Mechanical properties environmental effects

Keywords Natural fiber, biocomposites, mechanical properties, environmental effect... 

Dry state mechanical properties Environmental effects on mechanical properties Conclusions References... 

Surfmers , i.e. surfactants which also acted as copolymerisable monomers, were synthesised from the hemi-ester of a fatty alcohol and maleic anhydride and were then used in the preparation of self-crosslinking dispersions by seeded semi-continuous emulsion polymerisation of acrylate monomers. Water-borne exterior wood stains were prepared from the dispersions and their properties were studied. The use of surfmers as sole emulsifiers in emulsion polymerisation was considered and data were obtained on the effects of surfmers on film formation, water barrier properties, gloss retention and mechanical properties. Environmental aspects of the use of products involving surfmers were examined. 6 refs. 

The moisture sensibility is remarkable, certain natural fibers can easily be influenced by environmental effects. Generally speaking, the mechanical properties are lowered with rising moisture content. 

The mechanical properties of composites are mainly influenced by the adhesion between matrix and fibers of the composite. As it is known from glass fibers, the adhesion properties could be changed by pretreatments of fibers. So special process, chemical and physical modification methods were developed. Moisture repel-lency, resistance to environmental effects, and, not at least, the mechanical properties are improved by these treatments. Various applications for natural fibers as reinforcement in plastics are encouraged. 

Such processing-induced residual stresses that influence properties as mechanical, physical, environmental, and aesthetic factors (which also exist in other materials like metals and ceramics) can have favorable or unfavorable effects, depending on the application of the load with respect to the direction of the stresses or orientation. 

The progress of Green Chemistry impacts the established scenarios for the chemical industry (98,99). Future catalysts will likely become more enzyme-like in the sense that they will more efficiently balance the properties of effectiveness and fragility. An overarching environmental consideration holds a synthetic catalyst should simply go away by some mechanism when its work is done. Nature has developed enzymes with limited lifetimes. After their task is completed, their constituent molecules and atoms become recyclable to serve as useful resources for the... 

The effect of environmental concerns on future developments in the paint industry is discussed. Particular attention is paid to volatile organic compound regulations, developments in powder coatings, and radiation-curable coatings. Tabulated information is presented on applications, backbone type and typical mechanical properties of Incorez W830 series PU dispersions and Incorez W2000 series uiethane/aciylic hybrids. 10 refs. EUROPEAN COMMUNITY EUROPEAN UNION UK WESTERN EUROPE... 

Durability in its broadest sense covers all aspects of irreversible property change with time and use. This includes all types of environmental agent that contribute to degradation and all aspects of mechanical action. This guide seeks to be comprehensive but concentrates on the most common environmental effects and the most important mechanical properties. More details of the test procedures used can be found in text books and the relevant international standards as referenced. 

Although numerous studies (1-3) have described work aimed at establishing criteria for the durability of adhesive joints, a thorough understanding of effects of the chemical and mechanical properties, on the durability of adhesive bonds is lacking. More specifically, the effects of surface preparation and dynamic loading, especially under environmental service conditions, has not been explored in detail for automotive structures. In this paper, a description of the effects of environment on the durability of adhesive bonds is presented. Particular attention is given to... 

FIGURE 14.9 Influence of temperature on the stress-strain behavior of a sample of poly(methyl methacrylate). (Modeled after Carswell, T.S. and Nason, H.K. Effects of Environmental Conditions on the Mechanical Properties of Organic Plastics, 1944. Copyright, ASTM, Philadelphia, PA. With permission.)... 

Radiation cross-linking of polyethylene requires considerably less overall energy and less space, and is faster, more efficient, and environmentally more acceptable. Chemically cross-linked PE contains chemicals, which are by-products of the curing system. These often have adverse effects on the dielectric properties and, in some cases, are simply not acceptable. The disadvantage of electron beam cross-linking is a more or less nonuniform dose distribution. This can happen particularly in thicker objects due to intrinsic dose-depth profiles of electron beams. Another problem can be a nonuniformity of rotation of cylindrical objects as they traverse a scanned electron beam. However, the mechanical properties often depend on the mean cross-link density. ... 

C. Cappelli B. Mennucci, S. Monti, Environmental effects on the spectroscopic properties of gallic acid A combined classical and quantum mechanical study. J. Phys. Chem. A 109, 1933 (2005)... 

A synergistic effect between the role of stress and environmental agents such as O3, SO2 and NO2 on degradation of the mechanical properties of Nylon fibers has been observed. This... 

Despite the severity of the problems associated with environmental degradation of mechanical properties, it is only recently that the ceramic composites community has begun to address them. In the following section, some of the approaches that attempt to inhibit the adverse effects of service environments are discussed for specific composite systems, and the relative effectiveness is assessed. 

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