and elastic modulus are observed, too. The homogeneity of PAN/DMSO/H2O systems is reflected through the logG′-logG″ plots as well as gel point temperatures. The theoretical analysis indicates PAN/DMSO/H2O spinning solutions with conventional PAN molecular weight are close to homogeneous systems, which are very suitable for gel spinning.