Q2. What is the effect of the constrained region on the permeability of polymers?
Since the main effect of the constrained region is to lower free volume, and this effect is not significant in crystalline regions, the constrained region of semicrystalline polymers does not significantly affect permeability unless the crystallinity is decreased.
Q3. Why have the packaging industry focused its attention on layered inorganic solids?
Although several nanoparticles have been recognized as possible additives to enhance polymer performance, the packagingindustry has focused its attention mainly on layered inorganic solids like clays and silicates, due to their availability, low cost, significant enhancements and relative simple processability.
Q4. What are the main properties of polymer composites?
Several composites have been developed by adding reinforcing compounds to polymers to enhance their thermal, mechanical and barrier properties.
Q5. What are the important factors affecting the effectiveness of nanoscale immobilization systems?
Nanoscale immobilization systems would have strongly enhanced performance, since they would increase the available surface contact area and modify the mass transfer, probably the most important factors affecting the effectiveness of such systems (Fernández et al., 2008).
Q6. Why is the use of edible and biodegradable polymers limited?
the use of edible and biodegradable polymers has been limited because of problems related to performance (such as brittleness, poor gas and moisture barrier), processing (such as low heat distortion temperature), and cost.
Q7. What is the effect of bentonite on the mechanical properties of polymers?
Petersson and Oksman (2006a) reported that bentonite was able to improve strength and modulus of a polylactic acid (PLA) matrix, but it drastically decreased elongation of the material.
Q8. What is the effect of a constant filler content on the interface layers?
According to Jordan, Jacob, Tannenbaum, Sharaf, and Jasiuk (2005), for a constant filler content, a reduction in particle size increases the number of filler particles, bringing them closer to one another; thus, the interface layers from adjacent particles overlap, altering the bulk properties significantly.
Q9. What is the effect of organophilization on the clay?
The organophilization reduces the energy of the clay and improves its compatibility with organic polymers (Paiva, Morales, & Díaz, 2008).
Q10. What is the effect of CNTs on the tensile strength of polyethylene?
even in concentrations as low as 0.1 wt.%, greatly improved thermal stability as well as tensile strength and modulus of PEN.
Q11. What is the role of organoclays in polymer nanocomposites?
products from interactions between clay minerals and organic compounds, have found an important application in polymer nanocomposites.
Q12. What is the effect of surface modifiers on the permeability of polymer composites?
The surface modifier region (1–2 nm) binds the clay with the polymer; it is assumed to be small enough to have little effect on the permeability of the composite.
Q13. What is the effect of nanoreinforcements on the elongation of polymers?
According to Jordan et al. (2005), the addition of nanoreinforcements with poor interaction with the matrix causes the elongation and the strength of the material to decrease; on theother hand, the modulus seems not to be dependent on such interactions.
Q14. What is the main method used to obtain cellulose whiskers?
The main method used to obtain cellulose whiskers has been acid hydrolysis, consisting basically in removing the amorphous regions present in the fibrils leaving the crystalline regions intact; the dimensions of the whiskers after hydrolysis depend on the percentage of amorphous regions in the bulk fibrils, which varies for each organism (Gardner, Oporto, Mills, & Azizi Samir, 2008).
Q15. What is the main limitation to the application of cellulose fibers?
Another limitation to the application of cellulose fibrils, also related to its hydrophilic surface, is their high water absorption capacity, which is undesirable in many potential applications (Hubbe et al., 2008).
Q16. what is the widely known theory to explain the improved barrier properties of polymer–clay?
The most widely known theories to explain the improved barrier properties of polymer–clay nanocomposites are based on a theory developed by Nielsen (1967), which focuses on a tortuous path around the clay plates, forcing the gas permeant to travel a longer path to diffuse through the film.
Q17. What is the effect of cellulose nanofibrils on polyurethane?
Wu et al. (2007) observed that, while the elongation of polyurethane was improved by cellulose nanofibrils, it was decreased by a conventional microscale cellulose filler.
Q18. What is the effect of adding chitin whiskers on the tensile properties?
Lu et al. (2004) added chitin whiskers to soy protein isolate (SPI) thermoplastics, and reported that the whiskers greatly improved not only the tensile properties (tensile strength and elastic modulus) of the matrix, but also its water resistance.
Q19. What is the role of nisin in the development of antimicrobial films?
Zhang, Zhao, and Rudra (2006) suggested that antimicrobial peptides, such as nisin, could be integrated with LbL structures to develop antimicrobial films.
Q20. How does the model predict permeability of polymer–clay composites?
Nielsen’s model predicts permeability of systems at clay loading rates of less than 1%, but experimental data deviates significantly from predicted values at higher loading rates and more extensively in certain polymers.
Q21. What is the reason why the biopolymer industry is concerned with sustainability?
since industries are concerned with sustainable development, the production cost of biopolymers has decreased,allowing biopolymer-based materials to be increasingly developed.
Q22. What can be done to improve the miscibility of cellulose nanoreinforcements?
A variety of surface modifications on cellulose nanoreinforcements can greatly improve their miscibility within hydrophobic matrices.
Q23. What is the effect of cellulose nanoreinforcements on the tensile properties?
Cellulose nanoreinforcements have been reported to have a great effect in improving modulus of polymer matrices (Bhatnagar & Sain, 2005; Helbert et al., 1996; Wu et al., 2007).
Q24. What are the main problems of biopolymers?
The use of biopolymers by the food industry has faced feasibility problems related mainly to their relatively high cost and poor overall performance when compared to those of synthetic polymers.
Q25. What is the role of nanoparticles in the development of biopolymers?
nanoparticles have an important role to improve feasibility of use of biopolymers for several application, including food packaging.