Ultraviolet Radiation Induced Cold Chemi‐Crystallization in Syndiotactic Polypropylene Clay‐Nanocomposites

Dynamic Mechanical Properties of a Maxillofacial Silicone Elastomer Incorporating a ZnO Additive

“…340 vs 368 nm, respectively). These results are in accordance with the results of Mouzakis et al, 27 who studied the influence of UV-C radiation on polypropylene claynanocomposites and found an increase of stiffness of the polymer material. UV radiation usually results in molecular alternation, which influences the dynamic mechanical properties of the material.…”

“…An explanation for this is the formation of new highly flexible chain segments tending to rearrange themselves into higher-order formations, resulting in a phenomenon reported as chemicrystallization, which may be responsible for the increase of the polymer stiffness. 27 Additionally, the interesting observation of the reduction of tanC at 0.5 and 1 wt% ZnO concentrations in sunlight implies material sensitivity to this type of aging and stiffening of the polymer matrix, probably due to postcuring. TanC provides useful information about the energy transitions of a material under dynamic mechanical testing and is correlated to the molecules' movement in a concrete temperature.…”

“…Indeed, reduction of molecular weight being caused by chain scission due to radiation can provoke both E ¶ and )µ reductions. 27 Dynamic storage modulus (E ¶) expresses modulus of stiffness of the material, whereas loss modulus (Eµ) expresses the heat released in the environment because of friction. These 2 parameters determine the mechanical behavior of a material under dynamic testing.…”

Nanocomposites of irradiated polypropylene with clay are degradable?

“…In the environmental ageing, the chain scission occurs on the NC1 and the crystallinity tends to be higher after 6 months as for chemicrystallization effect, as reported by Mouzakis et al, (2006). The amount of clay is not enough to prevent the chemicrystallization at long time.…”

Study of the stress oscillation phenomenon in syndiotactic polypropylene/montmorillonite nanocomposites

“…Interestingly, the crystallinity of the nanocomposite-unstretched samples is almost 400% higher than the stress oscillated areas. Probably, this is the effect of the montmorillonite [16], which favours the crystal- lization of helical form I of sPP [9,16] during the isothermal crystallization phase. However, as seen from Figure 5 these conformations tend to vanish when mechanical stress is imposed.…”