blends [ 13 ]. The graftcopolymers of xanthan gum with acrylamide [ 14 ] are used as turbulent drag reducers in sprinkler irrigation and as a flocculants in wastewater treatment, ore treatment and as coatings for slow release urea fertilizers. Methyl
Authors:F. Carrillo, B. Defays, X. Colom, J. Suñol, and M. López-Mesas
In the present work Lyocell fibers were subjected to graft copolymerization of poly-N-isopropylacrylamide (pNIPAAm) thermosensitive
polymer. The thermal degradation and stability of lyocell/pNIPAAm copolymers gels were characterized by differential scanning
calorimetry (DSC) and thermogravimetric analysis (TG). pNIPAAm/lyocell copolymers are thermally stable and more resistant
to temperature than lyocell fibres. Thermal characterization was analyzed as a function of percentage by mass of the pNIPAAm
grafted. It has been shown that for pNIPAAm/lyocell copolymers, degradation occurs at higher temperature when increasing the
degree of grafting.
Authors:C. Vasile, L. Odochian, M. Sabliovschi, and C. Vidacov
The thermal (under high vacuum, 10−5 mm Hg) and thermoxidative decompositions of ternary grafted copolymers of ABS type were studied, the dependence of the characteristic thermal data on the overall composition being followed over narrow ranges of variation of comonomer content.
The thermal stability of gelatine-polyacrylonitrile graft copolymers fibres obtained under various conditions of deformation
has been studied. The thermal properties of examined fibres depend on the synthetic component of the fibre forming material
– polyacrylonitrile which appears in the form of grafted PAN chains and PAN homopolymer. It was stated that the highest thermal
stability have those fibres which formation process included two stages of drawing with the use of deformation close to the
maximal values, with the value of the total draw ratio amounting to 691%. It should be supposed that with such a drawing process,
already in its first stage, are created advantageous conditions for the formation of paracrystalline regions to a larger extent
and their orientation along the fibre axis.
of the grafted poly(methyl methacrylate) (PMMA) side chains was in the range of 430 000 (for a dose of 10 kGy) and practically independent of grafting degree. However, the number of branches per graft copolymer molecule increases from 0.3 to 0.8 when the degree of grafting increases from 32% to 88%. Similarly, the radiation yield, i.e. the number of branches formed per 100 eV of energy absorbed in the substrate polymer increases from 0.75 to 1.94. The value and meaning of molecular weight of graft copolymer is discussed along with the mechanism of polymer chain termination.
Authors:A. P. Polikarpov, L. P. Krul, I. F. Osipenko, and N. R. Prokopchuk
The processes of thermal and thermal-oxidative degradation taking place in polyethylene (PE) films modified by graft polyacrylic acid (PAA) have been studied by TG and DTA. The mutual influence of the components on the degradation of the macromolecules present in the graft copolymer has been revealed. The increase in thermal stability of PE in the graft copolymers is explained by the decrease in the molecular mobility in PE amorphous regions containing microphase particles of graft PAA.
Positron lifetime spectra were measured as a function of the time for metallocene polyethylene (mPE), poly(methyl methacrylate) (PMMA), polyamide (PA), and polycarbonate (PC). A decrease in o-Ps intensity with the elapsed time was observed in mPE and PC measured at room temperature and in PMMA measured at 225 K. Formation of free radicals has been supposed to be one of the causes of this effect. The effect of maleic-anhydride (maH) grafted copolymers and its ionomers in mPE/PA blends was also studied. The change in the positron lifetime distribution with increasing maH and the ionomer content revealed an enhanced interaction between mPE and PA phase and the decrease of dispersed mPE particles, which reflected good compatibility of the blend.
Both poly[2-(dimethylamino) ethyl methacrylate] (PDMAEMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) were
radiation grafted onto polypropylene films (PP) using gamma radiation from a 60Co source. PP was pre-irradiated by gamma ray for modification following by grafted PDMAEMA and PEGMEMA by a one step method.
Grafting was studied as a function of the pre-irradiation dose between 20 and 180 kGy, dose rate of 10.4 kGy/h, and monomer
concentration 50% of PDMAEMA/PEGMEMA (1/1) in different solvents (toluene, acetone, and methanol). FTIR-ATR, TGA, and DSC
were carried out in the characterization of the graft copolymer obtained. Stimuli-responsive behavior and critical pH point
were studied by swelling in water. pH and thermo-responsive films of PE-g-(DMAEMA/PEGMEMA) presented a lower critical solution
temperature (LCST) of 50 °C and critical pH point around 8.7.
Graft copolymers of 2-(dimethylamino)ethylmethacrylate (DMAEMA) and acrylic acid (AAc) onto polypropylene films were investigated
for obtaining a pH- and thermo-sensitive material. DMAEMA and AAc were grafted by direct irradiation and pre-irradiation methods,
respectively, using a 60Co γ-source. Due to the acidic and basic nature of the monomers, this novel copolymer corresponds to the class of polyzwitterions.
Their behavior was studied in presence of different buffer solutions from pH 2 to 12 for different grafting percentages (from
9 to 362%) of AAc and keeping the DMAEMA grafting percentage constant. These modified films showed the same critical pH point
at 7.6 in a range of temperatures from 23 to 37 °C. The swelling percentage showed a dependence on AAc content and pH. The
lower critical solution temperature was observed at 36 °C when AAc content was less than 30% of grafting. The grafted films
were characterized by swelling behavior, FTIR-ATR and UV–Vis spectrometry for study of loading and release of vancomycin as
a model drug at room temperature.