No abstract

ABSTRACT:The flammability properties of an intumescent fire retardant polypropylene added with magnesium hydroxide was discussed in this study. To evaluate the flammability of the material, limit oxygen index, smoke emission, tensile strength, and our exploitation dynamic flammability evaluation system, tests were assessed in experiments. The results showed that the intumescent flame retardant ammonium polyphosphate-filled polypropylene has superior flammability properties but higher carbon oxide (CO) concentration and smoke density. By adding some magnesium hydroxide additives in intumescent fire retarded polypropylene, the smoke density and CO concentration decrease; and the compound also has superior fire properties. It is concluded that intumescent system and magnesium hydroxide additives are effective on improving combustion properties for polypropylene. ᭧ 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: [989][990][991][992][993][994][995] 1998

Granular tapioca was thermally blended with poly(lactic acid) (PLA). All blends were prepared using a plasti-corder and characterized for tensile properties, thermal properties and morphology. Scanning electron micrographs showed that phase separation occurred, leading to poor tensile properties. Therefore, methylenediphenyl diisocyanate (MDI) was used as an interfacial compatibilizer to improve the mechanical properties of PLA/tapioca blends. The addition of MDI could improve the tensile strength of the blend with 60 wt% tapioca, from 19.8 to 42.6 MPa. In addition, because PLA lacked toughness, acetyl tributyl citrate (ATBC) was added as a plasticizer to improve the ductility of PLA. A significant decrease in the melting point and glass-transition temperature was observed on the basis of differential scanning calorimetry, which indicated that the PLA structure was not dense after ATBC was added. As such, the brittleness was improved, and the elongation at break was extended to several hundred percent. Therefore, mixing ATBC with PLA/tapioca/MDI blends did exhibit the effect of plasticization and biodegradation. The results also revealed that excessive plasticizer would cause the migration of ATBC and decrease the tensile properties.

Maleic anhydride grafted poly(lactic acid) (PLA g MAH) was prepared by blending with wood flour (WF). The effect of MAH and WF inclusion on the mechanical and thermal properties of the compos ites was examined. PLA g MAH/WF had optimum tensile properties compared with PLA/WF. Scanning electron microscopic images indicated poor interfacial adhesion of the PLA/WF. It was enhanced after MAH was grafted onto PLA; the PLA g MAH/WF showed excellent compatible morphology. Results also revealed that the biodegradation of PLA and PLA g MAH was improved with increasing of WF content.

ABSTRACT:The aggregation structure and mechanical properties of liquid silicone rubber, polyurethane (PU), and epoxy (EP) blends were studied. The molecular structure was evaluated by FTIR, and the intermolecular interaction of the three-phase polyblends was measured by dynamic mechanical analysis. The mechanical properties, including the tension, compression, shear, and tear performance, were measured by a material testing system. From the relationship between the intermolecular interaction and mechanical properties, we found that the aggregation structure of the three-phase blends was influenced by the reaction between silicone and PU, silicone and EP, and PU and EP, which resulted in a change of the crosslinking density and an interpenetrating polymer network structure. Thus, the dominant three-phase mechanical properties are closely related to the aggregation structure.