Naslov
Hydrotalcite as a secondary stabiliser for PVC

Autori
Gilbert, Marianne ; Chin Ho, Kok ; Hitt, David J. ; Vrsaljko, Domagoj

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
POLYCHAR 20 World Forum on Advanced Materials - Book of Abstracts / Rogošić, Marko ; Macan, Jelena - Zagreb : Fakultet kemijskog inženjerstva i tehnologije Sveučilišta u Zagrebu, 2012, 13-13

ISBN
978-953-6470-57-0

Skup
POLYCHAR 20 World Forum on Advanced Materials

Mjesto i datum
Dubrovnik, Hrvatska, 26.03.2012. - 30.03.2012

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Hydrotalcite; PVC

Sažetak
Hydrotalcite is a double layered hydroxide that is capable of ion exchange reactions. From around 2000, it has been increasingly used as a polymer additive, and is capable of scavenging acidic by- products in halogenated polymers. It has also been added to flame retardant systems, and will act as a flame-retardant and smoke suppressant. An important application is its use as a secondary stabiliser for PVC. As part of the 2010 Europe wide voluntary commitment1, it was agreed to phase out 50% of lead heat stabilisers currently used by 2020, a target now well ahead of schedule. The majority of the lead stabilisers have been replaced by more acceptable calcium/zinc soaps, but these are less effective. Their performance can be enhanced by the addition of hydrotalcite as a secondary stabiliser2. This paper considers the function of hydrotalcite in PVC compounds. Rigid (UPVC) and flexible (i.e. plasticised) PVC (PPVC) mouldings were oven aged at 180°C for up to 200 min. The aged samples were examined by the following techniques: colour was compared and measured ; solubility in tetrahydrofuran to detect crosslinking ; UV/visible spectrophotometry to monitor the development of short unsaturated sequences and Raman spectroscopy to detect longer unsaturated sequences (sequence length n=14)3. The observed behaviour of UPVC and PPVC was different. Differences were attributed to the lower processing temperature and reduced shear heating in PPVC due to the lower melt viscosity resulting from the presence of plasticiser. UPVC samples degraded much more rapidly than PPVC. The latter only showed significant ageing effects after ≥ 120 min. When the concentration of hydrotalcite was increased in PPVC, degradation was reduced further ; with 5 phr hydrotalcite no discolouration was detected after 200 min at 180°C. In UPVC degradation produces a distinct red colouration, whereas PPVC follows the more usual yellow/ orange/ brown/ black sequence. The red colour increases with increase in hydrotalcite concentration, and it was found that hydrotalcite reduces crosslinking, thus longer unsaturated sequences, which result in the red colouration, remain. For PPVC crosslinking was again reduced, but significant degradation was completely prevented, so no red colour was seen. UV/visible spectrophotometry showed that short unsaturated sequences are produced during processing. The level of these did not change during ageing. For UPVC the amount was unaffected by hydrotalcite, but hydrotalcite increased the concentration of short sequences for PPVC, possibly due to increased melt viscosity. The optimum level of hydrotalcite in UPVC was found to be 2 phr ; for PPVC increasing hydrotalcite concentration up to the 5 phr used in this work improves long term stability.

Izvorni jezik
Engleski

Znanstvena područja
Kemijsko inženjerstvo, Temeljne tehničke znanosti

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