Study Of The Structure Evolution And Surface Properties Of The Polyethylene Modified Blown Films

The manufacturing of the blown films is one of the complex processes for polymers which have received attention recently for both the practice and research point of view.Despite of the much research efforts the distinct understanding of the molecular parameters which decide the valuable properties of the blown films such as haze,transmittance and the wettability are not fully formulated.In this dissertation,the underlying question is to explore the structural behavior of modified polyethylene during processing through blown films,and the interpretation of optical and wettability of resulting films.For this purpose we have used the powerful tool of synchrotron radiations based in-situ Small-and Wide-angle scattering(SAXS and WAXS)along with the temperature sensor to explore the microstructural analysis.The haze and transmittance measured by the haze and transmittance meter for the optical properties and the contact angle tested by the goniometer for the wettability.According to the prescribed quality,for the modified polyethylene,we have used various composition of the ionomers(polyethylene methacrylic acid)and the hyperform nucleating agent(HPN 20E).Both of these materials have greatly influenced the microstructural features,haze and wettability.Specific objectives and consequences are presented in the following paragraphs.In the first study,a homemade blown film methodology simultaneously coupled with the in-situ SAXS and WAXS was used to investigate the miscibility and its effect on the structural evolution of PE/surlyn blends' films at the different composition of surlyn.On the basis of the crystallinity curve,the results were defined into three regions from the exit of the die to the certain length 160 mm along the bubble including the position of frost line.Interestingly the equatorial streak in SAXS images indicates the phase separation between PE and surlyn whose appearance is terminated up to the frost line(Af).The whole process of the phase separation is exothermic which further helps to suppress the process of crystal cross-linked network formed during the bubble formation.This is due to the decrease in crystallinity with the higher lamellae orientation in the Region I and the tendency remains irregular in the defined regions II and ? which is the consequence of the late formation of the stable non-deformable scaffold up to the completion of crystallization along the bubble.This work can be supportive for extended study of the polymer blends through blown film technology.In the second work we have used nucleating agent,which provides heterogeneous nucleation to investigate the blowing of PE/HPN 20E.Similar to above the same approach was used for the experiments.The structural behaviors such as crystallinity,lamellae long period and orientation parameter of the PE containing HPN studied for various compositions from the die exit to the position above the frost line...the structural evolution shows various features.The dispersion of HPN in the PE melt is inhomogeneous at the higher composition of HPN(0.5 wt.%)which dramatically influences nucleation process.At small distances,corresponding to the high temperature,the flow and nucleating agent of polymer entanglement network induce both the homo-and heterogeneous nucleation,which form a deformable crystal-crosslinked network that in turn accelerate crystallization kinetics and gradually evolves into a non-deformable crystal scaffold to decide the bubble properties.The scaffold is further covered up by crystals with reduction in crystallization kinetics.The crystallinities for the formation of crystal-crosslinked and crystal scaffold depend on the composition of HPN.The crystallinity at the frostline for the formation of non-deformable scaffold also vary with the take up ratio(TUR).The results suggest that the structure parameter are controlled by the molecular parameter and nucleating agents near to the die exit while after the frost line later addition to those two factors it is determined by the processing parameter.In our last work we have studied the properties of the blown films.Blends of PE/surlyn and the PE/HPN 20E were prepared by melt mixing method which were further blown to some micron size films by varying the take up.The change in the film properties such as wettability was successfully prevailed using the surlyn ionomer by the processing.The wettable surface(hydrophilicity at contact angle of 45°)for the"adhesion or dye-ability" was achieved at high flow(TUR30),which was elaborated by dominancy of the functional carboxylic polar groups on the surface during.The dramatic optical behavior of an adversely increment in the haze with the slight change in transmittance of the film surfaces for both PE and modified PE was observed.This was explained by the surface roughness,phase segregation,concentration and size of mounds(spherulitic structure).The WAXS and SAXS results support the previous research:The minor participation of the internal structure of the film to the haze increment over the film surface roughness.This kind of polymer films can be used as the mate or milky films for the high potential applications in covering of roof,privacy of windows and in the print packaging.