繊維充填液晶ポリマー成形品の繊維配向性とその機械的性質

書誌事項

タイトル別名
  • Fiber Orientation and Mechanical Properties of Injection-Molded Fiber Filled Liquid Crystalline Polymers
  • センイ ジュウテン エキショウ ポリマー セイケイヒン ノ センイハイコウセイ ト ソノ キカイテキ セイシツ

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抄録

A thermotropic liquid crystalline polymer (LCP) and its carbon fiber (CF) and glass fiber (GF) filled systems were injection-molded into dumb-bell shaped specimens in order to investigate the effects of the processing conditions on their fiber orientation and mechanical properties. Minimal damage was found for either fiber under the processing conditions in this study. Microscopic observations of the cross sections of the molded specimens for their fiber orientation showed that the orientation distribution was greatly affected not only by the molding condition, but also by the gate geometry. This, in turn, suggested that the injection rate (Q) had a great effect on the fiber orientation in the molded products. The molds used in this study were designed using two different gate geometries-gate I (with a cross section with thickness and width both less than the thickness and width of the specimen) and gate II (with a cross section with thickness slightly larger than the thickness of the specimen but a width equal to the specimen width). The CF-filled specimens obtained with the mold using gate II showed better CF orientation along the flow direction in the center (core) layer than those produced with the mold using gate I. This phenomenon, not observed with a conventional general-purpose polymer, well represents the characteristics of thermotropic liquid crystalline polymers. In addition, it was found that the specimens produced using a gate with a reduced channel shape like gate II showed better fiber orientation aligned along the flow direction than in the case of those obtained using a gate with an enlarged channel shape like gate I, although the degree of the fiber orientation was not found to always increase in proportion to the injection rate (Q). It was also confirmed that the mechanical properties of the dumb-bell shaped specimens were greatly affected by the fiber orientation and the flow pattern of the melt during its injection into the mold. More specifically, the tensile modulus (E) of the unfilled and CF-filled LCP specimens produced with gate II decreased with increasing injection rate (Q), while the relationship between E and Q was reversed for the GF-filled LCP specimen. In addition, the E value of the CF-filled specimen was approximately two times higher than those of the unfilled and GF-filled LCP specimens, showing that CF and GF are different in their effects on the E values of the resultant fiber-filled LCP specimens. CF and GF also showed a difference in their effects on the dependency of the tensile strength (σB) of the resultant fiber-filled LCP specimens upon the injection rate (Q). However, the unfilled LCP specimen showed higher tensile strength (σB) and rupture elongation (εB) than the CF-and GF-filled specimens when produced at a low injection rate. Both CF-and GF-filled LCP specimens gave larger values of E, σB and εB when produced using gate II than gate I both at their dumb-bell ends and parallel sections. Microscopic observations suggest that this is because of the multilayer structure for both the unfilled and fiber-filled LCP systems.

収録刊行物

  • 成形加工

    成形加工 13 (6), 374-383, 2001

    一般社団法人 プラスチック成形加工学会

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