Heat-shrinkable films have widely been used for various applications such as shrinkable labels and cap seals. These plastics have generally a short life. The biodegradable polymers can thus be an ideal candidate for such applications. This work aimed to study the stretching and shrinking ratio of poly(lactic acid)/ethylene vinyl acetate through reactive blends system for heat-shrinkable films application. The reactive agents, Joncryl® and Perkadox were used as in situ compatibilizers. PLA/EVA with 100/0, 97/3, 95/5, 93/7, and 90/10 ratios were prepared in the twin screw extruder. Neat PLA and PLA/EVA films were fabricated by blown film extrusion. The results revealed that the elongation at break of PLA in the TD direction was improved when adding EVA. PLA and EVA film with 0.1 phr of Perkadox was found to be sufficient as evident by FESEM micrograph and DMTA results. The films were stretched and shrunk at a temperature of 70 °C. The percentage of shrinkage of the stretched PLA/EVA reactive blend films, two and three times were, 100%, approximately. On the other hand, the four-times stretched films shrunk less than 100% because of the excessive stretching, which resulted in film breakage and defect.
New homoleptic zinc and magnesium
complexes containing constrained
reduced Schiff base ligands based on substituted 7-hydroxy-1-indanone
were successfully synthesized and used as a catalyst for the polymerization
of lactide. The ligands contain a side arm having different basicity
because dimethylamino, pyridyl, and furfuryl groups are shown to greatly
affect the polymerization rates. The homoleptic zinc complex containing
constrained reduced Schiff base ligands and a dimethylamino side arm
was highly active, giving a 92% conversion of l-lactide in
3 min using [LA]:[Zn]:[BnOH] = 500:1:2 at room temperature. The polymerization
is pseudo-first-order dependent on the LA concentration. Well-controlled
and living behavior of the zinc complex was observed and demonstrated
in the preparation of stereodiblock and triblock copolymers of l
-, d-, and rac-lactide
in a one-pot sequential synthesis with a predictable block length,
block sequence, and narrow dispersity rapidly in 10 min. Stereocomplex
formation was observed for PLA made sequentially from 100 l-LA, 100 rac-LA, and 100 d-LA having a
high T
m of up to 220 °C.
Bis(amidinate) tin(II) complex (1) was reported as active catalyst for ring‐opening copolymerization of cyclic anhydrides and epoxides via a binary catalyst system. Polymerizations of six combinations of epoxides and cyclic anhydrides were carried out giving highly alternating poly(anhydride‐alt‐epoxide) with narrow dispersities, except for cyclohexene oxide where significant amount of ether linkage up to 62 % was observed. This ether linkages could be diminished by increasing the amount of cocatalyst to over 3 equiv. Six well‐known cocatalysts were screened where PPNCl was found to be the best cocatalyst.
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