A facile and highly efficient method for adhesion improvement of PET/TPU laminates was introduced. A considerable improvement in adhesion was achieved by treating PET fabric with isocyanate (MDI) in toluene solution. Compared with unmodified ones, the maximal peel strength reaches to 2.27 kN/m (up to three times). The fabrics were also treated with NaOH and CDT (corona discharge treatment) and the results were compared respectively. It is considered that the improvement mainly depends on the strengthening of chemical bonding and mechanical interlocking between the fiber and the adhesive matrix. As the difference directly affects the effective transference of the stress (tension force) from matrix to fiber. The failure surface of PET fiber was severely destroyed which could be examined by scanning electron microscopy (SEM).
Polyurethane elastomers (PUEs) based on 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BDO) and two kinds of aliphatic polycaprolactone (PCL) diols with molecular weight of 1000 Da and 2000 Da have been synthesized and melt-blended with polycarbonate (PC). The compatibility of PC and PUEs was investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). The results indicated that the glass transition temperature (Tg) of PC decreased by 0–40°C when 0–10 wt % of PUEs incorporated into the PC matrix. Phase separation in the blends was not detected by means of DSC characterization, but measurements of DMA and SEM indicated that phase separation existed in the blends of PC and PUEs synthesized with 1000 Da PCL-diol. As for PUEs/PC blend in which 2000 Da PCL-diol as PUEs' soft segments, it turned from completely compatible to partially when the NCO/OH ratio for the PUEs prepolymer was increased from 2 : 1 to 4 : 1. The compatibilities of PC and PUEs were greatly influenced by the molecular weight of polyols and the ratio of NCO/OH in the PUE prepolymer, higher molecular weight of polyols and lower NCO/OH ratio resulted in better compatibility. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
A series of linear polyurethane (PU) elastomers containing various amounts (ca. 2–10 wt%) of a diol-functionalized polyhedral oligomeric silsesquioxane (diolPOSS) were synthesized from organic solvent dispersions. Fourier transform infrared spectroscopy was used to characterize the chemical structure of the diolPOSS-reinforced PU. Transmission electron microscopy (TEM) indicated that the diolPOSS aggregation was formed in the polymer matrix at the scale of 20–50 nm. The introduction of diolPOSS into such system led to high glass transition temperature, enhanced storage modulus, and improved stability compared with the pristine PU according to the differential scanning calorimetry, dynamic mechanical analysis, and thermal gravimetric analysis, respectively. Moreover, contact angle measurements indicated a significant enhancement in surface hydrophobicity as well as a reduction in surface free energy after introducing diolPOSS into the synthesized PU. The improvement of surface properties could be ascribed to the enrichment of the diolPOSS moiety on the surface of the hybrids. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Enhancing the stability of plasticized poly(L-lactic acid) (PLLA) with poly (ethylene glycol) (PEG) is necessary for its practical application. In this study, plasticized PLLA (PLLA/PEG 80/20 wt/wt) was crosslinked under γ-ray (Co60) in the presence of triallyl isocyanurate (TAIC) as crosslinking agent. FTIR analysis revealed that PLLA, PEG, and TAIC formed a cocrosslinking structure. Crystallization behavior and mechanical properties of the crosslinked plasticized PLLA were investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), and tensile tests. Experimental results indicated that the crystallization behaviors of both PEG and PLLA in the blends were restrained after irradiation. The melting peak of PEG in the crystallized samples disappeared at a low irradiation doses about 10 kGy. Although PLLA still owned the behavior of crystallize, its cold crystallization temperature and glass transition temperature shifted to higher temperature. Mechanical properties of the plasticized PLLA were strengthened through crosslinking. Both yield strength and elastic modulus of the samples increased after crosslinking. Elongation at break of the crosslinked plasticized PLLA decreased with the increase of crosslinking density but remained a high value over 200%. SEM images of fracture surfaces confirmed that the ductile fracture behavior of plasticized PLLA was kept after suitable crosslinking. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Finding a suitable plasticizer for polylactide (PLA) is necessary to overcome its brittleness and enlarge its range of applications. In this study, commercial PLA was melt-blended with a new plasticizer, an ethylene glycol/propylene glycol random copolymer [poly(ethylene glycol-co-propylene glycol) (PEPG)] with a typical number-average molecular weight of 12 kDa and an ethylene glycol content of 78.7 mol %. The thermal properties, crystallization behavior, and mechanical properties of the quenched blends and the properties of the blends after storage for 2 months under the ambient conditions were investigated in detail. The advantage of using PEPG is that it does not crystallize at room temperature and has good compatibility with PLA. The quenched PLA/PEPG blends were homogeneous and amorphous systems. With an increase in the PEPG content (5–20%), the glass-transition temperature, tensile strength, and modulus of the blends decreased, whereas the elongation at break and crystallizability increased dramatically. The cold crystallization of PLA resulted in phase separation of the PLA/PEPG blends by annealing of the blends at the crystallization temperature. After storage under the ambient conditions for 2 months, the PLA/PEPG blends retained good toughness but still lost some flexibility. The reasons for the aging of the blends were the enthalpy relaxation and cold crystallization of PLA and the induced phase separation. Poly(ethylene glycol) with a typical number-average molecular weight of 10 kDa was also blended with PLA for comparison. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Summary: Bisphenol A solid epoxy serves as an effective reaction compatibilizer to the bisphenol A polycarbonate (PC)/PMMA bilayer systems. Addition of epoxy to the bottom PMMA layer can retard or even prevent the dewetting of PC films by introducing crosslinking between both components at the interface. This is the first investigation of polymer bilayers stabilized by chemical reactions.
The blends of low molecular weight triacetin (TAC) and oligomeric poly(1,3-butylene glycol adipate) (PBGA) were used as multiple plasticizers to lubricate poly(lactic acid) (PLA) in this study. The thermal and mechanical properties of plasticized polymers were investigated by means of dynamic mechanical analysis and differential scanning calorimetry. Atomic force microscopy (AFM) was used to analyze the morphologies of the blends. Multiple plasticizers were effective in lowering the glass transition temperature (Tg) and the melting temperature (Tm) of PLA. Moreover, crystallinity of PLA increased with increasing the content of multiple plasticizers. Tensile strength of the blends decreased following the increasing of the plasticizers, but increased in elongation at break. AFM topographic images showed that the multiple plasticizers dispersed between interfibrillar regions. Moreover, the fibrillar crystallite formed the quasicrosslinkings, which is another cause for the increase in elongation at break. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1583–1590, 2006
The surface and interface morphologies of polystyrene (PS)/poly(methyl methacrylate) (PMMA) thin-film blends and bilayers were investigated by means of atomic force microscopy (AFM) and X-ray photoelectron spectroscopy. Spin-coating a drop of a PS solution directly onto a PMMA bottom layer from a common solvent for both polymers yielded lateral domains that exhibited a well-defined topographical structure. Two common solvents were used in this study. The structure of the films changed progressively as the concentration of the PS solution was varied. The formation of the blend morphology could be explained by the difference in the solubility of the two polymers in the solvent and the dewetting of PS-rich domains from the PMMA-rich phase. Films of the PS/PMMA blend and bilayer were annealed at temperatures above their glass-transition temperatures for up to 70 h. All samples investigated with AFM were covered with PS droplets of various size distributions. Moreover, we investigated the evolution of the annealed PS/PMMA thin-film blend and bilayer and gave a proper explanation for the formation of a relatively complicated interface inside a larger PS droplet. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 9–21, 2006
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