Interactions between different components in α-starch based composite binder for green sand mould/core were investigated by using XRD, IR spectra, 1H NMR spectra and SEM. Several adhesive hardening structures and the...Interactions between different components in α-starch based composite binder for green sand mould/core were investigated by using XRD, IR spectra, 1H NMR spectra and SEM. Several adhesive hardening structures and theories of the binder at room temperature were proposed according to the interactions between various compositions. Thus, the reasons for the binder to have excellent combination properties and unique adhesive bonding and self-curing characteristics were explained by these theories successfully. And the theories are of great directive importance to design and development of composite binder for green sand mould/core.展开更多
Hygroscopicity-resistance of an α-starch based composite binder for dry sand molds (cores) has been studiedexperimentally and theoretically. Focus is placed on the relationship between the hardening structure andhumi...Hygroscopicity-resistance of an α-starch based composite binder for dry sand molds (cores) has been studiedexperimentally and theoretically. Focus is placed on the relationship between the hardening structure andhumidity-resistance of the composite binder. The results show that the α-starch composite binder has goodhumidity-resistance due to its special complex structure. SEM observations illustrate that the composite binder consists ofreticular matrix and a ball- or lump-shaped reinforcement phase, and the specific property of the binding membrane withheterogeneous structure is affected by humidity to a small extent. Based on the analyses on the interplays of differentingredients in the binder at hardening, the structure model and hygroscopicity-resistant mechanisms of the hardeningcomposite binder were further proposed. Moreover, the reasons for good humidity-resistance of the composite binderbonded sand are well explained by the humidity-resistant mechanisms.展开更多
Objective: To investigate the effects of acetylation and pregelatinization of cassava and sweet potato starches on the mechanical and release properties of directly compressed paracetamol tablet formulations in compar...Objective: To investigate the effects of acetylation and pregelatinization of cassava and sweet potato starches on the mechanical and release properties of directly compressed paracetamol tablet formulations in comparison with official corn starch.Methods: The native starches were modified by acetylation and pregelatinization. The tablets were assessed using friability(Fr), crushing strength(Cs), disintegration time(Dt) and dissolution parameters. Results: Starch acetylation produced paracetamol tablets that were stronger and had the best balance of mechanical and disintegration properties, while pregelatinization produced tablets that were more friable but had a better overall strength in relation to disintegration than formulations made from natural starches. Correlations mainly existed between Dt and the dissolution parameters t80, t2 and k1 in the formulations. Conclusions: Modification of the experimental starches improved the mechanical and release properties of directly compressed paracetamol tablet formulations. Thus, they can be developed for use as pharmaceutical excipients in specific formulations.展开更多
Objective:The quantitative effects of formulation and processing variables affecting the binding properties of Chinese yam starch（Dioscorea oppositifolia） in chloroquine phosphate tablet formulations have been inves...Objective:The quantitative effects of formulation and processing variables affecting the binding properties of Chinese yam starch（Dioscorea oppositifolia） in chloroquine phosphate tablet formulations have been investigated in comparison with corn starch using a 23 factorial experimental design.Methods:Chinese yam starch,representing the "low" level,and corn starch,representing the "high" level were used as binders at concentrations of 2.5%w/w and 10%w/w in chloroquine phosphate tablet formulations.The mechanical properties of the tablets,measured by the tensile strength（T） and brittle fracture index（BFI） as well as the release properties measured by the disintegration time（DT） and dissolution time(t<sub>80</sub>- time for 80%drug release),were used as assessment parameters.Results:The ranking of the individual coefficient values for the formulations on T was D 】 N 】】C,on BFI was N 】 D 】】C,on DT was D 】 N 】 C and on t<sub>80</sub> was C 】 N 】 D while the ranking of the interaction coefficient on T was N-D 】 C-D 】】 N-C,on BFI was N-D 】 N-C = C-D,on DT and t<sub>80</sub> was N-C 】 N-D 】 C-D.Changing the binding agent from Chinese to corn starch,led to a decrease in T,DT and t<sub>80</sub> but increase in BFI of the tablets.There were significant（P 【 0.001 ） interactions between the nature of binder,N and the other two variables,C and D.Conclusion:The result showed that Chinese yam possessed stronger binding capacity than corn starch and could be useful as an alternative binder when tablets with high mechanical strength with minimal problems of lamination,and slow release are required.展开更多
基金This work was supported by the China Postdoctoral Science Foundation(China Fund[1998]6)that was entitled“Synthesis of Modified Starch Binder and Its Application in Foundry”.Authors would like to thank academician Jinzong YANG and lecturer Hua ZHANG for the kind analyses and discussions.
