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Poly(vinylidene fluoride) (PVDF)/montmorillonite (MMT) nanocomposites were prepared by melt blending a kind of organically modified montmorillonite with PVDF. The morphological structures of the nanocomposites were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). The results indicate that organically modified montmorillonites are in the form of intercalation, exfoliation, and fragments in the PVDF matrix. For the composites, the (001) peak position of MMT was found to shift to a lower angle in XRD patterns, and some MMT fragments could be observed under TEM. MMT loading was favorable to producing the piezoelectric β phase in the PVDF matrix and caused internal stress in α crystals. At the same time, the crystallinity and spherulite size of PVDF decreased with the MMT content. MMT induced β phase is stable even at high temperatures (160℃). For these changes in morphological structures, some possible explanations were proposed based on the experimental results.organically modified montmorillonite, nanocomposite, crystalline structure Polymer/MMT nanocomposites represent new class materials during the last decade. Compared with conventional filled grades of polymer, the nanocomposites exhibit the following characteristics: (1) Adding small amounts of MMT (below 5wt%) to polymers increases the yield strength, tensile modulus, improve toughness, and barrier properties, and also lowers materials weights.(2) The nanocomposites were found to have excellent thermal stability and better dimensional stability. (3) These nanocomposites exhibit superior mechanical properties to conventional fiber-reinforced composite materials. (4) The plane orientation of nano-size silicate platelets in polymer matrix leads to reduced flammability. (5) Layered MMT is abundant in natural resources and has a low price. Therefore, nanocomposits have attracted great interest from researchers in recent years [1][2][3] . Many polymer/MMT nanocomposites have been prepared so far, and their structure and properties have been studied extensively; however, some fundament mechanisms in the nanocomposites are not well understood yet.For crystalline polymer matrix, this problem turns out to be more complicated, because the addition of silicate platelets impacts not only the conformation and morphology of the polymer chains, but also the crystalline behavior [4] . Evidence has been shown that the silicate platelets affect the formation of the lamella [4] , the formation of spherulites [5,6] , the crystallization rate [7] , and the crystalline phase [8,9] .PVDF is a crystalline polymer which has at least four crystalline phases, i.e., α, β, γ and δ phases. The α phase is the most common in melt crystallization. The δ phase does not form except at high temperatures (170℃). The γ phase is normally obtained and applied an extremely high electric filed to α phase. Among the four polymorphs, however, more attention has been paid to the β

Thirteen triazole polymers were prepared as potential rocket propellant binders by the reactions of various diacetylenes and diazides. The reaction of E300 dipropiolate (1) with diazide (2) obtained from tetraethylene glycol was selected to study the effects of concentration of the tetraacetylene functionalized crosslinker (3) on the mechanical properties of resulting triazole polymers. The modulus of the polymers increased, whereas the strain (% elongation at failure) decreased with increasing percentage of crosslinker. The resulting triazole polymers also showed that the desired mechanical properties could be obtained by adjusting the crosslinker concentration during the polymerization. Addition of 43 wt % aluminum filler did not significantly affect the strain. The modulus of these triazole polymers was comparable with typical polyurethane elastomeric matrices for rocket propellants.

ABSTRACT:The mechanical properties of crosslinked polymers depend on their structural features, one of which is the functionality of the crosslinks in a polymer network. To study the effect of crosslink functionality (U) on the mechanical properties of 1,2,3-triazole polymers for potential application as rocket propellant binders, crosslinkers with different U's (3, 4, 6, 16, 32, and 64) were used in the polymerization. As the percentage of acetylenic groups provided by crosslinker was kept constant and the functionality of the crosslinker increased, the resulting polymer showed a higher modulus but a lower strain. Compared to traditional polyurethane binders, 1,2,3-triazole polymers showed comparable mechanical properties, although the stress and modulus tended to be lower and the strain capability tended to be greater for the triazole-linked rubbers.