Effects on properties

An alternative process is electroslag remelting (ESR). More oxide inclusions are found in ESR steel than in VAR steel, but thek size and distribution are such that they normally have no noticeable adverse effect on properties (141). 

Similar mechanical data for a series of ionomers derived from a single ethylene—acryflc acid copolymer have appeared (13) (Table 3). Comparison of the data from Tables 2 and 3 shows that the substitution of acryflc acid for methacrylic acid has only minor effects on properties. 

X-ray diffraction work (11,15) shows that there is an ionomer peak at 4°C which is absent in the acid precursor. This low, broad peak is not affected by annealing or ion type and persists up to 300°C. Since the 4°C peak corresponds to a spacing of about 2.5 nm, it is reasonable to propose a stmctural feature of this dimension in the ionomer. The concept of ionic clusters was initially suggested to explain the large effects on properties of relatively sparse ionic species (1). The exact size of the clusters has been the subject of much debate and has been discussed in a substantial body of Hterature (3,4,18—20). A theoretical treatment has shown that various models can give rise to supramoleculat stmctures containing ionic multiplets which ate about 10 nm in diameter (19). 

An extensive investigation of the dilute solution properties of several acrylate copolymers has been reported (80). The behavior is typical of flexible-backbone vinyl polymers. The length of the acrylate ester side chain has Httle effect on properties. 

In addition to the considerable difference of the properties of the cured resins with different hardeners it must also be stressed that the time and temperatures of cure will also have an important effect on properties. As a very general rule, with increasing aliphatic amines and their adducts the time of cure and temperature of cure (up to 120°C at least) will improve most properties . ... 

It has been shown throughout this chapter that the properties of plastics are dependent on time. In Chapter 1 the dependence of properties on temperature was also highlighted. The latter is more important for plastics than it would be for metals because even modest temperature changes below 100°C can have a significant effect on properties. Clearly it is not reasonable to expect creep curves and other physical property data to be available at all temperatures. If information is available over an appropriate range of temperatures then it may be possible to attempt some type of interpolation. For example, if creep curves are available at 20°C and 60°C whereas the service temperature is 40°C then a linear interpolation would provide acceptable design data. 

The type of counterion present in an ionomer may, or may not, have a significant effect of properties. For polyethylene-based ionomers, where the presence of crystallinity has an appreciable effect on properties, the type of counterion present does not appear to have a significant effect on either modulus or tensile strength, as Fig. 4 indicates. However, in amorphous ionomers, the effects of changing the counterion from a monovalent one, as in Na or K, to a divalent one, such as Ca, may be appreciable. 

In this chapter, we will explore the effect of various environmental conditions and the polymers5 chemical composition and structure on its stability. We will examine the mechanisms associated with degradation and will explore several well studied polymeric systems. Finally, we will discuss the role of additives and their effects on properties. 

In both the roles, insurance companies deal with the management of risk activities. In fact, climate change risk is managed by the insurers through the risks they accept from clients, given that climate change causes an increase in intensity and spreading the distribution of extreme weather events with resultant effects on property claims that could be catastrophic.5... 

Thus initiator residues get incorporated into the polymer at one or both the ends of the Polymer chain. These residues do not have any appreciable effect on properties of polymers. 

Structural effects on properties were also studied in detail by a group from Tohoku University, who prepared poly(methylphenylsilylene) (PMPS Mv = 3,120, Mw/Mn = 1.76) and poly(phenylsilyne) (131 poly(penfafluorophenylrilyne)(PPS) 4/w = 1,090, Mw/M = 1.30) by Wurtz-type coupling using sodium and 18-crown-6 in hot toluene and compared their optical and electrical properties.359,360... 

Where exposure to the liquid in service is intermittent it may be of interest to know the effect on properties after drying. ISO 175 [16] includes procedures for measuring tensile stress, strain and hardness after a drying period in an oven. Depending on the application, measurements before or after drying may be required and possibly both will be of relevance. 

Table 3.9 Examples of toughening effects on properties of polyamide and polyacetal...

The moisture uptake in the cured samples appears to have no effect on the room temperature tensile properties as demonstrated in Table I. A critical study to be done is to determine the moisture effect on properties at elevated temperatures. 

The small cell size only has limited effects on properties, but can have advantages for further processing. If foamed sheet is to be thermoformed, it must have a cell diameter much less than the sheet thickness to avoid failure. 

Lattice defects also play a prominent role in the reactivity of pyrotechnic materials, where the displacement or absence of atoms or ions from their normal positions within a lattice can have a pronounced effect on properties, as can the introduction of foreign species or dopants within a crystal. 

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