Abstract
Poly(cyclohexylene dimethylene cyclohexanedicarboxylate) (PCCE) is a kind of copolyester polymer with excellent toughness and outstanding flexibility. However, the opacity caused by crystallization limits the widespread application of PCCE in products that have transparency requirements. The effects of 1,3:2,4-Di-p-methylbenzylidene sorbitol (MDBS) on the crystallization behavior, transparency, and mechanical properties of a PCCE melt were investigated via differential scanning calorimetry (DSC), spectrophotometry, and tensile testing. The results suggest that the transparency and mechanical properties of PCCE drastically improve and that its crystallization behaviors are obviously influenced by the addition of MDBS. PCCE with 0.6 wt% MDBS was then selected as a representative sample, and its thermal behavior and crystal morphology were further investigated by DSC, hot-staged polarizing microscopy (HSPLM), and scanning electron microscopy (SEM). The quantitative results suggest that, compared to neat PCCE resin, PCCE/MDBS has a lower isothermal and nonisothermal crystallization activation energy, which indicates a rapid crystallization process. The results also show that, compared to the pure PCCE melt, the PCCE/MDBS melt experiences a greater increase in the number of crystals and a greater decrease in the crystal size during cooling. The acceleration of the crystallization process and reduction in crystal size can be both attributed to the nucleation effect of the MDBS. In conclusion, because the addition of the nucleating agent improves the transparency and tensile properties of PCCE by adjusting and controlling its thermal and crystallization behaviors, the proposed technique of using a compounding nucleating agent to control crystallization is therefore suitable for PCCE.
Highlights
Transparency is one of the most important focuses in polymer engineering, because it is a requirement for many applications, such as packaging, electronic instruments, and optical apparatuses.It is known that the transparencies of amorphous polymers are generally better than those of crystalline materials
The selected Poly(cyclohexylene dimethylene cyclohexanedicarboxylate) (PCCE)/6MDBS and neat PCCE samples were observed by hot-staged polarizing light microscopy (HSPLM, BX61, OLYMPUS, Beijing, China) with the following heating/cooling procedure: the samples were heated from 25 ◦ C to 240 ◦ C at 10 ◦ C/min, held isothermally for 5 min, and cooled to 25 ◦ C at 10 ◦ C/min
Compared to the ΔE value of neat PCCE in the nonisothermal crystallization process, which is −146 kJ/mol, a decrease of 25.9 kJ/mol for the PCCE/6MDBS is obtained; this result indicates that the MDBS makes the molecular chains of PCCE easier to crystallize in the nonisothermal crystallization process
Summary
Transparency is one of the most important focuses in polymer engineering, because it is a requirement for many applications, such as packaging, electronic instruments, and optical apparatuses. Commonly used NAs have difficulty improving the transparency of the matrix because of their relatively weak nucleation effect and inappropriate crystallization behavior Sorbitol products, such as dibenzylidene sorbitol (DBS) and methylbenzylidene sorbitol (MDBS), have a special chemical structure of butterfly-shaped groups that can self-organize into a nanofibrillar network [21]. To the best of our knowledge, there has been little research related to the macroscale mechanical, optical performances or microscale crystallization structures of micro- or nanoparticle/fiber-filled PCCE composites. This limitation in the literature has aroused our interest to explore the topic. To avoid the possible influence of fabrication methods, extruded and injection-molded samples were both prepared and characterized
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