Reprocessing recycled polyolefins is always accompanied with degradation, crystallization, and consequent processability problems, which result from molecular chain scission
, branching, and crosslinking.
Also, some virgin polymers experience chain scission
("scissoring" of molecular chains) during melt processing, and the resultant recycle resin has poorer mechanical properties compared with the starting virgin resin due to lower molecular weight.
is the degradation of a polymeric material in the absence of a chemical agent, in particular without oxygen.
Quantum Yields (a) of Chain Scission
and Gas Evolution for UV Irradiation of Different Polymers Polymer UV Wavelength Quantum Yield (nm) of Scission (Gas) Poly(phenyl isopropyl 254 0.
The narrowing of the molecular weight distribution was due to the simultaneous disappearance of the high molecular weight compound due to chain scission
events and of the low molecular weight compounds as they diffuse out of the films into the medium .
of macromolecules may superpose the effect of cross linking on crystallization due to a strong nucleating effect (Ehrenstein et al, 2004) of short chain molecules.
Chemical peptizers are materials usually based on a combination of a free radical scavenger and a so-called booster material, as an effective source of oxygen radicals that serve to increase oxidative chain scission
at higher temperatures.
Fourier Transform Infrared Spectroscopy (FTIR) study indicates that the oxidation and chain scission
reactions are likely the origins of the surface morphological changes.
They are not, however, resistant to UVB degradation, which will eventually cause a loss of binder and chalking probably through a mechanism of chain scission
An example of this type of mechanism is the understanding that a specific polymer coating degrades by chain scission
However, the amount and compounding time of a peptizer should be optimized, as excessive amount and compounding time of a peptizer are detrimental to the physical property of the matrix by excessive chain scission
In addition to effective recycling by remolding, oil and gas are recovered in essentially quantitative yields by thermal chain scission
above 400[degree]C (Figure2).