复合材料课件6

6.2 Preparation of nanocomposite
6.2 Preparation of nanocomposite y Blending is generally just mixing of the silica nanoparticles into the polymer; y a sol-gel process can be done in situ in the presence of a preformed organic polymer or simultaneously during the polymerization of the monomer(s); y the method of in situ polymerization involves the dispersion of nanosilica in the monomer(s) first and then polymerization is carried out
Other solution
y Another excellent solution is thermal spraying. y Thermal spray generally is a process in which a material is heated, accelerated, and propelled by a high-temperature jet through a confining nozzle toward a surface. y The individual molten or softened droplets impact, spread, cool, and solidify to form continuous coatings. High-velocity oxy-fuel (HVOF) provides thermal energy for heating provided by combusting fuels with oxygen.
6.2 Preparation of nanocomposite
The organic component can be introduced as y (i) a precursor, which can be a monomer or an oligomer, y (ii) a preformed linear polymer (in molten, solution, or emulsion states), or y (iii) a polymer network, physically (semicrystalline linear polymer) or chemically (thermosets, elastomers) cross-linked.
6.2 Preparation of nanocomposite The mineral part can be introduced as (i) a precursor (e.g., TEOS) or (ii) preformed nanoparticles. Organic or inorganic polymerization generally becomes necessary if at least one of the starting moieties is a precursor.
the small size of the fillers leads to a dramatic increase in interfacial area as compared with traditional composites. This interfacial area creates a significant volume fraction of interfacial polymer with properties different from the bulk polymer even at low loadings.
Inorganic nanoscale building blocks
Nanotubes; layered silicates (montmorillonite, saponite), nanoparticles of metals (Au, Ag), metal oxides (TiO2, Al2O3), semiconductors (PbS, CdS), and so forth.
Effects of the nanoparticles y the reinforcing and toughening effects of the nanoparticles on the polymer matrix could be fully brought into play at a rather low filler loading (less than 3 vol %) y The technique was characterized by many advantages:
Chapter 6 Polymer Nanocomposite
outline 6.1 Introduction 6.2 Preparation of nanocomposite 6.3 Colloidal Nanocomposites 6.4 Incompatibility of polymers and minerals 6.5 Characterization and Properties 6.6 Applications
Advantages 1. inorganic material y Rigidity; y thermal stability 2. organic polymer flexibility, dielectric, ductility, processability
Defining feature of polymer nanocomposites
6.2.1 Blending
y The traditional and simplest method of preparing polymer/silica composites is direct mixing of the silica into the polymer. y The mixing can generally be done by melt blending and solution blending. y The main difficulty in the mixing process is always the effective dispersion of the silica nanoparticles in the polymer matrix, because they usually tend to agglomerate.
6.2.1.3 Other Blending Methods y the melt or solution route becomes infeasible when the particle load is high, the polymer melt is viscous, or the polymer just does not melt at all. y overcome these problems is : to process the polymer in the solid state, which avoids the thermal and solvent problems encountered with traditional technologies while providing almost infinite design flexibility and processing simplicity.
6.2.1.2. Solution Blending y The location for solution blending is not limited to a solution y and can include a latex or a suspension. y A method through solution blending y and then compression molding is also applied.
9 being simple, 9 low cost, 9 easy to control 9 and broadly applicable.
Effects of the nanoparticles y A double percolation of stress volumes around the nanoparticles and their agglomerates, explained the reinforcing and toughening effects of the treated nanoparticles.
6.1 Introduction When inorganic phases in organic/inorganic composites become nanosized, they are called nanocomposites. Organic/inorganic nanocomposites are generally organic polymer composites with inorganic nanoscale SiO2 is viewed as being very important. polymer/silica composites are the most commonly reported in the literature. They have been employed in a variety of applications.