Shikai Luo

Microstructure and Properties of Microcellular Poly (phenylene sulfide) Foams by Mucell Injection Molding

A series of microcellular poly (phenylene sulfide) (PPS) foams were prepared by Mucell injection molding. The cell structure, mechanical properties, crystallization behavior and dielectric property of microcellular PPS foams were systemically investigated. The results showed that the longer the length of flow passage of injection mold, the larger cell size of microcellular PPS foams. The injection parameter of shot size played an important role in relative density of microcellular PPS foams. When the relative density of microcellular PPS foam reached to 0.658, the tensile strength, flexural strength and impact strength of PPS foam materials achieved 10.82 MPa, 52.99 MPa and 0.305 J/cm2, respectively. Meanwhile, with the relative density decreasing, the dielectric constant of PPS foam materials reduced, while the volume resistivity of its uprated.

Foaming behaviors of polyetherimide/ polypropylene-graft-maleic anhydride blends in the microcellular injection molding process

In this study, foaming behaviors of polyetherimide (PEI)/polypropylene-graft-maleic anhydride (PPMA) blends with different fractions of PPMA are investigated by the microcellular injection molding (Mucell) using N2 as the blowing gas. The results indicate that the addition of PPMA can obtain more the interface in blends than PP. Meanwhile, the microcellular PEI/PPMA foams achieve higher void fraction and cell density than that of PEI/PP and neat PEI matrix, and then the cell diameter also significantly decreases from 30 µm to less 10 µm. The excellent cell properties can be attributed to interfacial effect of binary blends. The binary interface decreases the nucleation energy barrier and forms sufficient paths which improve diffusibility of blowing gas, so the microcellular PEI/PPMA foams obtain more nucleating points and paths of supporting cell growth.

Microcellular Crosslinked Silicone Rubber Foams: Influence of Nucleation Agent (Polyhedral Oligomeric Silsesquioxane) on the Rheological, Vulcanizing, Cell Morphological Properties

ABSTRACT A series of microcellular silicone rubber/silica/polyhedral oligomeric silsesquioxane (POSS) foams were prepared by supercritical carbon dioxide. The effect of POSS particles on the rheological behavior, vulcanizing, and cellular morphology of the composites was investigated. The results showed that the POSS grafted carboxylic acid group can improve the matrix strength of silicone rubber. POSS grafted carboxylic acid group act as inhibiting agent in the vulcanizing process. POSS particles play an important role in the microcellular structure formation. When the POSS content was 2.0 wt%, the cell size and cell density can reach to 3.77 µm and 7.99 × 109 cell/cm3, respectively. GRAPHICAL ABSTRACT

Preparation and characterization of microcellular injection molded foams from high-performance blends based on PPS-modified PPBESK

Obtaining foams of poly-containing biphenyl moieties (phthalazinone ether sulfone ketone; PPBESK) by applying the microcellular injection molding method is very difficult because of the high melt viscosity of the materials used. To overcome this limitation, polyphenylene sulfide (PPS) was used to improve the rheological properties of PPBESK. PPBESK/PPS blends of different proportions were prepared using the melt mixing method. The rheological behavior, phase behavior, interfacial tension, and mechanical properties of the blends were then investigated. The results clearly indicate that PPS can improve the melt processability of PPBESK. However, due to the strong adhesion between the PPS and PPBESK phases, the introduction of PPS did not cause any loss of the mechanical and thermal properties of PPBESK. Accordingly, microcellular foams from modified PPBESK were prepared by microcellular injection molding with supercritical nitrogen as foaming agent. A closed cell microcellular morphology with an average cell size of 17.7 um and cell density of 109 cells cm−3 was obtained.