Natural compounds from Punica granatum peel as multiple stabilizers for polyethylene

Punica granatum peel extractive (PPE), a novel stabilizer of polyethylene, is investigated in this study. Oxidation onset temperature (OOT), carbonyl index (CI), melt flow rate (MFR), tensile strength, and elongation at break are used to characterize the effects of PPE, which are also compared with commercial antioxidant (Irganox 1010) with the presence of tetrakis (2,4-di-tert-butylphenol)[1,1-biphenyl]-4,4′-diylbisphosphite (PEPQ). Long-term and short-term aging results show that samples modified by PPE or Irganox 1010 (PE-PPE_0.12%-P and PE-1010_0.12%-P samples) have comparable CI value and stability of OOT. However, compared with PE-PPE_0.12%-P sample, much higher CI and larger change of MFR is detected for PE-1010_0.12%-P after UV irradiation and five extrusions. It suggests that PPE is better protector for PE against UV light and mechanical shear force. All results indicate that the effect of PPE in protecting PE is comparable or much better than Irganox 1010 and it can be used as multiple stabilizers for PE. Moreover, the stabilities of PE modified with PPE alone (PE-PPE_2%) is also investigated. Results show that PE-PPE_2% sample has good thermo-oxidative, UV and processing stabilities. All results reveal that PPE is a good candidate of PE stabilizer and it could avoid the usage of PEPQ in protecting PE.     

Melt blending of poly(ethylene terephthalate) with polypropylene in the presence of silane coupling agent

A silane coupling agent (SCA) was used as a compatibilizer for polypropylene–poly(ethylene teraphthalate) (PP–PET) blends with 20, 40, 50, and 60% PET compositions by weight. PP–PET mixtures were blended with and without an SCA by a single‐screw extruder. The effect of silane modification on the tensile and impact properties of the blends was investigated. The morphology and thermal behavior of the blends were examined with scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The presence of the SCA used in this work extensively improved the mechanical properties of the blends. Mechanical properties were found to be highly dependent on the numbers of extrusions. SEM studies showed that substantially different morphology with better adhesion existed when SCA‐treated blends were compared to nontreated PP–PET blends. The presence of individual melting temperatures of the polymers in all compositions with no significant T_m depression indicated that PET and PP were crystallized separately. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1039–1048, 2003     

Effect of Reprocessing Cycles on the Morphology and Properties of Poly(propylene)/Wood Flour Composites Compatibilized with EBAGMA Terpolymer

The present study is aimed to investigate the effect of multiple extrusions of iPP/WF composites with and without EBAGMA used as compatibilizer. The degradation induced by the recycling processes was evaluated through changes in molecular structure, morphology, rheology, thermal and mechanical properties. The results showed that after six cycles, the presence of WF imparts stability to the composite materials. This effect was enhanced for the compatibilized samples. Further, SEM revealed better dispersion of the WF in the matrix. In contrast, it was confirmed that after the first recycling, both the molecular weight and the properties of PP drastically decreased due to chain scission resulting from degradation.

     

XPS and SEM study of UV laser surface modification of polymers

Several commercial polymers—poly(ethylene) (PE), poly(propylene) (PP), poly(vinylidene fluoride) (PVF₂), poly(vinyl chloride) (PVC) and polystyrene (PS)—were treated in air with an argon-fluorine UV excimer laser (λ = 193 nm). The polymer etch rate was investigated by two methods: quartz crystal microbalance (QCM) and piercing of films. X-ray photoelectron spectroscopy (XPS) analysis was performed on the modified surfaces after laser exposure at various fluences. Samples were subsequently analysed by scanning electron microscopy (SEM). From our results, polymers may be classified into two categories concerning their reactivity towards UV laser light. — the weakly absorbing polymers (e.g. PE, PP, PVF₂) where a photothermal process (thermal degradation) dominates the interaction. — the strongly absorbing polymers (e.g. PVC, PS) where a photochemical process (photoablation) dominates the interaction.     

