摘要:

Thin films were prepared with urethane acrylate oligomer in combination with a number of acrylate monomers. Two monofunctional monomers such as 2-ethylhexyl acrylate (EHA) andN-vinylpyrrolidone (NVP); two difunctional monomers, e.g., hexanediol diacrylate (HDDA) and tripropylene glycol diacrylate (TPGDA); and a trifunctional monomer, trimethylol propane triacrylate (TMPTA), were used to prepare the films. These were cured under UV radiation. Their physicomechanical properties were studied. TMPTA film showed the highest hardness with the least tensile properties (tensile strength and elongation at the break). However, NVP exhibited the best performance among all these functional monomers as far as physicomechanical properties are concerned.

ISSN:0360-2559    

DOI:10.1080/03602559408010727

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Diffusion coefficients of five elastomer membranes, viz., nitrile butadiene rubber, styrene–butadiene rubber, ethylene–propylene–diene terpolymer, neoprene, and natural rubber with acetic acid and dichloroacetic acids have been obtained from gravimetric sorption experiments. For acetic acid, the diffusion seems to follow the expected Fickian mechanism whereas for dichloroacetic acid, the diffusion appears to follow the non-Fickian mechanism for natural rubber and nitrile butadiene rubber membranes. While most membranes remain intact during immersion experiments, only natural rubber has shown degradative reactions. The concentration dependence of diffusivity has also been studied.

ISSN:0360-2559    

DOI:10.1080/03602559408010728

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Blending of ethylene–methyl acrylate (EMA) copolymer and polydimethyl siloxane (PDMS) rubber led to miscibility of the two components under the processing conditions of 180°C and 100 rpm rotor speed, and the miscibility was assumed to be due to reaction between EMA and PDMS rubber. A plausible mechanism has been suggested. The mechanism has been confirmed by infrared and solid-state MAS nuclear magnetic resonance spectroscopy, which show a reduction in the vinyl group concentration of PDMS rubber and an increase in the‒CH2‒bridge concentration of EMA in the vicinity of the α-carbon atom in the blend.

ISSN:0360-2559    

DOI:10.1080/03602559408010729

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This paper reports experimental results from the use of pure natural honey for drag reduction in capillary tubes, with particular reference to biomedical engineering. The effects of the capillary tube diameter, the Reynolds numbers, concentration percentages, and honey type on the drag reduction were investigated. The maximum drag reduction obtained in this investigation is very much dependent on both the diameter of the capillary tubes and the concentration of the honey. Maximum drag reductions of 17.1%, 46.9%, and 37.3% at concentrations of 1000 ppm were obtained for the tube diameters of 1 mm, 1.3 mm, and 1.5 mm, respectively. Increasing the concentrations to 2000 ppm gave maximum reductions of 43%, 36.5%, and 50% for the tube diameters of 2 mm, 2.5 mm, and 3 mm, respectively.

ISSN:0360-2559    

DOI:10.1080/03602559408010730

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A proposed styrene polymerization process for the production of crystal polystyrene is evaluated. The present process consists of an autorefrigerated stirred tank, followed by a tubular reactor. A flash tank devolatilizer is then used to remove volatiles from the reactor effluent. A mathematical model has been developed to include three different types of polymerization reactors: (i) polymerization in a stirred tank, (ii) polymerization in a plug flow reactor, and (iii) polymerization in a real tubular reactor. The styrene conversion and polystyrene quality were determined as a function of temperature and residence time in a reactor. It was found that an ideal process would be prepolymerization in a stirred tank to a 70–75% conversion, followed by postpolymerization in a tubular static mixer to 90% conversion. The pipe has an internal diameter of 0.254 m. Equilibrium considerations were used to estimate the content of residual volatiles in the devolatilized polystyrene melt. The results show that a lower vacuum pressure would be more helpful than a higher devolatilization temperature in reducing the volatile content.

ISSN:0360-2559    

DOI:10.1080/03602559408010731

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Besides tire production, natural and synthetic rubber in vulcanized form are used to prepare various rubber goods such as mechanical goods, hoses, soles, linings to avoid corrosion in chemical processes, gaskets, etc. In the vulcanization of rubber, carbon black and other ingredients are used in the compounding recipes as well as sulfur. Carbon black gives strength to the vulcanized rubber, but carbon black is an expensive filler. Therefore other fillers partially replacing carbon black are also used in the vulcanization processes to reduce the cost of rubber products while maintaining their desired properties. In our work, inorganic fillers, to be used instead of or together with carbon black, were investigated and selection criteria were developed.

ISSN:0360-2559    

DOI:10.1080/03602559408010732

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effects of the addition of interface modifiers on the structure and properties of wood fiber-filled polypropylene (PP) have been studied. Although an increase in the wood fiber loading reduces the overall cost of composites, the mechanical properties of such composites are very poor in the absence of a suitable interface modifier. The poor mechanical and thermal properties of the unmodified composite are attributed to increased heterogeneity induced in the system with increased concentration of wood fiber. A significant improvement in tensile strength and thermal resistance of these composites in the presence of a suitable interface modifier such as maleated polypropylene, itaconic anhydride, or bismaleimide-modified polypropylene is due to the improved dispersity of wood fibers in the polypropylene matrix as well as to the development of a stable interface effected by chemical interaction. In general, all modifiers are found to affect the crystallinity of PP in composites, and an improvement of tensile strength is marked by a lowering of crystallinity of PP.

ISSN:0360-2559    

DOI:10.1080/03602559408010733

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Partially stereoregular poly(propylene oxide) (PPO) samples synthesized by Pruitt–Baggett catalyst (PBC) were dissolved in benzene, and Fe in the polymer was extracted with acidic aqueous solutions. The Fe in the polymer could be extracted gradually with 3 M HCl, but it could not be extracted with water and dilute HCl solutions. The Fe in the aqueous solutions was determined by ICP-AES (inductively coupled plasma–atomic emission spectrometry). It has been found that increasing the Fe in the aqueous solutions decreases the molecular weights of polymer samples.

ISSN:0360-2559    

DOI:10.1080/03602559408010734

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The behavior of three different high molecular weight polyisobutylenes (PIB) in solutions of hexane and cyclohexane at 30°C has been investigated by viscometry. Mark–Houwink relations have been examined, the polymer–solvent interaction is discussed in terms of the calculated Huggins constant,k; parameteraof the Mark–Houwink equation; and equivalent hydrodynamic volumesVe. The molecular weights of the three sample of polyisobutylene are remarkably well fitted with the intrinsic viscosity data.

ISSN:0360-2559    

DOI:10.1080/03602559408010735

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor