SYNOPSISComposite propellants based on hydroxyl-terminated polybutadiene ( HTPB ) resin are the most common contemporary solid propellants for launch vehicle and missile applications. A series of HTPB resins, manufactured by free-radical polymerisation using a peroxide initiator, with varying molecular weights and hydroxyl values, was used in propellant formulation experiments with a view to studying the resin production variables and their influence on the resultant propellant properties. It is seen that HTPB resins with a wide range of hydroxyl values could be effectively utilized in propellant formulations. Also, propellants with higher strain capability and chain flexibility could be produced from lower hydroxyl value resins.

SYNOPSISThere has been a constant endeavor to improve the mechanical properties of hydroxylterminated polybutadiene ( HTPB ) -based composite solid propellants. A systematic study has been conducted on different batches of HTPB resins with varying molecular weights and hydroxyl values. Propellant formulation experiments were conducted wherein the ratio of chain extender to crosslinker was systematically varied, with a view to achieve the maximum possible strain capability and moderately high tensile strength, keeping all other parameters constant. The influence of increasing hydroxyl content from trimethylolpropane at the expense of hydroxyl content from butanediol, on the mechanical properties of the finished propellant, has been depicted on 3-dimensional graphs. The isoproperty lines, plotted as a triangular chart with the percentage hydroxyl contents from the three constituents, can be used to arrive at the suitable formulation for a specified application depending upon the OH value of the resin. HTPB resins with high molecular weight, low functionality, and low hydroxyl value require higher levels of trifunctional curing agent and higher NCO/ OH ratios to obtain outstanding mechanical properties, especially elastic properties, compared to low molecular weight, high functionality resins. The impact of hard and soft segment domain structure on the mechanical behavior of the cured systems is more pronounced in the low molecular weight resin formulations due to the higher hard segment content compared to those attainable in high molecular weight resin formulations. I NTRO DUCT10 NThere has been a constant endeavor to improve the mechanical properties of HTPB-based composite solid propellants. In order to have a better understanding of the influence of resin variabilities like hydroxyl value, molecular weight, functionality, etc. on the resultant propellant properties, a coordinated program was undertaken. Under this scheme, a series of HTPB resins with varying molecular weights and hydroxyl values were produced at Vikram Sarabhai Space Centre.' Details of the first set of experiments conducted on these batches of resins by varying the ratio of curing agent to resin, i.e., R values, keeping the chain extender to crosslink ratio the same, have been reported in Part 1.'

Cardanol incorporated‐phenol‐formaldehyde novolac resins were synthesized by acid and base catalyzed reactions. The novolacs were transformed to their cyanate esters. The thermal cure characteristics of the cyanate esters depended upon the composition. The presence of cardanol proportionately facilitated the curing. The thermal characterization of the novolacs and the corresponding cured phenolic‐triazine networks indicated a dedicated a detremental effect of cardanol on the thermal stability and char residue of the resins. © 1995 John Wiley & Sons, Inc.

In this paper, mechanical properties of the fibers extracted from the areca fruit are determined and compared with the other known natural fiber coir. Further these Areca fibers were chemically treated and the effect of this treatment on fiber strength is studied. Areca fiber composite laminates were prepared using Phenol Formaldehyde with randomly distributed fibers. Composite laminates were prepared with different proportions of phenol formaldehyde and fibers. Other tests like adhesion tensile test, moisture absorption test, and biodegradable test of areca-reinforced phenol formaldehyde composite laminates were conducted and reported.

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