Morphologies of polyethylene–ethylene/propylene/diene monomer particles in polypropylene‐rich polyolefin blends: Flake structure

Morphologies of polyethylene–ethylene/propylene/diene monomer (PE/EPDM) particles in 93/7 polypropylene (PP)/PE blends were investigated. SEM micrographs of KMnO₄‐etched cut surfaces and fracture surfaces of the blends revealed the existence of the “flake” structure. In the particles, crystalline PE formations with flake shape, which remain after etching, are called flakes. In addition to the PE‐crystalline flakes, amorphous PE, located between PE crystalline lamellae and EPDM rubber, complement the flake structure. The flakes are usually linked with the PP matrix, as seen in the heptane‐treated cut surfaces. These links, although observed with compatibilized samples, originate from the crystalline nature of PE particles, if no compatibilizer is added. Separately, the morphology of Royalene (consisting of high‐density PE and EPDM rubber, used as a PP/PE compatibilizer) was investigated by low‐voltage scanning TEM. The interaction of the components in the PE/EPDM blends can explain the formation of the flakes and toughening of the PP/PE blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3087–3092, 2003     

Hydrolytic degradation of poly[(R)-3-hydroxybutyric acid] in the melt

Poly[(R)-3-hydroxybutyric acid] [R-P(3HB)] was hydrolyzed in high-temperature and high-pressure water at the temperature range of 180-300 °C and for a period of 360 min. The formation, racemization, and decomposition of 3-hydroxybutyric acids (3HBs) and molecular weight change of R-P(3HB) were investigated. The highest yield of (R)-3-hydroxybutyric acid (R-3HB), ca. 80%, was obtained at 200 °C in the hydrolytic degradation periods of 240-360 min. Too-high hydrolytic degradation temperature such as 300 °C induced the decomposition and racemization of formed 3HBs, resulting in decreased yield of R-3HB. The hydrolytic degradation of R-P(3HB) proceeds homogeneously and randomly via a bulk erosion mechanism. The molecular weight of R-P(3HB) decreased exponentially without formation of low-molecular-weight specific peaks originating from crystalline residues. The hydrolytic degradation rates in the melt estimated from M_n changes were lower for R-P(3HB) than for poly(l-lactide) (PLLA) in the temperature range of 180-220 °C. The activation energy for the hydrolytic degradation (ΔE_h) of R-P(3HB) in the melt (180-250 °C) was 30.0 kcal mol⁻¹, which is higher than 12.2 kcal mol⁻¹ for PLLA in the melt in the temperature range (180-250 °C). This study reveals that hydrolytic degradation of PHB in the melt is an effective and simple method to obtain (R)-3HB and to prepare R-P(3HB) having different molecular weights without containing the specific low-molecular-weight chains, because of the removal of the effect caused by crystalline residues.     

Viscosity effect in polyolefin ternary blends and composites

Ternary blends of PP (80) /rubber (EPM, EPDM) (10) / PE (10) and PP (80) / rubber (10) / CaCO₃ (10) composites were prepared in a twin-screw extruder. With polyethylene (PE) viscosity comparable to, or higher than that of rubber, the dispersed phase formed a reticulate structure with reduced size. On the contrary, when the viscosity of PE was significantly lower than that of rubber, the dispersed phase formed almost homogeneous morphology. With reticulate morphology, PE crystallinity content, hardness, modulus, and elongation at break of the ternary blend increased. In polypropylene (PP) / rubber / CaCO₃ composites, better dispersion of CaCO₃ in the PP matrix was obtained when the viscosity of rubber was significantly higher than that of matrix. With better dispersion, hardness and tensile properties were improved, but the impact strength more or less decreased. © 1993 John Wiley & Sons, Inc.     

Improvement of Mechanical Properties of Jute Fibers-Polyethylene/Polypropylene Composites: Effect of Green Dye and UV Radiation

Jute-reinforced polyethylene (PE), polypropylene (PP) and mixture of PP/PE composites were prepared. It was found that 90% PP and 10% PE matrices based jute reinforced composites performed the better results. UV radiation at different intensities was applied both on matrices and jute. Mechanical properties of the irradiated jute- and matrices-based composites were found to increase significantly. Optimized jute fabrics were also treated with different concentrations of green dye (0.1–1%, w/w) with 2% K₂O₈S₂ in methanol solution for 2–8 min. A composite made of 0.5% green dye jute (5 min soaking time) and irradiated matrix showed the best mechanical properties.     

