Date of this Version
Rapid prototyping and interpenetrating network systems (IPNs) ideas and technologies were studied in order to develop a rapid prototyping machine capable of producing IPNs. This work was done as collaboration between the University of Nebraska-Lincoln and the University of Rouen, France, and is part of a project of controlling material property distribution by means of gradient IPN production within a rapid prototyping machine.
A standard stereo-lithography rapid prototyping (RP) machine was built and then modified for the purpose of producing an IPN system composed of an acrylic component, bisphenol A propoxylate diacrylate (BPA-PDA) and an epoxy component, 3,4 epoxycyclohexyl-methyl 3,4 epoxycyclohexane carboxylate (ECH). The acrylic and epoxy based system was produced within the machine by photo curing followed by thermal post curing. Various weight compositions of the IPN system were produced and characterized.
Control IPN systems were produced with the same materials and compositions as the samples made in the RP machine. These were bulk samples photo cured under a polychromatic light source, and then analyzed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), atomic force microscopy (AFM), dynamic mechanical testing (DMA), and tensile testing. The results show a change in the thermal stability with composition, a single glass transition temperature that changes with composition, homogeneous phase distributions, and changes in mechanical properties. These are consistent with the expectations that the system is a true IPN at the molecular level.
From TGA, DSC, AFM, and DMA analysis of the RP machine made system showed similar characteristics to the bulk polymerized IPN system. This includes changes in thermal stability with composition, a single glass transition temperature changing with composition, and observed homogeneous phase distributions. These characteristics follow the same trends as those of the control system, leading to the identification of the system as true IPNs. However, lower glass transition temperatures and thermal stabilities were observed for the samples made within the RP machine.
Lowered thermal stabilities and glass transition temperatures of thermally cured acrylic and epoxy homopolymers, observed in TGA and DSC, reveals that the rapid prototyping machine light source is not as powerful as the light used in the bulk curing, resulting in a similar, but different curing. Yet, it was concluded that the rapid prototyping machine is capable of producing IPN systems but requires increased light source power to increase the curing conversion of the acrylic and epoxy based system.
Advisor: Mehrdad Negahban