Effect of Heavy Filler on Dynamic Mechanical Properties of Polymer Composites

Experimental studies on the effect of frequency and temperature on the dynamic mechanical properties of filled composites are studied poorly and require further research. The purpose of theresearch is to study the effect of heavy fillerbarite (BaSO4), on the dynamic characteristics of a highly filled composite based on butyl rubber, and to compare the efficiency of barite in the composite with similar light filler. The conclusions are made on the basis of a comparative analysis of the temperature-frequency dependences of the loss tangent and the storage modulusat various percentages of filler, obtained by the DMA method. It has been established that while increasing barite concentration the elasticity of the composite material decreases, the glass transition temperature shifts upwards, and the reverse occurs in the zone of highly elastic state of the composite: the higher the barite concentration, the higher the damping properties. The authors provided a rationale that the heavy filler shows the effect only in the highly elastic zone if compared with the light one. The article is of practical value for the development of new vibration insulation materials.

A Survey of Fertility Program Responses of Kentucky Dark Fire-Cured Tobacco (Nicotiana tabacum L.) Yield and Quality for Cigars Manufacture in the Benevento Province (Southern Italy)

SummaryNitrogen (N) fertilization of Kentucky dark fire-cured tobacco can be used to increase weight of high quality cured leaves for cigar manufacture. We conducted field experiments at 11 different locations in the province of Benevento (Southern Italy) where the following four N treatments were compared: 1) unfertilized control (N0); 2) a site-specific N rate, calculated by a N fertilization plan (NFP) based on physical and chemical soil characteristics, which ranged between 113 and 145 kg N ha−1; 3) 200 kg N ha−1 (rate commonly used by farmers, N200); 4) 100 kg N ha−1 (half of the rate commonly used by farmers, N100). Yields of the following five commercial quality categories of cured leaves were measured: i) wrappers, ii) heavy filler (Fh), iii) light filler (Fl), iv) heavy shredded (Sh) and v) light shredded (Sl). Fh cured products of B1, B4, B6 and B10 locations were analyzed for: total alkaloids, reducing sugars, chlorides, total N (Kjeldahl), ammonium-N (NH4-N), nitrate-N (NO3-N), and tobacco specific nitrosamines (TSNA). Color parameters: Lightness (L), Chroma (C) and Hue (H) were determined on five cured leaves / plot of both Fh and Fl types at B1, B2, B3, B6, B8 and B10. A blind evaluation of cured leaves collected across locations was conducted by a panel test who considered the main basic characteristics of cured leaves (stalk position, leaf structure, texture, etc.). The total yield of cured products increased with fertilization across locations, up to NFP treatment, without any statistically significant increase at N200 treatment. Fertilization increased yield of wrappers at B1 up to NFP treatment (113.5 kg N ha−1), without any significant increase at N200 treatment. Yield of light filler product was positively influenced by fertilization up to the maximum dose only in 5 out of 11 locations. Total alkaloids significantly increased with increasing fertilization up to 100 kg N ha−1 without any significant changes at higher N rate. Fertilization hardly increased L and C of Fl leaves, which appeared light-brown but brilliant-colored. There was a reduction in the H value of Fh products which indicated a darker tone of those leaves with respect to Fl. Increasing N rate affected production costs more than revenues. According to agronomic results, in most locations the best results in terms of net revenues were obtained by NFP treatment. Considering that N rates above the NFP would disqualify growers from the economic aids provided by EU agrienvironmental measures, by economic point of view the NFP treatment would be recommended over the current grower standard (N200).

The Preparation and Performance of Gypsum-Based Composites

Gypsum-based composites was produced using gypsum power(cement), PVA, white latex and sawdust via pouring process. The influences of water/ cement ratio, PVA/ cement ratio and glue/ cement ratio on release time, density and impact strength of the gypsum-based composites were investigated through orthogonal experiment. The results showed that PVA strengthened obviously impact strength, and also delayed the s release time of the Gypsum-based composites. Sawdust as light filler reduced the composites density. Low content of white latex is beneficial to increase the impact strength, while high content of white latex is easy to form micelle in the gypsum crystallization process and is enclosed in crystals, which decreases the impact strength of composite materials.