Thermal stability of surface-esterified cellulose and its composite with polyolefinic matrix

Surface-esterified cellulose fiber in a polypropylene matrix: impact of esterification on crystallization kinetics and dispersion

“…In case of the iPP/C-PA, the t 1/2 are similar to those of neat iPP if the T c,iso is, again, below 130°C. In connection with previous study of the thermal stability of the esterified materials (Janicek et al 2013), one can presume, the material tends to degrade at the higher temperatures, which may influence the speed of crystallization. The vicinity of t 1/2 in case of neat iPP and iPP/C-PA at low temperatures could be explained after revealing the filler distribution and dispersion with the microscopy as described below.…”

“…On the other hand, the cellulose modified with OA showed similar water adsorption (hydrophility) as the PAmodified one (Janicek et al 2013). The slightly hydrophilic character of the C-OA may thus result in poor surface interaction with the matrix and inappropriate dispersion in comparison with the iPP/C-DA.…”

“…The fibers were high-purity cellulose (99.8 %) with a relative density of 0.6, 50-350 lm in length; their diameter was in the range of 12-15 lm and the crystallinity of 65 % (data provided by the supplier). To increase the hydrophobicity of the cellulose, the material was surfaceesterified with oleic acid (OA), decanoic acid (DA) and propionic acid (PA) as described elsewhere (Uschanov et al 2010;Janicek et al 2013). The used method then gave cellulose with a degree of substitution (DS, calculated from XPS data) of about 1.49 and 1.25 in case of DA and OA, respectively (Uschanov et al 2010).…”

“…A previous article (Janicek et al 2013) showed that the modification reduces the hydrophility among the tested materials particularly in the decanoyl ester. On the other hand, the cellulose modified with OA showed similar water adsorption (hydrophility) as the PAmodified one (Janicek et al 2013).…”

“…In some cases, the esterification may primarily influence the content of the b-phase polypropylene polymorph (Borysiak 2009); in others, the impact of surface modification is mainly negative, since the epitaxiality is usually disturbed, as shown, for example, by Borysiak (2012) with wood esterified with propionic or succinic anhydrides. The question then arises concerning whether the hydrophobization done with long carboxylic acids (Uschanov et al 2010;Janicek et al 2013) enables some nucleation activity or the epitaxial surface is modified to such an extent that no nucleation can occur. Uschanov et al (2010) also showed the different degrees of substitution achievable with various acids and noted the phenomenon connected with a lower degree of substitution when long or unsaturated acids are used.…”