Good Weather Resistance Research Articles

Decay and conservation of PińczóW porous limestone. I. Lithology and weathering

AbstractThree lithological factors were identified as controlling the durability of the porous limestone from Pinczow. Coarse-grained texture, high crystallinity and lack of quartz give good weathering resistance to the stone. Gypsum formation deep within the stone fabric is the dominating deterioration factor. The structure of the stone controls the rate of gypsum formation. This corrosion process then changes the original porosity of the stone.

Influence of fillers on constrained‐layer vibration‐damping capabilities of chlorobutyl elastomers

A chlorobutyl elastomer formulation has been developed at this laboratory (USRD) for potential vibration damping applications. It combines the attractive engineering properties of low compression set, good weather and ozone resistance, and good tensile and tear properties with desirable viscoelastic behavior for vibration control. An intensive investigation of the effects of plasticizers and different types and loadings of fillers upon physical properties and damping capability of the base polymer was conducted. Measurements of the dynamic Young's modulus and loss tangent over an extended frequency range were used in conjunction with the Ross‐Ungar‐Kerwin model [Structural Damping, edited by J. E. Ruzicka (American Society of Mechanical Engineers, New York, 1959), Sec. 3] to predict the damping of simple three‐layer constrained structures. The model predictions were compared with actual damping measurements of composite plates. The observed differences between elastomers with different types of fillers are discussed in terms of mechanisms of interaction between the fillers and the gum phase of the elastomer. [Work supported by Code 1962 of David Taylor Research Center.]

Polysulfide Sealants

Abstract Sealants based on polysulfide liquid polymers are widely used in a number of applications. These sealants are solvent and chemical resistant, having good flexibility and adherence to many substrates such as steel, aluminum, glass, concrete, wood, etc. These are used to line fuel tanks of aircraft and to seal fuel tanks and rivetted joints in aircraft. These sealants, being water resistant, are widely used in ship building to seal decks and planking. Since these sealants have good weather resistance and can withstand stress and strain, they are widely used in the building industry. They are found to be very satisfactory in modern curtain walls and in sealing windshields of motorcars. Their use in airfield and runway constructions is well known. These sealants generally have a two-pot system consisting of (i) a base caulk containing a liquid polysulfide polymer, fillers, plasticizers, adhesive promotors, thickening agents, accelerators or retarders and (ii) a curing agent. Sometimes accelerators and retarders are used as a third pot system to regulate the pot life of caulking compounds.

Expanded Flexible Closed Cell Elastomeric Materials

Expanded flexible closed cell rubber produced by a free blown process began to be widely used about fifteen years ago as pipe and duct work insulation. This closed cell crosslinked rubber foam has a somewhat unique combination of properties that include ex cellent flex life, good weathering and chemical resistance and low permeability to moisture. This resilient foam rubber is useful in a range of applications including gasketing and cushioning. Certain formulation and processing techniques are peculiar to free blown expanded rubber. This article considers industry specifications and performance parameters for this class of materials. Properties pertinent to insulation application are discussed with emphasis on MVT and K factors.

Development of Synthetic Resin Adhesives

THE development of synthetic resin adhesives has proceeded very fast since about 1937 when the first urea formaldehyde wood glues were being produced on a pilot scale. The excellent resistance of these materials to weathering conditions has enabled very considerable advances in structural design both in wooden structures and rather more recently in metal aircraft. These synthetic resin adhesives are basically ‘thermosetting’, that is to say, they harden by the addition of catalysts or by the application of heat, the chemical process which takes place being irreversible and not dependent upon the evaporation of solvents. This concept leads not only to good weather resistance, but also to the practicality of sticking together non‐porous materials such as metal. The first use of bonding of mstal in aircraft structures was in the de Havilland Hornet in 1943,1 and since then bonding has proved its advantages over other methods of joining for both primary and secondary structures. Other new methods of fabrication have appeared since that time and the requirements for structures in terms of loading and environment have changed considerably; but both mctal‐to‐metal bonding and its newer partner honeycomb sandwich show signs of much more extensive use in the future. These two most important applications of synthetic resin adhesives in modern aircraft will now be considered.