A Novel Thermoplastic Elastomer by Reaction-Induced Phase Decomposition from a Miscible Polymer Blend

SMART THERMOPLASTIC ELASTOMERS WITH HIGH EXTENSIBILITY FROM POLY (VINYLIDENE FLUORIDE) AND HYDROGENATED NITRILE RUBBER: PROCESSING–STRUCTURE–PROPERTY RELATIONSHIP

Novel smart thermoplastic elastomers (TPEs) with very high extensibility were prepared by blending polyvinylidene fluoride (PVDF) with hydrogenated nitrile rubber (HNBR) at an appropriate ratio, and their processing–structure–property relationship was investigated. Although the rubber phase was found to be dispersed in the matrix of PVDF for all compositions, morphology was shear sensitive and changed significantly after each processing step. Dropletlike structure was observed after the mixing in an internal mixer and compression molding, which changed to the lamellar structure after milling and injection molding. The compression molded sample exhibited very high extensibility (∼1600% elongation at break for 30/70 PVDF/HNBR blend) and a tensile strength of ∼6 MPa due to the formation of a strong interface. The elongation at break was much higher than any of the TPEs reported so far. Theoretical calculation of rubber particle size was also in agreement with the experimental observation. Dissipative particle dynamics simulation was run to capture the morphology, where HNBR chains were more sensitive to the shear force than the PVDF chains. The electromechanical sensitivity of the blend was 14.3 MPa−1, much better than the existing reported elastomeric actuator as well as pristine PVDF. Dynamic vulcanization gave further improvement in tensile strength and tension set properties.

Deformation mechanisms of sub-micrometer thermoplastic vulcanizates obtained by reaction-induced phase separation of miscible poly(ε-caprolactone)/dimethacrylate systems

The micromechanical deformation mechanisms of sub-μm thermoplastic vulcanizates (TPVs) based on poly(ε-caprolactone) (PCL) and cross-linked methacrylate rubbers were studied by time-resolved small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) measurements in order to better understand the underlying deformation mechanisms responsible for the high elongation at break and good elastic recovery of sub-μm TPVs. It is demonstrated that, in contrast to neat PCL, the interlamellar void formation in the PCL matrix and subsequent coalescence of voids is suppressed by the presence of the rubber (nano)particles in these TPVs. The deformation of the TPVs under tensile conditions is dominated by yielding of the PCL matrix, which is initially localized at the equatorial regions of the rubber particles and progresses towards the polar regions at higher strains. Re-ordering of the crystal structures is both time and stress dependent, and stress relaxation of the TPV under tension is primarily governed by the break-up of the crystal lamellae at the equatorial regions of the rubber particles. This study demonstrates that the rubber particle size as well as chemical grafting of thermoplastic polymer chains onto the surface of cross-linked rubber particles are important parameters to control the mechanical deformation behavior of TPVs.

Novel heat and oil-resistant thermoplastic vulcanizates based on ethylene-vinyl acetate rubber/poly(vinylidene fluoride)

Thermoplastic vulcanizates (TPVs) combine the excellent elasticity of conventional vulcanized rubbers and the easy processability and recyclability of thermoplastics.

Selective dispersion of carbon fillers into dynamically vulcanized rubber/plastic blends: a thermodynamic approach to evaluate polymer reinforcement and conductivity enhancement

Phase selective and thermodynamically controlled dispersion of filler particles into the dynamically vulcanized rubber/plastic blends depicting higher abundance of carbon black in the thermoplastic phase with the progressive filler addition.

Effects of dynamic vulcanization on the kinetics of isothermal crystallization in a miscible polymeric blend

Is it possible to determine the state of phase separation using the free energy of folding parameter?

Does dynamic vulcanization induce phase separation?

Immiscible and miscible blends of poly(vinylidene fluoride) (PVDF) and acrylic rubber (ACM) were subjected to dynamic vulcanization to investigate the effect of crosslinking on phase separation. As a result of different processability, mixing torque behavior of miscible and immiscible blends was significantly different from one another. Scanning electron microscopy (SEM) was used to investigate the morphology of the system. After dynamic vulcanization, submicron ACM droplets were observed in the samples near the binodal curve of the system under mixing conditions. Small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) analysis were used to investigate the effect of dynamic vulcanization on the lamellar structure of the system. It was shown that for samples near the boundary of phase separation, increasing the crosslink density led to a decrease in the lamellar long period (L) as a sign of increment of crosslink density induced phase decomposition. Effects of shear rate on the final morphology of the system were investigated by changing the mixing temperature and by comparing the results of dynamic vulcanization at one phase and two phase regions.

Influence of miscibility phenomenon on crystalline polymorph transition in poly(vinylidene fluoride)/acrylic rubber/clay nanocomposite hybrid

In this paper, intercalation of nanoclay in the miscible polymer blend of poly(vinylidene fluoride) (PVDF) and acrylic rubber(ACM) was studied. X-ray diffraction was used to investigate the formation of nanoscale polymer blend/clay hybrid. Infrared spectroscopy and X-ray analysis revealed the coexistence of β and γ crystalline forms in PVDF/Clay nanocomposite while α crystalline form was found to be dominant in PVDF/ACM/Clay miscible hybrids. Flory-Huggins interaction parameter (B) was used to further explain the miscibility phenomenon observed. The B parameter was determined by combining the melting point depression and the binary interaction model. The estimated B values for the ternary PVDF/ACM/Clay and PVDF/ACM pairs were all negative, showing both proper intercalation of the polymer melt into the nanoclay galleries and the good miscibility of PVDF and ACM blend. The B value for the PVDF/ACM blend was almost the same as that measured for the PVDF/ACM/Clay hybrid, suggesting that PVDF chains in nanocomposite hybrids interact with ACM chains and that nanoclay in hybrid systems is wrapped by ACM molecules.

Thermally cross-linked and sulphur-cured soft TPVs based on S-EB-S and S-SBR blends

Novel thermally cross-linked and sulphur-vulcanized TPVs based on S-EB-S and S-SBR blends have registered good mechanical and dynamic mechanical properties with reduced hardness suitable for automotive applications.

Mechanochemical Milling of PP/Ground Tire Rubber Blends in Solid-State

In this study, solid-state mechanochemical milling was investigated as a viable strategy to produce high performance blends composed of polypropylene (PP) and ground tire rubber (GTR), thereby providing a potentially new route to recycle discarded tires. The improved dispersion of the blends after mechanochemical milling was confirmed by fluorescence microscopy and polarized optical microscopy (POM) observation. After 20 cycles of milling, the tensile strength of PP/GTR (100/40) blends was enhanced by 13.8%, and the elongation at break was over 12 times than that of the unpretreated blend. The formation of smaller and less ordered spherulites of PP after mechanochemical milling as confirmed by POM observation and wide-angle X-ray diffraction analysis might be the reason for the significant enhancement of the elongation at break.