Reinforced thermoplastics, dimensional

Dimensional Stability of Reinforced Thermoplastics. Thermoplastics have relatively large linear coefficients of thermal expansion. This can... 

Figures 7.6-7.S indude combinations of glass fibers with mica or mineral fillers that are normally used to control warpage and improve dimensional stability. Additional extensive information on the properties of injection-molded glass reinforced thermoplastics can be accessed via the web sites of glass suppliers, resin producers, and...

The glass-reinforced thermoplastic polyester resins are nnusual in that they are the first thermoplastic that can compare with, or are better than, thermosets in electrical, mechanical, dimensional, and aeep properties at elevated temperatures (approximately 150°C), while having superior impact properties. The glass fiber concentration usually ranges from 10 to 30 percent in commercially available grades. In molded parts, the glass fibers remain slightly below the surface so that finished items have a very smooth surface finish as well as an excellent appearance. 

Furthermore, the production of complex shaped parts is still a challenge for the composite industry. Parts with relatively simple geometries are commonplace today for reinforced thermoplastic composites the pultrusion of simple sections and the compression molding of parts with simple curvature are examples of well-developed technologies. But the production of complex three-dimensional parts usually requires injection or compression molding. Assembly technologies used to obtain complex geometries are sometimes inefficient and costly. 

Talc reinforced thermoplastics yield higher heat distortion temperatures and lower thermal expansion. These characteristics indicate an extended service temperature range and improved dimensional stability. In processing, talc builds torque which promotes fusion in rigid vinyls. Talc also provides good hot strength for downstream operations. 

Materials with totally new property combinations may be achieved by blending two or more polymers together. Through blending of thermotropic main-chain LCPs with engineering thermoplastics, the highly ordered fibrous structure and good properties of LCPs can be transferred to the more flexible matrix polymer. LCPs are blended with thermoplastics mainly in order to reinforce the matrix polymer or to improve its dimensional stability, but LCP addition may modify several... 

Nylon (Polyamide) PA is a crystalline plastic and the first and largest consumption of the engineering thermoplastic. This family of TPs are tough, slippery, with good electrical properties, but hygroscopic and with dimensional stability lower than most other engineering types. Also offered in reinforced and filled grades as a moderately priced metal replacement. 

Matrix flow relative to the reinforcing fibers is caused by thermal expansion of the fiber-matrix mass within the confines of the die and by the geometrical constriction of the die taper. Once the matrix flow distribution is known, the matrix pressure distribution may be determined using a flow rate-pressure drop relationship. One-dimensional flow models of thermoset pultrusion have been reasonably well verified qualitatively [15-17]. A onedimensional flow model of thermoplastic pultrusion [14,18] has similarly been compared with experimental data and the correlation found to be encouraging [19]. 

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