Skin/core crystallinity of injection-molded poly (butylene terephthalate) as revealed by microfocus X-ray diffraction and fast scanning chip calorimetry

Alicyn Marie Rhoades, Jason Louis Williams, Nichole Wonderling, René Androsch, Jiaxi Guo

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

The semicrystalline morphology of a poly (butylene terephthalate) was formed under the shear, pressure, and thermal gradients of the injection-molding process, and subsequently studied regarding the crystallinity of the skin layer and the core using fast scanning chip calorimetry (FSC) and microfocus X-ray diffraction. Test bars of 3 mm thickness were molded via a broad tab gate at one end of the part, designed to facilitate a linear flow path and to minimize shearing of the polymer as it passes through the gate. Simulation of the injection-molding process suggests a gradient in the cooling rate through the test part that varies from 50 K s−1 100 µm below the surface to 10 K s−1 in the core, at the temperature of crystallization after the cessation of flow. Analysis of the crystallinity reveals skin and core crystallinities of 35 and 46 %, respectively, near the gate, while there were observed values of 42 and 48 % at the end of fill; XRD data consistently confirmed the crystallinity difference between skin and core, and between the near and far gate positions. The observed cooling-rate-controlled crystallinity values are in excellent agreement with data of the degree and kinetics of quiescent melt-crystallization obtained in a former study. For the first time, the reliability of FSC data obtained during first heating, in order to gain thermal-history/processing-controlled structure information, is demonstrated.

Original languageEnglish (US)
Pages (from-to)939-946
Number of pages8
JournalJournal of Thermal Analysis and Calorimetry
Volume127
Issue number1
DOIs
StatePublished - Jan 1 2017

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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