文摘Interactions between different components in α-starch based composite binder for green sand mould/core were investigated by using XRD, IR spectra, 1H NMR spectra and SEM. Several adhesive hardening structures and theories of the binder at room temperature were proposed according to the interactions between various compositions. Thus, the reasons for the binder to have excellent combination properties and unique adhesive bonding and self-curing characteristics were explained by these theories successfully. And the theories are of great directive importance to design and development of composite binder for green sand mould/core.
文摘Hygroscopicity-resistance of an α-starch based composite binder for dry sand molds (cores) has been studiedexperimentally and theoretically. Focus is placed on the relationship between the hardening structure andhumidity-resistance of the composite binder. The results show that the α-starch composite binder has goodhumidity-resistance due to its special complex structure. SEM observations illustrate that the composite binder consists ofreticular matrix and a ball- or lump-shaped reinforcement phase, and the specific property of the binding membrane withheterogeneous structure is affected by humidity to a small extent. Based on the analyses on the interplays of differentingredients in the binder at hardening, the structure model and hygroscopicity-resistant mechanisms of the hardeningcomposite binder were further proposed. Moreover, the reasons for good humidity-resistance of the composite binderbonded sand are well explained by the humidity-resistant mechanisms.
文摘Objective: To investigate the effects of acetylation and pregelatinization of cassava and sweet potato starches on the mechanical and release properties of directly compressed paracetamol tablet formulations in comparison with official corn starch.Methods: The native starches were modified by acetylation and pregelatinization. The tablets were assessed using friability(Fr), crushing strength(Cs), disintegration time(Dt) and dissolution parameters. Results: Starch acetylation produced paracetamol tablets that were stronger and had the best balance of mechanical and disintegration properties, while pregelatinization produced tablets that were more friable but had a better overall strength in relation to disintegration than formulations made from natural starches. Correlations mainly existed between Dt and the dissolution parameters t80, t2 and k1 in the formulations. Conclusions: Modification of the experimental starches improved the mechanical and release properties of directly compressed paracetamol tablet formulations. Thus, they can be developed for use as pharmaceutical excipients in specific formulations.
文摘Objective:The quantitative effects of formulation and processing variables affecting the binding properties of Chinese yam starch（Dioscorea oppositifolia） in chloroquine phosphate tablet formulations have been investigated in comparison with corn starch using a 23 factorial experimental design.Methods:Chinese yam starch,representing the "low" level,and corn starch,representing the "high" level were used as binders at concentrations of 2.5%w/w and 10%w/w in chloroquine phosphate tablet formulations.The mechanical properties of the tablets,measured by the tensile strength（T） and brittle fracture index（BFI） as well as the release properties measured by the disintegration time（DT） and dissolution time(t<sub>80</sub>- time for 80%drug release),were used as assessment parameters.Results:The ranking of the individual coefficient values for the formulations on T was D 】 N 】】C,on BFI was N 】 D 】】C,on DT was D 】 N 】 C and on t<sub>80</sub> was C 】 N 】 D while the ranking of the interaction coefficient on T was N-D 】 C-D 】】 N-C,on BFI was N-D 】 N-C = C-D,on DT and t<sub>80</sub> was N-C 】 N-D 】 C-D.Changing the binding agent from Chinese to corn starch,led to a decrease in T,DT and t<sub>80</sub> but increase in BFI of the tablets.There were significant（P 【 0.001 ） interactions between the nature of binder,N and the other two variables,C and D.Conclusion:The result showed that Chinese yam possessed stronger binding capacity than corn starch and could be useful as an alternative binder when tablets with high mechanical strength with minimal problems of lamination,and slow release are required.
