Resin whiskers into

Considering epoxy resin filled with potassium titanate whisker as an example, the specific operation is as follows. Mix bisphe-nol A-glycidyl methacrylate (bis-GMA) and triethylene-glycol dimethacrylate at a mass ratio of 1 1 as a resin matrix add initiator benzoyl peroxide (BPO) and the polymerization inhibitor butylated hydroxytoluene (BHT, 264) and blend uniformly. Then mix surface-modified potassium titanate whisker into the resin, fill into the mold, and cure in an oven at 120°C for 30 minutes. 

The thermal stability of a material sometimes is represented by the temperature of 5% decomposition and usually can be determined by a thermogravimetric method. Because inorganic fillers have a high melting point, adding inorganic fillers into resin can improve the heat resistance of the polymer. A composite material is prepared by filling calcium carbonate whiskers into PP material. The thermal decomposition temperature (5% decomposition) of the composite material increased from 366.7 to 400.6°C as the whisker content was enhanced. 

He found that zinc oxide whiskers can effectively improve the conductive property of PP resin. When the whisker volume fraction reaches 3%, the resistivity of the material decreases to below 10 Q cm, which is seven orders of magnitude lower than the resistivity of a pure PP matrix, whose resistivity is 10 Q cm and could meet the requirement of a general antistatic material. Wan and Jin put zinc oxide whiskers into an epoxy resin and obtained the same findings. Zhou et al. believed that there are three kinds of conductive mechanisms in the system network conduction, tunnel effect, and point discharge effect. 

Fibers having an aspect ratio of above 10, such as glass fibers, asbestos, wollastonite, cellulose fibers, carbon fibers, and whiskers, act as reinforcing agents. Composites may be classified into four groups, as shown in Table II. In modern composites, such as in the case of epoxy resins reinforced with carbon fibers (51). the polymer matrix has only a secondary function to separate the individual fibers from one another and to transfer energy to the fiber surface the fibers almost completely withstand the mechanical load. 

Magnesium sulfate whiskers have both reinforcing and flame retardant effects when hlled into plastic or resin matrix to make composite materials. Composites manufactured with magnesium sulfate whiskers can be used in some parts of trains, trucks, and other motorcars because of their excellent chemical and physical performances. Figure 3.10 shows the microstructure of magnesium sulfate whiskers. ... 

The method for bismaleimide resin filled with whiskers is similar to the preceding. The mass ratio of BMI (bismaleimide) and BA (diallyl bisphenol A) is 1 0.8. First, heat BA to 130°C, then add BMI slowly, prepolymerize for 20 minutes, add the whisker, mix uniformly, pour into a glass mold coated with a release agent, vacuum and deaerate at 120-130°C for 15 minutes, and cure according to the following sequence l45°C/2 h + l60°C/2 h + 180°C/2 h + 200°C/2 h. Finally, posttreat at 220°C for 6 h. 

Guo et al. 5 ook resin matrix composites filled with SIC whiskers as an example and analyzed the effect of the inter-facial zone state on mechanical properties of composite materials by finite element method. They hold that when whiskers are randomly distributed in a resin matrix with a certain volume fraction, they demonstrate a periodic distribution from the statistical point of view. It is assumed that the SIC whisker-reinforced phase in resin matrix composites is arranged in one direction without considering the effect of whisker orientation, the analysis model can be simplified as a rotator shape with the large cylindrical part as the polymer matrix and the small cylindrical part as the whisker. Therefore, a three-dimensional problem turns into an axisymmetric problem, and only a quarter part of the body model is taken in the calculation. 

The heat conduction of whiskers relies mainly on lattice vibration, namely phonon vibration thus thermal conductive performance is excellent, whereas the heat conduction of polymer materials depends mainly on internal vibration between atoms, which makes the thermal conductive performance poor. If whiskers are filled into polymers, they overlap with each other in a matrix and form pathways of heat conduction. Therefore the thermal conductivity of the composite will be greatly increased. Zhou found that low filling content can effectively improve the thermal conductivity performance of epoxy resin. When the whisker content is only 10%, the thermal conductivity of the material increased by 3 times compared with the pure matrix. Li et al. found that the thermal conductivity of PP filled with 30% zinc oxide whiskers increased by 55.9% over pure PP. 

Carbon fibers, when used without surface treatments, produce composites with low mechanical properties. This has been attributed to weak adhesion and poor bonding between the fiber and matrix. Therefore, the carbon fibers are given surface treatments, the exact nature of which is a trade secret. This surface treatment increases the surface active sites which results in the improvements of the bonding between the fibers and the resin matrix. This tends to increase the wettability of the carbon fibers and enhances the mechanical properties [4-7]. Surface treatments may be classified into oxidative and nonoxidative treatments. An oxidative treatment involves gaseous oxidation, liquid-phase oxidation carried out chemically or electrochemically and catalytic oxidation. The nonoxidative surface treatments involves deposition of more active forms of carbon or metals such as whiskerization, pyrolytic coating, the grafting of the polymers, and metal deposition on the carbon fiber surfaces [8-11]. 

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