Weight stabilization

Molecular formula Molecular weight Stability in alkaline solution... 

Another method of achieving the desired molecular weight is by addition of a small amount of a monofunctional monomer, a monomer with only one functional group. Acetic acid or lauric acid, for example, are often used to achieve molecular weight stabilization of polyamides. The monofunctional monomer, often referred to as a chain stopper, controls and limits the polymerization of bifunctional monomers because the growing polymer yields chain ends devoid of functional groups and therefore incapable of further reaction. Thus, the use of benzoic acid in the polyamide synthesis yields a polyamide (XI) with phenyl end groups that are unreactive toward polymerization. 

Loss of Weight Stability Tests. Expls are heated at some predetd temp and the loss of weight is measured periodically. Usually, the greater the weight loss, the less stable is the expl... 

On the other hand, with the inclusion of a low molecular weight stabilizer in the lower compartment, i.e. 2 mol dm-3 NaCl, the evolution of the structures or structured flows was much more uniform and regular (Fig. 13b). The structures may be stable for several days. 

In the first two subjects (Patients 1 and 2), who received 2.7 mg of zinc daily, the weight loss was more pronounced in comparison with the second pair of subjects (Patients 3 and A), who received 3.5 mg of zinc dally. After repletion with zinc, the weight stabilized in three out of four subjects and in one subject (Patient 1), although the weight loss continued during the zinc-supplemented period, the rate of weight loss as determined by the slope of the curve was decreased. 

Polyfunctional polycondensates were prepared from formaldehyde and a mixture of two different low molecular weight stabilizers, e.g. of 2-hydroxybenzophenone or its derivatives with various 4-alkylphenols [170], e.g. stabilizer 133 (a combination of LS and AO), of a phenol with benzoxazole [171] or 4-nonylphenol and... 

A sulfur moiety introduces a hydroperoxide deactivating effect into the stabilizer molecule. Moreover, the condensation of low molecular weight compounds with halides of sulfur represents an easy synthetic approach to the increase of the molecular weight and consequently to the improvement of the physical persistency of stabilizers. Efficient AO were prepared by this way from alkylphenols, aromatic amines or phenothiazine [21,174]. Most of them contain two active units connected with a sulfide/disulfide bridge and should be listed rather among high molecular weight stabilizers. Antioxidant 136 (n > m), prepared from pyrocatechol and... 

Combinations of Polymeric and High Molecular Weight Stabilizers... 

Temperatures or temperature ranges of chemical or physical decompositions accompanied by weight losses can be detected provided they are separated from each other by sensible ranges of weight stability. The major limitation of TGA is that systems exhibiting strong temperature dependence or slow rates of reaction are equally difficult to study. This limitation could be overcome if it were possible to provide an infinitely slow, linear temperature increase. However, useable information can be obtained if the observed weight losses are identical with calculated proportions of reaction products. 

Thirteen samples were analyzed using heating rates ranging from 1.0 to 50.0°C/min. The samples were heated to a maximum of 500°C. This temperature was maintained until the sample weight stabilized. 

In practice, monocarboxylic acids, such as acetic acid or lauric acid, are often used to achieve molecular weight stabilization of polyamides. 

In the last few years, it has become fully appreciated that polymeric antioxidants are effective in retarding the thermal and autooxidation. Such polymer-bound stabilizers are similar in efficiency to the low molecular weight stabilizer incorporated into the polymer by blending. The polymer-bound stabilizer should have a flexible spacer between the point of attachment to the polymer and the functional group of the phenolic antioxidants. 

First, if the colloidal particles are small in size and fully coated by well-anchored, high molecular weight stabilizing moieties, the observed CFPT is essentially independent of... 

Molecular weight Stabilizing Anchor polymer moieties Diameter/nm Area/nm LCFT/K 0i /K... 

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