Additives controlled degradation

Due to their radical nature, all polymers can be stabilized against rapid deterioration by a suitable additive. Physical-mechanical degradation alone is not influenced by antioxidants or other additives. Controlled degradation is a suitable way to enhance some PO properties. 

A crosslinked starch was described as a fluid loss additive for drilling fluids [632,1626]. The additive resists degradation and functions satisfactorily after exposure to temperatures of 250° F for periods of up to 32 hours. To obtain crosslinked starch, a crosslinking agent is reacted with granular starch in an aqueous slurry. The crosslinking reaction is controlled by a Brabender... 

After the completion of the fracturing treatment, the fluid viscosity should decrease to allow the placement of the proppant and a rapid fluid return through the fracture. It is important to control the time at which the viscosity break occurs. In addition, the degraded polymer should produce little residue to restrict the flow of fluids through the fracture. 

MD M28 rocket propellant and burster hydrolysates slurried with shredded and micronized dunnage that has had the hydrolyzed aluminum removed by filtration. These tests included the results of aluminum filtration tests. This test also demonstrated a modified chemistry for controlling solids transport through the reactor without the use of an additive that degrades the titanium reactor material. 

Paabo and his colleagues took extraordinary precautions in their analyses, comparing their results with controls that did not contain any Iceman samples. The researchers showed that several sequences found in the samples were contaminants, but Otzi s DNA was slightly different and, as expected, more degraded because of age. As an additional control, the researchers performed several experiments in a different laboratory, showing that the DNA they found was not a contaminant contributed by their own equipment. 

Polymers that exhibit controlled degradation through the incorporation of prodegradant additive masterbatches or concentrates. Such polymers oxidise and embrittle in the environment and erode under the influence of weathering. 

O CONTENTS Introduction to Series An Editor s Foreword, Albert Padwa. Introduction, Timothy J. Mason. Historical Introduction to Sonochemistry, D. Bremner. The Nature of Sonochemical Reactions and Sonoluminescence, M.A. Mar-guli. Influence of Ultrasound on Reactions with Metals, B. Pugin and A.T. Turner. Ultrasonically Promoted Carbonyl Addition Reactions, J.L. Luche. Effect of Ultrasonically Induced Cavitation on Corrosion, W.J. Tomlinson. The Effects of Ultrasound on Surfaces and Solids, Kenneth S. Suslick and Stephen J. Doktycz. The Use of Ultrasound for the Controlled Degradation of Polymer Solutions, G. Price. 

Whereas the purpose of the antimicrobial additives, heat and UV stabilizers treated in previous sections is to preserve valuable plastic products, other research and development efforts have been attempting to realize just the opposite, i.e., controlled degradability of certain semifinished and finished plastic products, mainly the standard plastics PE, PVC, and PS out of which packaging materials are made in large quantities. The aim of rationalized use of such products is to reduce plastic waste volume by means of time-controlled photochemical or biochemical degradation. 

In recent years, many researchers (Azizi et al., 2008 Samsudin et al., 2006) are aware and have made considerable interests in dedicating their work in modifying the chain configuration of PP to alter the melt flowability of the material. The most preferred method is by additions of degradation substance such as peroxides. These peroxides are introduced to control the rheological behaviour of PP by lowering the viscosity of the viscous PP melts... 

Zweifel, H. (2001).Plastic additives Handbook, Chl4, Crosslinking and Controlled Degradation of Polyolefin, ISBN 3- pp.723, 446-19579-3, Switzerland... 

Some stabilizers are aimed at very specific uses such as antistatic agents (eliminating static electricity) and stabilizers active against bacteriological attack. Currently there are also additives for controled degradation of the polymer after the product has been used. 

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