Plasticizer loss

The ECPI approach has been adopted by the European Commission in their "Technical Guidance Document on the Risk Assessment of Notified New Substances" as the model for assessment of environmental exposure from additives in plastics. It is important to note, however, that due to the effect of ultraviolet degradation and microbial attack, a significant proportion of the emissions from flexible PVC consists of plasticizer degradation products. In these instances, therefore, the level of plasticizers appearing in the environment will be significantly less than indicated by the plasticizer loss data. 

Emissions During Exterior End Use. When flexible PVC is used in exterior appHcations plasticizer loss may occur due to a number of processes which include evaporation, microbial attack, hydrolysis, degradation, exudation, and extraction. It is not possible, due to this wide variety of contribution processes, to assess theoretically the rate of plasticizer loss by exposure outdoors. It is necessary, therefore, to carry out actual measurements over extended periods in real life situations. Litde suitable data have been pubHshed with the exception of some studies on roofing sheet (47). The data from roofing sheet has been used to estimate the plasticizer losses from all outdoor appHcations. This estimate may weU be too high because of the extrapolation involved. Much of this extracted plasticizer does not end up in the environment because considerable degradation takes place during the extraction process. 

The modulus of elasticity can also influence the adhesion lifetime. Some sealants may harden with age as a result of plasticizer loss or continued cross-linking. As a sealant hardens, the modulus increases and more stress is placed on the substrate—sealant adhesive bond. If modulus forces become too high, the bond may faH adhesively or the substrate may faH cohesively, such as in concrete or asphalt. In either case the result is a faHed joint that wHl leak. 

Small flux decline after 30 days No sign of flux decline or carrier and plasticizer losses after 10 days. Stable after 10 months storage in air Small flux decline after 15 days but no evidence of carrier and plasticizer loss Small flux decline after 20 days but no evidence of carrier and plasticizer loss Stable flux after 1 month... 

Flux decline began slowly after 100 days but no evidence of carrier and plasticizer loss... 

Flux decline and carrier/plasticizer loss began after 30 days... 

One variation on heat aging tests is to measure plasticizer loss by using an absorbant material such as charcoal and determining weight loss. Other tests for particular materials have been devised, for example thermal stability of PVC can be measured by the rate of evolution of hydrogen chloride, For rubbers, aging in oxygen at elevated pressure is sometimes used to accelerate the test further. 

The majority of investigations on the degradation of cellulose acetate have been conducted on photographic film (cellulose triacetate) rather than moulded material. like cellulose nitrate, cellulose acetate (CA) is deteriorated by both physical and chemical factors and the physical cause of degradation is plasticizer loss. Three-dimensional objects moulded from cellulose acetate comprise 20-40 per cent by weight plasticizer. Typical plasticizers include triphenyl... 

Relative volatihty of plasticizers can be determined by this method. Plasticizers are placed in a circulating air oven on a rotating table. The oven is set to either 105 or 155°C and the samples are cooled and weighed after 2,4, and 24 hours. Weight loss is calculated and reported in percent of plasticizer loss between time intervals, as a loss relative to rmit area of ejqtosed surface, or as an average volatility rate (amount lost per surface area and time). Results depend on control of temperatore and air flow. It is crrstomary to compare different plasticizers in the same experiment to avoid interference of experimental conditions. 

These simple examples included only polymer and plasticizer. In normal formulations many other components exist and interact. Many studies address this subject in order to determine how to limit plasticizer loss. Montmorillonite clay was used as filler in PVC/ PMMA composite. The filler was used in its original and intercalated form to make polymer hybrid in which filler is dispersed on a molecular level. Totally different behavior was observed when composites were immersed in a solvent plasticizer mixture followed by drying. The sample containing the intercalated filler absorbed 50% less plasticizer than did any other sample studied. Thus plasticizer movement may be restricted by other than chemical interaction. These include physical obstacles in migration pathways that can also influence plasticizer distribution in a matrix. 

Figure 10.43 shows that the temperatures to 50% loss of plasticizer tested alone and mixed with polymer are related to boiling temperature of plasticizer. The temperature of 50% plasticizer loss from the pure plasticizer is always slightly lower (e g., 9°C for DBF and 2°C for DIDP) than temperature to 50% weight loss of plastisol. It is difficult to understand reasons for the differences between various plasticizers but it is quite possible that the presence of poly-... 

Several theoretical models were used to determine the best method of data interpretation and prediction of loss rate. It was found that the following relationship is useful for the analysis of data on plasticizer loss ... 

Figure 10.44. Rate of plasticizer loss from PVC formulation eontaining 50 phr plasticizer vs. molecular weight of plastieizer. [Data from Dedov A V, Bablyuk E B, Nazarov V Q Polym. Sci., Ser. B, 42, Nos.5-6, May-June 2000, p. 138-9.]...

It has to be pointed out that the plasticizer loss occurs at any temperature and it is substantial at temperatures well below the boiling point of the plasticizer or conditions... 

From thermal degradation studies it was shown that temperatures available in environmental conditiorrs ( 100°C) accelerate plasticizer diffusion. Thirs plasticizer loss may... 

Figure 10.62. Staining of flooring based on plasticized PVC vs. plasticizer loss during extraction for 96 h by kerosene. [Data from Colletti T A Renshaw J T Schaefer R E, J. Vinyl Additive Technol., 4, No. 4,...

Volatility of pure plasticizers and the volatility of plasticizers in plasticized PVC differ (Figure 11.60). Temperatiue of loss of a pure plasticizer is consistently lower than the temperature of plasticizer loss from plastisol. This is due to interaction between plasticizer and PVC chain. In order to remove the plasticizer from plastisol, additional energy is required to overcome the energy of hydrogen bonding. Compatibility between the plasticizer and the polymer also plays a role since small differences are recorded for higher molecular weight (less compatible) plasticizers. ... 

Figure 11.62. Plasticizer loss from PVC plasticized with 10 phr of epoxidized soybean oil and 40 phr of di-(2-ethylhexyl) phthalate and 40 phr of poly(ethylene-co-vinyl acetate-eo-earbon monoxide). [Data from Audic J-L Poncin-Epaillard F Reyx D Brosse J-C, J. Appl. Polym. Sci., 79, No.8, 22nd Feb.2001, p.l384-93.]...

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