Susceptibility of starch-filled and starch-based LDPE to oxygen in water and air

The susceptibility of starch-filled and starch-based polyethylenes to oxygen in water and air was analyzed and compared. LDPE containing 7.7% starch and a pro-oxidant formulation in the form of masterbatch (LDPE-MB) was compared to pure LDPE, LDPE with 7.7% starch (LDPE-starch), and a blend with 70% starch and 30% ethylene maleic anhydride (starch-EMA). Thermal ageing at 80°C in air and water was followed by monitoring the molecular weight changes, the formation of carbonyl groups, and degradation products by SEC, FTIR, and GC-MS. It was demonstrated that LDPE-MB was the most susceptible material to degradation in both environments, although the degradation was faster in air than in water. The slower degradation in water is explained by a deactivation or leaching out of the pro-oxidant during the aging. The degradation of pure LDPE and starch-EMA is faster in water than in air. LDPE-starch was the only material that did not degrade during 11 weeks in water at 80°C. The addition of starch to LDPE made this material even more stable than pure LDPE to aging in water. The molecular weight distribution of LDPE-MB narrowed during aging in air. In water, on the other hand, the MWD of LDPE-MB, LDPE, and LDPE-starch broadened. The lower oxygen concentration in water increases the probability for molecular enlargement reactions in comparison to the case in air. Mono- and dicarboxylic acids were the major products identified in both environments. Ketoacids were formed in both air and water, but ketones and hydrocarbons were only identified after aging in air. Either these products are not formed or they remain in the polymer matrix rather than migrate out into the water. Lactic acid and 2-furancarboxaldehyde were only identified in the starch-EMA material degraded in water at 80°C. LDPE, LDPE-starch, and starch-EMA did not form any degradation products during 11 weeks at 80°C in air in agreement with the neglible molecular weight changes observed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 959–967, 1997     

Effect of film draw temperature (FDT) on physical properties of polyethylene

Thin polymer films (0.06 mm thick) were prepared with LLDPE (coded as A) and LDPE (coded as D) at different film draw temperatures (FDTs) from 5 to 65°C. There was about a 42% enhancement of the tensile strength when the LLDPE film was drawn at 45°C and LDPE at 35°C and the ultimate elongation increased between 14 and 32%. When various additives were incorporated into these resins A and D, the tensile strength slightly decreased, but the ultimate elongation increased. Films which attained the highest tensile properties showed the maximum resistance against degradation by natural outdoor weathering. Although irradiation of these films by a gamma source caused reduction of their tensile properties, there was a general tendency of resisting this reduction with increase of the FDT. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 459–465, 2003     

Characterization and properties of LDPE film with gallic‐acid‐based oxygen scavenging system useful as a functional packaging material

We prepared and characterized active, oxygen‐scavenging, low density polyethylene (LDPE) films from a non‐metallic‐based oxygen scavenging system (OSS) containing 1, 3, 5, 10, and 20% of gallic acid (GA) and potassium chloride (PC). We compared the surface morphology and mechanical, permeability, and optical properties of the oxygen‐scavenging LDPE film with those of pure LDPE film. The surface morphology, gas barrier, and thermal properties indicate that the OSS was well incorporated into the LDPE film structure. The surface roughness of the film increased with the amount of oxygen scavenging material. The oxygen and water vapor permeability of the developed film also increased with the amount of oxygen scavenging material, though its elongation decreased. The oxygen scavenging capability of the prepared film was analyzed at different temperatures. The initial oxygen content (%) in the vial headspace, 20.90%, decreased to 16.6% at 4 °C, 14.6% at 23 °C, and 12.7% at 50 °C after 7 days of storage with the film containing 20% OSS. The film impregnated with 20% organic oxygen scavenging material showed an effective oxygen scavenging capacity of 0.709 mL/cm² at 23 °C. Relative humidity triggered the oxygen scavenging reaction. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44138.     

Development of value-added polyethylene grades with extended service lifetime: Weathering resistant flame retarded materials for outdoor applications

The current article deals with the development of different novel, tailor-made polyolefin formulations exhibiting both low flammability and high weathering resistance, so as to provide value-added polyethylene grades with extended service lifetime. Two low-density (LDPE) and one linear low-density (LLDPE) polyethylene grades were modified via melt compounding with an additive system comprising: (a) a nitrogen-phosphorous intumescent system for flame retardance and (b) a hindered amine light stabilizer and a benzophenone-type UV absorber for UV/heat stabilization, at a total loading of 30–35 wt%. The target was to reach V0 classification in UL94V flammability tests, while to a large extent maintaining the mechanical properties, such as, tensile and impact strength of the investigated polymers, thus ensuring that the additives do not interfere significantly with the material quality. Subsequently, the compounds were subjected to separate artificial UV and heat aging at 100°C for 1500 h; the formulations showed good flame retardance, even after prolonged artificial weathering, but there was an observable, although acceptable, decrease in the mechanical properties. Nevertheless, all the results show that the developed polyethylene compounds are very promising for outdoor applications, such as, irrigation piping and profiles, where long-term weathering stability is important, and where flame retardance is important for safety during storage.     

