Glass-reinforced Polyester Research Articles

Greater Environmental Protection for Electrical Equipment Through New Technology

Corrosive environments have long presented problems in application, installation, and maintenance of electrical equipment. The causes of corrosion and the means taken to date to combat corrosive environments are briefly reviewed. The application of new technology in the glass-reinforced polyester plastics field is described as a solution to the problem of long-term protection of electrical equipment installed in aggressive environments. This new technology involves the use of chemical thickening of special polyester resins suitably formulated to provide high levels of structural strength and corrosion resistance both indoors and outdoors. Data are presented on the environmental resistance of the chemically thickened glass-reinforced polyester systems, and these are interpreted in terms of the diffusion of the environment into and out of the plastic. Examples are given of the application of chemically thickened glass-reinforced plastics in heavy duty industrial plugs and receptacles, industrial type light reflectors, and enclosures for electrical equipment. The degree of protection afforded by the chemically thickened glass-reinforced plastic is important in electrical installations in the petroleum, petrochemical, food, drug, fertilizer, and other process industries.

The concept of one polymer composites modelled with high density polyethylene

One polymer composite materials have been prepared using a difference in melting points between the components. This depends on the fact that aligned and extended chains provide thermodynamically more stable crystals, which thus will have higher melting points than conventionally crystallized melts. The growth of transcrystalline regions in the melt matrix at the interface plus an observed partial melting between fibre and matrix are indications of a strong and intimate interfacial bond with a gradient in morphologies for the system studied, high-density polyethylene. The pull-out test is a simple and adequate method for evaluating the interfacial shear strength of one polymer composites. The value for the high-density polyethylene composite falls between the strengths for glass-reinforced polyester and epoxy resins. However, the interfacial strength in the polyethylene composites is due mainly to the unique epitaxial bonding rather than the radial forces from compressive shrinkage. The low critical aspect ratio for the filaments in these polyethylene composites suggests possible advantageous uses as short fibrereinforced materials where the interfacial strength is a controlling factor.

Experimental Bridge Girder of Reinforced Plastic

A girder suitable for a primary load-bearing component in a bridge structure and composed entirely of glass-reinforced polyester resin was designed, fabricated, and tested to failure under short-term static loads. The girder was designed with a solid flange and open web by classical procedures based on a pinned-end truss configuration. Reasonably close agreement was achieved between theoretical and experimental measurements. The web and lower chord elements were fabricated by winding continuous glass roving impregnated with polyester around preformed web stiffeners. Measured strains and deflections varied linearly with load. Structural failures usually occurred in joints formed with adhesives. An ultimate live load of 93 times the dead weight of the member was achieved for one of the specimens.

Macroscopic Fracture Mechanics of Glass Reinforced Polyester Resin Laminates

Failure stresses for (a) plate specimens of glass chopped strand mat (CSM) and plain weave fabric-reinforced polyester resin laminates containing holes of various sizes, and (b) box-section beams of CSNI/polyester resin laminate containing a notch or hole in the tension flange were determined. Experimental values were compared with predicted values calcu-Iated from separately determined critical stress intensity factor, Kc, values. The Kc values were corrected using Irwin's crack tip zone correction factor together with an equivalent yield stress. For both types of specimen measured and predicted failure stresses were in reasonably good agreement.

Mechanism of surface microcracking of matrix in glass-reinforced polyester by artificial weathering

The first stage in the deterioration of glass-fibre reinforced polyester (GRP) composites, fibre prominence, has been reported. The mechanism of the second stage, surface microcracking, is now described. Under controlled conditions GRP sheets were subjected to cyclic variation of moisture and temperature and to radiation. It is proposed that surface microcracking takes place under the combined action of radiation-induced tensile stresses in the surface region and physically-induced stress-fatigue. Tensile stresses in the surface region are caused by shrinkage of the matrix that results from cross-linking induced by the ultra-violet portion of radiation. Stress fatigue is imposed on the composite system by physically-induced alternating stresses produced by cyclic variation of temperature and, probably, moisture resulting from thermal and moisture gradients and inhomogeneities. Stress-fatigue probably plays a dominant role in microcracking induced by artificial weathering, whereas radiation-induced stresses in the surface region are more important in microcracking occurring in outdoor weathering.

Critical Stress Intensity Factors Applied to Glass Reinforced Polyester Resin

Geometrically similar double edge-notched fracture toughness speci mens of glass reinforced polyester resin were tested and the critical stress intensity factor ( Kc) determined. For a unidirectional fabric reinforcement with the crack positioned parallel to the fibres Kc did not depend on crack length. For chopped strand mat and balanced weave fabric reinforcement Kc increased with crack length. Using an equivalent yield stress corrected values of K c independent of crack length were determined. Using the corrected Kc values the failure of specimens containing a circular hole was predicted with reasonable accuracy.

Characterization of polymer composites by electron microprobe analysis

AbstractThis paper describes the use of an electron microprobe for characterizing filler and polymer dispersios in polymer composites. Examples described are: filler distribution in sisal reinforced polyester; aggregation of titanium dioxide in glassreinforced polyester; mixing behavior in a blend of silicone rubber, natural rubber, and titanium dioxide; and distribution of silica in a low‐gloss paint on an ABS plastic surface. The limitations of electron microprobe analyses for qualitative and quantitative studies, the use of back scattered electrons for surface topography, and techniques for preparing specimens are mentioned.

New process mates vacuum forming and glass-reinforced polyester spray-up : Stayner, V. Reinforced Plastics, Vol 14, No 13, p 378 (September 1970)

New process mates vacuum forming and glass-reinforced polyester spray-up : Stayner, V. Reinforced Plastics, Vol 14, No 13, p 378 (September 1970)

Prediction of mechanical properties of polymers, tensile strength of glass reinforced plastics : Journal of Applied Polymer Science, Vol 13, No 9, p 1899 (September 1969)

Tensile strength data at high and low rates of loading were obtained for a glass-reinforced polyester and a glass-reinforced epoxy. Analysis of the data by a rate method indicated that such a method may be used to predict behavior of polymers from limited test data.

Prediction of mechanical behavior of plastics undergoing decomposition from the combined effects of environmental exposure and stress

AbstractA study was made to determine whether the behavior of plastics undergoing breakdown from the effects of stress, elevated temperatures, and chemical attack could be predicted by means of a mechanical‐chemical equation of state. Five systems were studied, the first four of which were tested for retention of strength at room temperature after environmental exposure: (a) glass‐reinforced polyester laminate exposed to an alkaline medium at elevated temperatures; (b) cellulose laminate exposed to elevated temperatures, resulting in oxidative degradation; (c) paper‐phenolic laminate exposed to elevated temperatures, resulting in further crosslinking followed by oxidative degradation; (d) heat‐resistant glass fiber polyester resin laminate exposed to very high degradative temperatures; and (e) same material and treatment as (d) except that the specimens were under stress during the exposure (stress rupture). It is concluded that the effects of the various environments on the mechanical properties of the plastics under study can be predicted accurately by use of a parameter of the equation of state representing a second‐order chemical reaction.

A method for depositing copper films on reinforced plastics

A relatively simple method of depositing an electrically conducting film of copper on glass-reinforced polyester laminates is described. Photomicrographs and unit resistance measurements of copper deposits are given, together with an example of the use of the method for producing simple printed circuits.