Poly microfibrils

If the melt viscosities of polypropylene and poly(ethylene terephthalate) polymers are reasonably matched under extrusion conditions, a finely dispersed blend may be produced in fiber form. Orientation of such fibers yields strong filaments in which microfibrils of the two partially crystallized polymers are intertwined and unable to separate. Similar fibers with a sheath of one polymer surrounding a core of the other have no mechanical integrity [27]. 

Poly(l,4-benzamide) or terephthalamide dispersed in PA rigid microfibrils enhanced modulus and improved the thermal behavior Takayanagi la/., 1980... 

H. Lbnnberg, L. Fogelstrbm, M. A. S. Azizi Samir, L. Berglund, E. Malmstrom, and A. Hult, Surface grafting of microfibrillated cellulose with poly( -caprolac-tone). Synthesis and characterization, Eur. Polym. J., 44 (2008) 2991-2997. 

Dong XM, Revol J-F, Gray DG (1998) Effect of microcrystallite preparation conditions on the formation of colloid crystals of cellulose. Cellulose 5 19-32 Dubief D, Samain E, Dufresne A (1999) Polysaccharide microcrystals reinforced amorphous poly (beta-hydroxyoctanoate) nanocomposite materials. Macromolecules 32 5765-5771 Dufresne A (2000) Dynamic mechanical analysis of the interphase in bacterial polyester/cellulose whiskers natural composites. Compos Interfaces 7 53-67 Dufresne A (2006) Comparing the mechanical properties of high performance polymer nanocomposites from biological sources. J Nanosci Nanotechnol 6 322-330 Dufresne A, Vignon MR (1998) Improvement of starch film performances using cellulose microfibrils. Macromolecules 31 2693-2696... 

Loimberg H, Fogelstrom L, Malstrom E et al (2008) Microfibrillated cellulose films grafted with poly(e-caprolactone) - for biocomposite applications. Nordic Polymer Days, Stockholm, 11-13 June... 

Conventional fibers for advanced composites, such as carbon fiber and Kevlar fiber, are aggregates of fibrils and microfibrils, and therefore they contain many inherent defects that can initiate cracks and lead to premature failure of the composite. The idea of "molecular (level) composites" is based on the fact that an individual rigid-rod molecule, such as a poly(p-phenylene terephthalamide) (PPTA) molecule, has no defect therefore, the theoretical strength due to covalent bonds in the... 

On the next micrograph (Figure 11.2(b)), representing again a cryofracture but taken from the sample after the blend has been subjected to a cold drawing (fibrillation step, Figure 11.1) excellent microfibrils of the reinforcement (poly(ethylene terephthalate) (PET) in the present case) are observed. Their diameters are around 1 pm. 

Leung K L, Easteal A and Bhattacharyya D (2008) In situ formation of poly(ethylene naphthalate) microfibrils in polyethylene and polypropylene during extrusion. Compos Part A 39 662-676. Shields R J, Bhattacharyya D and Fakirov S (2008) Fibrillar polymer-polymer composites morphology, properties and applications, J Mater Sci 43 6758-6770. 

Li Z M, Yang M B, Huang R, Yang W and Feng J M (2002) Poly(ethylene terephthalate)/poly-ethylene composite based on in situ microfibril formation, Polym Plast Technol Eng 41 10-32. 

Quan H, Li Z M and Zhong G J (2007) The role of poly(phenylene sulfide) microfibrils in isothermal crystallization of isotactic polypropylene under shear, J Macromol Sci Part B Phys 46 285-294. 

Jiang C H, Xu X B and Li Z M (2008) Application of in situ microfibrillization to recycling ultraviolet-aged poly(ethylene terephthalate) (PET) and high density polyethylene (HDPE), J Macromol Sci Part B Phys 47 10-25. 

Xu X B, Li Z M, Yang M B, Jiang S and Huang R (2005) The role of the surface microstructure of the microfibrils in an electrically conductive microfibrillar carbon black/poly(ethylene terephthal-ate)/polyethylene composite, Carbon 43 1479-1487. 

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