Radiation-induced grafting of N,N-dimethylacrylamide onto polytetrafluoroethylene

Grafting of N,N-dimethylacrylamide (DMAA) onto polytetrafluoroethylene (PTFE) has been carried out by using gamma rays from a ⁶⁰Co source. Degree of grafting was affected by grafting conditions. Especially, solvent for the grafting was found to be a very significant parameter to obtain a higher grafting yield. When ethylacetate or acetone was used as the solvent, grafting yield greater than 5% was obtainable while the graftcopolymerization scarcely occurred in the presence of other kinds of solvent such as ethanol or water. Apparent activation energy of the grafting in ethylacetate was calculated to be 7.90 Kcal/mol, and initial grafting rate of it was proportional to 0.55 power of dose rate.     

Modification of natural rubber tubes for biomaterials. II. Radiation-induced grafting of N,N-dimethylaminoethylacrylate (DMAEA) onto natural rubber (NR) tubes

Radiation-induced simultaneous grafting of N,N-dimethylaminoethylacrylate (DMAEA) onto NR tubes has been studied to improve blood compatibility of NR tubes. In the grafting of DMAEA onto NR tubes, effect of grafting parameters such as solvent, monomer concentration, temperature, dose, and dose rate on the grafting yield was investigated. As the results, it was found that the grafting proceeds effectively in the presence of carbontetrachloride (CCI₄) as a solvent. The initial rate of grafting was found to be proportional to 0.70 power of dose rate and to 0.95 power of monomer concentration. The activation energy for this grafting system was calculated to be 6.78 kcal/mol. The evaluation of blood compatibility of NR-g-DMAEA was carried out by ex vivo test. Blood compatibility of those samples was found to be dependent on only grafting yield. When the degree of grafting is higher than 30 wt %, blood compatibility of NR tube could be improved by DMAEA grafting. This is the same tendency which that of previous grafting system of NR-g-DMAA.     

Electron-induced crosslinking of polypropylene with the addition of hydrogen-donating hydrocarbons

Electron-induced crosslinking of polypropylene with the addition of hydrogen-donating hydrocarbons produced from petroleum (HHAP) together with A-TMPT (trimethylpropanetriacrylate) was studied, and the following results were obtained: (1) Effective cross-linking was achieved at lower doses under 10 kGy. (2) HHAP functions as an effective radical scavenger to suppress scissions. (3) Distinguished improvements in properties such as elongation and heat distortion temperature were achieved by the irradiation. (4) Distinct diminution in melt flow rate and evident increase in average molecular weight with the irradiation at lower doses were observed. (5) It was confirmed that the oxidative degradation during mixing and molding was noticeably inhibited by the addition of HHAP. This effect as an antioxidant during these procedures along with the irradiation seems to be a cause to promote cross-links. These effects are attributable to the high radical scavenging effects of HHAP and its pure hydrocarbon constitution without functional groups containing heteroatoms. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 311–319, 1997.     

Modification of natural rubber tubes for biomaterials I. Radiation-induced grafting of N,N-dimethyl acrylamide onto natural rubber tubes

Radiation-induced simultaneous grafting of N,N-dimethyl-acrylamide (DMAA) onto natural rubber (NR) tubes has been studied to improve blood compatibility of the NR tubes. Concerning grafting of DMAA onto NR tubes, it was found that the grafting proceeds effectively in the presence of carbon tetrachloride (CCl₄) as a solvent. The degree of grafting was found to be saturated at about 26 wt%, but a higher degree of grafting can be obtained by either “so called two-step grafting” or “putting a standing time for a while before irradiation.” The initial grafting rate was proportional to 0.85 power of dose rate. The apparent activation energy of the graft-copolymerization was 7.42 kcal/mol. Evaluation of blood compatibility of DMAA-grafted NR tubes has been carried out by ex vivo test. According to the results, significant improvement of blood compatibility was obtained for the samples in which degree of grafting is higher than 30 wt%.