Preparation Of Inorganic Whisker/POSS Hybrid Material And It's Enhanced In PVA Properties

Inorganic whiskers are a new type of micro-nano-reinforced materials with excellent mechanical properties and chemical stability.They are widely used as reinforcing agents in plastics,ceramics,coatings,rubber and other materials.Whereas,owing to their strong polarity and high surface energy,inorganic whiskers aggregate easily and have poor dispersionin polymer matrix,which leads to decreased performanceof the target composites.Therefore,in this paper,the key problems of easy agglomeration and poor interfacial force in inorganic whisker reinforced polymer composites are studied by surface modification ofmagnesium hydroxide sulfate hydratewhisker?MHSH?by means of thiol-ene click chemical reaction.A polyhedral oligomeric silsesquioxane?POSS?was introduced into the surface of the thiolated MHSH whisker to create a new class of inorganic whisker/POSS multiscale hybrid materials that are used to enhance polyvinyl alcohol?PVA?for high performance.Firstly,MHSH was first thiolated by silane coupling agent?KH590?according to the traditional wet modification to obtain MHSH-SH with-SH grafted on the surface.The effects of reaction temperature,time and the amout of KH590 on the surface contact angle of MHSH-SH were investigated.The results showed that the hydroxyl groups of alcohols in KH590 after hydrolysis combined with the hydroxyl groups on MHSH surface by intermolecular hydrogen bonding,which resulted in the mercaptosylation of the whisker surface.When m?KH590?:m?MHSH?=1:6,reaction temperature is 70 ^oC and reaction time is 4 h,the contact angle of MHSH-SH reaches the maximum value of 80.09^o.At this time,the grafting ratio of KH590 is9.35%,which was calculated from TG datas.The surface of magnesium hydroxide sulfate hydrate changes from hydrophilicity to hydrophilicity.Secondly,a new type of magnesium hydroxide sulfate hydratewhisker/POSS multiscale hybrid material?MHSH-SH-POSS?was synthesized by anti-Markov addition reaction of MHSH-SH the octavinyl POSS which have external reactive group of-C=C to complete the grafting of rigid POSS.The structure and properties of MHSH-SH-POSS were analyzed analyzed through FI-IR,XRD,XPS,HRTEM and contact angle.It can be found that the contact angle of MHSH-SH-POSS is as high as 103.12^o,which proves that the whisker surface has changed from hydrophilic to hydrophobic.When m?OVPOSS?:m?MHSH-SH?=0.4,the surface free energy of MHSH-SH-POSS is reduced to a minimum of 26.27 mJ·m^-2,which is reduced by about 35.38 mJ·m^-2 compared with the surface free energy of unmodified MHSH of61.55 mJ·m^-2.The reduction of surface free energy effectively reduces the agglomeration of basic magnesium sulfate whiskers.Finally,PVA/MHSH and PVA/MHSH-SH-POSS composites were prepared by solution casting method,and the effects of MHSH and MHSH-SH-POSS hybrid materials on the properties of PVA were discussed.The results showed that the more uniform particle dispersion and better compatibility of MHSH-SH-POSS hybrid materials in PVA matrix lead to stronger interfacial bonding between hybrid materials and PVA matrix,which improves the corresponding mechanical properties,thermal stability,water resistance and thermoplasticity of PVA composites.When the content of MHSH-SH-POSS is 2 wt%,the tensile strength,elongation at break and storage modulus of PVA/MHSH-SH-POSS composites reach 97.04 MPa,139.63%and 7930MPa respectively,which are 123.59%,36.20%and 23.52%higher than pure PVA,respectively.Hydroxyl groups in the PVA chain react with hydroxyl groups on the surface of MHSH to form hydrogen bonds,which make MHSH play a physical cross-linking role in the PVA matrix,improve the compatibility between MHSH and PVA,and make the interface between MHSH and PVA matrix stronger.