Polyolefin Films Research Articles

Surface modification of polyolefins by photografting of acrylic monomers

AbstractHigh‐speed surface modification of polypropylene (PP) and polyethylene (PE) films has been achieved by liquid phase photograft polymerisation of acrylic acid (AA) and hydroxypropyl acrylate (HPA). Benzophenone was used as photoinitiator to generate polymer radicals at the surface of the polyolefin film. The grafting reaction was carried out in aqueous solution or with the neat monomer, which was laminated between two PP films, in the presence of air. Under the intense illumination of a UV‐curing line, acrylic acid was grafted within seconds to polypropylene films or fabrics, which were thus made hydrophilic. Direct evidence of surface grafting was obtained through infrared spectroscopy analysis and surface energy measurements. This continuous photografting process proved to be very efficient to improve the adhesion of UV‐cured acrylate coatings on polyolefin‐made materials.

MODIFIED-ATMOSPHERE PACKAGING OF FRUITS AND VEGETABLES: REDUCING CONDENSATION OF WATER IN BELL PEPPERS AND MANGOES

A dynamic model of gas and water vapor exchange in a package containing fresh fruit and vegetables was based on the Michaelis-Menten equation combined with Fick's diffusion law. A computer simulation evaluated package specifications which would provide best conditions for storage of a given commodity. Model predictions were confirmed by measured observations. Perforating the film greatly affected O 2 and CO 2 concentrations and water condensation, but not the in-package relative humidity. Bell peppers packaged in perforated film lost less weight and maintained higher quality during storage than fruit stored in open carton boxes and, at the same time, had lower decay levels than peppers kept in non-perforated packages. Perforating the film negated inhibition of ripening that prevailed for mango in non-perforated packages. Perforated packages retained most advantages of the modified atmosphere. Non-perforated film of the polyamide type had similar effects to perforated polyolefin film. Water condensation on the fruit and container walls was prevented by use of absorbers.

Vacuum deposition of Silicon oxide on the nylon 6 films utilizing silicon monooxide as an evaporation material.

Silicon monoxide (SiO) amorphous layer was deposited on the biaxially oriented nylon 6 films in a vacuum evaporator. This deposited layer tightly attaches to the nylon film. SiO deposited nylon 6 films thus obtained are transparent and show a high barrier to the water vapor and oxgen. Wettability of the SiO surface of the film to the water, ink, and the adhesives are satisfactory for the gravure printing and lamination with polyolefin films. It was found that the gloss of nylon film, which reflects the surface roughness of the film, affects the uniformity of SiO deposited layer on the nylon film and barrier property of the deposited films. Permeabilities of the water vapor and oxygen through the SiO deposited nylon films were fairly high just after the deposition, especially when the deposited layer was thin, and then decreased to lower equilibrium values. These equilibrium values are surprisingly low comparing with other high barrier films such as nylon and polypropylene films coated with poly (vinylidene chloride). Further the SiO vacuum deposition was continuously carried out on the running nylon film. We found that the thickness of the silicon oxide layer on the nylon film and the water permeability are strongly related to the running velocity of the nylon film and the applied electric current to the heater.

Electrical conduction in highly resistive polyolefin films modified by polar groups

Electrical conduction in highly resistive polyolefin films modified by polar groups

Electrical conduction in highly resistive polyolefin films modified by polar groups

Electrical conduction and space charge distribution in oxidized low-density polyethylene (samples A1–A6) and copolymers of ethylene and carbon monoxide (samples B1–B3) with different carbonyl contents have been studied. A V-shaped dependence of conduction current on carbonyl content was observed for samples A1–A6, while the current decreases monotonically with an increase in carbonyl content for samples B1–B3. The effect for polar groups on electrical conduction is discussed, focusing on their bonding forms in polymer molecules. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(3): 9–16, 1997

Influence of film wrapping and UV irradiation on cactus pear quality after storage

