Zhiwei Jiao

Interfacial Diffusion and Bonding in Multilayer Polymer Films: A Molecular Dynamics Simulation.

As a stacked form of ultrathin polymer films, multilayer nanostructures are of great interest in various applications. Coarse-grained molecular dynamics simulations were carried out to understand the behaviors of interfacial diffusion and bonding of multilayer polymer films. We found two obvious stages for the interfacial diffusion of polymers in the multilayer film, and it is 3 times faster in the first stage than in the second one due to the evolution of molecular conformations. The polymers near the interfaces have an in-plane mobility much higher than the out-of-plane one. The strength of interfacial bonding has been characterized by the fast tensile stress-strain curve along the normal direction. It shows multiple yielding points for the multilayer polymer films, which is distinct from the tensile behavior of the bulk. The ultimate tensile stress (UTS) and corresponding separating strain, surprisingly, do not necessarily increase with diffusion time. Because of the dramatic molecular rotation and extension during the first stage of interfacial diffusion, the interlayer interpenetration is nonuniformly distributed in the plane of the interface. Such a nonuniform distribution may be one of the reasons for the decrease of the UTS and separating strain.

Clamping characteristics study on different types of clamping unit

Plastic products are becoming more and more widely used in aerospace, IT, digital electronics and many other fields. With the development of technology, the requirement of product precision is getting higher and higher. However, type and working performance of clamping unit play a decisive role in product precision. Clamping characteristics of different types of clamping unit are discussed in this article, which use finite element numerical analysis method through the software ABAQUS to study the clamping uniformity, and detect the clamping force repeatability precision. The result shows that compared with toggled three-platen clamping unit, clamping characteristics of internal circulation two-platen clamping unit are better, for instance, its mold cavity deformation and force that bars and mold parting surface suffered are more uniform, and its clamping uniformity and repeatability precision is also better.

Automatic control and energy-saving mechanism of internal circulation two-platen injection molding machine

Injection molding machine (IMM) is an advanced manufacturing equipment, which integrates mechanical, electronic, hydraulic and automatic control technology. IMM is the most important production tool and more than 80% of plastic products is manufactured by injection molding. In the new injection molding machine, the external circulation is omitted and hydraulic system is simplified because of the internal circulation cylinders used, thus significant energy saving and energy saving; At the mold-moving or mold-locking stage, different cylinders was used respectively which not only balanced force and velocity well but obtained excellent mold-locking properties and high processing stability. This paper details the automatic control principle of the internal circulation two-platen IMM, especially the internal circulation mold-locking cylinder and analyses its energy-saving mechanism; Finally the energy-saving effect is verified by experimental methods.

Design of polymer multilayer heterostructure broadband reflector for the near-infrared using genetic algorithm

Abstract. A broadband reflector for the near-infrared (NIR) was designed using a multilayer heterostructure consisting of several quarter-wave stacks (QWSs), which were composed of polymethyl methacrylate (PMMA) and polyethylene terephthalate (PET) films. Taking the solar power density as the target and using the Bragg wavelength of each QWS as the variable, the genetic algorithm was applied to look for the optimal multilayer heterostructure for broadband NIR reflection. As high as 99.46% total energy reflectivity in the short-wavelength NIR region (780 to 1100 nm) and 89.56% total energy transmissivity in the visible light region (380 to 780 nm) were realized by a multilayer heterostructure consisting of six quarter-wave PMMA/PET stacks, which can be easily fabricated based on the micronano multilayer coextrusion technology. The designed structure possesses good stability, and its total energy reflectivity is not sensitive to the incident angle of light. The proposed broadband NIR reflector can be applied to buildings as energy-saving films.

The movement performance of clamping unit in the internal circulation two-platen injection molding machine

Injection molding machine (IMM) is an advanced manufacturing equipment, which integrates mechanical, electronic, hydraulic and automatic control technology. IMM is the most important production tool and more than 80% of plastic products is manufactured by injection molding. Clamping unit is an important component of IMM. Thanks to the use of internal circulation cylinders, no additional oil is needed during the mold-moving stage and thus ensures the high mold-moving speed. The connection of the four mold-locking cylinders ensures even pressure in the cylinders. This results in completely uniform force distribution. The platen can be self-adjusted according to the parting surface of the mold. Equipping with gear-type mold height adjusting mechanism shortens the mold-locking cylinder stroke and the time of pressure rising. This paper describes the classification of two-platen clamping unit and details how the internal circulation clamping unit works. The movement performance is analyzed combined with experimental tests and theoretical calculations finally.