This innovation provides a simple and generalizeable method to synthesize Janus colloidal particles in large quantity. Janus particles offer unique opportunities...
This innovation provides a simple and generalizeable method to synthesize Janus colloidal particles in large quantity. Janus particles offer unique opportunities in particle engineering for building particular structures; offering insight into the movement of particles and serving as a basis for new materials and sensors. Earlier methods to produce Janus particles of colloidal size (=1m in dimension) have been severely limited in the amount of product, but this method has overcome limitations on yield.
At the liquid-liquid interface of emulsified molten wax and water, untreated particles adsorb and are frozen in place when the wax solidifies. The exposed surfaces of the immobilized particles are modified chemically.
The wax is then dissolved and the inner surfaces are modified chemically. Janus particles, which have different chemical properties at different locations, could be used as potential building blocks for new 3D self-assembled structures. However, this purpose in particular requires a method to produce large quantities of material.
This invention offers tremendous control over the Janus Balance, the ratio of the two treated areas on each particle. The invention includes a number of ways to control this Janus Balance, giving the developer one more parameter to use in optimizing the end product.
This technique for liquid composite molding uses a solid catalyst recrystallized onto preplaced fiber reinforcements to produce high-strength polymer matrix...
This technique for liquid composite molding uses a solid catalyst recrystallized onto preplaced fiber reinforcements to produce high-strength polymer matrix composites. The polymerization is initiated by the preform itself, eliminating the need to mix multiple resins and catalysts before filling the mold. Having polymerization triggered by the preform simplifies the process, saves time, and eliminates mixing equipment.
Liquid composite molding processes have been popular since the 1940s. In the last 10 to 15 years, significant improvements have been made in developing low-viscosity thermosetting resin systems necessary to obtain high fiber volume parts. Also, automatic methods like weaving, braiding, and knitting have greatly reduced the cost of producing fiber preforms.
All liquid composite molding processes require that the resin injected into the mold is a reactive liquid. Some resins such as epoxy and urethane are highly reactive and must be kept separate until just before they are injected into the mold. Other resins are activated by a catalyst in the holding tank. These multipart resin systems require complex mixing, metering, and use of injection equipment with accurate ratio control. The multipart resin systems also may require heating tanks, hoses, pipes, and pumps; motionless mixing; efficient circulation to help prevent cure or degradation of the resin in a holding tank; and easy and safe cleaning/purging.
This new liquid composite molding technique uses a one-part monomer and a solid catalyst crystallized onto the fiber reinforcement. The polymerization is initiated by the preform itself, eliminating the need to mix or add multiple resins and catalysts before filling the mold.
Since it uses a single resin, the process also eliminates the need for the mixing equipment and reduces the heating and cleaning requirements of the injection equipment.
The best material system for use with this technology is one that uses polydicyclopentadiene (pDCPD). This polymer forms very rapidly at room temperature by a ring-opening metathesis polymerization (ROMP) of its low-viscosity monomer. The first step in this process requires recrystallizing the catalyst onto the fiber preform. The reactive fiber preform is then placed into the mold, the mold is closed, and the monomer is injected into it. Once the monomer has had time to react with the catalyst on the fiber preform and polymerize, the completed part is removed from the mold.
This technique can be used in liquid composite molding, such as resin transfer molding (RTM), vacuum-assisted RTM (VARTM), and structural reaction injection molding (SRIM), for parts with end-use applications in:
Because multiple resins and catalysts do not need to be added or mixed before being pumped into the mold, this process: