Embellish and be embellished

Nanoparticles have the functions of high temperature resistance, high temperature resistance, high temperature resistance, high temperature resistance, oxidation resistance, good weather resistance, good weather resistance, and excellent performance. It involves two aspects of nanomaterials, which is a hot spot. It involves matter and matter.

First of all, other nanoparticles, like nanoparticles, can look the same as nanoparticles on the surface part of the surface, in the middle part of the surface part and active, have a surface area that is very easy to aggregate, its surface is very easy to aggregate, the surface The area reduction is based on this characteristic, which can greatly improve the surface activity.

Provided, the water-polymerizing agent can be polymer, polymer, linear, low viscosity, polymer, etc.) substances with a special property for four different types of polymers to meet the requirements of use.

1. The "modified" of nano-alumina powder

01 Surface physical modification

Surface physical modification generally refers to the physical action of nano-alumina particles by using modifiers, such as adsorption, coating and coating by van der Waals force, or the surface modification of nano-powders by purely physical means, such as ultrasonic treatment, photoelectron irradiation treatment, heat treatment and plasma treatment.  The common modification methods include adsorption, coating and photoradiation treatment.  

(1) Adsorption  

The dispersion of nano-alumina particles in aqueous solution is very poor and easy to agglomerate.  Using surfactants can prevent the agglomeration of nanoparticles and make them more evenly dispersed.  Surfactants with two groups of different polarity, the polar hydrophilic group and water soluble, non-polar hydrophilic base adsorption to the surface of the particle, so in the particle surfactant outward extension to form a particle beam, prevent the particles from contacting each other, avoid the occurrence of agglomeration.  

(2) Cladding  

As with the adsorption method, coating is also through the van der Waals force and other heterogeneous materials deposited on the surface of nano alumina, the formation of a nuclear layer of nano alumina, shell and alumina without chemical combination of the "core-shell" structure, to prevent the agglomeration between particles, usually the amount of coating is larger than the adsorption.  

(3) Irradiation treatment  

Irradiation technology is a new technology of physical and chemical effects produced by the interaction between ionizing radiation and material. It uses high-energy rays to interact with material to transfer energy to alumina in a short time, so that the surface of alumina is ionized and excited, and various effects are produced, so as to achieve the modification of alumina particles.  For example, uv treatment of nano-size α -al2o3 dispersion is good, when the nano-alumina content of 6%, PVC plastic wear resistance is improved to the greatest extent.  

(4) Other methods  

In fact, there are many physical modification methods available in the dispersion of nano-powder, such as surface deposition, surface electroless plating, etc., often form alumina based composite materials, improve the dispersion of nano-particles at the same time, but also to a certain extent covered up the characteristics of nano-particles.  

02 Chemical modification method

The residual hydroxyl and residual charge on the surface of nano-alumina can be used to select the modifier for chemical reaction, change the structure and state of alumina surface, and achieve the purpose of surface modification.  The common methods of surface chemical modification of nano-alumina are as follows: ① coupling agent method;  ② Grafting method;  ③ Grafting - coating method.  

(1) Coupling agent method  

The surface energy of nano-alumina particles is higher than that of organic systems with lower surface energy.  When the two mix, it is easy to form phase separation.  The solution is usually coupling technology.  Coupling agent is generally a compound of bifunctional group, can react with inorganic and organic matter at the same time, when the coupling agent treatment, its one end is combined with the hydroxyl group on the surface of alumina, the other end acts with the disperse medium.  Silane coupling agent and titanate coupling agent are commonly used in the surface treatment of nano alumina.  

(2) Grafting method  

As mentioned above, there are active hydroxyl groups on the surface of nano-alumina. Hydroxyl groups are used as the active point of graft reaction to graft oil-soluble groups, and the grafted objects are generally small molecules. In essence, the coupling treatment is also equivalent to graft.  The advantages of this method are that the amount of grafting can be controlled and the efficiency is high.  

(3) Grafting - coating method  

In this method, a layer of organic matter (mostly small molecules) is formed on the surface of nano-alumina by grafting or coupling technology, and then the monomer is grafted and polymerized on the organic layer of particle surface by initiator. Finally, the inorganic-organic "core-shell" structure is formed with alumina as the core and polymerization layer as the shell.  The advantage of this method is that the shell thickness can be controlled by adding amount.  

2. Nano-alumina powder modified polymer

(1) Modified polyolefin  

Due to industrial production needs higher strength, wear resistance and stronger engineering and functional materials with special functions, so the study is particularly active in polyolefines modification at home and abroad, through the nano modified polyolefin resin, strength, toughness and electric properties generally can be improved, its application field is also growing.  In recent years, the modification of polyolefin by nano-alumina has been one of the hot topics in nano-modification research.  

(2) Modified polyester  

Baskaran et al. studied the influence of mass fraction of nano-al2o3 on unsaturated polyester (UPR).  The results show that the tensile strength, bending strength, impact strength, glass transition temperature and energy storage modulus of UPR/Nano-al2o3 reach the maximum when nano-al2o3 content is 5%.  Tang Guodong et al. prepared polymethyl methacrylate (PMMA)/acrylonitrile-styrene-acrylate terpolymer (ASA) alloy by melting blending method, and investigated the effect of nano-al2o3 content on the properties of PMMA/ASA alloy.  The results show that the surface wear decreases greatly with the increase of nano-al2o3 content.  

(3) Modified polyamide  

Chen Yufei et al prepared nano-al2o3 modified Nadiximide composite by sol-gel technology, and studied the effect of nano-al2o3 addition amount on the corona resistance and heat resistance of the composite.  The results show that with the increase of nano-al2o3 content, the corona resistance of the material is significantly enhanced.  

Zhang Yuqing et al. used silane coupling agent KH-560 to surface treat nano-al2o3 and then fused with nylon 6 (PA6) to prepare PA6 / nano-al2o3 composite material. The section morphology of the material was observed by scanning electron microscope.  The effects of raw material ratio and cooling rate on crystallization properties of PA6 / nano-al2o3 composites were studied by differential scanning calorimeter.  The results show that nano-al2o3 plays a heterogeneous nucleation role in the crystallization of PA6, which restricts the movement of PA6 molecular chain and increases the glass transition temperature and crystallinity of the composites.  

(4) Modified rubber  

Zhou Yuanxiang et al. prepared liquid silicone rubber (SiR)/nano-al2o3, and measured the influence of nano-al2o3 mass fraction on space charge characteristics of SiR by electro-acoustic pulse method.  The trap depth of SiR with different nano-al2o3 mass fraction was calculated according to the space charge dissipation process, and the effect mechanism of space charge on SiR performance was analyzed.  The experimental results show that with the increase of nano-al2o3 mass fraction, the space charge accumulation of SiR sample increases under the same applied field intensity, and dissipates more rapidly after pressure removal.  

Faghihi et al. studied the NBR/Nano-al2o3 mixture system by scanning electron microscopy and thermogravimetric analysis.  The results show that the tensile strength of NBR/Nano-al2o3 is 15% higher than that of pure NBR when nano-al2o3 is 2.5% of NBR mass.  The elongation at break of the composite decreases from 224% (pure NBR) to 159% (NBR/nano-al2o3) when nano-al2o3 is 7.5% of NBR mass.  At the same time, the addition of nano-al2o3 can improve the thermal stability of the mixed system. When the addition amount of nano-al2o3 is 5% of the mass of NBR, the maximum thermal weight loss temperature of NBR/nano-al2o3 is 3℃ higher than that of pure NBR.