Mechanical Properties Of Graft Copolymers Research Articles

Strengthening mechanism of the mechanical properties of graft copolymers with incompatible pendant groups: nano-clusters and weak cross-linking.

It is known that the adhesive property and mechanical strength of an apolar polymer can be improved by grafting with polar side chains, whereas the underlying mechanism is still elusive. In this work, the equilibrium structure and mechanical moduli of the melt of graft copolymers have been explored by dissipative particle dynamics. Due to the strong immiscibility of the non-polar backbone and polar side chains, nano-clusters of side chains formed and acted as physical crosslinkers. Moreover, non-affinity adsorption of polar side chains in the melt to the wall was observed, revealing an improvement in the adhesion property. Subjecting graft copolymers to cyclic deformation, the storage and loss moduli were acquired, and they grew with increasing grafting density. The melt strength in terms of the crossover frequency ascended with more side chains on the backbone. Our findings reveal that the strengthening of the mechanical properties of graft copolymers can be attributed to the formation of weakly cross-linked structures, thus offering an insight into the molecular design to aid the development of stronger graft copolymers.

Fully biobased thermoplastic elastomers: Synthesis of highly branched linear comb poly(β-myrcene)-graft-poly(l-lactide) copolymers with tunable mechanical properties

Biobased thermoplastic elastomers are of interest for their merits, especially renewability and sustainability. In this work, a series of fully biobased linear comb poly(β-myrcene)-graft-poly(l-lactide) (PM-g-PLLA) copolymers consisting of interior rubbery block and exterior semicrystalline block were synthesized via ring-opening polymerization of l-lactide using hydroxylated poly(β-myrcene) as macroinitiator. To evaluate the effects of branch length and graft density of poly(β-myrcene) on the performances of these obtained copolymers, the chemical compositions and molecular weights, crystal structures and spherulite morphologies, phase morphologies, thermal and mechanical properties were systematically analyzed by various techniques. Analysis of NMR and GPC indicated that graft copolymers were successfully obtained as designed. Two distinct glass transitions corresponding to the two building blocks observed from both DMA and DSC measurements suggested the occurrence of microphase separation, which was further confirmed by SAXS and AFM morphological characterizations. Results of DSC, WAXD, and POM showed that the crystallization behavior of the graft copolymers depends on graft density and branch length. Tensile test suggested that the mechanical properties of graft copolymers depend on PM/PLLA composition, particularly graft density and branch length, which could be readily tailorable to different applications.

Optimization grafting conditions and characterization of methyl cellulose grafted polyacrylonitrile copolymer

Methyl cellulose-graft-polyacrylonitrile (MC-g-PAN) copolymer was synthesized by free-radical polymerization using cerium ammonium nitrate (CAN) as an initiator in an aqueous medium. The characteristics were found to depend primarily on the polyacrylonitrile content rather than the graft density or the polyacrylonitrile chain length according to reaction parameters, such as CAN concentration, acrylonitrile concentration, reaction temperature, and reaction time. The successful grafting was confirmed using various analytical tools including FTIR, 1H NMR, XPS, XRD, and TGA. The percentage of graft copolymerization increased with increasing monomer and CAN concentration. The mechanical properties of graft copolymers were measured and investigated as a function of the ratio of grafting.

Synthesis and characterization of hydroxypropyl methylcellulose and ethyl acrylate graft copolymers

The synthesis of hydroxypropyl methylcellulose- g-poly (ethyl acrylate) was carried out by potassium persulfate induced graft copolymerization in homogeneous aqueous medium. By varying the reaction conditions, graft copolymers with different percentage of grafting were prepared. These graft copolymers were characterized by fourier transform infrared spectra (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analyses (TGA), X-ray diffraction analysis (XRD), and dynamic light scattering (DLS) methods. The molecular weight of grafted and ungrafted polymer chains determined by gel permeation chromatography (GPC) increased with increasing monomer and matrix concentration but decreased with increasing initiator concentration and reaction temperature. The mechanical properties of graft copolymers were measured as function of the percentage of grafting. In addition, the equilibrium humidity adsorption behavior and the disintegration time of the grafted copolymer films were also studied.

