Paper‐sheet biocomposites based on wood pulp grafted with poly(ε‐caprolactone)

Abstract

Kraft pulp fibers were used as substrates for the grafting of poly(ε‐caprolactone) (PCL) from available hydroxyl groups through ring‐opening polymerization, targeting three different chain lengths (degree of polymerization): 120, 240, and 480. In a paper‐making process, paper‐sheet biocomposites composed of grafted fibers and neat pulp fibers were prepared. The paper sheets possessed both the appearance and the tactility of ordinary paper sheets. Additionally, the sheets were homogenous, suggesting that PCL‐grafted fibers and neat fibers were compatible, as demonstrated by both Fourier transform infrared spectroscopy microscopy and through dye‐labeling of the PCL‐grafted fibers. Finally, it was shown that the paper‐sheet biocomposites could be hot‐pressed into laminate structures without the addition of any matrix polymer; the adhesive joint produced could even be stronger than the papers themselves. This apparent and sufficient adhesion between the layers was thought to be due to chain entanglements and/or co‐crystallization of adjacent grafted PCL chains within the different paper sheets. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42039.

Grafting of poly(ε‐caprolactone) from Abaca cellulose fibers via ring‐opening polymerization resulting in facile one‐pot biocomposites

“…SEC analyses show larger values of Mn SEC of the free polymer from these grafting reactions than many of those previously reported for free PCL from comparable grafting protocols. This suggests that the surface in pulp of AFs used herein in combination with the pretreatments leads to higher molecular weight of the PCL chains and more efficient grafting [28,33,41,42] …”

“…The actual DPs of the PCL chains were tailored by varying the reaction time [33] . Longer polymerization time (1–10 h) results in a linear increase in conversion of ε‐CL to PCL (from 19% up to 42%, 1 and 6 h, respectively, see Figure 2B) and thus in increasing molecular weight of PCL (Table 1).…”

“…Molecular weights from solution 1 H‐NMR are assessed either by initiating‐group analysis (benzylic protons) or chain‐end analysis (methylene group adjacent to the terminal hydroxyl chain‐end) according to previous work [33] . The relationship between the different methods of molecular weight estimation, Mn theoretical , Mn BnOH, Mn chain‐end, and Mn SEC are kept constant for the different reactions of 1, 6, or 10 h, despite showing different specific numbers, which indicates good repeatability in characterizations.…”

“…Prior to solvent exchange, different pretreatments were investigated: (P1) dried AFs were directly placed into acetone from the 20 wt% pulp, (P2) dried fibers were re‐dispersed in water by magnetic stirring (at 1 wt%) before being added into acetone and (P3) dried fibers were disintegrated again in water at 10,000 rpm three times (at 1 wt%) before being added to acetone. Then, a sequential solvent exchange was applied using a water‐acetone‐toluene gradient approach in order to remove the water and transfer the fibers into an organic solvent suitable for the grafting, following a previously reported protocol 33 …”

“…Following a previous work by Bruce et al, [33] the AFs were grafted by ROP of ε‐caprolactone to afford “AF‐gX‐PCL,” where X indicates the reaction time. Briefly, in a round‐bottom flask equipped with a magnetic stirrer, the solvent exchanged AFs (10 g dry weight) were dispersed in a mixture of ε‐CL (210 g, 1.84 mol) and toluene (60 ml).…”