Design and performance evaluation of multilayer packaging films for blister packaging applications

Five multilayer packaging film structures consisting of amorphous poly(ethylene terephthalate) (APET), low‐density polyethylene (LDPE), polypropylene (PP), and acrylonitrile/methyl acrylate copolymer (Barex) films [i.e., APET/polyethylene (PE), APET/PP, APET/PE + UV inhibitor, APET/PP/PE, and APET/Barex/PP] for blister packaging applications were designed and produced. Blister containers with APET/PE and APET/Barex/PP structures were prepared, and their optical, mechanical, barrier (O₂, CO₂, and H₂O), physical, and product/package compatibility performance properties were evaluated. Package/product compatibility with simulants (soy sauce and sunscreen skin cream) at 37.8°C was evaluated for 3, 7, 14, and 28 days in the multilayer films and the blister containers. APET/Barex/PP film showed significantly better O₂ and CO₂ barrier performance than the other four film structures. The UV inhibitor had no significant effect on the barrier properties in the APET/PE film structure. All of the film structures showed high enough elastic storage modulus values to be applied to blister packaging in a broad range of temperatures between ?45 and 80°C. The glass‐transition temperature of APET, which was responsible for the elastic modulus of the multilayer structure, decreased after the samples were exposed to the skin cream. This decrease may have been due to the sorption of the skin cream's active ingredients, such as ethylhexyl methoxycinnamate. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Grafting of polystyrene branches to polyethylene and polypropylene

Polyethylene (PE) and polypropylene (PP) were reacted with benzoyl peroxide (BPO) and 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) to prepare PE‐TEMPO and PP‐TEMPO macroinitiators, respectively. Molecular weight of PP decreased, whereas that of PE increased during the reaction with the BPO/TEMPO system. Polystyrene (PS) branches were grafted to PE and PP backbone chains as a result of bulk polymerization of styrene with the PE‐TEMPO and PP‐TEMPO macroinitiators. A significant amount of PS homopolymer was produced as a byproduct. Weight of the resulting PE‐g‐PS and PP‐g‐PS increased with the polymerization time up to 20 h and then leveled off. Melting point of PE and PP domains in PE‐g‐PS and PP‐g‐PS, respectively, lowered as the content of PS in the copolymers increased. However, glass transition of the copolymers was almost identical with that of PS homopolymer, indicating that the constituents in the copolymers were all phase‐separated from each other. In scanning electron microscopy of the incompatible PE/PS, PP/PS, and PE/PP/PS compounded with PE‐g‐PS and PP‐g‐PS, any clear indication of enhanced adhesion between the phases was not observed. However, phase domains in the blends were, nevertheless, reduced significantly to raise mechanical properties such as maximum stress and elongation at break by 20–75%. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1103–1111, 2002     

Effects of rosin‐type nucleating agent and low density polyethylene on the crystallization process of polypropylene

In this article, the influence of rosin‐type nucleating agent (Nu–Na) and low density polyethylene (LDPE) on the crystallization process of polypropylene (PP) from the melt state was studied by differential scanning calorimeter and polarization microscope. It was found that LDPE obstructed the crystallization of PP, decreased the crystallization rate of PP. The rosin‐type nucleating agent Nu–Na substantially improved the rate of crystallization, and decreased the size of spherulites also. The cooperative effect of LDPE and Nu–Na made the crystallization rate of PP increase greatly, the spherulites of PP became much smaller and dispersed more uniformly, and the transparency of PP was further improved evidently. The crystallization temperature (T_c) and melting temperature (T_m) of PP and LDPE in PP/LDPE/Nu–Na (97:3:0.5) were not affected by the number of mixed passes—the nuclei migration from PP to PE had not happened in the mixed passes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2804–2809, 2003     

Studies on heterogeneous degradation of polypropylene/talc composite: Effect of iron impurity on the degradation behavior