‘Gialla’ cultivar (cv) cactus pear fruit were either exposed or not to ultraviolet light (UV-C at 254 nm) and packaged or not with a polyolefinic film before cold storage for 1 month at 9°C plus 1 week of simulated shelf-life conditions at 20°C (SL). UV exposure did not affect fruit weight loss, while wrapping reduced significantly these losses to 1/4 after cold storage and 1/10 at the end of SL, with respect to unpackaged fruit. The overall visual rating of fruit appearance was higher in all the packaged fruit, while those unwrapped were affected by extended skin shrinkage both at the end of storage and SL periods. Skin damage, attributed to chilling injury and UV exposition, resulted higher in unwrapped fruits, in which the onset of these disorders was significantly reduced even when the fruit was UV subjected. Decay percentage was neither reduced by UV exposure nor by wrapping and reached values of about 10% at the end of the SL in all cases. Internal quality attributes and fruit taste were neither affected by wrapping nor by UV application. Wrapping the fruit with polyolefinic film had a beneficial effect in preserving fruit freshness and colour brightness, which were lost in unwrapped fruit.

Influence of film wrapping and UV irradiation on cactus pear quality after storage

'Gialla' cultivar (cv) cactus pear fruit were either exposed or not to ultraviolet light (UV-C at 254 nm) and packaged or not with a polyolefinic film before cold storage for 1 month at 9°C plus 1 week of simulated shelf life conditions at 20°C (SL). UV exposure did not affect fruit weight loss, while wrapping significantly reduced these losses to a quarter after cold storage and a tenth at the end of SL, with respect to unpackaged fruit. The overall visual rating of fruit appearance was higher in all the packaged fruit, while those unwrapped were affected by extensive skin shrinkage at the end of both the storage and SL periods. Skin damage, attributed to chilling injury and UV exposure, was higher in unwrapped fruits, in which the onset of these was significantly reduced even when the fruit was subjected to UV. The percentage decay was reduced neither by UV exposure nor by wrapping and reached values of about 10% at the end of SL In all cases. Internal quality attributes and fruit taste were neither affected by wrapping nor by UV application. Wrapping the fruit with polyolefinic film had a beneficial effect in preserving fruit freshness and colour brightness, which were lost in unwrapped fruit. © 1997 John Wiley & Sons, Ltd.

フィルム付着水がハウス内の日射透過，温湿度環境に及ぼす影響

Light transmittance, temperature and humidity of greenhouses covered with three PolyOlefin films of PO1 (Mikado Chemical M.F.G. Co., Super solar 0.15mm in thickness), PO2 (Sumitomo Chemical Co., Cleantate-LF, 0.15mm in thickness), and PO3 (Mikado Chemical M.F.G., Co., U-lack, 0.1mm in thickness), and a ploy vinyl chloride film PVC (Mitsubishi Chemical MKV Co., Clean Ace-CPM, 0.13mm in thickness) were examined to elucidate the differences of microclimate inside the greenhouses. All the films were covered in October 1993 except PO3 which was covered in October 1994. Several kinds of vegetables such as spinach, daikon-radish, Chinese-cabbage and red-radish were cultivated under usual management in each autumn-winter-spring season. Air temperature, humidity, solar rediation, and soil heat flux inside and outside (control) each greenhouse were measured during every winter-spring season. Dewdrop and/or condensation water on the covering film and the water content in the air were measured in order to check the humidity conditions in each greenhouse. The relationship between light transmittance and the dewdrop on films of the greenhouses was analyzed using the data obtained mainly in 1995-1996 season and 1997. The main results are as follows.1. Transmittance of solar radiation of PO1, PO2, PO3-greenhouses was 76.7%, 79.7%, and 63.5%, respectively, while that of the PVC-greenhouse was 71.6% at early March in 1996.2. Ventilation rate of PO1 and PO2-greenhouses was high but that of PVC was very low. The differences in ventilation rate were caused by different draft condition of each greenhouse.3. As compared to other three greenhouses, air temperature difference between the inside and outside of the PO3-greenhouse was lower by 2-4°C during daytime, resulting from the heavy dewing on the covering film.4. Average dewdrop on the films of the PVC and PO3-greenhouses was from 140-250g/m2 on cloudy day, while that of the PO1 and PO2-greenhouses was less than 40g/m2. Dewing on the greenhouse films reduced the transmittance of the solar rariation at a rate of exp (-0.9d), where d is equivalent water film thickness of dewdrop and/or condensation.5. An empirical equation was obtained using the relationship between light transmittance and the dewdrop thickness in order to estimate the air temperature difference between the inside and outside of greenhouse. Estimated values agreed well with measured values, suggesting that the effect of the dewdrop on the heat budget of the greenhouse can be quantified accurately.6. High level of dewdrop was caused by a lack of the drip control performance (runoff function) of films which decreased light transmittance, thereby increasing humidity and decreasing air temperature inside greenhouses.

Surface-Anchored Hindered-Amine Light Stabilizers for Improved UV Stability of Polyolefins

Abstract Hindered-amine light stabilizers (HALS) were surface anchored to polyolefin films by reacting the HALS, namely, 1,2,2,6,6-pentamethyl-4-piperidinol and 1,2,2,6,6-pentamethyl-4-aminopiperidine, with succinic anhydride functionalized polyolefin surfaces. The photostability of polyolefin films with surface-anchored HALS were compared with films stabilized with commercial HALS (Tinuvin 770) by melt blending. It is shown that the photostabilizing efficiency of surface-anchored HALS is superior that of melt-blended polyolefins.

Polarization modulated transmission spectro-ellipsometry

A polarization modulated transmission spectro-ellipsometer (PMTSE) features high sensitivity for retardation and high-speed data acquisition. Although optical servo control of a photoelastic modulator (PEM) has improved the accuracy of the system, the residual birefringence mainly of the PEM hinders detection of minute retardation. We have installed a compensator in order to cancel out the residual birefringence and realized base line shift that is within 0.2% of full scale. Optical anisotropies are formulated in the Mueller matrices. Accuracy for a large signal was verified from measurements of a sheet polarizer and a quartz rotator. Detectability was ascertained from the retardation spectrum, <1 nm, of a amorphous poly-olefin film and aqueous solution of a chiral metal complex, Δ−[Co(en)3]3+, whose peak signal magnitude is <1% of full scale. A time resolution of 1 ms was utilized in the dynamic response measurement of a liquid crystal, 5CB, that had a response time of 3–4 ms.

Polyolefin stretch films maintain the quality of sweet corn during storage and shelf-life

Abstract Sweet corn cobs can be transported for sale in distant markets after being sealed in Polyvinylchloride (PVC) film to delay quality loss through the reduction of water loss and shrivelling. However, this package does not prevent decay of the cut ends. Polyolefin films, AM and K-400T, were tested as substitutes for PVC as an overwrap for sweet corn placed on either cardboard (CB) or polystyrene (PS) trays. Increased levels of CO 2 and decreased oxygen atmospheres were generated through the use of the new films compared with PVC, which reduced decay, and maintained quality during 12 days storage at 1 °C and two days at 20 °C. CB trays were found to be preferable to PS ones.

From a waterlogged site to the archaeologist's desk — new packing methods with a minimum of handling

AbstractIn connection with a large-scale wetland excavation, new packing methods for heavily deteriorated waterlogged objects have been introduced. The paper describes effective field methods for cleaning, packing and transportation with a minimum of handling. Waterlogged wood is cleaned thoroughly and sealed in perforated polyolefin film, Cryovac, for wet storage. Iron objects are vacuum-packed in airtight bags after flushing with an inert gas. A refrigerated container on site ensures safe storage and transport to the laboratory. The packing procedures are designed to fit the subsequent conservation processes. Different impregnation methods, followed by freeze-drying of the waterlogged wood and dehydration and vacuum impregnation of metals, are described briefly.

Measurements of surface roughness of polyolefin films by atomic force microscopy.

コンタクト型原子間力顕微鏡(AFM)を用いてポリオレフィンフィルムの表面粗さを測定した.試料は直鎖低密度ポリエチレンと低密度ポリエチレンのブレンド,高密度ポリエチレンと低密度ポリエチレンのブレンド,キャストポリプロピレンである.表面粗さはAFM像を構成する断面プロフィルから,10点平均粗さRzとして求めた.高分子フィルムの透明性を表す尺度の一つのヘイズ(曇り度)と比較したところ,表面粗さは外部ヘイズと相関があり,表面粗さが増すと外部ヘイズが増加すること,又この相関はポリオレフィンの樹脂の種類によらずに成り立つことが分かった.