Structure–property relationships of composite films

Coextruded multifilms of varying chemical composition and structure were studied by the dynamic mechanical technique. The films studied were two- and three-ply combinations of a polyimide (Kapton) and fluorinated ethylene–propylene copolymer (FEP) and four other two-ply polyethylene and modified polyethylene composites: low-density polyethylene (LDPE)–ionomer, rubber-modified high-density polyethylene (HDPE)–ionomer; ethylene–vinyl acetate (EVA) copolymer–LDPE, and EVA-modified HDPE–LDPE. The mechanical spectra of individual film components were also obtained at 110 Hz between ?120° and 120°C (220°C for the Kapton–FEP system). Mechanical relaxations were examined to determine the degree of interaction between adjacent films and correlate them with tensile and ultimate properties of the composite.     

Surface modification of low‐density polyethylene (LDPE) film and improvement of adhesion between evaporated copper metal film and LDPE

To improve the interfacial adhesion between evaporated copper film and low‐density polyethylene (LDPE) film, the surface of LDPE films was modified by treating with chromic acid [K₂Cr₂O₇/H₂O/H₂SO₄ (4.4/7.1/88.5)]/oxygen plasma. Chromic‐acid‐etched LDPE was exposed to oxygen plasma to achieve a higher content of polar groups on the LDPE surface. We investigated the effect of the treatment time of chromic acid in the range of 1–60 min at 70°C and oxygen plasma in the range of 30–90 sec on the extent of polar groups created on the LDPE. We also investigated the surface topography of and water contact angle on the LDPE film surface, mechanical properties of the LDPE film, and adhesion strength of the evaporated copper metal film to the LDPE film surface. IR and electron spectroscopy for chemical analysis revealed the introduction of polar groups on the modified LDPE film surface, which exhibited an improved contact angle and copper/LDPE adhesion. The number of polar groups and the surface roughness increased with increasing treatment time of chromic acid/plasma. Water contact angle significantly decreased with increasing treatment time of chromic acid/plasma. Combination treatment of oxygen plasma with chromic acid drastically decreased the contact angle. When the treatment times of chromic acid and oxygen plasma were greater than 10 min and 30 sec, respectively, the contact angle was below 20°. With an increasing treatment time of chromic acid, the tensile strength of the LDPE film decreased, and the film color changed after about 10 min and then became blackened after 30 min. With the scratch test, the adhesion between copper and LDPE was found to increase with an increasing treatment time of chromic acid/oxygen plasma. From these results, we found that the optimum treatment times with chromic acid and oxygen plasma were near 30 min and 30 sec, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1677–1690, 2001     

Thermal properties of poly[N,N′-(4,4′-diphenyl ether) 4-amidophthalimide] film

The aging behavior of a polyamide–imide film was investigated. Film samples have been exposed to temperatures from 225° to 350°C for various times and the mechanical and electrical properties measured. This information was used to construct log life plots to gain an insight into the service life of this material. TGA and DTA results coupled with the information from the aging tests indicate that this film can be used at temperatures of 180° to 200°C for extended periods of time. Mechanical properties, especially elongation, of the film deteriorate faster than the electrical properties.     

Effects of aging on the thermomechanical properties of poly(lactic acid)

In this study, we examined the role of environmental parameters and physical structure in the aging process of poly(lactic acid) (PLA). The role of heating history on the aging behavior of the material was also investigated. PLA samples with a D ‐content of 4.25% were exposed to a relative humidity of 80% at three different temperatures, 20, 40, and 50°C (below the glass‐transition temperature of the material), at various aging periods of 30, 60, 80, 100, and 130 days. Selected samples were subjected to two consecutive heating runs. The stability of PLA was monitored by a number of techniques, including size exclusion chromatography, differential scanning calorimetry, dynamic mechanical analysis, and tensile measurements. The initial thermal processing (150°C) of the material resulted in an overall molecular weight reduction. A substantial lowering of properties was observed for PLA samples aged at 20°C for 30 days. No further loss of properties was observed for samples aged up to 40°C for several time intervals. A major portion (80–90%) of the induced changes in the tensile properties could be reversed after drying. At 50°C and 100 days of aging, a sharp decrease in the overall properties was noticed. The results seem to confirm the earlier finding that PLA degradation driven by hydrolysis needs a higher temperature (>50°C) in combination with ample time to take place. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of the environment during a photodegradation of multilayer films

