PBT Polymer Blends

Over the last 25 years, many commercial products have been made by melt blending PBT with other resins. Blending is most commonly carried out by extmding the PBT resin with a second resin component. Other additives, fillers, or reinforcements may be added to the blends as well. 

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Figure 3.14 TEM image of PC-PBT polymer blends with mass-density contrast. The specimen is stained with Ru04. (Reproduced with permission of Jingshen Wu.)...

PBT polymer blends combine the properties of partially crystalline PBT with those of amorphous thermoplastics such as polycarbonate or ABS. The amorphous partner improves the impact strength and warpage behaviour, while the PBT ensures the chemical resistance of the blend. 

Also, PBT is blended with poly(ethylene terephthalate) (PET), polysulfone, and SMA (303). PET may also be blended with a number of other engineering polymers, such as PC and impact modifiers. 

In a molded polymer blend, the surface morphology results from variations in composition between the surface and the bulk. Static SIMS was used to semiquan-titatively provide information on the surface chemistry on a polycarbonate (PC)/polybutylene terephthalate (PBT) blend. Samples of pure PC, pure PBT, and PC/PBT blends of known composition were prepared and analyzed using static SIMS. Fn ment peaks characteristic of the PC and PBT materials were identified. By measuring the SIMS intensities of these characteristic peaks from the PC/PBT blends, a typical working curve between secondary ion intensity and polymer blend composition was determined. A static SIMS analysis of the extruded surface of a blended polymer was performed. The peak intensities could then be compared with the known samples in the working curve to provide information about the relative amounts of PC and PBT on the actual surface. 

Pellow-Jarman, M. and Hetem, M., The effect of the polybutylene terephthalate constituent on the reactions occurring in PBT-polycarbonate polymer blends below their decomposition temperature, Plast. Rubber Composites Proc. Appl., 23, 31-41 (1995). 

After having studied in our laboratory, polymer blends of amorphous polymers poly-c-caprolactone and poly (vinyl chloride) (1,2) (PCL/ PVC), blends with a crystalline component PCL/PVC (3,4), poly(2,6-dimethyl phenylene oxide) (PPO) with isotactic polystyrene (i-PS) (5) and atactic polystyrene (a-PS) with i-PS (6), we have now become involved in the study of a blend in which both polymers crystallize. The system chosen is the poly(1,4-butylene terephthalate)/poly(ethylene terephthalate) (PBT/PET) blend. The crystallization behavior of PBT has been studied extensively in our laboratory (7,8) this polymer has a... 

In summarizing the results from the last three sections, one can conclude that the systematic variation of microhardness under strain performed on (a) homo-PBT (Section 6.2.1), (b) its multiblock copolymer PEE (Section 6.2.2) and (c) on blends of both of these (this section) is characterized by the ability of these systems to undergo a strain-induced polymorphic transition. The ability to accurately follow the strain-induced polymorphic transition even in complex systems such as polymer blends allows one also to draw conclusions about such basic phenomena as cocrystallization. In the present study of a PBT/PEE blend two distinct well separated (with respect to the deformation range) strain-induced polymorphic transitions arising from the two species of PBT crystallites are observed. From this observation it is concluded that (i) homo-PBT and the PBT segments from the PEE copolymer crystallize separately, i.e. no cocrystallization takes place, and (ii) the two types of crystallites are not subjected to the external load simultaneously but in a sequential manner. 

A key paper involving the experimental interfacial aspects of polymer blends discussed the blends of more than two components wherein a polymeric constituent will concentrate at the interface between two of the blend constituents [Hobbs et al., 1988]. Employing the concepts of interfacial relationships, it was shown that a ternary component can concentrate at the interface between the other constituents and allow for compatibilization of dissimilar and incompatible components. As an example, it was shown that in the ternary blend of PMMA/PC/PBT, PC encapsulates PMMA as a dispersed phase in a matrix of PBT. PC, which exhibits partial miscibility with PMMA and PBT thus compatibil-izes PMMA/PBT blends. 

Most of the discussion has been centered around just the neat polymer or the polymer plus a modifier or additive. Coloring issues further escalate when polymer blends are used or when multiple additives are incorporated. Would it be difficult, and would the color gamut be somewhat restricted, if one was to color an impact modified, flame retardant, glass reinforced PBT/polycarbonate alloy The answer now better be a resounding YES ... 

Complex viscosity (t) ) of polypropylene (PP)/polyethylene (PE)-2 and PBT/PE-2. For PP/PE-2 (a), the effect of fibril concentration is compared. For PBT/PE-2 (b), the effect of morphology is compared. The dependence of concentration is also compared. (Reproduced from Hong, J. S., J. L. Kim, K. H. Ahn, and S. J. Lee. 2005b. Morphology development of PBT/PE blends during extrusion and its reflection on the rheological properties. Journal of Applied Polymer Science 97 1702-1709, with permission.)... 

Run M, Song A, Wang Y, Yao C (2007) Melting, crysttillization behaviors, and nonisothermal crystallization kinetics of PET/PTT/PBT ternary blends. J Appl Polym Sci 104 3459-3468 Salaneck WR (1997) Conjugated polymer surfaces and interfaces. Philos Trans R Soc Lond A... 

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