Flame surface modification of polypropylene film

Contact-angle measurements, the ASTM standard wetting test for polyolefin films, and X-ray photoelectron spectroscopy (XPS or ESCA) were used to characterize flame-treated polypropylene (PP) films. Two combustion models, STANJAN and PREMIX, were then used to determine the chemical and physical properties of the flames used to treat the PP films. Both the flame equivalence ratio and the position of the PP film in the flame are important variables in determining the extent of oxidation and improvement in wettability obtained by flame treating. The optimal equivalence ratio for the flame treatment of PP is 0.93, while the optimal luminous flame-to-film distance is 0-2 mm. Modeling of the combustion processes occurring in the flame provides evidence that the extent of treatment correlates closely with the concentrations of H, O, and OH radicals present in the flame. The extent of surface modification of the flame-treated PP does not appear to correlate with either the flame temperature or the concentraion of oxygen molecules. The mechanism of surface oxidation by flame treatment probably involves polymer-radical formation by O and OH, followed by rapid reaction of the polymer radicals with O, OH, and O2.

Plasma surface modification of propylene‐based polymers by silicon and tin‐containing compounds

AbstractPlasma surface modifications of homo‐, co‐, and terpolymers of propylene films in the presence of selected organosilicon and organotin compounds were investigated. For this, organosilan(stannan)e type compounds (such as vinyltriethoxysilane, 3‐aminopropyltriethoxysilane, and tetraethylstannane) as well as organosiloxan (stannoxan)e type compounds (such as hexamethyldisiloxane and hexabutyldistannoxane) were exployed in plasma. Plasma surface modification of polyolefin films with organosilicon plasma has led to increase of the hydrophobicity, while the presence of organotin compounds in plasma produced less hydrophobic surfaces. Reaction of plasma‐activated polyolefin films further with vinyltriethoxysilane‐maleic anhydride oligomer also led to an increase in the hydrophobicity of polypropylene surfaces. It is observed that the degrees of swelling of (virgin, plasma‐treated, and plasma‐modified) polypropylene films in cyclohexanone strongly depend on the nature of the organoelement compounds used, organosilicon plasma causing lower degrees of swelling. The changes of surface properties observed are explained by different surface structures produced in plasma: in the case of organosilicon compounds, it is believed that poly(organosiloxane) and for organotin compounds poly(organotincarboxylate) fragments are formed primarily. © 1995 John Wiley & Sons, Inc.

Interactions in the thermal and light stabilising action of novel aromatic phosphites with a 2-hydroxybenzophenone and hindered piperidine stabiliser in polyolefin films

The interactions of two novel phosphite stabilisers with a commercial polymeric hindered piperidine stabiliser, Chimassorb 944, and a 2-hydroxy-4-n-ctoxybenzophenone stabiliser, Cyasorb UV 531, have been examined in the thermal and photooxidation of polypropylene and high density polyethylene films using FTIR spectroscopy. The two structures are based on a bis-hindered phenolic moiety coupled to a 2-hydroxybenzophenone and a 4-amino-tetramethylpiperidine (3) chromophore. Thermal oven ageing and photooxidation of the polyolefin films showed that the hindered piperidine phosphite (phosphoramide) is synergistic over a wide concentration ratio with both commercial stabilisers. The only exception is in polyethylene with the Chimassorb 944, wherein the latter shows poor solubility in polyethylene. Generally, the phosphoramide is found to be more effective as a thermal antioxidant than as a UV antioxidant. The 2-hydroxybenzophenone phosphite was generally ineffective as a light stabiliser and exhibited unusual S-shaped profiles in combination with both the commercial stabilisers, suggesting the involvement of two distinct processes. With Cyasorb UV 531 the antagonistic/synergistic patterns were reversed from polypropylene to polyethylene. With Chimassorb 944 strong synergism is observed at high phosphite ratios while antagonism is prevalent at low ratios. In general, one interesting feature of the results is that the thermal and UV effects often exhibit a similar behaviour.

