Novel self-healing supramolecular elastomers based on polydimethylsiloxanes (SESi) were synthesized from a mixture of polydimethylsiloxanes derivers with single, di-, or tri-carboxylic acid groups (PDMS-COOH x , where x ¼ 1, 2, and 3, respectively), diethylene triamine, and urea with a two-stage procedure. The reactions and the final products were tracked, characterized, and confirmed by Fourier transform infrared spectroscopy, 1 H-NMR, differential scanning calorimetry, dynamic mechanical analysis, and gel permeation chromatography. Compared with a supramolecular rubber based on dimer acid (reported previously) with a similar synthesis procedure, the SESi showed a lower glass-transition temperature of about À113 C for the softer chain of polydimethylsiloxane and showed real rubberlike elastic behavior and self-healing properties at room temperature or even lower temperatures.

Supramolecular elastomers obtained through a two-step reaction of linear carboxyl-terminated polydimethylsiloxane oligomers (PDMS–COOH2) with diethylenetriamine (DETA) and urea show reasonable hysteresis and acceptable self-healing properties.

Carbon black (HAF) filled powdered natural rubber (P(NR/HAF)) was prepared and the particle size distribution, mechanical properties, and micromorphology of P(NR/HAF) were studied. A carbon black-rubber latex coagulation method was developed for preparing carbon black filled free-flowing, noncontact staining NR powders with particle diameter less than 0.9 mm. A powdering mechanism model was put forward to describe the powdering process, which shows that the key technical points consist in the surfactant with good emulsification properties and the polymer coating resin with good film forming properties. SEM analysis shows that carbon black and rubber matrix have formed a macroscopic homogenization in the P(NR/ HAF) particles without contact staining, and carbon black particles are well dispersed in rubber matrix with diameter of about 50 -150 nm. P(NR/HAF) vulcanizate showed better mechanical properties than bale natural rubber/carbon black blends (NR/HAF) and simple NR latex/carbon black blends (NRL/HAF), which depends primarily upon the absence of free carbon black, the fine dispersion of filler on the rubber matrix, and the better interaction between carbon black and rubber matrix due to the proper preparation condition of noncontact staining carbon black filled powdered NR.

Well‐defined statistical and diblock copolymers with acrylamide and acrylic acid were synthesized by inverse miniemulsion RAFT polymerization. Statistical copolymers with various composition ratios were synthesized. Compositional drift was observed during polymerization. Acrylamide was polymerized with a water‐soluble initiator (VA‐044) at 60 °C to give the RAFT‐agent‐containing acrylamide homopolymer with a narrow molecular‐weight distribution (PDI < 1.3), which was then chain‐extended with acrylic acid to obtain the diblock copolymer.magnified image

ABSTRACT:The surface modification of nano calcium carbonate (nCaCO 3 ) particles was carried out with a soluble compound of lanthanum via a coating process of chemical deposition, and nCaCO 3 particles covered with a compound of lanthanum (nCaCO 3 -La) were prepared. The polypropylene (PP)/nCaCO 3 and PP/nCaCO 3 -La composites were prepared with a two-roll mill. The measurements of the mechanical properties showed that the impact strength of the composites increased at first and then decreased with the addition of fillers, and the tensile strength was reduced at the same time. The impact strength of PP/nCaCO 3 -La was higher than that of PP/nCaCO 3 , and the impact strength of PP/nCaCO 3 -5La was three times that of virgin PP. Transmission electron microscopy and scanning electron microscopy showed that nCaCO 3 -La dispersed well in the PP matrix, the size distribution of the particles was uniform, and nCaCO 3 -La adhered to the PP matrix very closely. The crystallization properties of virgin PP and its composites were studied with differential scanning calorimetry and wide-angle X-ray diffraction. The results showed that the ␤-PP phase easily formed with the addition of the lanthanum compound. In comparison with virgin PP, the addition of nCaCO 3 -La led to a higher crystallization temperature. The size of the crystallites increased with the addition of nCaCO 3 -La, and the nucleation of PP crystalline was also improved.