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Chemical Stability and Degradation

Plasticizers are additives that could be present up to 30 wt% in PLA formulations. Their impact on the chemical ageing of PLA could be considered by either a negative or a positive role depending on their chemical architecture and hydrophilicity and also on their use in medical or commodity applications. [Pg.159]

Positive outcomes from the addition of a plasticizer into PLA are the increase in the environmental degradability at the end-of-life treatments. In fact, the slow degradation rate of neat PLA is often considered to be a major drawback for biomedical applications, leading to long in vivo life-time, which could be up to years in some cases. Solutions to increase the abiotic degradation rate in biomedical applications could be an inspiration to optimize the degradation of PLA in other applications, such as food packaging. [Pg.160]


Similar to accelerated studies, stress tests give a general picture of the chemical stability and degradation pathways under exaggerated conditions, such as under extreme pH conditions (acids and bases), heat, oxidative or reductive conditions, hydrolysis, and light irradiation (light irradiation tests at not less than 1.2 million lux hours are formalized as described in ICH QIB). These mostly non-formalized stress tests are only evaluated over a short term, e.g., 1 month. [Pg.112]

Membranes used for the pressure driven separation processes, microfiltration (MF), ultrafiltration (UF) and reverse osmosis (RO), as well as those used for dialysis, are most commonly made of polymeric materials. Initially most such membranes were cellulosic in nature. These ate now being replaced by polyamide, polysulphone, polycarbonate and several other advanced polymers. These synthetic polymers have improved chemical stability and better resistance to microbial degradation. Membranes have most commonly been produced by a form of phase inversion known as immersion precipitation.11 This process has four main steps ... [Pg.357]

PP Klemchuk (ed.), Polymer Stabilization and Degradation. ACS Symposium Series 280. Washington, D.C. American Chemical Society, 1985. [Pg.683]

In this review, some of the electroactive polymers most commonly studied during the past one and a half decades have been selected to illustrate the type and level of information obtainable from XPS core-level spectra. It concerns (a) the intrinsic structure, (b) the CT interaction, and (c) the stability and degradation behavior. The review is meant to be comprehensive, although emphasis has been placed on some specific issues related to these three basic physicochemical properties. For example, the chemical nature of the nitrogens in PPY and PAN has been critically compared on the basis of XPS data. Some of the major discrepancies in the XPS literature of electroactive polymers have also been examined. In most cases, preference has been given to results for which proper justification and careful comparison with available data are possible. Finally, some future trends in the application of XPS and other more surface sensitive techniques to the study of highly reactive conjugated polymer surfaces have been mentioned. [Pg.185]

Part V Properties determining the chemical stability and breakdown of polymers. In Chapter 20, on thermomechanical properties, some thermodynamics of the reaction from monomer to polymer are added, included the ceiling and floor temperatures of polymerization. Chapters 21 and 22, on thermal decomposition and chemical degradation, respectively, needed only slight extensions. [Pg.1022]

Niosomes In order to circumvent some of the limitations encountered with liposomes, such as their chemical instability, the cost and purity of the natural phospholipids, and oxidative degradation of the phospholipids, niosomes have been developed. Niosomes are nonionic surfactant vesicles which exhibit the same bilay-ered structures as liposomes. Their advantages over liposomes include improved chemical stability and low production costs. Moreover, niosomes are biocompatible, biodegradable, and nonimmunogenic [215], They were also shown to increase the ocular bioavailability of hydrophilic drugs significantly more than liposomes. This is due to the fact that the surfactants in the niosomes act as penetrations enhancers and remove the mucous layer from the ocular surface [209]. [Pg.748]

In addition, PCTFE has exceptional barrier properties and superb chemical resistance. It is attacked by a number of organic solvents. It has low thermal stability and degrades upon reaching its melting point, requiring special care during processing. [Pg.1038]

In Polymer Stabilization and Degradation Klemchuk, P. ACS Symposium Series American Chemical Society Washington, DC, 1985. ... [Pg.222]


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