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ABSTRACT:The effects of various types of compatibilizers on the mechanical properties of high-density polyethylene/ wood flour composites were investigated. Functionalized polyolefins, including maleated polyethylenes, polypropylene, and styrene-ethylene/butylene-styrene copolymer, were incorporated to reduce the interfacial tension between the polyethylene matrix and wood filler. Of these, maleated linear lowdensity and high-density polyethylenes gave higher tensile and impact strengths for the composites, presumably because of their better compatibility with the high-density polyethylene matrix. Similar but less enhanced improvements in the mechanical properties, depending on the compatibilizer loading, were seen for a maleated styrene-ethylene/butylene-styrene triblock copolymer, whereas maleated polypropylene only slightly improved the tensile modulus and tensile strength, which increased with increasing compatibilizer loadings. Scanning electron microscopy was used to reveal the interfacial region and confirm these findings. Dynamic mechanical thermal measurements showed the interaction between the filler and the matrix. Fourier transform infrared spectroscopy was used to assign the chemical fixation and the various chemical species involved on the surfaces of the fillers before and after surface treatment.

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The melt mixing technique was used to prepare various polypropylene (PP)‐based (nano)composites. Two commercial organoclays (denoted 20A and 30B) served as the fillers for the PP matrix, and two different maleated (so‐called) compatibilizers (denoted PP‐MA and SMA) were employed as the third component. The results from X‐ray diffraction (XRD) and transmission electron microscope (TEM) experiments revealed that 190 °C was an adequate temperature for preparing the nanocomposites. Nanocomposites were achieved only if specific pairs of organoclay and compatibilizer were simultaneously incorporated in the PP matrix. For example, PP/20A(5 wt %)/PP‐MA(10 wt %) and PP/30B(5 wt %)/SMA(5 wt %) composites exhibited nanoscaled dispersion of 20A or 30B in the PP matrix. Differential scanning calorimetry (DSC) results indicated that the organoclays served as nucleation agents for the PP matrix. Generally, their nucleation effectiveness increased with the addition of compatibilizers. The thermal stability enhancement of PP after adding 20A was confirmed with thermogravimetric analysis (TGA). The enhancement became more evident as a suitable compatibilizer was further added. However, for the 30B‐included composites, thermal stability enhancement was not evident. The dynamic mechanical properties (i.e., storage modulus and loss modulus) of PP increased as the nanocomposites were formed; the properties increment corresponded to the organoclay dispersion status in the matrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4139–4150, 2004

The effects of various types of compatibilizers on the mechanical properties of high‐density polyethylene/wood flour (HDPE/WF) composite were investigated. Functionalized polyolefins such as maleated and acrylic acid grafted polyethylenes, maleated polypropylene (PPgMA) and styrene‐ethylene/butylene‐styrene triblock copolymer (SEBSgMA) were incorporated to reduce the interfacial tension between the polyethylene matrix and the wood filler. Among them, it was found that maleated linear low‐density polyethylene (LLDPEgMA) gave maximum tensile and impact strength of the composites, presumably because of better compatibility with the HDPE matrix. Similar but less enhanced improvements in the mechanical properties, depending on the compatibilizer loading, were seen for the SEBSgMA system. Whereas acrylic acid grafted high‐density polyethylene (HDPEgAA) and maleated polypropylene (PPgMA) only slightly improved tensile modulus and tensile strength; and they both increased with increasing loadings of compatibilizers. A scanning electron microscopic study was employed to reveal the interfacial region and confirm these findings. In addition, dynamical mechanical thermal measurements also revealed the interaction between filler and matrix, and FTIR spectroscopy was used to assign the chemical fixation and the various chemical species involved at the surface of the wood fillers before and after surface treatment.

ABSTRACT:The vital differences between the use of untreated starch and gelatinized starch in blends with poly(butylene succinate) (Bionolle) were thoroughly examined in this study. The melting temperature decreased slightly with increasing dosages of untreated and gelatinized starch. The added starch perhaps tended to disrupt the intermolecular hydrogen bonding within the Bionolle matrix. On the other hand, a large increase in the crystallinity was seen with the addition of starch. Starch appeared to play a nucleating role in the blends. The trend of the glass-transition temperature decreasing with the starch level was similar to the trend of the melting temperature. For the same starch content, the glass-transition temperature showed some variations. For blends containing a certain amount of gelatinized starch, the thermal stability remained to a certain degree but continued to decrease. This was ascribed to the relatively low heat stability of starch. As for the mechanical properties, a significant increase in the tensile strength (up to 2 times) was observed when untreated starch was replaced with gelatinized starch in the blends. Similarly, the tear strength increased up to 1.5 times if gelatinized starch was employed. Apparently, the gelatinization of starch was efficiently achieved for promoting its compatibility with Bionolle. In all cases, the mechanical properties of Bionolle blended with gelatinized starch were better than those of Bionolle blended with untreated starch. A morphological investigation provided evidence in support of these findings. This relatively low-cost gelatinization approach provides an alternative to a high-cost compatibilizer approach for improving the performance of biodegradable blends.

A thermoplastic polyurethane elastomer/silica hybrid (TPU/SiO 2 ) was prepared using the sol-gel process. This work was undertaken to investigate the thermal and physical properties of this type of hybrid by employing different catalyst systems during sol-gel processing. Two types of catalyst systems including acetic acid (HOAc) and hydrochloric acid (HCl) were used to prepare sol particles. The mixing of the sol solution and TPU solution was then carried out to form a TPU/silica hybrid. Fourier transform IR spectra and dynamic mechanical properties were recorded to depict the enhanced interfacial interaction. Thermogravimetric analysis was used to determine the actual silica content forming in the hybrid and to evaluate the heat resistance of the hybrid. Mechanical properties such as the tensile strength and cutting strength were investigated at various concentrations of in situ silica. The tensile strength increased at all concentrations of silica. In contrast, the cutting strength decreased, probably because of a reduction of the energy dissipation from silica as physical crosslinks. The HOAc catalyzed system showed better optical properties than the HCl catalyzed system. The fracture surface was revealed through scanning electron microscopy to observe the degree of dispersion of SiO 2 , which in turn confirmed the results for the optical and mechanical properties.