Effects of Heat and Moisture

In Section 19.12, it was pointed out that the cross section of fibers is determined by the cross section of the spinnerette holes and the nature of the spinning process. This plays an important role in establishing the properties of the fiber. For certain applications, the spun fibers are textured after spinning. Carpet fibers, for example, are often given a heat-set twist and/or are crimped by passing them through a pair of gear-like rollers. 

Static electricity can be a big problem with carpets. Many carpet fibers therefore incorporate an anti-static agent (Section 20.3.13) to bleed off static charge. 

The same polar bonding sites that make fibers dyeable also make them stainable. In the past, the finished item, a carpet, for example, would be treated with an anti-staining agent such as a fluorocarbon telomer. Nowadays, these coatings are often applied to the fibers before weaving. Another approach is to make use of bicomponent fibers. For example, a core fiber of nylon 6/6 could be coated with a sheath of highly stain-resistant polypropylene. 

The polarity of the polymer also directly influences its degree of water absorption. Other things being equal, the more polar the polymer, the higher its equilibrium moisture content under any given conditions of humidity. As with 

Perhaps the most important effect of moisture on polar polymers is as a plasticizer. Since fiber-forming polymers are linear, heat is also a plasticizer. This explains why suits wrinkle on hot, humid days, and why the vrankles can be removed by steam pressing. Wash-and-wear and permanent-press fabrics are produced by operations that cross-link the fibers by reacting with functional groups on the chains, such as the hydroxyls on cellulose. The more hydrophobic polymers are inherently more wrinkle resistant because they are not plasticized by water. Wash-and-wear shirts, therefore, usually are made of blends of polyethylene terephthalate and cotton, about 65%/35% 

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Initial Investigations of the Effects of Heat and Moisture Dissipation from a Large Natural-Draft Cooling Tower... 

Much of the use of karaya is dependent upon its viscosity and capacity for water absorption. The viscosity of the crude gum is influenced to a large extent by the weather conditions and season during which the gum is collected. After collection, karaya loses viscosity. Particle size, heat, and moisture are important factors contributing to this deterioration. In the crude gum, where the size of the tear is relatively large, the loss in viscosity occurs at a slow rate. When the gum is powdered, the rate of loss of viscosity is appreciably increased. It is not the fine division of the gum, in itself, that is responsible for the increased deterioration, but rather the increased effect of heat and moisture on such material. The conditions described that increase the rate of acetic acid liberation are similar to those that cause viscosity deterioration. A loose correlation is, therefore, suggested between the loss of acetic acid and the decrease in viscosity. 

Discriminating between the various effects of heat and moisture on the strength of cyanoacrylate metal-to-metal bonds is not easy. The environment can affect the adhesive, the metal surface, or the interface between them. The reduction in strength may be due to heat alone, or to water, or to both. The most durable adhesive possible today would probably contain a room temperature active crosslinking agent and an adhesion promoter resistant to both heat and moisture. Table XII lists the water durability modifiers discussed in this section. 

Edward A. Metz, Effects of Heat and Moisture on Fiberglass Reinforced Nylon , Machine Design (February 17,1966). 

Effect of Heat and Moisture on Fish Meal Conditions of Treatment... 

Huang and colleagues (Huang et al, 2005 Pan et al, 2008 Yang et al, 2006) studied the moisture sensitivity of types of SMPU fibers that were prepared by MHI, which was synthesized from MDI, EDO, adipic acid, ethylene glycol, ethylene oxide, polypropylene oxide (PPO) andbisphenol A. MHI did not disclose the exact SMPU formula, but it is assumed to be of PPO/MDI/BDO compositiom This chapter therefore aims to reveal the effects of heat and moisture conditions on the mechanical and thermal properties of wet-spun SMPU fibers. 

Moisture Resistance of Wood-Adhesive Joints. This recent standard defines procedures where the degrading effects of heat and moisture on bond quality are measured in such a way that the data can be analyzed by means of classical rate process equations. Results have shown that usefal, long-term extrapolations of environmental effects can be made. 

Combined or single effects of heating and acid production by the starter bacteria increase whey syneresis and establish moisture levels for a given variety of cheese. Almost 96% of the moisture lost in Cheddar cheese during cooking occurs in the first 30 min (Lawrence 1959). A comprehensive review of syneresis has been written by Walstra et al. (1985). 

