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allow for the increased volume that the solvent had to extract through, the extraction time was extended first to 48 hours and then up to 240 hours. To obtain a reasonable amount of extract the sample size was increased from 2gms to 20gms. Although a hot methanol extraction was carried out, subsequent

to the ether extraction, only a minute extract was obtained and it was not adopted as part of the general extraction

programme. The different extraction conditions and the weight of extracted materials are given in table 17,

It had been suggested [181] that variations in the weight of extracted additives probably resulted from the minor

variations in composition, between batches, arising from the day-to-day changes in processing conditions. Allowing for this,

the sheet contained approximately 2.9% extractable additives whilst both the rod materials contained approximately 4.1% extractable additives. This difference is believed to be due to the different types and levels of additives required for the different processing conditions. These levels are in agreement with those quoted by Comes and Hqward [93] .

The levels of additives indicated that neither impact modifiers, plasticisers nor processing aids were used in these materials, since these additives would normally be present at the 10% level.

A second method of separating the polymer from the additives, the THE recovery method also recommended by

Haslam et al [180], was used to confirm the levels of additives in the clear sheet and to allow the determination of the

filler in the filled sheet. The clear sheet material was found to contain 3.75% soluble additives and 1.3% insoluble additives. Although these values are higher than those from the Soxhlet extraction,they confirm the level of additives as being no higher than the 5% level. The difference is thought to be due to :

1) the granules used in the Soxhlet extraction being of a sufficient size to prevent complete extraction.

2) the insoluble additives centrifuged off probably containing both some crosslinked polymer and the dirt particles trapped in the material during processing ( a visual examination of the sheet reveals numerous inclusions within the sheet).

The recovery method was only used to separate the filler from the filled UPVC sheet and the insoluble additive content was found to be 12%.

4.3.2. Analysis of Additive-Free Polymer

After Soxhlet extraction, the polymer granules were subjected to various drying procedures, in an attempt

get a constant weight measurement. However, the granules were found to increase in weight with increasing time of

exposure to air, see table 8 for drying conditions used and the resulting granule weights. The granules were found to gain approximately 2% weight compared to the sample

weight prior to extraction. This would indicate an increase in polymer weight of approximately 6%, allowing for the removal of additives.

After the ether extraction the granules appeared unchanged. However, the granules of both sheet and clear rod developed a milky white translucence during drying after the methanol extraction. Sample granules, taken after the methanol extraction, were found to contain voids when cut open and examined using a light microscope. It is thought that the hot methanol swells the polymer granules during extraction and

during drying the granules are constrained to their swollen shapes. The polymer can return to its normal density only by forming internal voids.

Dried granules of both sheet and clear rod were subjected to a DSC analysis, see fig. 57. The resulting thermograms

indicate a reduction in polymer T to approximately 45°C.₈

This, combined with the increased weight of the granules, suggests they still retain some solvent which is acting as a plasticiser [182].

4.3.3. Analysis of Extracted Additives

The author would like to take this opportunity to acknowledge the assistance of Dr. G. Corfield and Dr. A. Ellis in the

following work and the co-operation extended by the technical services sections of I.C.I., Hoechst Chemicals and Ciba-Geigy.

The analysis programme chosen reflected the need to gather the maximum information in the shortest time. It was expected that some of the additives would remain unidentified and that

no quantitative information concerning the level of the individual additives would, he obtained.

The programme consisted of submitting the dried extracts,

without further separation, to analysis using standard I-R,

U-V, NMR and DSC techniques. The first three are recommended by Haslam et al 1183]. The last was expected to provide melting point information and thus allow an estimate of the

number of additives present in each extract. The results

for the extracts from these methods were then compared against results obtained for pure samples of a range of

additives, selected as possibly being present in the extract, and against results given by Haslam et al 11843. It was appreciated that the identification of some of the additives would prove impossible due to chemical changes brought about by processing and that some would be masked by other

additives in the extract.

The extracts from both the clear sheet and the I,C.I. rod were similar in appearance. Both were a brown slurry which largely solidified with time, though they melted if warmed in the hand. The clear rod extract was a blue slurry which solidified with time and also melted if warmed in the hand.

The I-R, U-V, and NMR spectra for the sheet and two rod