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Hyperbranched polymers (HBPs) formed by a self-condensing vinyl polymerization (SCVP) of copolymerization of AB* monomers slowly added into trifunctional C 3* cores under various feed rates were investigated by a kinetic model. The dependences of average molecular weight, polydispersity, degree of branching, and number of structural units of the hyperbranched polymers on the feed rate were calculated by a generating function method. It was found that the final polydispersity index (PDI) can be attained below 1.5 by a slow addition of AB* at a feed rate parameter, φ, less than 2. While the AB* monomers fed quickly, the system with a lower content of the C 3* cores results in a broader molecular weight distribution. A high degree of branching, about 0.66, can be achieved by addition of AB* monomers into a small amount of C 3* cores at φ lower than 10.

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In this study, the foaming of nonwoven fabrics and bulk polymers was investigated. Four different polymers that are commonly used for textiles including polyethylene terephthalate, thermoplastic polyurethane, thermoplastic polyether ester elastomer and polypropylene were foamed by batch foaming. Among the polymers, thermoplastic polyurethane seems to be the most promising material since it possesses the highest cell density and smallest cell size. In addition, nanoclay was added to thermoplastic polyurethane to promote cell nucleation and to increase the cell density. The results showed that well dispersed nanoclay in thermoplastic polyurethane served as an excellent nucleation agent and the cell structure was improved. The cell size of thermoplastic polyurethane nanocomposite foam decreased to 1 µm while the cell density increased to 3 × 1011 cells/cm3.

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ABSTRACT:The composites based on ethylene-propylene-diene monomer rubber (EPDM) with aluminum hydroxide (ATH), nanoclay, vulcanizing agent, and curing accelerator were prepared by conventional mill compounding method. The thermal stability and the flame retardant properties were evaluated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 test, cone calorimeter, and smoke density chamber tests. The results indicated that the substitution of the nanoclay in the EPDM/ATH composites increased the 50% weight loss temperature and the LOI value, and reduced the peak heat release rate (pk-HRR), the extinction coefficient (Ext Coef), the maximal smoke density (Dm), and the whole smoke at the first 4 min (VOF4) of the test specimens. The synergistic flame retardancy of the nanoclay with ATH in EPDM matrix could imply that the formation of a reinforced char/nanoclay layer during combustion prevents the diffusion of the oxygen and the decomposed organic volatiles in the flame. The mechanical properties of the composites have been increased by replacing more of the nanoclays into the EPDM/ATH blends. The best loading of the nanoclay in EPDM/ATH composites is 3 wt %, which keeps LOI in the enough value, the V-0 rating in the UL-94 test, and the improved mechanical properties with better dispersion and exfoliation of the nanoclays shown by transmission electron microscopy (TEM) micrographs.

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