The influence of different stratosphere parameters on the degradation of a multilayer film was investigated. The selected multilayer was a three polymeric layers film, a polyamide 6 film inserted between two poly(ethylene terephthalate) (PET) films. Samples were exposed for several ageing under ultraviolet radiations (filtered at 270 nm), varying the atmosphere at 55 mbar pressure (atm, atm + ozone, N₂, and T = ?55 °C or +23 °C). Evolution of it mechanical properties defined by uniaxial tractions, thermo‐optical properties defined by spectrophotometry UV–vis‐NIR, chemical properties defined by FTIR‐ATR, and thermal and dielectric properties defined, respectively, by differential scanning calorimetry (DSC) and dynamical dielectric spectroscopy (DDS), were investigated. Our results showed that UV irradiation causes multilayer films degradations, that is, principally decrease of UV transmittance and stress and strain at break (?50%). An increase of the ageing temperature causes an acceleration of these degradations. Degradations principally occur on the PET side of the multilayer exposed to UV radiation. Moreover, the DDS analysis shows a plasticization effect of the primary mode in the polyamide 6 due to photo‐oxidation. Oxygen diffusion is the principal element for this plasticization, indeed it not occurs in a nonoxidative environment (nitrogen), or at low ageing temperature (?55 °C). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44075.     

3D printing of high solid loading zirconia feedstock via screw-based material extrusion

Zirconia ceramic (3Y-TZP) feedstocks with solid loadings from 50 vol% to 68 vol%, in a 60:40 paraffin wax to LDPE ratio binder system, were prepared and printed using a screw-based material extrusion printer. A two-step debinding process involving solvent debinding (cyclohexane + ethanol) and thermal debinding (140 °C–600 °C at 0.2 °C/min) followed by sintering at 1500 °C for 2 h was employed. Tests performed include TGA, density test, Vickers hardness and fracture toughness, XRD, and SEM. The TGA result showed two significant drops in weight starting at 180 °C and 380 °C, which corresponds to the decomposition of paraffin wax and LDPE, respectively. A minimum of 40 wt% of soluble binder was removed from the green sample after solvent immersion for 3 h at 40 °C for solid loadings ≥55 vol%. High solid loading feedstocks produced samples with comparable density, Vickers hardness and fracture toughness, which are 97.5%, ∼12.3 GPa, and ∼5.5 MPa m^1/2, respectively; while XRD and SEM shows no adverse tetragonal to monoclinic phase transformation and grain growth, respectively. This study demonstrates that 3D printing of granular 3Y-TZP ceramic feedstock via screw-based material extrusion technique is feasible even with high solid loadings, which is usually difficult to fabricate into flexible filaments and print due to high viscosity.     

Surface oxidation of low‐density polyethylene films to improve their susceptibility toward environmental degradation

Polyethylene wastes, particularly as films, have accumulated over the last several decades resulting in a major visual litter problem. The aim of this study was to investigate the ability of chemical reagents to oxidize the low‐density polyethylene (LDPE) film surface to increase their susceptibility toward photodegradation and thermal degradation. Three chemical agents, namely, potassium permanganate, potassium persulfate, and benzoyl peroxide, were used to oxidize the film surface to generate chromophoric groups, such as carbonyl groups, which are the main reason for the enhanced environmental degradation of photolytic polymers, such as ethylene–carbon monoxide and ethylene–vinyl ketone copolymers. For the chemical treatment, LDPE films of 70 ± 5 μm thickness were prepared by a film‐blowing technique and subsequently reacted with the aforementioned oxidizing agents. To aid the oxidation process, the reaction with potassium persulfate and potassium permanganate was performed under microwave irradiation heating. In the case of benzoyl peroxide aided oxidation, the films were subjected to repeated coating–heating treatments up to a maximum of 10 cycles. The treated films were subjected to accelerated aging, that is, xenon‐arc weathering and air‐oven aging (at 70°C), for extended time periods. The chemical and physical changes induced as a result of aging were followed by the monitoring of changes in the mechanical, structural, and thermal properties. The results indicate that the surface‐oxidized LDPE films exhibited enhanced susceptibility toward degradation; however, the extent was reduced as compared to photolytic or other degradable compositions. The ability of the chemicals to initiate degradation followed the order potassium persulfate < potassium permanganate < benzoyl peroxide. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Low‐temperature UV irradiation induced the color change kinetics and the corresponding structure development of PVC film

