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Previously, we used ozone to initiate molecular breakdown and oxidization of PP macromolecules with highly efficiency during extrusion process. Excessive ozone flowed into ozone destructor and decomposed. Neither byproducts nor residual peroxide was left in PP matrix. Conditions of this synthesis process such as polymer flow rate, reaction temperature and TMPTA concentration is discussed. Prior to pursuing FT-IR analysis, about 1 g sample of PP extrudates was dissolved into refluxing xylene ml and then precipitated into a large excess of acetone.
In this way, the cleaned polymers were rid of unreacted and homopolymerized TMPTA which are soluble in acetone. The purified samples were hot-pressed into films which are ready to analyze with the FT-IR spectrometer. Molecular data was measured by high-temperature size-exclusive chromatography SEC coupled with a multiangle laser light scattering MALLS detector, a differential refractive index RI detector and a capillary viscometer detector CV. The eluent solvent was TCB 1,2,4-trichlorobenzene stabilized with 0.
The influence of the industrial processing on the degradation of poly(hidroxybutyrate) - PHB
The solvent was injected to the system and the elution flow rate was fixed at 1. The frequency range was 0.
The sample sheets were cut into pieces with a width of 10 mm and a length of 17 mm for the measurements. The elongational rate was 0. Before each measurement, a pre-stretch for 9 s was performed to ensure that no slipping occurred between the sample and the fixture. The amount of the insoluble portion macrogel in the samples was determined by Soxhlet extraction in refluxing xylene for 24 hours. TMPTA copolymers were removed via acetone.
Synthesis and Degradation Rheology and Extrusion
Under the experimental conditions used, the modified PPs are gel-free. The parameters of average molar mass and molar mass distributions are given in Table 1. This fact leads to the conclusion that the chain scission process is predominant for this ozone induced reaction. These results indicated a change from degradation reaction to the competitive branching reaction. Based on the fact that branched polymer chains in solution are denser and have lower root-mean-square radius of gyration than linear chains of the same molecular weight, these plots could provide information about LCB distributions.
The slope of 0. The two plots of original PP and PP-T0 were very close to the line and deviated a little in high molecular weight region due to experimental error. In high molecular weight region, the negative deviation of the slope from linear behavior in modified PP plots appeared. MFI is inversely related to viscosity and most of the MFI conditions are at much lower shear than those prevailing in commercial processing. Low molecular weight fractions and long chain branching fractions of PP can apparently influence the flow properties. The IR spectra of all samples were shown in Fig.
Linear viscoelastic measurement has been proved to be a reliable method for verification of existence of LCB on polymeric chains. The evaluated data from this fitting equation were listed in Table 1. For ozone-degraded PP sample, we could see that the complex viscosities decreased over the entire frequency range compared with the original PP. The transition zone from Newtonian-plateau to shear-thinning regime shifted to higher frequency, and Newtonian-zone was broader than original PP samples. At low frequency, the zero-shear viscosity of original PP is Pa s and it reached a lower value of Pa s for the ozone-degraded PP-T0 sample.
Furthermore, the transition from Newtonian-plateau to shear-thinning regime is shifted to lower frequency. A broader transition zone between the Newtonian behavior and the power-law region is observed for the branched polypropylenes, which is typical of long-chain branched polymers. Besides zero-shear viscosity, the storage modulus and the loss angle are even more sensitive to LCB.