The siccity is an effect of cold as of heat, and moisture is the principal subject on which heat and cold act. When the latter is powerful, it condenses the moisture we see it in snow, ice and hail. From this comes the fall of leaves in autumn. If the cold increases, winter succeeds, the moisture in the plants congeals, the pores close, the stalk becomes weak through lack of nourishment they finally wither. If the winter is severe, it bears the dryness even to the roots it attacks the vito-humidum and the plants perish. How can one say after this that cold is a quality of Water, since it is its enemy, and since Nature does not suffer that an Element act upon itself. One speaks, it seems to me, more correctly, when one says that the cold has burned the plants. Cold and heat bum equally, but in a different manner heat by expanding, and cold by contracting the parts of the Mixts. 

A very dangerous fire hazard in the form of a solid or dust when exposed to heat or flame. It can react violently with air, CI2, F2, HNO3, NO, Se, S, water, NH3, BrFs, trichloroethylene, nitryl fluoride. During storage it may form a pyrophoric surface due to effects of air and moisture. Depleted uranium (the by-product of the uranium enrichment process, with relatively low radioactivity) is used in armor-piercing shells, ship or aircraft ballast, and counterbalances. Uranium is also used in making colored ceramic glazes. 

Waterproof fabric, which is laminated or coated with micro-porous or hydrophilic films, is frequently used in the design of functional clothing for the weather of low temperature, wind, rain, and even more extreme situations. With waterproof fabric, the elothing can effectively protect the body from the wind and water as well as reduce the heat loss from the body to the environment. These functions of waterproof fabric, scientifically, are achieved by signifieantly affecting the processes of heat and moisture transfer through the textile products. 

Plastic laminated sheets produced in 1913 led to the formation of the Formica Products Company and the commercial introduction, in 1931, of decorative laminates consisting of a urea—formaldehyde surface on an unrefined (kraft) paper core impregnated with phenoHc resin and compressed and heated between poHshed steel platens (8,10). The decorative surface laminates are usually about 1.6 mm thick and bonded to wood (a natural composite), plywood (another laminate), or particle board (a particulate composite). Since 1937, the surface layer of most decorative laminates has been fabricated with melamine—formaldehyde, which can be prepared with mineral fiUers, thus offering improved heat and moisture resistance and allowing a wide range of decorative effects (10,11). 

In the presence of the organic siHcate, the heavy-metal salts trigger the chain extension and cross-linking reactions that lead to siHcone mbber and volatile ethanol as a byproduct. Useful metal soaps iaclude stannous octanoate [1912-83-0], ziac octanoate [557-09-5], dibutyltin dilaurate [77-58-7], and dibutyltin diacetate [1067-33-0]. The reactivity of the different salts varies considerably. Stannous octanoate effects a cure ia 0.5—2 min ziac octanoate may require 24—96 h the dibutyltin dilaurate, 10—20 min. Heat and moisture accelerate the curing rate, but to a lesser degree than ia the case of the polysulfide mbbers. 

There have been some indications, although controversial, of increased precipitation downwind of major metropolitan areas. Urban addition of nuclei and moisture and urban enhancement of vertical motion due to increased roughness and the urban heat island effect have been suggested as possible causes. 

Effect of heat. When anhydrous, it detonates at about 210°. The material with one H20 deflagrates about 230°, when heated slowly, as compared to 275—290° for Pb Styphnate. Contact with flame or a red-hot wire results in immediate detonation if the material is dry, but when wet it is difficult to detonate or ignite Thermal stability and volatility. No loss in wt was observed when stored for 300 days at 50° for 150 days at 70°, or 50 days at 90° Hygroscopicity. More hygroscopic than Pb Styphnate. When stored at 90% RH for Q days it absorbed 0.24% moisture, and for 20 days, 0.90% moisture... 

In a 500-ml. distilling flask arc placed 107 g. (0.40 mole) of 7-bromopropylphthalimide (Note 1) and 240 ml. of xylene. Solution is effected by heating, and 24 ml. of xylene is distilled to remove traces of moisture. After cooling, the solution is transferred to a 1-1. round-bottomed flask with a ground-glass joint and treated with 107 g. (140 ml., 0.83 mole) of di- -buty]amine. 

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