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  • Wiley  (4)
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  • Wiley  (4)
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  • 1
    Online Resource
    Online Resource
    Microcellular foaming of poly(lactic acid) branched with food‐grade chain extenders
    Wiley ; 2021
    In:  Journal of Applied Polymer Science Vol. 138, No. 29 ( 2021-08-05)
    Details
    In: Journal of Applied Polymer Science, Wiley, Vol. 138, No. 29 ( 2021-08-05)
    Abstract: This study evaluated the effectiveness and efficiency of two food‐grade multifunctional epoxies chain extenders (CE) in branching PLA and improving its foamability. Both CE grades were effective in branching PLA causing increased end mixing torque, shear, elongational viscosities, molecular weight but decreased crystallinity of poly(lactic acid) (PLA) with CE content, due to chain entanglements. CE with low epoxy equivalent weight (EEW) was more efficient than the counterpart with high EEW due to its high reactivity. Neat PLA foams showed poor cell morphology with areas without nucleated cells and had a low expansion, owing to its low elongational viscosity. By contrast, there was a considerable change in the morphology of the PLA foam structure caused by its branching. Chain‐extended PLA foams had uniform cell morphology with a high void fraction (up to ~85%) and expansion ratio (an eightfold expansion over unfoamed PLA) due to their high elongational viscosities, suggesting that melt properties of branched PLA were appropriate for optimum cell growth and stabilization during foaming. Overall, CE with low EEW was the most effective grade and 0.25% the optimum content that provided appropriate melt viscosity to produce PLA foams with a homogeneous structure, fine cells, high void fraction, high volume expansion ratio, and cell‐population density.
    Type of Medium: Online Resource
    ISSN: 0021-8995 , 1097-4628
    URL: Issue
    URL: Article
    DOI: 10.1002/app.v138.29
    DOI: 10.1002/app.50686
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1491105-X
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  • 2
    Online Resource
    Online Resource
    Performance of poly(lactic acid)/ cellulose nanocrystal composite blown films processed by two different compounding approaches
    Wiley ; 2018
    In:  Polymer Engineering & Science Vol. 58, No. 11 ( 2018-11), p. 1965-1974
    Details
    In: Polymer Engineering & Science, Wiley, Vol. 58, No. 11 ( 2018-11), p. 1965-1974
    Abstract: This study was aimed to identify the best approach of incorporating cellulose nanocrystals (CNCs) into a poly(lactic acid) (PLA) matrix by examining two different CNC addition approaches. The first approach consisted of melt‐blending (MB) PLA and CNCs in a three‐piece internal mixer whereas the second method involved direct dry‐mixing of PLA and CNCs in a high intensity mixer. The compounded materials were then blown into films and compared in terms of particle dispersion, optical, thermal, molecular weight and barrier properties. Good distribution was achieved by both the direct dry‐ and MB methods. However, some agglomerations were still present that resulted in reduced transparency of the composite films. Furthermore, the PLA/CNC films thermally degraded during the blending processes indicated by the drop in their molecular weights due to chain scissions. More chain scissions occurred in melt‐blended (MB) films than the dry‐blended (DB) counterparts. The addition of only 1% CNCs into the PLA matrix by the direct dry‐ and MB approaches improved the water barrier properties of PLA films by 30% and 24%, and oxygen barrier properties by 60% and 39%, respectively. The inferior performance of the MB films compared to the direct DB counterparts could be attributed to more chain scissions in these films. Thus, the direct dry‐blending (DB) process appeared to be the better approach of incorporating CNCs into the PLA matrix. POLYM. ENG. SCI., 58:1965–1974, 2018. © 2017 Society of Plastics Engineers
    Type of Medium: Online Resource
    ISSN: 0032-3888 , 1548-2634
    URL: Issue
    URL: Article
    DOI: 10.1002/pen.v58.11
    DOI: 10.1002/pen.24806
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2006718-5
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  • 3
    Online Resource
    Online Resource
    Extrusion blown films of poly(lactic acid) chain‐extended with food grade multifunctional epoxies
    Wiley ; 2019
    In:  Polymer Engineering & Science Vol. 59, No. 11 ( 2019-11), p. 2211-2219
    Details
    In: Polymer Engineering & Science, Wiley, Vol. 59, No. 11 ( 2019-11), p. 2211-2219
    Abstract: The effectiveness and efficiency of two food grade multifunctional epoxies with low and high epoxy equivalent weights in chain extending/branching poly(lactic acid) (PLA) were studied in a torque rheometer. Processing PLA and chain extender (CE) at 200°C for 300 s not only chain‐extended PLA effectively as indicated by a significant increase in the mixing torque as well as PLA's melt viscosity and molecular weight, but also branched it leading to its reduced crystallinity. Chain extension occurred through the ring opening reaction of epoxy groups in the CE with PLA's hydroxyl and/or carboxyl groups. CE with lower epoxy equivalent weight was more efficient due to its higher reactivity. Secondly, the processabilities of PLA films chain‐extended and branched with various amounts of the most efficient CE were assessed. Like in torque rheometer, chain extension and branching also occurred during film production as indicated by PLA's increased molecular weight and decreased crystallinity when blended with CE. However, film manufacture was feasible only for blends with up to 0.5% CE, becoming unprocessable above this content due to chain entanglement leading to increased viscosity. Chain extension/branching of PLA was beneficial in overcoming film's brittleness since its impact strength increased almost linearly with the CE content. POLYM. ENG. SCI., 59:2211–2219, 2019. © 2019 Society of Plastics Engineers
    Type of Medium: Online Resource
    ISSN: 0032-3888 , 1548-2634
    URL: Issue
    URL: Article
    DOI: 10.1002/pen.v59.11
    DOI: 10.1002/pen.25224
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2006718-5
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  • 4
    Online Resource
    Online Resource
    Blown film extrusion of poly(lactic acid) without melt strength enhancers
    Wiley ; 2017
    In:  Journal of Applied Polymer Science Vol. 134, No. 34 ( 2017-09-10)
    Details
    In: Journal of Applied Polymer Science, Wiley, Vol. 134, No. 34 ( 2017-09-10)
    Abstract: Processing strategies were developed to manufacture poly(lactic acid) (PLA) blown films without melt strength enhancers (MSEs). The effects of processing temperature on PLA's melt properties (shear and elongational viscosities), PLA grades, and other processing conditions [ratio of take‐up roller to extruder's rotational screw speeds or processing speed ratio (PSR) and internal air pressures] on film's blow‐up ratio were examined. Experimental results indicate that extrusion‐blown amorphous and semicrystalline PLA films can be successfully manufactured without MSEs by controlling melt rheology through processing temperature and other extrusion processing conditions. PLA processed at lower extrusion temperature had higher melt viscosities, which favored the formation of stable films depending on the PSR and internal air pressure used. Inappropriate control of PSR and internal air pressure led to unstable films with various processing defects such as melt sag, bubble dancing, or draw resonance, irrespective of the lower extrusion processing temperature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45212.
    Type of Medium: Online Resource
    ISSN: 0021-8995 , 1097-4628
    URL: Issue
    URL: Article
    DOI: 10.1002/app.v134.34
    DOI: 10.1002/app.45212
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 1491105-X
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