## 4 Morphological Aspects of _in Situ_ Polymerized Fiber Glass  
Figure 3 shows the scanning electron micrograph of GFs without any treatment and its corresponding EDX spectrum, which is used as standard. Peaks of Si, O, Al and Ca for the E-glass fiber chemical composition can be seen. Note that the peak of C is undetectable, so it is not possible to establish an initial C/Si ratio. A complete morphological study was performed on all reaction products  
Figure 2: Experimental methodology. Figure 5: SEM micrographs for sample F1% and its corresponding EDX spectrum. (**a**) 600\(\times\); (**b**) 6,000\(\times\); (**c**) and (**d**) 10,000\(\times\). Figure 6: SEM micrographs for sample F1.5% and its corresponding EDX spectrum. (**a**) 200\(\times\); (**b**) 600\(\times\); (**c**) 2,000\(\times\) and (**d**) 6,000\(\times\). For all _in-situ_ polymerizations, the EDX spectra show large C peaks and obviously O, Al, Si and Ca. The C peak corresponds to PP adhered to the glass surface. Note that in some cases, when the amount of C is very large (F1% in Figure 5) the typical peaks from the fiber (Si, Al, O) are relatively reduced, as expected. In low magnification, the micrographs show that the degree of coverage for different concentrations of hydroxy-\(\alpha\)-olefin used is different. In extreme conditions (F0.5% and F2%) the coverage is not homogeneous, presenting zones with larger polymer agglomerates. At high magnifications, it is evident that the polymer onto fibers presents different morphologies. These crystalline forms are typical of the crystallization during polymerization of polyolefins, particularly PP. [PERSON] shows similar results for PP, where the difference between the spherical macroscopic crystalline forms attached to the polymer is first generated and then crystallized, nucleated by a particle of the catalyst. The smaller rod-shaped particles are those where the crystallization occurs as the polymer is formed [42, 43]. Taking into account that the objective is the improvement of adhesion, a homogeneous polymer layer on the fibers is needed. F1% and F1.5% samples show the highest degree of coverage while F0.5% and F2% samples have agglomerated polymer. The greater the amount of hydroxy-\(\alpha\)-olefin, the greater the number of anchor points and the lower the PP chain length. [PERSON] _et al._[44, 45], report that an increase in the concentration of hydroxy-\(\alpha\)-olefin reduces the rate of consumption of propylene when other polymerization conditions are kept constant..  
From these results it appears that the length of the PP chains decreases when the concentration of hydroxy-\(\alpha\)-olefin increases. These observations also agree with the EDX results. Comparing the EDX spectra, it is clear that in all polymerizations the C peak appears, but its relative intensity is much greater for conditions F1% and F1.5% that for F0.5% and F2% samples. Thermal characterization of the polymer grafted onto fibers was performed by Differential Scanning Calorimetry (DSC) and Thermogravimetrictical analysis (TGA). Figure 8 shows the DSC thermograms of the PP grafted onto fibers with different percentages of hydroxy-\(\alpha\)-olefin and compared with untreated fibers. Low melting temperatures (110-122 \({}^{\circ}\)C) in PP copolymerized onto  
Figure 7: SEM micrographs for sample F2% and its corresponding EDX spectrum. (**a**) 200\(\times\), (**b**) 2,000\(\times\) and (**c**) 6,000\(\times\). fibers is typical of \(\gamma\)-PP metallocene polymerization. TGA gives the evidence that molecules grafted onto the fibers at the optimal condition are PP ones. The thermograms obtained allow the evaluation of the mass changes that occur at different temperatures, indicating the transformations taking place at all times. Figure 9 shows the weight loss as a function of temperature.