Microinjection molding (µIM) appears to be one of the most efficient processes for the large-scale production of thermoplastic polymer microparts. The microinjection molding process is not just a scaling down of the conventional injection process; it requires a rethinking of each part of the process. This review proposes a comparative description of each step of the microinjection molding process (µIM) with conventional injection molding (IM). Micromolding machines have been developed since the 1990s and a comparison between the existing ones is made. The techniques used for the realization of mold inserts are presented, such as lithography process (LIGA), laser micromachining and micro electrical discharge machining (µEDM). Regarding the molding step, the variotherm equipment used for the temperature variation is presented and the problems to solve for each molding phase are listed. Throughout this review, the differences existing between µIM and conventional molding are highlighted.

Molecular dynamics (MD) simulations have been used to examine the structure and dynamics of a system containing an inorganic nanoparticle embedded in a polymer matrix. This paper represents a preliminary investigation into the feasibility of examining such relatively large systems using atomistic modeling techniques. No attempt is made here to model any specific system. A generic linear polymer “united-atom” model is first created in an amorphous phase before the insertion of an atomistically detailed silica nanoparticle of diameter ∼4.4 nm. A novel method to insert a nanoparticle into a polymer matrix is given. The entire system is contained in a standard periodic simulation cell of side length ∼10 nm. The volume fraction of silica corresponded to ∼4.5%. The composite system was subsequently relaxed at 300 K and at two different pressures using standard MD techniques, the gmq suite of programs being used for this purpose. Results are presented regarding the variation of the structure and dynamics of the system with respect to the distance from the polymer−nanoparticle interface and as a function of pressure. A clear structuring of the polymer chains around the nanoparticle is seen with prominent first and second peaks in the radial density function and a concurrent development of preferred chain orientation. The probability of trans conformers is also higher close to the interface and shows a distinct gradient. In contrast, evidence for chain immobilization is less obvious overall although dynamic properties are more sensitive to changes in the pressure. Comparisons are also made between the bulk moduli of the pure polymer and composite systems.

Molecular dynamics simulations have been used to examine the effect of the size of a spherical inclusion in generic model polymer nanocomposite systems. Results are presented concerning the effect of the increasing particle size on the thickness of the interphase, i.e., the perturbed zone of polymer surrounding the inclusion. The behavior of the mass density, molecular orientation, fraction of trans conformers, as well as dynamic properties are presented as a function of the distance from the nanoparticle surface. The effect of temperature on these distributions is also discussed. Long simulations have been carried out to determine the variation in the glass transition of the filled polymers as compared to the pure systems. It is established that, within errors, the interphase thickness is independent of the size of the nanoparticle for the range of particle sizes analyzed. This information is particularly important for the second stage of the project where it is used in continuum micromechanical calculations to try to explain the behavior of the mechanical properties of the model nanocomposites. The confrontation between continuum and atomistic approaches will be the subject of a future publication.