Aging polymer blends

Figure 14.5. DSC thermograms for aged polymer blends (a) polyvinylchloride/poly isopropyl methacrylate, immiscible blend, aged at a temperature of 60°C, and (b) polyvinyl chloride/polymethylmethacrylate, miscible blend, aged at 80°C. Time of aging, t in hours, is shown alongside each curve. Broken lines represent the un-aged samples for comparison.

Ljungberg, N. and Wesslen, B. 2004. Thermomechanical film properties and aging of blends of polyjlactic add) and malonate oligomers. Journal of Applied Polymer Science 94 2140-2149. 

For ageing experiments the toluene solution of the grafted polymer was first treated with an excess of triphenyl phosphine (reduction of residual hydroperoxides into alcohols), then suitable amount of the parent polymer was added and co-precipitation was performed into methanol. The polymer blend was vulcanized by adding dicumyl peroxide (5% w)prior precipitation (pressing conditions became 190°C, 190 bar, 5 min). 

Monakov YB, Sabirov ZM, Zaikov GE (2002) Aging of Polymers, Polymer Blends and Polymer Composites. Nova Science, Hauppauge, NY 1 237 and references therein... 

Polymer Age, 46 Polymer blends, 71, 98 Polymer Chemistry Innovations, Inc., 189 Polymer cycle, 178-179, 179 Polymer science future of, 203-219 history of, 45-79 relationships of, xxiv... 

All samples were dried in a constant stream of air for several hours and then dried for at least four days under vacuum at room temperature. After drying, the films were aged in desiccators at room temperature for at least two weeks. This allows the PCL crystallinity to approach its equilibrium value (6). Throughout this chapter the blends are designated by the weight percent of the polymer blended with polycaprolac-tone. Thus 25% PVC is a 25/75 blend of PVC/PCL. 

A group of new, fully miscible, polymer blends consisting of various styrene-maleic anhydride terpolymers blended with styrene-acrylonitrile copolymer and rubber-modified versions of these materials have been prepared and investigated. In particular the effects of chemical composition of the components on heat resistance and the miscibility behavior of the blends have been elucidated. Toughness and response to elevated temperature air aging are also examined. Appropriate combinations of the components may be melt blended to provide an enhanced balance of heat resistance, chemical resistance, and toughness. 

The selection of polymers and polymer blends for use as specific materials requires the consideration of how these will withstand the environmental conditions to which these will be subjected. The long term stability of a polymer will depend on its aging characteristics both physical and chemical. 

Table 14.13. Physical aging in polymer blends, studied by Stress relaxation, Mijovic equation parameters ...

Improving the long-term service fife and performance of polymer blends (thermal aging/ embrittlement resistance, creep and fatigue resistance, weatherabUity, etc.). 

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