Synthesis And Application Of Carboxymethylcellulose-Methyl Methacrylate Graft Copolymers (CMC-g-PMMA)

The carboxymethylcellulose grafted methyl methacrylate copolymer(CMC-g-PMMA) was synthesized by potassium persulfate induced graft copolymerization in homogeneous aqueous medium as an effective additive for reinforcing rice hull fiber/cement compositesFourier transforms infrared spectra was used for studying the MMA functional group modifications and graft to carboxymethylcellulose for qualitatively observing the graft reaction taking place of carboxylmethylcellulose and methyl methacrylate after synthesis.FTIR of the CMC-g-PMMA confirmed the existence of a chemical link between the CMC and the PMMA. Various graft copolymers were synthesized by varying the reaction temperature,the pH value of the reaction solution,the dosage of monomer and initiator.The results indicated that the optimal reaction conditions for the synthesis of CMC-g-PMMA were reaction temperature 80℃and pH 9;the content of the initiator had little influence on the graft copolymer synthetic.Analyze the reaction mechanism of this synthesis reaction.The synthesis reaction divides into four steps:S₂O₈^2- decomposes into SO₄^-;SO₄^-free radical transfer to CMC-OH;CMC-O·initiate MMA polymerize;MMA polymerize into side chain.The SEM photos prove the reaction has taken place.The number of MMA unit in the dextrose unit was counted by the EDAX measure.Thermal analysis(TGA and DSC) were carried out in order to evaluate the effect of the chemical modification on the thermal stability of CMC.The Non-isothermal thermal decomposition kinetics of copolymers was studied.The experiment results indicate that:in the temperature range from 300℃to 450℃,the kinetics process was autocatalysis reaction.The activation energy E is 41.96kJ/mol,and ln A is17.31.The result of the X-ray diffraction spectra is an important evidence for the grafting reaction, which is according with the above mentioned reaction mechanism.Grafted copolymer chains enlarge the proportion of amorphous regions of CMC.Adding MMA has damage effect on the crystallization.The peaks of the X-ray diffraction patterns spectra of the samples are different obviously when varies of MMA were added.Furthermore,it is well known that heterogeneities in the bulk structure of the cellulose gave rise to accessible and inaccessible regions where reactions took place first in more accessible amorphous regions and then on the surface of elementary crystallites.The evidence from XRD results shows that grafted PMMA chains were formed after the graft copolymerization,which enlarges the proportion of amorphous regions and reduces the percentage of crystallization region.The product that fully maintained CMC crystal has no other crystal.It shows that MMA was all grafted on CMC in the reaction.No PMMA homopolymer proves that the reaction has a good response to this selectivity. The synthesis of carboxylic methylcellulose-g-poly Methyl Methacrylate was added to composites as surface treatment.The density,flexes property,surface topography,acoustics property and fire retardant property of composites was characterized.The sample adding carboxylic methylcellulose-g-poly Methyl Methacrylate(CMC-g-PMMA) had higher flex strength and flex modulus.When the composites contained 20%hull and 1%CMC-g-PMMA, the flex strength and flex modulus of the composites change to 2.27 times and 2.71 times compare with the sample contained 20%rice hull only.CMC-g-PMMA was effective agent for reinforces plant fiber-cement composites.The strength mechanism was that:the CMC-g-PMMA cladding rice hull,so reduce the carbohydrate transudation;CMC-g- PMMA improved the compatibility of the rice hull fiber and the cement;the CMC-g- PMMA formed the polymer film in the cement composites,so the characteristic of composites was improved.