Weathering properties effects

The weathering properties of polyethylene are improved by the incorporation of carbon blacks. Maximum protection is obtained using blacks with a particle size of 25 p,m and below. In practice finely divided channel or furnace blacks are used at 2-3% concentration and to be effective they must be very well dispersed into the polymer. The use of more than 3% black leads to little improvement in weathering resistance and may adversely affect other properties. 

The effect of make-up of roofing asphalts on weathering properties, in terms of the fractions asphaltenes, resins, and oils, has been studied by Thurston (120). Increase of either asphaltenes or oils reduced resistance to weathering, while apparently an optimum content of resins aided permanence under exposure. Weathering properties were dependent not only on the quantities but also on the sources of these fractions, but the effect of source was not sufficiently clarified. 

The addition of pigments to polymers is a very effective practical method for increasing the resistance to photodegradation. Carbon black is by far the most effective. It has been used for years as a filler in rubber vulcanites, but in thermoplastic materials such as polyolefins it also has a protective effect against photodegradation. This was shown for the first time in 1950 by Wallder et al. [126] they demonstrated that the weathering properties of polyethylene are improved by the addition of about 2% carbon black. The effect is dependent on the degree of dispersion and on the size of the particles. Channel Black (particle size about 30 nm), for instance, is more efficient than Furnace Black (particle size 80 nm). The role of carbon black is not only to prevent the absorp-... 

These studies show that high concentrations of formaldehyde vapor can be effectively used to rapidly crosslink water-wetted wool to Improve wet wrinkle recovery, felting shrinkage characteristics, and light-induced weathering properties of the wool. Future studies will concentrate on formaldehyde vapor crosslinking of reduced wetted wools to achieve maximum Improvement In wrinkle recovery characteristics of the wool. 

Chem. Descrip. Fumed silica, aq. dispersion CAS 112945-52-5 EINECS/ELINCS 231-545-4 Uses Thixotrope, suspending agent for water-based acrylic, silicate, and alkyd polyesters coatings, some effectiveness in PUs/epoxies Features Corrosion resist., antisag/slump, and effective for weathering Properties Sp.gr. 1.10 00.15 vise. < 150 mPa-s pH 8.5-9.5 20 01% solids... 

Lee C-H, Hung K-C, Chen Y-L. Effects of polymeric matrix on accelerated UV weathering properties of wood-plastic composites. Holzforschung 2012 66 (8) 981-987. 

The weathering properties of thermoplastic matrix cellulose fiber composites have been studied more extensively than other matrix types. HDPE-based composites have received most attention, followed by polypropylene (PP) matrix composites. The response of these composites to both natural weathering and accelerated weathering conditions has been studied, and Table 15.8 includes a summary of some of the studies into the effects of accelerated weathering on mechanical properties of cellulose fiber-reinforced thermoplastics. It is clear from the table that weathering has adverse effects on the mechanical properties of almost all the composites studied. 

O Dell [84] studied the weathering properties of jute fiber/unsaturated polyester composites and compared them with glass fiber/unsaturated polyester composites. Samples were exposed to cycles of continuous UV exposure for 102 min, followed by 18 min of water spray for a total of 1200 hours. It was noted that there were no observable visual differences between weathered glass and jute fiber specimens in color changes or surface erosion effects. 

Weathering audits Effect on Mechanical Properties of Sisal RPP Composites... 

As a general rule, cellulosics do not constitute any major use but are encountered daily in a number of smaller items such as name plates, electrical component cases, high impact lenses, and other applications requiring a transparent plastic with good impact resistance. Weathering properties of the materials are good, particularly that of propionate, but overall chemical resistance is not comparable to other thermoplastics. Water and salt solutions are readily handled, but any appreciable quantity of acid, alkali, or solvent can have an adverse effect on the plastic. 

Recently, market forces have combined to reduce the supply and increase the cost of linear sidechain dialkyl phthalate plasticizers. Diisodecyl phthalate (DIDP) is, in many ways, an attractive alternative to these linear plasticizers but questions remain about its effects on weathering properties of flexible PVC. This paper looks at the effects of using DIDP or blends of DIDP with linear phthalate in flexible PVC exposed to outdoor weathering. Degradation mechanisms and additive packages to limit weathering damage are also discussed. 

Optical Properties and Radiation Effects. Within the range of wavelengths measured (uv, visible, and near-ir radiation), Teflon PFA fluorocarbon film transmits slightly less energy than FEP film (29) (Table 6). In thin sections, the resin is colorless and transparent in thicker sections, it becomes translucent. It is highly transparent to it radiation uv absorption is low in thin sections. Weather-O-Meter tests indicate unlimited outdoor life. 

Minerals normally considered nonmagnetic may be rendered magnetic by elemental substitution of a small amount of a magnetic element in the crystal lattice. Magnetic properties may also be affected by partial alteration in weathering effects. 

Such degradation of the surface causes little effect on either flexural strength or flexural modulus of elasticity but the influence on the impact properties is more profound. In such instances the minute cracks form centres for crack initiation and samples struck on the face of samples opposite to the exposed surface show brittle behaviour. For example, a moulded disc which will withstand an impact of 12 ftlbf without fracture before weathering will still withstand this impact if struck on the exposed side but may resist impacts of only 0.75 ftlbf when struck on the unexposed face. 

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