Poly(ɛ-caprolactone)-grafted acetylated anhydroglucose oligomer by ring-opening polymerization—Synthesis and characterization

A novel acetylated anhydroglucose oligomer (AGU-oligomer), prepared by acid catalyzed transglycosidation of potato starch triacetate and ethylene glycol, was used as a multifunctional coinitiator for the ring-opening polymerization of ε-caprolactone (ε-CL). The polymers were synthesized using different weight ratios of the starting materials and were characterized by NMR, SEC, and MALLS. The results confirmed the expected P(AGU/CL) polymer structure, namely a ‘comb-like’ graft-copolymer having the AGU oligomer as backbone with PCL grafts of variable chain lengths (LCL = 4–21). Thermal and mechanical properties of graft-copolymers with different ε-CL block lengths were examined. By changing the graft length, crystallinity was controlled and amorphous polymers were obtained with AGU-oligomer contents higher than 50 wt %. The tensile properties varied with the composition and a copolymer having 40 wt % of AGU-oligomer behaved like soft elastomer, showing high elongation at break. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1633–1641, 2006

Mechanical properties of graft copolymers of polyethylene and acrylonitrile obtained by the inhibited graft polymerization method

Etude comparative des copolymeres greffes avec ou sans addition d'inhibiteur de degradation thermooxydante

Investigation of the mechanical properties of graft copolymers of gelatin with synthetic polymers and their mixtures

A study was made of the mechanical properties of graft copolymers of gelatin with polyacrylonitrile (PAN) and with polybutylacrylate (PBAC), and these were compared with those of pure gelatin. The experimental results show that the elasticity of the system is increased by grafting of the flexible chain PBAC, while the grafting of PAN leads to increased rigidity. For graft copolymers of gelatin with PBAC it was found that shrinkage in the course of heating to 120° is greatly reduced, and this reduction is attributed to the formation of a microheterogeneous structure, the disperse phase of the latter including gelatin and PBAC in its composition. Model mechanical mixtures consisting of these components with approximately the same degree of dispersion of PBAC show shrinkage behaviour during heating to 120° resembling that of pure gelatin.

Mechanical Properties of Reduced Wool and Methyl Methacrylate Graft Copolymers

Graft copolymeriration of methyl methacrylate was performed onto wool reduced by various chemicals using ferrous ammonium sulfate and hydrogen peroxide redox system at 45°C temperature. Reduced wools show higher percentage of polymer deposition as compared to natural because the thiol groups act as graft centers. Mechanical properties of MMA-reduced wool graft copolymers were studied. Results indicate that, with approximately 50% graft copolymeriza tion, the decrease in elongation is considerably high and the tensile strength is decreased slightly. In case of modulus, an initial increase with polymer deposition followed by a decrease. Density and moisture regain were also determined and the results were discussed in relation to mechanical properties of graft copolymers.

Graft polymerization of some vinyl monomers on to acrylic rubber: II. Mechanical properties of graft copolymers : Ide, F., Sasaki, I. and Deguchi, S. Journal of Applied Polymer Science, Vol 15, No 8, p 1809 (August 1971)

Graft polymerization of some vinyl monomers on to acrylic rubber: II. Mechanical properties of graft copolymers : Ide, F., Sasaki, I. and Deguchi, S. Journal of Applied Polymer Science, Vol 15, No 8, p 1809 (August 1971)

Mechanical Properties of Graft Copolymers of Methyl Methacrylate and Modified Wool

Graft copolymerization of methyl methacrylate was performed onto wool chemically modified with caustic soda, formic acid, thioglycollic acid, and sodium bisulfite using ferrous ion-hydrogen peroxide redox system at 45°C. The percent graft-on was found to be higher in modified fibers. The graft-on increases with reaction time up to about 10 hr. Some mechanical properties of such graft copolymers were studied. With polymer formation, the strength decreases a little, probably due to the initiator free radicals; the breaking elongation falls considerably, particularly in reduced fibers. The Young's static modulus decreases after acid and alkali treatment and increases after reduction. The modulus is found to decrease slightly with graft-on in normal, alkali-treated and formic acid-treated wool. However, in case of reduced wool, an initial increase of modulus with polymer uptake is followed by a decrease.

Dynamic mechanical properties of graft copolymers of nylon

Dynamic mechanical properties of graft copolymers of nylon