In this study, an effect of iron oxide (Fe₂O₃) impurity in talc on degradation behavior of polypropylene (PP)/talc composite was studied using a PP/Fe₂O₃ model composite sample. The thermal oxidative degradation was performed at 100°C. Although the degradation of a pure PP sample hardly occurred at such temperature, the existence of Fe₂O₃ induced the PP degradation. The degraded PP part was formed around the Fe₂O₃ grain in the PP/Fe₂O₃ sample. It was found from the optical microscope observation that the degraded PP was able to diffuse only within the PP amorphous part. The analysis of the oxidation distribution on the degraded PP surface was performed employing a scanning electron microscope/electron dispersive spectrometer. The result showed that the PP spots in the vicinity of the Fe₂O₃ grain were unoxidized during the initial degradation process, and the oxidized PP spots were located at around 6 μm distance from the Fe₂O₃ grain. It was concluded that the degradation was initiated microscopically away from the Fe₂O₃ grain so that the Fe₂O₃ had both the abilities to accelerate the decomposition of PP hydroperoxide compounds and to reduce the produced radical species into nonradical products. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Suppression of radiation‐induced oxidation of polymers by sputtered silicon oxide coating

Oxygen barrier coating on polymers was attempted to obtain polymeric composite materials with improved radiation resistance. Silicon oxide (SiO_1.6) films ranging from 120 to 240 nm thick were formed on polypropylene (PP) and polyethylene (PE) by radio frequency (RF) magnetron sputtering. Oxygen permeability after SiO_1.6 deposition was reduced significantly in all samples studied, indicating that silicon oxide is a useful gas barrier. The oxygen permeability coefficient of deposited films for PP was 1.7–2.2 × 10^?14 cm³‐cm/cm²/s/cmHg and that for PE was 2.8–4.8 × 10^?13 cm³‐cm/cm²/s/cmHg. We studied the effect of such films on the radiation resistance of polymers in the presence of oxygen by microscopic infrared (IR) absorption spectroscopy. Silicon oxide films 180 nm thick were deposited on the surfaces of PP and PE, and the formation of carbonyl groups after irradiation in air was measured as a function of depth from the surface. Results compared with those for uncoated PE and PP showed that the radiation‐induced polymer oxidation is dramatically suppressed by silicon oxide coating. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 186–190, 2002     

Characterization of polypropylene and ethylene–propylene copolymer blends for industrial applications

The crystalline structure and physico‐mechanical properties of polypropylene (PP) blended with ethylene–propylene copolymer (EPM) were investigated. WAXS diffractograms showed that the addition of EPM did not affect the crystalline structure of PP. DSC curves revealed the presence of two T_g peaks indicating the amorphous phases of EPM and PP. As EPM increased, the elastomeric domains cavitated from PP matrix increased while the tensile stress and modulus of elasticity decreased. Impact strength, on the other hand, increased, and showed a remarkable effect at 30% EPM/PP. The properties of the blended polymers were compared with the commercial PP impact copolymer, and it was found that polyblends containing 30% EPM was suited for applications on products requiring very high impact strength. Further addition of EPM from 40 to 50% produced very high impact strength, but the tensile stress and modulus of elasticity were very low. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1200–1208, 2000     

Polypropylene plasticization and photodegradation with a TiO2/poly(ethylene oxide)/methyl linoleate paint photocatalyst system

The photodegradation of polypropylene (PP) film was performed by a TiO₂/polyethylene oxide (PEO)/plant oil paint photocatalyst system. The photodegradation underwent two stages of development as follows: Initially PP reacted with linoleic acid radical originated from the photoreaction of plant oil component. Second, the linoleic acid graft‐polymer was decomposed, and then PP chain scission was caused. The process was studied using methyl linoleate (ML) in detail. The melting point of the 24 h‐photodegraded PP slightly decreased, and those of the 48 h‐ and 96 h‐ones drastically did as compared with the pristine PP. The crystallinity (χ_c) decreased at the 48 h photodegradation time and drastically increased at the 96 h one. The 24 h‐photodegraded PP showed the 77% Young's modulus, 88% tensile strength, and 103% strain at break values to those of the pristine PP. The ML graft‐polymerization and decomposition brought about the PP plasticizing and chemi‐crystallization, causing the PP degradation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39909.     

