Chopped Integral strands

Flexural Modulus. Figure 5 shows flex modulus values at 23 °C measured parallel and perpendicular to flow. The nonreinforced urethane polymer has a value of about 50,000 psi. Columns B and C show the results obtained with 8.5% and 20% loadings of milled glass fibers, respectively. Column D shows results obtained with 3.5% loadings of 1/8 chopped Integral strands. The flex modulus increased by about 20%. Column E shows data for 13.4% integral chopped strands the increase was more than 240% of the original... 

Impact Strength. Figure 6, notched Izod impact strength, shows one of the main reasons for the interest in chopped integral strands (c/s) as RRIM urethane reinforcement. The nonreinforced urethane polymer used in this study had an impact value of approximately 12 ft-lb/in. Reinforcement with 20% milled glass fibers lowers this value to about 5 ft-lb/in. (Column B). 

Tensile Strength. Tensile strength data (Figure 7) indicate that the highest value was obtained with milled glass fiber (20% loading) and the relatively low value obtained with chopped integral strands. This may be related to the aspect ratio of dispersed milled fiber in the composite compared to chopped... 

Urethane RIM panels reinforced with chopped integral strands have better impact strength, less heat sag, and less anisotropy than those reinforced with milled fiber, at the same loading level or higher. 

Tensile strength, elongation, and Impact properties of chopped strand RRIM urethane panels increased with increased integral strand aspect ratios flex modulus was not affected. 

Integral chopped fiber glass strands 1/8 In., and a hybrid of milled fiber glass and chopped strand. Six major panel properties were examined for surface... 

This paper reports the effects of loading level of Integral chopped strands mixture of milled fibers and Integral chopped strands on physical properties and surface quality of reinforced RIM urethane composites. 

Surface Quality. Class "A surface (after painting) is considered by the automotive industry as their first requirement for an exterior part. Comparing the surface quality of several reinforcements in RRIM urethane panels, it was found by visual examination that the best surface quality was the glass flakes and the worst was the integral chopped strands. Milled fiber is slightly worse than glass flakes, but it is still considered a "Class A" surface. 

Figure 3. Schematic of integral chopped strands coating and direct chopping process.

Anisotropy Increased with Increasing Integral chopped strand content for tensile strength and flex modulus of RRIM urethane panels. Higher glass content results In higher viscosity which causes well-defined flow and hence well-defined orientation. 

Hybrid reinforcement of Integral chopped strand and milled fiber Improved flex properties but hurt Impact strength and heat sag. This could be due to the amount of milled fiber In the mixture. The hybrid contained about 70% by weight of milled fiber. The overriding properties were that of milled fiber composites. 

When building a laminate for industrial use, it is generally made in at least two stages. First the so-called resin-rich corrosion barrier is laid down. This consists of two veil layers followed by two chopped strand mat layers. The resin content in the veil layers is usually around 90wt% while in the chopped strand mat layers it is between 70-80wt%. The thickness of this layer is normally between 2-3 mm. The purpose of this first section is to protect the subsequent layers from any chemical attack and it is not expected to contribute to the structural integrity of the vessel. 

To cater for the variety of composite fabrication techniques, fibres may be formed into woven rovings, knitted preforms or continuous random mats (CRM) or chopped into lengths of >20 mm to <5 mm for use in moulding compounds or assembling into chopped strand mat (CSM). For these textile processes, the polymeric component of the size is required to maintain strand integrity and filament strength. The random continuous and chopped strand mats require additional polymeric binders. 

Choppability. The ease of chopping into short lengths, retention of strand integrity, and the amount of static electricity produced by the roving when it is further processed into chopped strands. 

Four types of Si-PAA s were evaluated in 30% GR Valox-type PBT polyester. Aside from producing chopped strand with outstanding bundle integrity, the polyazamides generally outperformed A-llOO aminosilane in strength and thermal properties. Also, except for Y-5987, the polyazamides clearly outdistance the monomeric coupler in Izod impact strength. 

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