Plasticiser loss

PVC-P materials, subjected to ageing under model and climatic conditions, have been extensively tested. Properties are lost as a result of diffusion controlled desorption of the plasticiser and a mathematical description of the ageing process has been formulated to predict lifetime (277). Plasticiser loss on ageing has also been identified in the spectroscopic investigation of roof membranes in service for a varying number of years (240). 

Samples of plasticised PVC coatings backed with a thin polyamide fibre cloth used for arm and head rests of trains were analysed after both normal use in service and artificial ageing at 100 C. Two parameters were studied the effects of temperature inside the train and the influence of the polyurethane foam inside the rests. Plasticiser loss due to migration during ageing led to hardening of the... 

Several other approaches to reducing plasticiser loss, besides using DINP and similar products, have been considered. Alloys of PVC with polymers like thermoplastic polyurethanes, EVA and nitrile rubber can give fairly flexible materials without using plasticisers at all. Appropriate blends can offer flexibility and low temperature toughness. 

In the aforementioned round-robin [47] also solvent-and heat-extraction methods for plasticiser determinations were compared. Materials were chosen which do not exhibit polymer degradation in the range of plasticiser loss at 300°C (Table 6.27). 

For samples that meet the solubility requirements of the SEC approach, analyses were also reported for additives in polymers such as PVC and PS [28,29]. Direct SEC analysis of PVC additives such as plasticisers and thermal stabilisers in dissolution mode has been described [28,30,31 ]. In the analysis of a dissolved PS sample using a SEC column of narrow pore size, the group of additives was separated on a normal-phase column after elution of the polymer peak [21]. Column-loading capacity of HPSEC for the analysis of additives, their degradation products and any other low-MW compounds present in plastics has been evaluated for PS/HMBT, PVC/TNPP and PVC/TETO (glyceryl tri[l-14C] epoxyoleate) [31]. It was shown that HPSEC can be used to separate low-MW compounds from relatively large amounts of polymers without serious loss of resolution of the additives the technique has also been used for the group analysis of chlorohydrin transformation products of the TETO model compound [32]. 

This is an analytical technique used to obtain accurate quantification of the principal compound constituents such as plasticiser, polymer, carbon black and inorganic species, by monitoring weight loss across a temperature range. 

Mention should also be made of the 30 year ageing data on PVC, UPVC, HDPE, LDPE and a styrene-butadiene copolymer tested by Rapra in hot-dry and hot-wet environments shielded from sunlight, published by Brady and co-workers [25]. Exposure for such long periods is very rare. Dioctyl phthalate plasticised PVC, HDPE and LDPE showed little change and of the remainder loss of strain to failure was more noticeable than loss of strength. Updated results from this 40 year programme are not in the public domain at the time of writing. 

Post and co-workers [49] have used TG-FTIR to study the outgassing of a plasticiser (type and amount) from an ethylene-propylene-diene terpolymer (EPDM) compound. Figure 1.6 shows the thermogravimetric decomposition behaviour of the EPDM compound. The plasticiser emerges in the first mass-loss step, which was identified as adipic acid diisobutylester by on-line infrared analysis. 

TG-MS is an ideal technique for identifying residual volatiles in polymers. The detection of residual volatiles (and of other impurities) can often yield clues as to manufacturing processes. In many cases, such as in the determination of highly volatile materials, of residual solvents or plasticisers, use of TG-MS is requested. Specifically, there are reports on the entrapment of curing volatiles in bismaleimide laminates [145] and elastomers [48], on the detection of a curing agent (dicumylperoxide) in EPDM rubbers and of bromine flame retardants in electronic waste [50], of plasticisers such as bambuterol hydrochloride [142] or TPP and diethylterephthalate in cellulose acetate [143], on solvent extraction and formaldehyde loss in phenolic resins [164], and on the evolution of toxic compounds from PVC and polyurethane foams [146]. 

The extent, rate and mechanisms of deterioration of model and naturally aged PVC containing diethylhexyl phthalate were examined during thermal ageing in various environments. Weight loss was used to quantify loss of diethylhexyl phthalate, FTIR to quantify concentration of diethylhexyl phthalate at surfaces and optical densitometry to examine darkening of samples. Correlations were made between the rate and extent of deterioration of plasticised PVC and the migration and loss of diethylhexyl phthalate. 14 refs. 

Lubricants have been classified as either internal or external. Typically, internal lubricants have meant materials that are compatible with PVC that promote flow. The difference between internal lubricants and plasticiser is that the internal lubricant is only soluble at high temperature whereas the plasticiser is soluble and functional at room temperature. External lubricants on the other hand, are said to be incompatible and come to the surface and create metal release. It is reported that there are two distinct types of external lubricants. Internal lubricant efficiency can be readily predicted by simple mathematical formula and that partial substitution of esters for paraffin allows the reduction of modifier or increased filler levels to achieve savings without loss of any physical properties. 

THEORETICAL STUDY OF THE KINETICS OF LOSS OF PLASTICISER FROM PLASTICISED PVC FOILS... 

A kinetic model of the physical process of loss of plasticiser di-(2-ethylhexyl)-phthalate from plasticised PVC foil is developed. Experimental investigations are carried out using isothermal thermogravimetry in the temperature range of 120-150 deg.C. The thickness of the foil is 0.1 mm and the amount of the plasticiser in the plasticised polymer is 10-40%. The kinetic parameters... 

INFLUENCE OF BIODEGRADATION ON THE LOSS OF A PLASTICISER FROM POLYVINYL CHLORIDE... 

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