Journal of Polymer Research 

About: Journal of Polymer Research is an academic journal published by Springer Science+Business Media. The journal publishes majorly in the area(s): Materials science & Polymerization. It has an ISSN identifier of 1022-9760. Over the lifetime, 4954 publications have been published receiving 66870 citations.

Isothermal crystallization behavior of β-nucleated isotactic polypropylene with different melt structures

Abstract: A previous work reported that the polymorphic crystallization behavior of isotactic polypropylene (iPP) can be efficiently tuned by the combination of controlling the melt structure (i.e., creation of an ordered structure by tuning the fusion temperature Tf by self-nucleation) and the addition of the α-/β-dual-selective nucleation agent (dual-selective β-NA, tradename WBG-II). In this study, we further investigated the impact of isothermal treatment on the polymorphic behavior and the isothermal crystallization kinetics of a β-iPP sample with different melt structures by differential scanning calorimetry (DSC). The results of isothermal crystallization kinetics study illustrated that as Tf decreased gradually from Region I to Region II and Region III, two sharp increases of the crystallization rate took place at the transition temperatures of Region II, showing that the enhancement of β-phase crystallization took place in a certain crystallization rate window. The calculation of the Avrami exponent n revealed that the two-dimensional growth of crystallites with instantaneous nucleation took place before and after the occurrence of the synergetic effect between the ordered structures and the dual-selective β-NA (when Tf ≥ 168 °C). Moreover, it was found that the occurrence of the synergetic effect in the fusion temperature range of Region II can evidently enhance the βc of the sample: by tuning the fusion temperature Tf and the isothermal crystallization temperature Tc, the relative percentage of β-phase (βc) of the single β-iPP sample with only 0.03 wt.% β-NA can be efficiently tuned in the wide βc range of 0 %–95.0 %; meanwhile, the sensitivity of βc to the isothermal crystallization temperature Tc was reduced.

Chitosan- graft -poly(acrylic acid)/rice husk ash based superabsorbent hydrogel composite: preparation and characterization

Abstract: Rice husk ash (RHA), an industrial waste, was incorporated in the preparation of high performance chitosan (CTS) and poly(acrylic acid) (PAA) based superabsorbent hydrogel. Hydrogels filled with RHA previously calcinated at 900 °C (RHA900) showed better water uptake (225 gwater/gabsorbent) than those with husk calcinated at 400 °C (RHA400) (198 gwater/gabsorbent) due to the higher purity and crystallinity, at same composition. The hydrogel composite at 5 wt-% of RHA900 showed the best water uptake (255 gwater/gabsorbent). A clear reduction in swelling degree is observed by increasing the amount of crosslinker from 1 to 3 wt-% due to the increase in the crosslinking density forming more rigid hydrogels. On the other hand, an increase in the initiator amount from 1 to 3 wt-% increased the water uptake due to the formation of greater numbers of active sites increasing the number of PAA chains grafted into CTS backbone. Furthermore, the hydrogel composites presented responsive behavior in relation to both pH and sat solution. The data shows it is possible to obtain high performance materials by incorporating an industrial waste, rice husk ash, in the preparation of hydrogel composites.

Preparation and characterization of hydrophobic PVDF membranes by vapor-induced phase separation and application in vacuum membrane distillation

Abstract: Hydrophobic symmetric flat-sheet membranes of polyvinylidene fluoride (PVDF) for use in vacuum membrane distillation (VMD) were successfully fabricated by the vapor-induced phase separation (VIPS) method using the double-layer casting process. To avoid the delamination that often occurs in double-layered membranes, the same PVDF polymer was employed in both the upper layer and support layer casting solutions. Solutions with low and high PVDF contents were co-cast as the upper layer and support layer of the membrane that was formed. In the VIPS process, the low PVDF content solution favored the formation of a layer with a porous and hydrophobic surface, whereas the solution with a high PVDF concentration favored the formation of a layer with high mechanical strength. The effect of the vapor-induced time on the morphological properties of the membranes was studied. As the vapor-induced time was increased, the cross-section of the membrane changed from an asymmetrical finger-like structure to a symmetrical sponge-like structure, and the surface of the membrane became rough and porous. The membrane subjected to the longer vapor-induced time also exhibited a higher permeating flux during the VMD process. The best PVDF membrane fabricated in this study had a mean radial pore size of 0.49 μm, and the rough upper surface produced a static contact angle of 145° with water. During the VMD process with a 3.5 wt.% sodium chloride (NaCl) aqueous solution, the best membrane that was fabricated produced a permeating flux of 22.4 kg m−2 h−1 and an NaCl rejection rate of 99.9 % at a feed temperature of 73 °C and a downstream pressure of 31.5 kPa. This performance is comparable to or superior to the performances of most of the flat-sheet PVDF membranes reported in the literature and a polytetrafluoroethylene membrane used in this study.

Studies On The Crosslinking Of Poly (Vinyl Alcohol)

Abstract: This paper is concerned with the cross-linking of poly(vinyl alcohol) (PVA) using maleic acid as the cross-linker. The curative (maleic acid) dose and the curing temperature and time were varied between 2.5 and 60% (w/w), 120 and 160 °C and 30 and 120 min, respectively. From a thorough swelling study in both hot and cold water (percentage swelling, gel content, swelling ratio, etc-) the optimum curative dose and curing conditions have been evaluated. The molecular weight between the cross-links exhibited a sharp fall up to a maleic acid dose of 20% (w/w). A comparative evaluation of maleic acid cross-linked and heat-treated PVA films has been done. Better heat stability for maleic acid cross-linked PVA was observed from thermogravimetric analysis. A shift in glass transition temperature was observed for both heat-treated and maleic acid treated PVA compared with the virgin one. IR spectroscopic study indicated the presence of an ester linkage and an olefinic double bond in maleic acid treated and heat-treated PVA films, respectively. Maleic acid cross-linked PVA is quite stable in different polar and nonpolar solvents. A definite structural pattern has been observed in maleic acid cross-linked PVA films through scanning electron microscopy.

Thermo/chemo-responsive shape memory effect in polymers: a sketch of working mechanisms, fundamentals and optimization

Abstract: Based on the working mechanisms, a systematic literature review is logically presented to reveal that the thermo- and chemo- responsive shape memory effects (SMEs) are not the special phenomena of some particular polymers, but intrinsic features of most polymers (if not all). Subsequently, referring to the most recent experimental results and their theoretical origins, we reveal the fundamentals on the optimization of the SME in polymers and the approaches to design/synthesize polymeric materials with tailored features.