Cooperation between chemical and physical networks in crosslinked and plasticized PVC

Abstract

SYNOPSISThe effect of crosslinking of plasticized PVC on the mechanical properties has been investigated. Crosslinking was performed by using a dithioltriazine, and penetration as a function of temperature was used to follow the changes in mechanical properties. Changes in the melting behavior were detected by differential scanning calorimetry. Even rather low levels of gel content gave a substantial reduction in penetration in the interval 60-llO"C, while a more complete reaction prevented major penetration up to at least 200°C. The penetration curve of heavily crosslinked materials showed several plateaus and the transitions could be related to melting of different crystallites formed by annealing at different temperatures. The physical network formed by the crystallites constitutes an important complement to the chemical network in plasticized PVC crosslinked by dithioltriazine. Both the amount and the melting temperature of the crystallites increased after annealing. The introduction of the chemical network further improved the heat resistance of the crystallites. The presence of the two networks will therefore show a synergistic effect with respect to the mechanical properties at increased temperatures.

Structure-property relationships of lightly chemical crosslinked poly(vinyl chloride) thermoplastic elastomer

“…It can be seen that X c and T m change no more with the increase of gel fraction at the same annealing conditions. Hjertberg et al 19 observed the increase of T m for high crosslinked PVC and considered that chemical crosslinking would decrease the mobility of PVC chains. However, the conclusion from Table II seems to be that the effect of chemical crosslinking on the recrystallization process could be ignored for lightly crosslinked PVC-TPE.…”

Peroxide crosslinking of unplasticized poly(vinyl chloride)

“…Above T g , softening depends on the melting of these crystallites, but can be modified by a chemical crosslinked network. 22 The temperature at which high temperature softening was detectable was increased for all samples containing peroxide to approximately 190°C. The optimum peroxide concentration for minimum softening was 0.5-1.0 phr, and appeared to decrease within this range as TMPTMA concentration increased.…”

Aminosilane grafting of plasticized poly(vinyl chloride) I. Extent and rate of crosslinking

“…It is interesting to note that the catalyst does not appear to have an important effect on crosslinking rate. The effect of increasing the 34 mentioned that diffusion of that the catalyst is vital to shorten the crosslinkwater from the external environment has practiing time. Narkis et al, 30 however, mentioned that cally no effect on the crosslinking.…”