Milled glass fibers

Reinforced RIM (RRIM) elastomers are used. By the addition of reinforcing fillers such as milled glass fiber, glass flake, or mineral fillers in the polyurethane or short to long glass fiber in preforms, fabric, or mat forms placed in the mold cavity, the properties of the material can be altered to meet high performance requirements of the part (Chapter 15). The reinforced elastomers are used to increase flexural modulus, improve thermal properties, and improve dimensional stability.267... 

Table XI demonstrates the effect of fiber length on properties for a type of RIM processable material - the urethane modified isocyanurate which has low impact. Table XI ccnpares milled glass fibers with 1/8" chapped strand. The longer aspect length chopped strand provides for true reinforcement. However, it cannot be used in current RRIM equipment.

Many RIM formulated systems also incorporate milled glass fibers, or other kinds of fillers to bring about a reduction in linear thermal expansion and contraction, and increase part rigidity. 

Table III. Effect of IMR Plus Milled Glass Fiber Reinforcement on...

Likewise, when formulation C was also modified by 10% milled glass fiber, the toughness of the polymer remained Intact, as evidenced by low loss of elongation and retention of tear strength - a good measure of retained bond strength. These results are also shown In "Table HI". 

Reinforced RIM urethane using milled glass fibers (1/16 ) at 25% loading or more is now the "state of the art" reinforcement. 

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... 

The materials shown in Table I are available in varying molecular weights and filler compositions. For molded circuit applications, the most commonly used fillers comprise chopped or milled glass fibers and/or mineral talcs. In addition to these fillers, additional components may be incorporated to impart flammability resistance or to promote electroless plating. The latter is achieved by the addition of a proprietary mineral filler which renders the polymer "catalytic" to plating. 

This process, in which a high modulus urethane elastomer is reinforced by milled glass fibers is currently commercially used in a three piece air spoiler used on the 1980 Pontiac Sunbird. The first use of reinforced RIM urethane front fenders is scheduled for use on a 1981 model car. 

Studies of the effects of various types of fiber and particulate fillers have shown that milled glass fibers are in the near term the most suitable means to achieve part stiffness and the required reduction in the coefficient of linear thermal expansion to allow practical mating of RIM polyurethane panels with steel. 

It is the length of a particle divided by its diameter. For spherical or cubical particles, the aspect ratio equals to one. For calcium carbonate particles, the aspect ratio is typically 1-3. For talc, the aspect ratio is typically in the range of 5-20. For milled glass fiber, it is between 3 and 25. For mica, it is 10-70. For wollastonite, it is between 4 and 70. For chopped glass fiber, it is between 250 and 800. For natural fibers, such as cellulose, the aspect ratio can be from 20-80 to thousands. Low aspect ratio is below 10. However, the above figures are given for fillers not processed in a compounder and/or an extruder. Upon processing, aspect ratio can decrease from dozens and hundreds to as low as 3-10. 

Milled glass fiber, 125 Natural fibers, 125 Pine wood flour, 98 Salt cedar wood flour, 98 Talc, 125 Wollastonite, 125 Atactic, 57, 59... 

Milled Glass Filler - Milled glass fdlers are made by hammer-milling continuous glass strands. Used as anticrazing reinforcing fdlers for adhesives and in plastics. Also called milled glass fiber. 

Fig. 6. Rate of thermal contraction, Adiprene, castor oil, milled glass fibers.

Surfactant Blowing agent Milled glass fiber Component B Modified isocyanate based upon MDI... 

Fiber, one-ended A fiber so short in length it appears that it only has one end. Examples include very short length milled glass fibers and asbestos fibers. 

Figure 5.49 Milled glass fiber/ polyethylene blow molded water floatation wheels...

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