The phenomena of dispersion of filler in polymer matrix should be understood accurately to develop polymer composites. We reviewed the dispersion mechanisms and dominant factors about filler dispersion. The dispersion mechanisms are divided into two main types, rupture and erosion. These are essentially the same breakdown phenomenon, that is removing two particles until the distance interparticle force is not effected. Also for higher dispersion, the dominant phenomenon is erosion. There are two important factors for dispersion, stress and energy. The stress exceeding cohesive force of filler is necessary to initiate dispersion, and energy is necessary to advance it. These two factors should be considered concurrently when one studies filler dispersion. These two factors are used by modifying for appropriate form in many investigations. Specific energy is an effective index to evaluate the degree of dispersion. However, it is necessary to postulate the following conditions if we use it. First, it must be under the critical stress which is equal to tensile strength of filler. Moreover, the provided energy must be dissipated for dispersion. Numerical flow simulation technique is a useful way to estimate the dispersion index more accurately.

View full abstract

Weld lines are not only a cause of visual defects, but also lead to reductions of mechanical properties in injected molded parts. In cases of visual defects, after finishing the molding step, it is possible to repair these in the painting step. But in cases of reduction of mechanical properties, it is difficult to repair. This paper describes the effectiveness of forced flowing means in molding proc-ess. Soon after the injection process, by the use of core pin drive forced flowing means, the core layer around weld line is transferred. As a result, the following can be understood from our investigation.
(1) Even just a little force has an effect on the improvement of defects and strength.
(2) From the results of X-ray CT analysis, we found that the glass fiber orientation in resin is influenced by force.
(3) From the results of tensile test, the fracture modes vary by rate of force. (4) The maximum strength of force flow means that the specimen is 80% of non-weld specimen.

View full abstract