Xianzhong Wang

Isothermal Crystallization Kinetics of Fiber/Polylactic Acid Composites and Morphology

The isothermal crystallization behavior of fiber including glass fiber, carbon fiber and basalt fiber reinforced PLA composites was investigated by differential scanning calorimetry (DSC).The morphology of isothermally crystallized fiber/PLA composites was observed by polarized optical microscope (POM) equipped with a hot stage. The results showed that the presence of fiber greatly accelerated the bulk crystallization rate of PLA and changed the crystalline morphology of PLA from the spherulites to transcrystallization. And the reason for the development of transcrystallization was considered to be relevant to the compatibility of the interface between fibers and PLA.

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.

Morphology, mechanical and dielectric properties, and rheological behavior of EAGMA toughened microcellular PEI–EAGMA foam

A series of toughened polyetherimide (PEI)–ethylene-acrylate-glycidyl methacrylate (EAGMA) copolymer blends were prepared using a twin screw extruder and then injection molded by conventional and microcellular methods. The effect of the EAGMA content on the mechanical, thermal and dielectric properties, rheological behavior and morphology of the PEI–EAGMA blends was investigated. The results showed that the PEI–EAGMA blends exhibited a notched Charpy impact strength of 27.9 kJ m−2. This is 4–5 times higher than that of pure PEI and indicates that EAGMA had an excellent toughening effect on the PEI–EAGMA system. The interfacial tension calculation and SEM micrographs indicated that the PEI matrix was highly compatible with the EAGMA elastomer. The rheological results showed the restriction in the molecular mobility of PEI was more significant as the content of EAGMA increased. Moreover, the dielectric constant and loss of the materials can be effectively reduced through the technology of micro-foaming. EAGMA plays an important role in the microcellular structure formation and final dielectric properties of the PEI–EAGMA foam.

Preparation and properties of thermal conductive polyamide 66 composites

A series of the thermal conductive polyamide 66 (PA66) composites were prepared by two methods, including extrusion method (EM) and solution method (SM). The thermal conductivity, mechanical properties, thermal stability, and electric property of PA66 composites were investigated. The results showed that the maximum value of thermal conductivity of carbon fiber/PA66 composites containing 40 wt% carbon fiber prepared by SM achieves 2.537 W/m·K, which was superior to that of carbon fiber/PA66 composites prepared by EM at the same carbon fiber content. Moreover, its value was eight times more than that of pure PA66. The orientation of carbon fiber in process of injection had an influence on thermal conductivity of carbon fiber/PA66 composites, and the perpendicular distribution of carbon fibers helped in improving the thermal conductivity of composites. The carbon fiber/PA66 composites had good heat conducting performance but also had good material properties and electrical properties.

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.