摘要:

AbstractDynamic mechanical methods were used to study the effect of absorbed moisture on the properties of an epoxy resin matrix CFRP. The glass transition temperature (Tg)of the matrix resin, determined as the onset of the characteristic fall in dynamic modulus with increasing temperature, was found to decrease with increasing moisture content. Maximum shifts inTgof 80 to 90°C, relative to the dry material, were observed for a resin moisture content of 5.2% by weight. The effects of sample geometry, fibre orientation, and frequency of oscillation, on the dynamic mechanical properties are discussed. Results are given of an analysis of the observed dependence ofTgon water content using two theoretical models

ISSN:0007-1641    

DOI:10.1002/pi.4980180112

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractSurface‐tension measurements were used to investigate the surface adsorption and micellisation of a polystyrene‐b‐polyisoprene block copolymer inn‐hexadecane which is a selectively bad solvent for polystyrene. Measurements were made over a range of concentrations (1.29–2.88)x10−4mol dm−3and temperatures 25–40°C. The block copolymer was found to be positively adsorbed at then‐hexadecane/air interface. The linearity of plots of γ against Incjust below the critical micelle concentration (c.m.c.) indicated an approximately constant surface concentration. The area per block copolymer molecule at the surface had an average value of 4.1 nm2. A plot of In (c.m.c.) againstT−1gave a value for the standard enthalpy of micellisation of ‐41.9.3.0 kJ per mole of copolymer chains. The standard entropy contribution (‐TΔSΔ) to the standard free energy of micellisation was found to be 19.7.3.0 kJ mol−1. These thermodynamic values are in good agreement with results obtained earlier for this system by lig

ISSN:0007-1641    

DOI:10.1002/pi.4980180113

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effects of shear rate, extrusion temperature and heat treatment on a lamellar triblock copolymer of styrene‐butadiene‐styrene were studied using extrudates from a capillary rheometer. The rheological behaviour is mainly non‐Newtonian in the region studied and the flow curves can be time‐temperature reduced. The quality of the domain structure PS phase was measured mechanically in terms of the stress at yield and optically by birefringence. Some of the factors considered during the analysis of the results are: rearrangement of the imperfect original domain structure taking place in the barrel, before extrusion, for temperatures higher than 145°C; partial destruction of this pre‐developed structure during extrusion; orientation of the chains during extrusion and under some conditions, the development of sharkskin on the surface of the extrudate. The heat treatment induces the copolymer to undergo three processes: internal stress relaxation (∼135°C); rearrangement of the imperfect domain structure (145°CT240°C); and crosslinking in the rubbery

ISSN:0007-1641    

DOI:10.1002/pi.4980180114

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980180117

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980180119

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980180121

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980180123

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980180124

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980180101

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY