Thermal properties and degradation characteristics of polylactide,linear low density polyethylene,and their blends

Melt blending of linear low density polyethylene (LLDPE) and polylactide (PLLA) was performed in an extrusion mixer with post extrusion blown film attachment with and without compatibilizer-grafted low density polyethylene maleic anhydride. The blend compositions were optimized for tensile properties as per ASTM D 882-91. Based on this, LLDPE 80 (80 wt% LLDPE & 20 wt% PLLA) and M-g-L 80/4 (80 wt% LLDPE, 20 wt% PLLA and 4 parts compatibilizer per hundred parts of resin) were found to be an optimum composition. FTIR reveals that the presence of compatibilizer shifts carbonyl peak hence some increase in interaction between LLDPE and PLLA. Morphological characteristics of the fracture surface of with and without compatibilizer blends were examined by scanning electron microscopy. It shows that use of compatibilizer enhances the dispersions of PLLA in LLDPE matrix. Thermogravimetric (TG) analysis of blends shows the M-g-L 80/4 blend has higher thermal stability among studied blends. The degradation study under different pH of soil compost gives that in alkaline condition and the presence of compatibilizer was favorable for degradation. This blend may be used for packaging application.     

Degradation behaviors of linear low‐density polyethylene and poly(L‐lactic acid) blends

In this study, the degradability of linear low‐density polyethylene (LLDPE) and poly(L ‐lactic acid) (PLLA) blend films under controlled composting conditions was investigated according to modified ASTM D 5338 (2003). Differential scanning calorimetry, X‐ray diffraction, and Fourier transform infrared spectroscopy were used to determine the thermal and morphological properties of the plastic films. LLDPE 80 (80 wt % LLDPE and 20 wt % PLLA) degraded faster than grafted low‐density polyethylene–maleic anhydride (M‐g‐L) 80/4 (80 wt % LLDPE, 20 wt % PLLA, and 4 phr compatibilizer) and pure LLDPE (LLDPE 100). The mechanical properties and weight changes were determined after composting. The tensile strength of LLDPE 100, LLDPE 80, and M‐g‐L 80/4 decreased by 20, 54, and 35%, respectively. The films, as a result of degradation, exhibited a decrease in their mass. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Toughening of polylactide by melt blending with linear low‐density polyethylene

Melt blending of polylactide and linear low‐density polyethylene (LLDPE) was performed in an effort to toughen polylactide. In addition, two model polylactide‐polyethylene (PLLA‐PE) block copolymers were investigated as compatibilizers. The LLDPE particle size and the impact resistance of binary and ternary blends were measured to determine the extent of compatibilization. For the amorphous polylactide (PLA), toughening was achieved only when a PLLA‐PE block copolymer was used as a compatibilizer. For the semicrystalline polylactide (PLLA), toughening was achieved in the absence of block copolymer. To decrease the variability in the impact resistance of the PLLA/LLDPE binary blend, as little as 0.5 wt % of a PLLA–;PE block copolymer was effective. The differences that were seen between the PLA and PLLA binary blends were investigated with adhesion testing. The semicrystalline PLLA did show significantly better adhesion to the LLDPE. We propose that tacticty effects on the entanglement molecular weight or miscibility of polylactide allow for the improved adhesion between the PLLA and LLDPE. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3757–3768, 2003     

Linear low‐density polyethylene/poly(ethylene terephthalate) blends compatibilization prepared by an eccentric rotor extruder: A morphology,mechanical, thermal,and rheological study

In this study, various poly(ethylene terephthalate) (PET) and linear low‐density polyethylene (LLDPE) with maleic anhydride‐grafted LLDPE (LLDPE‐g‐MAH) compatibilizer were melt blended under an elongational flow. A novel extrusion device, eccentric rotor extruder (ERE), was developed to supply such flow during the process. Including morphology, mechanical properties, melting behavior, and rheological behavior were studied. The morphological study showed that the compatibility between LLDPE and PET was greatly improved with LLDPE loading up to 80 wt %. Mechanical tests indicated that LLDPE could toughen PET to some extent. Moreover, a comparison of samples prepared between ERE and conventional extruder was made and demonstrated the sample prepared by ERE can exhibit better mechanical properties. Differential scanning calorimetry results revealed that PET can promote the crystallinity of LLDPE. Rheological behavior indicated that the complex viscosity of the blends exhibited strong shear thinning phenomenon with increasing LLDPE content, particularly in high‐frequency range blend with the LLDPE weight ratio of 80 wt % was more sensitivity to shear rate than neat LLDPE. The G′‐G″ curves of the blends also revealed that the microstructure of the blends changed significantly with the addition of LLDPE which was consistent with the scanning electron micrographs that PET particles became smaller and distributed more uniform with increasing LLDPE content. Furthermore, the blends showed similar stress relaxation mechanism with adding LLDPE content from 60 to 100 wt %. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46489.     

Recycled poly(ethylene terephthalate)/linear low‐density polyethylene blends through physical processing

Poly(styrene‐ethylene/butylene‐styrene) (SEBS) was used as a compatibilizer to improve the thermal and mechanical properties of recycled poly(ethylene terephthalate)/linear low‐density polyethylene (R‐PET/LLDPE) blends. The blends compatibilized with 0–20 wt % SEBS were prepared by low‐temperature solid‐state extrusion. The effect of SEBS content was investigated using scanning electron microscope, differential scanning calorimeter, dynamic mechanical analysis (DMA), and mechanical property testing. Morphology observation showed that the addition of 10 wt % SEBS led to the deformation of dispersed phase from spherical to fibrous structure, and microfibrils were formed at the interface between two phases in the compatibilized blends. Both differential scanning calorimeter and DMA results revealed that the blend with 20 wt % SEBS showed better compatibility between PET and LLDPE than other blends studied. The addition of 20 wt % of SEBS obviously improved the crystallizibility of PET as well as the modulus of the blends. DMA analysis also showed that the interaction between SEBS and two other components enhanced at high temperature above 130°C. The impact strength of the blend with 20 wt % SEBS increased of 93.2% with respect to the blend without SEBS, accompanied by only a 28.7% tensile strength decrease. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of different compatibilizers on the rheological,thermomechanical, and morphological properties of HDPE/LLDPE blend‐based nanocomposites

The influence of two different compatibilizers and their combination (maleic anhydride grafted high density polyethylene, HDPE‐g‐MA; maleic anhydride grafted linear low density polyethylene, LLDPE‐g‐MA; and 50/50 wt % mixture of these compatibilizers) on the rheological, thermomechanical, and morphological properties of HDPE/LLDPE/organoclay blend‐based nanocomposites was evaluated. Nanocomposites were obtained by melt‐intercalation in a torque rheometer in two steps. Masterbatches (compatibilizer/nanoclay 2:1) were obtained and subsequently diluted in the HDPE/LLDPE matrix producing nanocomposites with 2.5 wt % of nanoclay. Wide angle X‐ray diffraction (WAXD), steady‐state rheological properties, and transmission electron microscopy (TEM) were used to determine the influence of different compatibilizer systems on intercalation and/or exfoliation process which occurs preferentially in the amorphous phase, and thermomechanical properties. The LLDPE‐g‐MA with a high melt index (and consequently low viscosity and crystallinity) was an effective compatibilizer for this system. Furthermore, the compatibilized nanocomposites with LLDPE‐g‐MA or mixture of HDPE‐g‐MA and LLDPE‐g‐MA exhibited better nanoclay's dispersion and distribution with stronger interactions between the matrix and the nanoclay. These results indicated that the addition of maleic anhydride grafted polyethylene facilitates both, the exfoliation and/or intercalation of the clays and its adhesion to HDPE/LLDPE blend. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1726–1735, 2013     

Blends of high density polyethylene and poly(l‐lactic acid): Mechanical and thermal properties

The blends of high‐density polyethylene (HDPE) and poly(l ‐lactic acid) (PLLA) were prepared by melt blending method in an extrusion mixer with a postextrusion blown film attachment. The ratios of HDPE/PLLA blends were taken as 100/0, 95/5, 90/10, 85/15, and 80/20. The 80/20 blend was further compatibilized by adding maleic anhydride‐grafted polyethylene in different ratios (up to 8 wt%). Based on the mechanical properties of the films, the compositions HDPE80 (80% HDPE and 20% PLLA) and HD80C4 (80% HDPE, 20% PLLA, and 4% compatibilizer) were found to be optimum and considered for further analysis. The thermal properties of these selected blends were investigated by means of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA study revealed that the addition of the PLLA somewhat decreased the thermal stability of HDPE. DSC investigation showed that the blends were partially miscible only. X‐ray diffraction (XRD) analysis enlightened that the crystallinity of blends was slightly increased with addition of PLLA. Immiscibility of the two polymers was diminished in the presence of compatibilizer, as indicated by the scanning electron microscopy (SEM) of the blends. These partially biodegradable blends may be used for flexible packaging applications. POLYM. ENG. SCI., 54:2155–2160, 2014. © 2013 Society of Plastics Engineers     

Properties of uncompatibilized and compatibilized poly(butylene terephthalate)–LLDPE blends

In this work, blends of poly(butylene terephthalate) (PBT) and linear low‐density polyethylene (LLDPE) were prepared. LLDPE was used as an impact modifier. Since the system was found to be incompatible, compatibilization was sought for by the addition of the following two types of functionalized polyethylene: ethylene vinylacetate copolymer (EVA) and maleic anhydride‐grafted EVA copolymer (EVA‐g‐MAH). The effects of the compatibilizers on the rheological and mechanical properties of the blends have been also quantitatively investigated. The impact strength of the PBT–LLDPE binary blends slightly increased at a lower concentration of LLDPE but increased remarkably above a concentration of 60 wt % of LLDPE. The morphology of the blends showed that the LLDPE particles had dispersed in the PBT matrix below 40 wt % of LLDPE, while, at 60 wt % of LLDPE, a co‐continuous morphology was obtained, which could explain the increase of the impact strength of the blend. Generally, the mechanical strength was decreased by adding LLDPE to PBT. Addition of EVA or EVA‐g‐MAH as a compatibilizer to PBT–LLDPE (70/30) blend considerably improved the impact strength of the blend without significantly sacrificing the tensile and the flexural strength. More improvement in those mechanical properties was observed in the case of the EVA‐g‐MAH system than for the EVA system. A larger viscosity increase was also observed in the case of the EVA‐g‐MAH than EVA. This may be due to interaction of the EVA‐g‐MAH with PBT. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 989–997, 1999     

Rheological,morphological, and heat seal properties of linear low density polyethylene and cyclo olefine copolymer (LLDPE/COC) blends

The rheological and morphological properties of linear low‐density polyethylene/cyclo olefin copolymer (LLDPE/COC) blends were investigated, as were their peel seal characteristics when heat sealed to films of either polyethylene (PE) or polyethylene terephtalate (PET). Three blend systems, with COC volume percentages of 5, 10, and 15%, were melt blended in a twin‐screw extruder. A partial phase miscibility/compatibility was initially suggested by Cole–Cole and equivalent plots of the dynamic rheological properties and subsequently confirmed by scanning electron microscopy. The investigation of the systems' heat sealing properties pointed out an interesting industrial potential for PET sheets covered with a fine layer of a LLDPE/COC blend before heat sealing to a PE film for packaging applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermostimulative shape memory effect of linear low‐density polyethylene/polypropylene (LLDPE/PP) blends compatibilized by crosslinked LLDPE/PP blend (LLDPE–PP)

A novel linear low‐density polyethylene (LLDPE)/polypropylene (PP) thermostimulative shape memory blends were prepared by melt blending with moderate crosslinked LLDPE/PP blend (LLDPE–PP) as compatibilizer. In this shape memory polymer (SMP) blends, dispersed PP acted as fixed phase whereas continuous LLDPE phase acted as reversible or switch phase. LLDPE–PP improved the compatibility of LLDPE/PP blends as shown in scanning electron microscopic photos. Dynamic mechanical analysis test showed that the melt strengths of the blends were enhanced with increasing LLDPE–PP content. A shape memory mechanism for this type of SMP system was then concluded. It was found that when the blend ratio of LLDPE/PP/LLDPE–PP was 87/13/6, the blend exhibited the best shape memory effect at stretch ratio of 80%, stretch rate of 25 mm/min, and recovery temperature of 135°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Dynamic rheological,morphology and mechanical properties of compatibilized LLDPE/EMA blends

Blends of linear low density polyethylene (LLDPE) and ethylene-co-methyl acrylate (EMA) having 60/40 composition was studied with and without compatibilizing agent. The compatibilizing agent used was maleic anhydride grafted linear low density polyethylene (LLDPE-g-MA). The LLDPE backbones of the compatibilizer are compatible with LLDPE blend component, whereas the maleic anhydride is affinated with carbonyl groups of EMA. The effectiveness of the compatibilizing agent was evaluated using different techniques like mechanical, thermal, scanning electron microscopy and rheological studies. Best compatibilization effect was found in the blend at a loading of 3 wt% of compatibilizer since at this level of compatibilizer complex viscosity, tensile strength, modulus, elongation at break, impact strength was found to be higher. The increase in the melt viscosity, storage modulus and thermal stability of the compatibilized blends indicated enhanced interactions between the discrete LLDPE and EMA phases induced by the functional compatibilizer.     

Processability and mechanical properties for binary blends of PP and LLDPE produced by metallocene catalyst

Processability at extrusion coating and mechanical properties of the films obtained are investigated by means of linear and nonlinear rheological measurements and tensile tests for blends of polypropylene (PP) and linear low‐density polyethylene (LLDPE). Both materials are produced by metallocene catalyst. The processability of PP is found to be improved by the addition of LLDPE; the blend shows low level of motor torque and head pressure in an extruder and small level of neck‐in as compared with pure PP. Further, the anisotropy of ultimate tensile strength, which is prominent for PP, is reduced by blending with LLDPE. As a result, the blend having 20 wt % of LLDPE shows appropriate properties in the molten state for extrusion coating and in the solid state as a film. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Fabrication and properties of poly(l‐lactide) nanofibers via blend sea‐island melt spinning

Poly(l ‐lactide) (PLLA) nanofibers were prepared by melt extrusion of immiscible blends of PLLA/low density polyethylene (LDPE) and subsequent removal of the LDPE matrix from the blend fibers. The effect of blends composition and draw ratio on the phase structure of the blend fibers, crystallization, mechanical properties, and the diameter of the PLLA nanofibers was investigated. It is found that the diameter of the PLLA phase gradually increases with the increase of PLLA content. With the variation of PLLA content from 50 to 60 wt %, the average diameter of acquired PLLA nanofibers changes from 119 to 153 nm under the draw ratio of 1.5. When further increasing the content of PLLA to 65%, it is difficult to acquire PLLA nanofibers due to the poor dissolving properties between PLLA and LDPE components. Oriented PLLA nanofibers with the average diameter of 92 nm can be fabricated from PLLA/LDPE (50/50, wt %) blends under the draw ratio of 2. The present results suggest that it is possible to acquire polymer nanofibers with high output using blend sea‐island melt spinning. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41228.     

Morphology and rheological properties of compatibilized low‐density polyethylene/linear low‐density polyethylene/thermoplastic starch blends

