Preparation And Properties Of Solvent-free Konjac Glucomannan Nanocrystal Fluid And Its Composite Materials

The development of modern science and technology is inseparable from resources,environment and materials.With the continuous exploitation of resources by mankind,mankind's destruction of nature is obvious to all.The excellent environmental compatibility,biodegradability,safety and environmental protection,and renewable characteristics of biomass polysaccharide nanocrystals have been gradually paid attention by researchers.It is the same as traditional inorganic nanoparticles and can be used as nanofillers to reinforce polymers.However,there are active hydroxyl groups on the surface of the polysaccharide nanocrystals,and their strong hydrogen bonds with each other,which lead to agglomeration in the polymer matrix,the role of reinforcing materials is greatly reduced,so they need to be surface modified.As a specialty resource of our country,konjac glucomannan(KGM)is abundant and is a natural polysaccharide.The environmentally friendly KGM nanocrystal is expected to replace inorganic nanoparticles as reinforcing fillers.The surface of KGM nanocrystal contains hydroxyl groups,which can be modified.The research contents are as follows:(1)KGM nanocrystal was prepared by acid hydrolysis of KGM,and infrared spectroscopy and X-ray diffraction(XRD)tests found that acid hydrolysis did not destroy the chemical structure of KGM nanocrystal,only increased the crystallinity.In order to adapt to different matrix material systems and preparation methods and improve the dispersion of KGM nanocrystal,surface modification is needed.First,KGM nanocrystal reacted with 3-(trimethoxysilylpropyl)octadecyl ammonium chloride(DC5700),and then achieve ion exchange with sodium nonylphenol polyoxyethylene ether sodium sulfate to obtain solvent-free KGM nanocrystal fluid.The infrared spectroscopy and elemental analysis tests proved the success of the modification.The transmission electron microscopy showed that after the modification,plate-like structure of KGM nanocrystals was retained.(2)KGM nanocrystal and solvent-free KGM nanocrystal fluid were added to the hydrophilic matrix PVA,and composite films with different contents were prepared by solution casting.The mechanical property test showed that the proper addition of KGM nanocrystals and solvent-free KGM nanocrystal fluids could enhance the toughness of PVA.XRD and thermal performance tests showed that the addition of KGM nanocrystals reduces the crystallinity of PVA and the thermal stability of the composite film decreases;and after modification of KGM nanocrystals,KGM nanocrystal fluid was just the opposite.Scanning electron microscopy images showed that at the same content,the solvent-free KGM nanocrystal fluid could be evenly dispersed in the PVA matrix compared to before modification,and the two have good compatibility.(3)KGM nanocrystal and solvent-free KGM nanocrystal fluid were added to the hydrophobic matrix PBS,and composite materials with different contents were prepared by melt blending.The mechanical property test showed that a small amount of KGM nanocrystals had a certain enhancement effect on PBS,and solvent-free KGM nanocrystal fluid improved the mechanical properties of materials more obviously.Scanning electron microscopy analysis showed that the KGM nanocrystalline fluid had better compatibility with the matrix PBS and was more uniformly dispersed in the matrix.Thermal performance tests show that a small amount of KGM nanocrystal had a limited effect on improving the thermal stability of the material,while solventfree KGM nanocrystal fluid did not improve the thermal stability of the material,and reduce the thermal stability of the material when there is too much content.