Graft Copolymerization of Methyl Methacrylate and Vinyltriethoxysilane onto Natural Rubber

Preparation and characterization of natural rubber grafted with methyl methacrylate (MMA) and vinytriethoxysilane (VTES) were performed in the present work. Graft copolymerization of methyl methacryate was carried out in latex stage, and VTES was added during the graft copolymerization of MMA. FTIR and NMR spectroscopy were used to investigate the structure of graft copolymer and determination of conversion and grafting efficiency of MMA. It confirmed that the poly(methyl methacrylate) (PMMA) and silica particles (PVTES) were successfully formed in NR-graft-PMMA-PVTES graft copolymer. Conversions of MMA were about 90-100%; however, MMA grafting efficiency decreased as the MMA concentrations increased. Tensile property of NR-graft-PMMA-PVTES was found to improve compared with that of pure NR.

Incorporation of amine functional group on surface of hydroxyapatite prepared fromstriped catfish (Pagasianodon hypophthalmus) bone

This study was conducted to incorporate amine functional groups on the surface of hydroxyapatite to enhance its potential application in biomedical materials. Hydroxyapatite particles (HA) were synthesized from striped catfish (Pagasianodon hypophthalmus) bone and surface modified by grafting with (3-aminopropyl)triethoxysilane (APTES). Important factors affected grafting efficiency such as concentration of APTES, water content, reaction temperature and reaction time were studied. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) were used to confirm the grafting reaction on HA surfaces. Grafting efficiency was evaluated based on intensity of characteristic absorption peaks of APTES. The experimental results showed that amine functional groups were successfully introduced on HA surface at optimal condition of 0.2 M APTES, 0.75 wt.% water content, at 60°C and 12-hour reaction time.

Ammonium Persulphate Initiated Graft Copolymerization of Aniline onto Chitosan-A Comparative Kinetic Study

Ammonium persulphate (APS) has been used as efficient initiator for graft copolymerization of the aniline (ANI) onto chitosan at 25±0.1°C. Graft copolymerization of ANI onto chitosan has taken place through the cation radical initiation process. The grafting parameters have been evaluated by varying concentration of ANI, APS and chitosan. The effects of concentration of APS, ANI, chitosan and reaction time on graft copolymerization were studied by determining the grafting percentage (%G), grafting efficiency (%E) and percentage add-on. It was observed that bout rate of homopolymerization (Rh) and rate of graft coplymerization (Rg) increased with the increase in concentration of each component. On the basis of the experimental observations, initiating steps have been proposed and a suitable rate expression for graft copolymerization has been derived. Electrical conductivity of grafted polyaniline (PANI) onto chitosan (Chit-g-PANI, chitaline) was measured by the four probe method.

Synthesis of an Addition-Crosslinkable, Silicon-Modified Polyolefin via Reactive Extrusion Monitored by In-Line Raman Spectroscopy

We present the modification of ethylene-propylene rubber (EPM) with vinyltetra-methydisiloxane (VTMDS) via reactive extrusion to create a new silicone-based material with the potential for high-performance applications in the automotive, industrial and biomedical sectors. The radical-initiated modification is achieved with a peroxide catalyst starting the grafting reaction. The preparation process of the VTMDS-grafted EPM was systematically investigated using process analytical technology (in-line Raman spectroscopy) and the statistical design of experiments (DoE). By applying an orthogonal factorial array based on a face-centered central composite experimental design, the identification, quantification and mathematical modeling of the effects of the process factors on the grafting result were undertaken. Based on response surface models, process windows were defined that yield high grafting degrees and good grafting efficiency in terms of grafting agent utilization. To control the grafting process in terms of grafting degree and grafting efficiency, the chemical changes taking place during the modification procedure in the extruder were observed in real-time using a spectroscopic in-line Raman probe which was directly inserted into the extruder. Successful grafting of the EPM was validated in the final product by 1H-NMR and FTIR spectroscopy.

MASTIC-G-POLY (ACRYLAMIDE): MICROWAVE-ASSISTED SYNTHESIS AND CHARACTERISATION

Objective: The objective of the present investigation was the synthesis of grafted co-polymer gum mastic using acrylamide as the monomer. Methods: 3-factor 3-level response surface Box-Behnken design, which requires 15 runs including three replicates of the central run, was used for the synthesis of graft copolymers of mastic gum with acrylamide using ceric ammonium nitrate as the free radical initiator. The critical synthesis and process parameters; CSPP (A = concentration of monomer, B = concentration of initiator and C= Temperature) to generate design space and optimize formulation with an aim to obtain critical quality attributes (CQA, Y1 =% Yield, Y2 =% Grafting, Y3 =% grafting efficiency). Result: Formulation F14 having a maximum % yield of 75.89% with % grafting of 210% and % grafting efficiency 51.57% was selected as best. Conclusion: The microwave-assisted grafted mastic gum was prepared successfully and optimized by using Box Behnken design.

Optimizing the Process Efficiency of Reactive Extrusion in the Synthesis of Vinyltrimethoxysilane-Grafted Ethylene-Octene-Copolymer (EOC-g-VTMS) by Response Surface Methodology

Thermoplastic polymers like ethylene-octene copolymer (EOC) may be grafted with silanes via reactive extrusion to enable subsequent crosslinking for advanced biomaterials manufacture. However, this reactive extrusion process is difficult to control and it is still challenging to reproducibly arrive at well-defined products. Moreover, high grafting degrees require a considerable excess of grafting reagent. A large proportion of the silane passes through the process without reacting and needs to be removed at great expense by subsequent purification. This results in unnecessarily high consumption of chemicals and a rather resource-inefficient process. It is thus desired to be able to define desired grafting degrees with optimum grafting efficiency by means of suitable process control. In this study, the continuous grafting of vinyltrimethoxysilane (VTMS) on ethylene-octene copolymer (EOC) via reactive extrusion was investigated. Successful grafting was verified and quantified by 1H-NMR spectroscopy. The effects of five process parameters and their synergistic interactions on grafting degree and grafting efficiency were determined using a face-centered experimental design (FCD). Response surface methodology (RSM) was applied to derive a causal process model and define process windows yielding arbitrary grafting degrees between <2 and >5% at a minimum waste of grafting agent. It was found that the reactive extrusion process was strongly influenced by several second-order interaction effects making this process difficult to control. Grafting efficiencies between 75 and 80% can be realized as long as grafting degrees <2% are admitted.

Gum colocasia-g-polyacrylamide: Microwave-assisted synthesis and characterization

In the present investigation, an attempt has been made for grafting of acrylamide on the backbone of Colocasia esculenta by using microwave-assisted grafting method, which is a convenient and versatile route for the development of polysaccharide-based materials. The dried mucilage of colocasia was prepared from fresh rhizomes. The optimization was performed by using Box Behnken matrix design (BBD) and response surface methodology (RSM) using design expert software. A series of graft polymers, varying in the amount of acrylamide, ammonium persulphate and microwave irradiation was prepared. The effect of Microwave time, gum concentration and power on percentage yield, percentage grafting and percentage grafting efficiency has been optimized and evaluated by 3D surface response graphs. It has been observed that power and irradiation time has a significant synergistic effect on % yield, % grafting and % grafting efficiency however gum concentration produce slight increment up to a limit after that the effect becomes almost constant. The selected optimized formulation is F8 with a percentage yield of 99.57%, percentage grafting of 634.33% and percentage grafting efficiency of 87.49%. Optimized formulation was subjected to Fourier transform infrared spectroscopy, Differential scanning calorimetry, X-ray diffraction and Scanning electron microscopy for characterization which committed the grafting of acrylamide on Colocasia esculenta.