To study polymer degradation

Arnosti, C., and D. J. Repeta. 1994b. Oligosaccharide degradation by anaerobic marine bacteria Characterization of an experimental system to study polymer degradation in sediments. Limnology and Oceanography 39 1865-1877. 

Similarly NMR can be used to study polymer degradation. Figure 4.10(A)... 

As previously stated, GPC is the method of choice for studying polymer degradation kinetics. The GPC trace, as given by the detector output, does not provide the true MWD due to various diffusion broadening processes inside the different parts of the equipment. The first step is to correct for instrument broadening if a precise evaluation of MWD is desired. Even with the best columns available, this correction may change the MWD significantly as can be visualized... 

Gall, B.L. and Raible, C.J. "The Use of Size Exclusion Chromatography to Study the Degradation of Water Soluble Polymers Used in Hydraulic Fracturing Fluids," Polvm. Mater. Sci. Eng. 1986, 55, 572 75, Anaheim. 

A few relatively recent published examples of the use of NMR spectroscopy for studying polymer degradation/oxidation processes will now be discussed briefly. At the early stages of degradation, the technique can be used to provide chemical identification and quantification of oxidised species for polyolefins, oxidation sites can be identified by the chemical shifts of -CH2- groups a and ji to carbons bonded to oxygen [85]. Spin-spin relaxation times may be determined by a pulse sequence known as the Hahn spin-echo pulse sequence. 

ESRI methods have been developed in our Detroit laboratory for the study of heterophasic systems such as ABS [14,40,59,87-89] and HPEC [61,90], both containing bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin 770) as the stabilizer, and exposed to thermal treatment and UV irradiation. The HAS-NO provided the contrast necessary in the imaging experiments. The major objectives were to examine polymer degradation under different conditions to assess the effect of rubber phase, polybutadiene (PB) in ABS and ethylene-propylene rubber (EPR) in HPEC, on the extent of degradation and to evaluate the extent of... 

Sample Preparation. The UHMWPE used in this study was a HiFax 1900 (Himont, Inc.) with an average molecular weight of 2-8 x 10. The UHMWPE was added to paraffin oil to concentrations from 2 to 5% w/w. To avoid polymer degradation at high temperatures, the polymer was stabilized with approximately 0.5% of BHT antioxidant. The mixture was stirred at 150 C. A solution was obtained that was clear until it was cooled to about 120 C when it became opaque and transformed into a gel-like or pseudo-gel. 

Chu, C.C. and Louie, M., 1985. A chemical means to study the degradation phenomena of polyglycohc acid absorbable polymer. J. Appl. Polym. Sci., 30 3133-3141. 

As the glass transition temperature Tg is approached, the friction coefficient C sharply increases [3] and hence becomes too small to be measured. Thus, self-diffusion measurements on undiluted polymers are usually made at temperatures far above Tg. For example, all the reported data on polystyrene melts (Tg 100°C) were taken in the range 150 - 250° C. Working at such high temperatures, however, is not simple for various technical reasons including polymer degradation. It is therefore advantageous to study polymers with Tg far below room temperature if nearly monodisperse samples are available (use of polydisperse samples should be avoided for basic research). Extimples of such polymers are poly(isoprene) and polybutadiene. 

Natural fiber-reinforced polyolefins are commonly apphed to automotive and constmction applications. The most abundantly used additive is fire retardant. Flammability is an important factor that often limits the application of composites to a specified field. Magnesium hydroxide is the most common flame retardant material used in the constmction industry. This filler responds well to surface modifiers and decomposes by an endofliermic reaction that releases water at temperatures close to the polymer degradation temperature as show in Eq. 6.1. Rothon et al. [78] studied the effects of magnesium hydroxide on polypropylene as a flame retarder of 60 % by weight. The smdy found less heat emission at 100 kWm after 6 min of fire exposure compared to filled PP without Mg(OH)2 at 500 kWm. ... 

Infrared spectroscopy is a popular method for identifying polymers [1-7]. In this present chapter, the application of infrared spectroscopy to the study of polymeric systems will be introduced. Infrared spectroscopy may be used to identify the composition of polymers, to monitor polymerization processes, to characterize polymer structure, to examine polymer surfaces and to investigate polymer degradation processes. 

Figure 6.20 Evolution of gases as a function of time from a blend of PMMA and Fe(iii) chloride, where a time of 8 min corresponds to a temperature of 160°C (ramp rate of 20°C min" ). Reprinted from Polym. Degrad. Stabil, 66, Wilkie, C. A., TGA/FTIR An extremely useful technique for studying polymer degradation , 301-306, Copyright (1999), with permission from Elsevier.

Many workers have used PyMS to study the structures of polymers, both natural and artificial. Understanding the performance of polymers in terms of cohesion and substrate adhesion is of immense commercial significance in the paint and adhesive industries. Similarly, the behavior of polymers under stress and when exposed to external factors such as ultraviolet light has been extensively studied by PyMS and is useful in the development of novel materials that have desirable properties, e.g., fire-retardant coatings and biodegradable fibers. There is much interest in polyhydroxyalkanoates as potentially biodegradable plastics, and PyMS has been a principal method used to study thermal degradation profiles of this material. Similarly, in forensic science, PyMS has been used to analyze fibers and to help match samples of automotive finishes to paint chips found at crime scenes. 

Furthermore, often it is not feasible or practical to study the degradation mechanisms of polymers using only retrieval studies or by implanting them into animals, because of the timescales involved of the projected lifetime of the polymer, possibly of the order of 20 years (Mahomed et al., 2010a). One... 

Malinauskas et al. have used an in situ Raman spectroelectrochemical technique to study the degradation kinetics of self-doped sulfonated polyaniline. When a positive potential (-1-0.9 V vj. Ag/AgCl) was applied to the polymer in a solution (pH ranging from 0.5 to 9), the intensity of Raman bands decreases with time due to electrochemical degradation of polymer, and the rate of which increased with decreasing pH. 

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