Synergistic effect of stereocomplex crystals and shear flow on the crystallization rate of poly(<scp>l</scp>-lactic acid): A rheological study

Wei, Xin-Feng; Bao, Rui‐Ying; Gu, Li; Wang, Yu; Ke, Kai; Yang, Jie; Xie, Bin; Yang, Mei; Zhou, Tao; Zhang, Aiming

doi:10.1039/c3ra45402a

Cited by 22 publications

(23 citation statements)

References 77 publications

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“…The onset crystallization temperature is 140 C. The subsequent heating curve shows two melting peaks at 175 C and 223 C corresponding to the melting of homo-crystals and SC, respectively. The melting temperatures are in agreement with those reported in the previous papers [36,38]. Under quiescent condition, no spherulites were observed at 170 C. However, when the supercooled melt was subjected to shear at 50 s À1 for 5 s, several crystallites were observed at the same temperature.…”

Section: In-situ Waxssupporting

confidence: 93%

“…According to Wei et al [36], the crystallization rate of a crystals was enhanced by the synergistic effect of small amounts of SC acting as nucleating agents and shear flow, which was mainly explained by the slow relaxation of oriented PLLA chains under the crosslinking effect of SC. In our system, although the supercooled PLLA/PDLA (50/50) melt was sheared with no SC existing at the beginning, crosslinking effect of shearinduced SC formed ahead of a crystals may exist, especially at lower temperatures.…”

Section: Mechanism For the Enhanced Sc Formation By Shearmentioning

confidence: 98%

“…It was reported that the nucleation rate of PLLA was enhanced after a step shear [29]. PLLA with a small amount of SC was more sensitive to flow-induced crystallization [36]. Recently, Matsuba et al [35] studied shear-induced crystallization of equimolar PLLA/PDLA at 200 C, which was above the melting temperature (T m ) of a crystal.…”

Section: Introductionmentioning

confidence: 98%

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Enhancement of stereocomplex formation in poly(l-lactide)/poly(d-lactide) mixture by shear

Song

Zhang

Yin

et al. 2015

Polymer

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Section: In-situ Waxssupporting

confidence: 93%

Section: Mechanism For the Enhanced Sc Formation By Shearmentioning

confidence: 98%

See 1 more Smart Citation

Enhancement of stereocomplex formation in poly(l-lactide)/poly(d-lactide) mixture by shear

Song

Zhang

Yin

et al. 2015

Polymer

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“…3,[17][18][19][20][21][22][23][24][25] However, the improvement achieved by using these NAs is indeed not enough to obtain high crystallinity products during practical processing. 26 For this issue, several research groups have combined NAs with other crystallization promoting ways, such as plasticizers 16,27 and shear flow, 26,[28][29][30] to further promote the crystallization kinetics.…”

Section: Introductionmentioning

confidence: 99%

High-melting-point crystals of poly(l-lactic acid) (PLLA): the most efficient nucleating agent to enhance the crystallization of PLLA

et al. 2015

Self Cite

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Even though self-nucleation is considered to be the ideal case for polymer nucleation, it has rarely been used to enhance polymer crystallization in practical processing techniques. Inspired by self-nucleation theory and by utilizing the large difference in melting points of various polyĲL-lactide) (PLLA) resins, we introduced high-melting-point PLLA (hPLLA) crystallites into a low-melting-point PLLA (lPLLA) matrix via melt blending at a processing temperature between the two melting points of the selected PLLA resins. The hPLLA crystallites turn out to be efficient nucleating agents (NAs) for lPLLA and high crystallinity (>40%) PLLA samples with a greatly accelerated crystallization rate can be easily obtained. The results of nonisothermal crystallization show that the crystallization process is remarkably accelerated with a small amount (0.1 wt%) of hPLLA. With a further increase of hPLLA content, the crystallization temperature of the blends continues to shift to higher temperature. This crystallization promoting effect results from the excellent nucleation ability of the hPLLA crystallites, as revealed by in situ optical microscopy observation.Furthermore, an incredibly high nucleation efficiency of 103.0% (exceeding 100%) was obtained for the PLLA sample with 5.0 wt% hPLLA. The nucleation mechanism for hPLLA was studied systematically. It was found that the lPLLA matrix and hPLLA crystallites possess an absolutely identical crystal structure of α-form crystals and an excellent interfacial interaction between the nucleating agent, i.e., hPLLA crystallite, and the lPLLA matrix is achieved, resulting in the reduction of the energy barrier for heterogeneous nucleation and acceleration of crystallization kinetics. Therefore, by using high-melting-point polymer crystals as NAs, the crystallization rate of their low-melting-point polymer matrix can be improved largely, thus providing a simple way to obtain high crystallinity products for semicrystalline polymers with very low crystallization rates.

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“…also showed that the crystallization half‐time of PLLA decreased sharply with the presence of TMC . Stereocomplex crystals (sc‐crystals), formed from the enantiomeric mixture of PLLA and poly( d ‐lactide) (PDLA), can act as a nucleation agent for PLLA crystallization . Anderson et al .…”

Section: Introductionmentioning

confidence: 99%

Effect of nucleating agents on the crystallization behavior and heat resistance of poly(l‐lactide)

Zhang

Meng

et al. 2015

J of Applied Polymer Sci

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Poly (L-lactide) (PLLA) blends with various nucleators were prepared by melt processing. The effect of different nucleators on the crystallization behavior and heat resistance as well as thermomechanical properties of PLLA was studied systematically by differential scanning calorimetry, X-ray diffraction, heat deflection temperature tester, and dynamic mechanical analysis. It was found that poly(D-lactide), talcum powder (Talc), a multiamide compound (TMC-328, abbreviated as TMC) can significantly improve the crystallization rate and crystallinity of PLLA, thus improving thermal-resistant property. The heat deflection temperature of nucleated PLLA can be as high as 1508C. The storage modulus of nucleated PLLA is higher than that of PLLA at the temperature above T g of PLLA. Compared with other nucleating agents, TMC was much more efficient at enhancing the crystallization of PLLA and the PLLA containing TMC showed the best heat resistance.

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Synergistic effect of stereocomplex crystals and shear flow on the crystallization rate of poly(l-lactic acid): A rheological study

Cited by 22 publications

References 77 publications

Enhancement of stereocomplex formation in poly(l-lactide)/poly(d-lactide) mixture by shear

Enhancement of stereocomplex formation in poly(l-lactide)/poly(d-lactide) mixture by shear

High-melting-point crystals of poly(l-lactic acid) (PLLA): the most efficient nucleating agent to enhance the crystallization of PLLA

Effect of nucleating agents on the crystallization behavior and heat resistance of poly(l‐lactide)

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