ABSTRACT:The filler action of dodecylamine (12C) intercalated montmorillonite (MNT) referred to as organomodified montmorillonite (12C-MNT) up to 4 wt % on natural rubber (NR) and styrene butadiene rubber (SBR) was studied and findings were compared with respect to the unmodified Na-MNT. X-ray analysis was used to calculate the interchain separation (R and RЈ), degree of crystallinity (X c ), and distortion factor (k). It is noted that R and RЈ showed the opposite trend, whereas X c as well as k showed overall increasing trend with an increasing amount of 12C-MNT on both NR and SBR. For Na-MNT (1 wt %) filled NR and SBR, the corresponding magnitude of R and R Ј and X c showed nearly no change, whereas k c increased significantly. The crosslinking density (v c ) does not show any significant changes in NR, whereas for SBR, it increases with increasing 12C-MNT as filler. Interestingly, in the case of 1 wt % pure Na-MNT used as filler for both NR and SBR, v c was lower compared to the virgin rubbers. Both swelling index (s i ) and sol fraction (Q) do not show any significant variation for NR composites, whereas these decrease for SBR composites with increasing concentration of 12C-MNT filler. On the contrary, NR and SBR with 1 wt % of Na-MNT filler show greater magnitude of s i and Q corresponding to the pure ones. Measurements of mechanical properties showed a significant increase in tensile strength and elongation at break for NR-12C-MNT (4 wt %) when compared with either virgin NR. In addition, modulus at the elongation at 100 and 200% in general increases with increasing loading of 12C-MNT filler in NR. Similar observations were also noted in the case of SBR. Interestingly, when only pure Na-MNT is used as filler, the strength of NR and SBR decreases drastically. Scanning electron microscopic studies were also to used support the mechanical behavior of NR-12MNT and SBR-12CMNT composites.
The present investigation reports the preparation of two types of 2D rod-like nano-hydroxyapatite (nHA) (unmodified and Polypropylene glycol (PPG) wrapped) of varying high-aspect ratios, by modified co-precipitation methods, without any templates. These nHA were successfully introduced into novel synthesized Thermoplastic Polyurethane (TPU) matrices based on polycarbonate soft segments, by both in-situ and ex-situ techniques. Physico-mechanical properties of the insitu prepared TPU/nHA nanocomposites were found to be superior compared to the ex-situ counterparts, and pristine nHA reinforced TPU. Improved biocompatibility of the prepared nanocomposites was confirmed by MTT assays using osteoblast-like MG63 cells. Cell proliferation was evident over an extended period. Osteoconductivity of the nanocomposites was observed by successful formation of an apatite layer on the surface of the samples, after immersion into simulated body fluid (SBF). Prothrombin time (PT) and activated partial thromboplastin time (APTT), as calculated from coagulation assays, displayed an increase in the clotting time, particularly for the PPG-wrapped nHA nanocomposites, prepared through the in-situ technique. Only 0.3% of hemolysis was observed for the in-situ prepared nanocomposites, which establishes the antithrombotic property of the material. The key parameters for enhancing the technical properties and biocompatibility of the nanocomposites are: the interfacial adhesion parameter (B y ), the polymer-filler affinity, the aspect ratio of filler and non-covalent modifications, and the state of dispersion. Thus, the novel TPU/polymer wrapped nHA nanocomposites have great potential for biomedical applications, in particular for vascular prostheses, cardiovascular implants, scaffolds, and soft and hard tissues implants.
Cardanol grafted natural rubber, prepared at room temperature, is a potential green substitute for carcinogenic aromatic oil plasticized natural rubber.
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