Morphology and rheological properties of low‐density polyethylene/linear low‐density polyethylene/thermoplastic starch (LDPE/LLDPE/TPS) blends are experimentally investigated and theoretically analyzed using rheological models. Blending of LDPE/LLDPE (70/30 wt/wt) with 5–20 wt % of TPS and 3 wt % of PE‐grafted maleic anhydride (PE‐g‐MA) as a compatibilizer is performed in a twin‐screw extruder. Scanning electron micrographs show a fairly good dispersion of TPS in PE matrices in the presence of PE‐g‐MA. However, as the TPS content increases, the starch particle size increases. X‐ray diffraction patterns exhibit that with increase in TPS content, the intensity of the crystallization peaks slightly decreases and consequently crystal sizes of the blends decrease. The rheological analyses indicate that TPS can increase the elasticity and viscosity of the blends. With increasing the amount of TPS, starch particles interactions intensify and as a result the blend interface become weaker which are confirmed by relaxation time spectra and the prediction results of emulsion Palierne and Gramespacher‐Meissner models. It is demonstrated that there is a better agreement between experimental rheological data and Coran model than the emulsion models. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44719.     

Melt rheology and morphology of LLDPE/EVA blends: Effect of blend ratio,compatibilization, and dynamic crosslinking

The melt rheological properties of linear low‐density polyethylene (LLDPE)/ethylene vinyl acetate (EVA) blends were investigated with special reference to the effect of blend ratio, temperature, shear rate, compatibilization, and dynamic vulcanization. The melt viscosity of the blends determined with a capillary rheometer is found to decrease with an increase of shear rate, which is an indication of pseudoplastic behavior. The viscosity of the blend was found to be a nonadditive function of the viscosities of the component polymers. A negative deviation was observed because of the interlayer slip between the polar EVA and the nonpolar LLDPE phases. The melt viscosity of these blends decreases with the increased concentration of EVA. The morphology of the extrudate of the blends at different shear rates and blend ratios was studied and the size and distribution of the domains were examined by scanning electron microscopy. The morphology was found to depend on shear rate and blend ratio. Compatibilization of the blends with phenolic‐ and maleic‐modified LLDPE increased the melt viscosity at lower wt % of compatibilizer and then leveled off. Dynamic vulcanization is found to increase the melt viscosity at a lower concentration of DCP. The effect of temperature on melt viscosity of the blends was also studied. Finally, attempts were made to correlate the experimental data on melt viscosity and cocontinuity region with different theoretical models. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3210–3225, 2002     

Morphology and mechanical properties of blends of linear low density polyethylene and poly(ethene‐propene‐1‐butene)

Blends of linear low density polyethylene (LLDPE) and ethene‐propene‐1‐butene copolymer (t‐PP) were obtained through mechanical mixing using a single‐screw extruder with different compositions: 20, 40, 50, 60, and 80 wt % of t‐PP. For this, two types of polyethylene were used: 1‐hexene comonomer and 1‐octene comonomer based. The same blends were prepared in a batch mixer and the torque and temperature were analyzed. The torque showed a decrease with increasing t‐PP content, indicating better processability of the mixture in comparison with LLDPE. The morphology of the blends was analyzed by SEM and showed a composition dependence. The mechanical properties of the blends were evaluated by tensile tests. The results revealed that the best properties were obtained in a 20% t‐PP blend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1255–1261, 2006     

Increasing the compatibility of poly(l‐lactide)/poly(para‐dioxanone) blends through the addition of poly(para‐dioxanone‐co‐l‐lactide)

To modify the mechanical properties of a poly(l ‐lactide) (PLLA)/poly(para‐dioxanone) (PPDO) 85/15 blend, poly(para‐dioxanone‐co‐l ‐lactide) (PDOLLA) was used as a compatibilizer. The 85/15 PLLA/PPDO blends containing 1–5 wt % of the random copolymer PDOLLA were prepared by solution coprecipitation. Then, the thermal, morphological, and mechanical properties of the blends with different contents of PDOLLA were studied via differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and tensile testing, respectively. The DSC result revealed that the addition of PDOLLA into the blends only slightly changed the thermal properties by inhibiting the crystallization degree of the poly(l ‐lactide) in the polymer blends. The SEM photos indicated that the addition of 3 wt % PDOLLA into the blend was ideal for making the interface between the PLLA and PPDO phases unclear. The tensile testing result demonstrated that the mechanical properties of the blends containing 3 wt % PDOLLA were much improved with a tensile strength of 48 MPa and a breaking elongation of 214%. Therefore, we concluded that the morphological and mechanical properties of the PLLA/PPDO 85/15 blends could be tailored by the addition of the PDOLLA as a compatibilizer and that the blend containing a proper content of PDOLLA had the potential to be used as a medical implant material. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41323.     

