| As a widely applied polymer, modifications of polypropylene(PP) have been an important research field. The hydrophobic of PP limits its application, such as dyeing, poor hydrophilicity, etc. At first, silica nano capsules(SNCs) were melt blended with PP, and then the composites were stretched to filament via melt-spun. Their composites enhanced the dyeing and mechanical properties of PP and expanded the application area of PEOS. The popular ways of generating nano and submicron fiber were employed in this dissertation- electrospun and forcespun. PP was melt blended with amphiphilic small molecular, then we studied the surface hydrophilicity of their melt electrospun fibers and forcespun meshes, which could enlarge specific surface area. Moreover, melt electropsinng has an adcantage of solvent free. Forcespinning uses centrifugal force to fabricate nanofibers rather than electrostatic force as in conventional electrospinning. The absence of electric fields provided a board opportunity for low dielectric materials and the utilization of centrifugal forces is environment friendly.Firstly, hyperbranched polyethoxysiloxanes(PEOS) were synthesized on a condensation reaction of tetraethoxysilane. Poly(ethylene glycol) substituted PEOS guided the formation of structured silica nano capsules via self-templating aggregation in water. PP was melt blended with SNCs via a corotating twin screw microcompounder. For the preparation of filaments, the molten polymer was stretched to filament by DSM Xplore Fiber Spin Line. Dispersion quality of silica nano capsules was examined by FE-SEM. The crystallization behavior, thermal and mechanical properties of composites were investigated. FE-SEM graphs showed unmodified SNCs formed large aggregates and unevenly distributed throughout the PP matrix. However, SNCs dispersed randomly in the PP after modified with hydrophobic alkyl chain. It was indicated that SNCs showed excellent dispersion in the PP matrix. TEM graphs from cryo ultramicrotome indicated that the modified SNCs were still undamaged and retained the core-shell structure even after melt blending process. Not only the melting temperature increased by the presence of modified SNCs, but the crystallinity of the peak also slightly increased. Higher crystallization peak temperature reflected the nucleating effect of SNCs on PP crystallization, which indicated that SNCs-C18 acted as heterogeneous nucleating centers. The crystal integrity was improved and the duffusion of dye became readily. The incorporation of a small quantity of modified SNCs could not deteriorate the thermal stability. What’s more, the incorporation of modified SNCs not only reinforced the PP filaments from 527.1 MPa to 537.9 MPa, but also increased the ductility from 13.8% to 15.8%. Dyeing experiments indicated that the colour yield of composites filaments with modified SNCs was improved. SNCs, which were prepared by selfassembling process, dispersed randomly in the PP after modified with hydrophobic alkyl chain, and the mechanical and dyeing properties of their composites for disperse dye were enhanced. The results of WPU/SNCs composites films showed the chemical crosslink between SNCs and WPU, which was quite different from the physical entangling between SNCs and PP.Secondly, PP was melt blended with amphiphilic small molecular, such as TWEEN20, TWEEN60 and modified polyethoxysiloxanes. The blends were melt electrospun to enlarge the specific surface area of fibers in order to improved the hydrophilic. The fitness of fiber has a special effect on its performance, so we discussed the factors which influenced the diameter of melt electrospun fiber of PP. And influence factors, such as flow rate, temperature of polymer melt, applied voltage, distance between nozzle and target and electric field force, were considered. The influence factors of electrospun fibers were determined by SEM graphs. Generally consideration, the parameters as follow: flow rate was 0.05 mL/h, temperature was 260/280℃(polymer melt/nozzle), voltage was-24.6 kV and distance was 30 mm. The electrospun fiber under the parameters mentioned above was 6.23 μm, standard deviation was 1.42. The PP blends electrospun fibers were performed by Attenuated Total Reflection Fourier-Transform Infrared(ATR FT-IR) Spectroscopy, X-ray photoelectron spectroscopy(XPS) and contact angle measurements. The thermodynamics of electrospun fibers were measured by Differential Scanning Calorimetry(DSC) analysis. The characteristic peaks of O-H and C-O from FT-IR spectrums indicated PP had been blended with TWEEN20. DSC graphs showed the crystallinity of PP increased with the increase of the load of TWEEN20. The crystallinity increased from 45.4% to 53.5% when TWEEN20 content increased form 0% to 5%. The crystalline structure of the PP was not influenced by the introduction of amphiphilic surfactant, which acted as heterogeneous nucleating centers as a result of the increasing crystallinity. XPS results demonstrated that substantial enrichment of TWEEN20 segments on the surfaces was detected. After blended with TWEENs, the contact angle of the electropsun fibers reduced considerably, especially when the load of TWEEN20 was up to 3%. The electropsun fibers exhibited excellent hygroscopicity even when the load of TWEEN20 was 5%. These indicated the hydrophilic of PP was significant improved after blending with TWEEN20. Howerver, the contact angle of 5%TWEEN60 began to reduce after 1.5 min and the wetted fibers started from 3.5 min. The effect of TWEEN60 was not so good as TWEEN20 because of itself longer alkyl chain.Finally, in order to overcome the disadvantage of melt electrospining, such as high voltage, we employed centrifugal force instead of electrostatic force. In this dissertation, PP was melt blended with amphiphilic small molecular via a co-rotating twin screw microcompounder, then PP meshes were prepared by Forcespinning technology. The factors were investigated by SEM and DSC, which determined fiber diameter distribution and crystallinity. The meshes showed continuous homogeneity along the length of the fiber when the system was employed at 225℃ and the rotate speed was kept at 14,000 rpm. It was evident that Tm and Tc of the meshes increased as rotate speed increased, which proved that the crystal integrity increased and crystalized at high temperature. The crystallinity decreased as the content of TWEENs increased to 5%, however the crystallinity increased when the content of TWEENs was up to 10%. The small molecule retarded the orientation of PP long chain when the small amounts of TWEENs dispersed in bulk. After enrichment of TWEENs segments on the surfaces, they preferred to form micelle in order to reduce the interface free energy, which acted as heterogeneous nucleating center. It could be concluded from TGA data that decomposition temperature did not decrease markedly afer the addition of TWEEN20 into PP. It could be seen that the incorporation of all the additives slightly decreased the material stiffness, which was indicated by the decreased tensile modulus. This effect was caused by the presence of alkyl acting as slipping agent in the surfactant-polymer interface, giving greater mobility to polymer molecules around the surfactant in the blends under the tensile stress conditions. With TWEEN60 increasing alkyl chain length, the interfacial slippage became more difficult due to increased interfacial interactions, resulting in higher tensile strain. XPS results indicated preferential distribution of additives on the surface. For all the samples, the content of O atomic on the surface was much higher than that of the corresponding theoretical values, indicating substantial enrichment of TWEENs segments on the surfaces. The forcespun meshes exhibited excellent hygroscopicity even when the load was 10%. These indicated the hydrophilic of PP forcepsun meshes was significant improved after blending with TWEENs. The hydrophilic modification of amphilic PEG-PEOS-Alkly was not effective as TWEENs due to their enormous network structure. |
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