Effect of branching of polyolefin backbone chain on catalytic gasification reaction

A basic study on the catalytic gasification of polyolefins such as PE and PP, which account for a major part of general waste plastics, was conducted in order to develop a technique for effective recycling of these wastes. In the case of PE, the gasification of PE is considered to consist of the following scheme: polymer → catalytically degraded polymer → catalytically degraded oligomer → liquid component → gas component. The gasification of PE does not occur directly from the polymer chains, but gaseous C₄ substances are selectively found from the liquid components with the highest branching frequency. The overall yield of C₄ components including isobutane was 74.5 and 60.5% molar for PE and PP. These liquid components (gasification precursors) have the branching frequencies. For example, a molecule with M?_w of 400 contains about eight branches for every 30 methylenes. From the catalytic gasification of PE, PP, and PIB, the gas conversion rate is also found to increase with increasing frequency of the backbone branching. It is concluded that the branching frequency is the key factor governing the gas conversion rate of polyolefins.     

Compositional differences of propylene–ethylene block copolymers manufactured by degradation and hydrogenation techniques

The purpose of the present work is to investigate the compositional difference of polypropylene–polyethylene block copolymers (PP‐b‐PE) manufactured industrially by the process of degradation and hydrogenation, respectively. Each of the PP‐b‐PE copolymers was fractionated into three fractions with heptane and chloroform. The compositions of the three fractions were characterized by ¹³C nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy, as well as differential scanning calorimetry (DSC) and thermal fractionation. The results showed that the Chloroform‐soluble fraction was amorphous ethylene‐propylene rubber, and the content of the rubber in PP‐b‐PE manufactured by hydrogenation was less than that by degradation. The degree of crystallinity of the chloroform‐insoluble fraction of the PP‐b‐PE manufactured by hydrogenation is higher than that of by degradation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3301–3306, 2006     

Surface modification of polyolefine by UV light/ozone treatment

The surface modification of polyethylene (PE) and polypropylene (PP) was investigated by UV light/ozone (UVO) treatment. The surface oxygenation was determined by electron spectroscopy for chemical analysis (ESCA). As shown from ESCA spectra, after UVO treatment, oxygen-containing functional groups, such as carbonyl, carboxyl, and ether groups, were produced in the sample surface. The dependence of oxygenation extent (as measured by O_1s/C_1s value of ESCA spectra) on different experimental conditions, such as irradiation time, temperature, and O₂ flow rate, was obtained. It was shown that after UVO treatment at suitable conditions the surface properties of polyolefine samples, such as hydrophilicity, adhesion property, and dyeability, were improved remarkably. Furthermore, UVO treatment in short time does not have notable effect on the ageing property. It was concluded that UVO treatment is a promising technique to modify polyolefine surface properties. © 1996 John Wiley & Sons, Inc.     

Photocatalytic Degradation of Polyethylene Plastic with Polypyrrole/TiO2 Nanocomposite as Photocatalyst

The photocatalytic degradation of polyethylene (PE) plastic was carried out directly under the sunlight irradiation with polypyrrole/TiO₂ (PPy/TiO₂) nanocomposite as photocatalyst, which prepared by sol-gel and emulsion polymerization methods. The photocatalytic degradation efficiency was determined by weight loss monitoring, gel permeation chromatography (GPC), atomic force microscopic (AFM) and FT-IR analysis. The photocatalytic degradations of PE plastic with pure TiO₂ and PPy were also investigated and compared with that of PPy/TiO₂. It was noticed that irradiating the PE plastic for 240 h by sunlight reduced its weight up to 35.4% and 54.4% of M _w, respectively. The AFM images showed the formation of cavities on PE plastic surface. FT–IR spectroscopic studies indicated that a strong interaction existed between the interface of PE and PPy/TiO₂ and caused the degradation of PE. The photocatalytic degradation mechanism was also discussed briefly.