Correlation between the morphology and dynamic mechanical properties of ethylene vinyl acetate/linear low‐density polyethylene blends: Effects of the blend ratio and compatibilization

The effects of the blend composition and compatibilization on the morphology of linear low‐density polyethylene (LLDPE)/ethylene vinyl acetate (EVA) blends were studied. The blends showed dispersed/matrix and cocontinuous phase morphologies that depended on the composition. The blends had a cocontinuous morphology at an EVA concentration of 40–60%. The addition of the compatibilizer first decreased the domain size of the dispersed phase, which then leveled off. Two types of compatibilizers were added to the polymer/polymer interface: linear low‐density polyethylene‐g‐maleic anhydride and LLDPE‐g phenolic resin. Noolandi's theory was in agreement with the experimental data. The conformation of the compatibilizer at the blend interface could be predicted by the calculation of the area occupied by the compatibilizer molecule at the interface. The effects of the blend ratio and compatibilization on the dynamic mechanical properties of the blends were analyzed from ?60°C to +35°C. The experiments were performed over a series of frequencies. The area under the curve of the loss modulus versus the temperature was higher than the values obtained by group contribution analysis. The loss tangent curve showed a peak corresponding to the glass transition of EVA, indicating the incompatibility of the blend system. The damping characteristics of the blends increased with increasing EVA content because of the decrease in the crystalline volume of the system. Attempts were made to correlate the observed viscoelastic properties of the blends with the morphology. Various composite models were used to model the dynamic mechanical data. Compatibilization increased the storage modulus of the system because of the fine dispersion of EVA domains in the LLDPE matrix, which provided increased interfacial interaction. Better compatibilization was effected at a 0.5–1% loading of the compatibilizer. This was in full agreement with the dynamic mechanical spectroscopy data. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4526–4538, 2006     

Effect of cross‐linked LLDPE/PP blend (LLDPE‐PP) as compatibilizer on morphology,crystallization behavior and mechanical property of LLDPE/PP blends

Moderate cross‐linked blend (LLDPE‐PP) of linear low‐density polyethylene (LLDPE) and polypropylene (PP) with benzoyl peroxide (BPO) were prepared by the reactive melt mixing in HAAKE mixer. Effect of LLDPE‐PP as compatibilizer on the morphology, crystallization behavior and mechanical properties of LLDPE/PP (87/13) blends were studied using scanning electron microscopy (SEM), polarized optical microscopy (POM), wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC) and mechanical testing machines. The results showed that LLDPE‐PP not only improved the interfacial adhesion between the LLDPE and PP but also acted as selective nucleating agent for crystal modification of PP. In the blends, the sizes of LLDPE and PP spherulites became smaller, and their melting enthalpies reduced in the presence of LLDPE‐PP. Furthermore, the mechanical properties of LLDPE/PP blends were improved with the addition of LLDPE‐PP, and when the concentration of LLDPE‐PP was 2 phr, the ternary blend had the best mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Studies on mechanical and thermal properties of ternary blends of polyethylenes. I

Six film samples of varying compositions of linear low‐density polyethylene (LLDPE), 10–35 wt %, and high‐density polyethylene (HDPE), 40–65 wt %, having a fixed percentage of low‐density polyethylene (LDPE) at 25 wt % were extruded by melt blending in a single‐screw extruder (L/D ratio = 20 : 1) of uniform thickness of 2 mil. The tensile strength, elongation at break, and impact strength were found to increase up to 60 wt % HDPE addition, starting from 40 wt % HDPE, in the blends and then decreased. The blend sample B‐500 was found to be more thermally stable than its counterparts. The appearance of a single peak beyond 45 wt % HDPE content in the blend in dynamic DSC scans showed the formation of miscible blend systems and this was further confirmed by scanning electron microscopic analysis. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1691–1698, 2005