The low‐temperature ultraviolet (UV) irradiation equipment, developed in our Lab, was used to study the photo‐aging of poly (vinyl chloride) (PVC) films at low temperature. The color change kinetics and corresponding structure development of PVC film during low‐temperature UV aging were studied through L*a*b* coordinates Commission International d' Eclau‐age (CIE 1976 color space) and Ultraviolet spectrophotometer (UV–vis) and Fourier transform infrared spectroscopy (FTIR). It was found that the yellowness difference (?b*) and color difference (?E*) of the PVC film increased almost linearly with the aging time. Their values had a slower change at lower temperature. The kinetic study showed that the relationship between the velocity of coloration of the PVC film and the temperature agreed well with Arrhenius equation at low temperature. The activation energy of coloration of the PVC film was calculated. The FTIR spectra indicated that photo‐dehydrochloration, resulting in the generation of conjugated carbon–carbon double bonds, was the main reaction for PVC during photo‐aging at low temperature. Meanwhile, the photo‐oxidation was also obvious and could not be neglected. It clearly confirmed that the absorption peaks of conjugated carbon–carbon double bond increased and shifted to longer wavelength during photo‐aging in the UV‐abs analysis. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Fe-Sr2Bi2O5光催化降解低密度聚乙烯膜

采用共沉淀法合成的新型光催化剂(Fe-Sr₂Bi₂O₅)与低密度聚乙烯(LDPE)通过熔融共混制备了一种新型光催化降解复合膜(Fe-Sr₂Bi₂O₅/PE)。通过力学性能、接触角、傅里叶变换红外光谱(FT-IR)和场发射扫描电镜(FESEM)等表征手段研究了该催化剂在室温条件下固相光催化降解LDPE复合膜的性能变化。结果表明:Fe-Sr₂Bi₂O₅在紫外光和可见光条件下对LDPE均具有较好的光催化降解能力,其中,紫外灯照射10 d后,Fe-Sr₂Bi₂O₅/PE复合膜断裂伸长保留率低于5%,拉伸强度保留率低于40%,接触角降低22.52°,已完全脆化;同时,LDPE复合膜中出现明显的羰基等降解特征吸收峰和降解孔洞;与Sr₂Bi₂O₅和TiO₂相比,Fe-Sr₂Bi₂O₅对LDPE具有更好的降解效果。综上所述,在紫外光和可见光条件下,Fe-Sr₂Bi₂O₅对LDPE具有明显的光催化降解作用,为未来光催化降解聚乙烯(PE)提供了一定的新依据。     

Characterization to the weathering extent of LLDPE/LDPE thin film

A kind of LLDPE (linear low density polyethylene)/LDPE (low density polyethylene) thin film for farm applications was subjected to accelerated and natural weathering. Carbonyl group, melting point, tensile elastic modulus, and high‐temperature shearing modulus of weathered films were investigated as function of weathering time. Two kinds of carbonyl index, I₁ and I₂, which result from infrared spectroscopy (IR) spectra of the weathered films, were defined to characterize the weathering extent of the LLDPE/LDPE thin film. Based on I₁ and I₂, a correlation is made between the artificial and natural weathering of the film: 1 h of the artificial weathering is equivalent to about 10.73 h of the natural weathering. The difference between the accelerated weathering and the natural weathering was also discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 12–16, 2003     

Ozone‐induced grafting of a sulfoammonium zwitterionic polymer onto low‐density polyethylene film for improving hemocompatibility

Ozone‐induced grafting was developed to improve the hemocompatibility of biomaterials based on low‐density polyethylene (LDPE). An LDPE film was activated with ozone and graft‐polymerized with N,N′‐dimethyl(methacryloylethyl)ammonium propane sulfonate (DMAPS). The existence of sulfobetaine structures on the grafted film was confirmed by X‐ray photoelectron spectroscopy and attenuated total reflection/Fourier transform infrared (ATR–FTIR). More DMAPS was grafted onto the LDPE film as the DMAPS concentration increased, as determined by ATR–FTIR. Static contact‐angle measurements indicated that the DMAPS‐grafted LDPE film had a significant increase in hydrophilicity. The blood compatibility of the grafted film was preliminarily evaluated with a platelet‐rich‐plasma (PRP) adhesion study. No platelet adhesion was observed on the grafted film incubated with PRP at 37°C for 180 min. This new sulfoammonium zwitterionic‐structure‐grafted biomaterial might have potential for biomedical applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3697–3703, 2006     

Monitoring food quality - effect of curcumin in the development of polyethylene/thermoplastic starch based smart packaging

Smart packaging relies on the one-to-one interaction of food with its packaging or its environment to monitor food quality and safety. Colorimetric pH indicators (synthetic, natural) working in a smart food packaging system are particularly striking when used with fresh foodstuffs such as fish and meat that perish quickly and require real-time freshness monitoring. In this study, curcumin (Cur) was used as a natural pH indicator to produce sustainable smart packaging material. Towards this objective, low-density polyethylene (LDPE) and thermoplastic starch (TPS) blend-based films containing Cur were prepared using a twin screw extrusion and hot-pressing processes. Besides, two different compositions of LDPE/TPS mixture (50/50 and 70/30) were used as the matrix. Thermal, mechanical, morphological properties, an affinity for water, and color change properties of LDPE/TPS/Cur films were investigated. They showed a significant color change from yellow to brown at pH: 10 at the end of the seventh day, especially in the 50 LDPE/50 TPS mixture. 50 LDPE/50 TPS mixture with 7% curcumin content gave the highest tensile strength of 8.03 Mpa. When the same mixture was used to monitor chicken meat spoilage at 25°C, meat samples have shown color changes from light yellow to light brown due to the increased content of total volatile basic amines. As a result, it has been suggested that 50 LDPE/50 TPS mixture containing 7% Cur can be used as a smart packaging material.     

农用薄型茂金属聚乙烯棚膜的开发与应用

以mLLDPE／LDPE共混树脂为主要原料，采用有膜泡内冷装置的3层共挤复合宽幅吹膜机组和6911／B215耐老化体系生产的薄型茂金属聚乙烯棚膜具有优异的综合力学性能和耐老化性能，应用效果良好。     

Natural weathering,artificial photo‐oxidation,and thermal aging of low density polyethylene: Grafting of acrylic acid onto aged polyethylene films

The photo‐oxidation and thermal initiation changes of commercial low density polyethylene (LDPE) films used in greenhouse covering, in the presence or absence of ultraviolet (UV) stabilizer, were monitored by infrared (IR) spectroscopy, by mechanical tests and by applying the grafting of acrylic acid onto the aged films. It was found that the resistance of PE films to UV irradiation and heat initiation as proved by tensile strength and elongation at break % was better for stabilized PE films compared with the unstabilized ones. A simple correlation was not observed between the fall in mechanical properties and the rate of film oxidation. On the other hand, an almost linear relation was obviously noticed between the degree of PE oxidation (C?O) measured by IR spectroscopy and the grafting level. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2365–2371, 2003     

UV-shielding antimicrobial zein films blended with essential oils for active food packaging

A comprehensive study on zein film blended with glycerol and essential oils (EOs) is presented in this work. In particular, ultra violet (UV) shielding property and antimicrobial efficacy of developed active zein films (ZF) are tested. The fabricated films show zero transmittance in the UV region as compare to commercial poly-film which shows 40%–80% of UV transmittance. Results show that films are effective against spoilage microorganisms. The incorporation of EOs in ZF significantly reduces the growth of microbes over fruit samples since day 3. Physical interactions existing between EOs along with glycerol and zein provide considerable barrier properties. The glass transition temperature of the film comes out to be 47.7°C having the tensile strength of 1.21 ± 0.05 MPa. TGA curves show major weight loss in the range of 220–375°C. In conclusion, edible active ZF can be used as healthy packages over food and drug to increase their shelf life.     

A quantitative analysis of low density polyethylene and linear low density polyethylene blends by differential scanning calorimetery and fourier transform infrared spectroscopy methods

Blends of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) are widely used for blown film applications. An accurate and rapid test scheme to identify the type and composition of α-olefin in LDPE/LLDPE blends has been developed that utilizes differential scanning calorimetery (DSC) and Fourier transform infrared (FTIR) spectroscopy techniques. The melting point of LDPE varies with density and usually is in the range of 106°C to 112°C for film grade resins. The DSC thermogram of LLDPE is characterized by a broad range of melting peaks with a lower melting peak around 106°C to 110°C and a higher one in the range of 120°C to 124°C. In a blend with LDPE, the ratio of the two endothermic peak heights changes. At a given weight percent of LDPE, this ratio depends on the type of LLDPE (i.e., the comonomer used). Separate calibrations for butene-1, hexene-1, and octene-1 LLDPEs have been developed to quantify the blend composition from DSC thermograms where the α-olefin type is successfully identified by FTIR over the entire blend composition range. The calibration curves are applicable to narrow melt index (MI) and density range conventional film grade LDPE and LLDPE resins and are not intended to be used for the metallocene type LLDPEs.