The performance of light stabilizers in accelerated and natural weathering

The performance of different classes of light stabilizers is compared in polyolefins. The evolution of stabilization in the past quarter century is illustrated with data generated with polyolefin tapes, multifllaments, films and plaques. The state-of-the-art, based on combinations of light stabilizers, mainly combinations of hindered amine light stabilizers (HALS) is discussed. The light stability data are generated either in various accelerated weathering devices or outdoors in various climates. Correlation between the various accelerated devices on the one hand and between accelerated and natural weathering data on the other hand was the subject of many publications. It is still one of the major problems encountered in assessing the durability of plastic materials for outdoor use. It is found that, even with adequate precautions concerning the light source and its intensity as well as sample temperature, correlation between natural and artificial weathering is the exception rather than the rule. Therefore, another model for lifetime forecasting is proposed. It is based on the quantitative laws deduced for HALS performance in polyolefins. They are, linear increase of performance with HALS concentration in PP and linear increase with the square root of HALS concentration in PE-HD. Then, the knowledge of the effect of one HALS concentration on outdoor weathering with a given polymer and sample form allows prediction of the lifetime with other HALS concentrations. As a consequence, the problem of lifetime forecasting is reduced to an analytical problem, i.e. determination of the stabilizer system.

Surface structures of fluoropolymer, polyolefin and polyester films after modification by graft polymerization

AbstractPristine and argon plasma pretreated polytetrafluoroethylene (PTFE), polystyrene (PS), high‐density polyethylene (HDPE) and poly(ethylene terrephthalate) (PET) films have been subjected to near‐UV light‐induced graft polymerization with water‐soluble acrylamide (AAm), the sodium salt of styrene sulfonic acid (NaSS), acrylic acid (AAc) and N,N‐dimethylaminoethylmethylacrylate (DMAEMA) monomers. The structure and composition at the substrate surface with grafted polymer were studied by angle‐resolved X‐ray photoelectron spectroscopy (XPS). In most cases, the density of surface grafting is enhanced by plasma pretreatment. For each polymer substrate with a substantial amount of grafting, the hydrophilic graft penetrates or becomes partially submerged beneath a thin surface layer of dense substrate chains. This stratified microstructure is consistent with the static secondary ion mass spectroscopy (SIMS) and Ar+beam depth profiling results. The two latter techniques also suggest that when the grafted polymer has a bulky substituent, there is less efficient penetration of the grafted polymer below the surface.

Thermal and photooxidative stabilisation behaviour of 4-naphthyl esters of 2-hydroxybenzophenone and 3,5-di- tert-butylphenol in polyolefin films

Two novel naphthyl ester derivatives have been synthesised and characterised based on a 2-hydroxybenzophenone and a 3,5-di- tert-butylphenol. Thermal and photochemical ageing studies have been carried out to determine their potential as stabilisers in polypropylene (PP). Whilst both compounds exhibit no oven ageing antioxidant properties alone they are somewhat effective melt stabilisers. Differential thermal analysis and mass spectrometry show both compounds fragment at the carbon-oxygen bond (CO) of the ester group. Whereas both compounds exhibit good oven ageing stability for PP with a thermal hindered phenolic antioxidant, Irganox 1010, antagonism is observed when combined with a hindered piperidine light stabilizer, Chimassorb 944. In the latter case the antagonism is significant in the presence of the benzophenone derivative. The benzophenone derivative is not an effective light stabiliser alone in PP despite its high absorptivity in the near-UV region 300–350 nm and its ability to act as an excited state quencher. However, it does exhibit strong synergism with both the hindered phenolic antioxidant and the hindered piperidine stabilisers. The naphthyl benzoate ester on the other hand is an extremely effective light stabiliser alone in PP, has weak absorptivity in the near-UV region and is unable to act as an excited state quencher. Strong synergism is observed with a hindered piperidine light stabiliser, Chimassorb 944 but not with a hindered phenolic antioxidant. Spectroscopic evidence indicates that the naphthylbenzoate ester undergoes a rapid initial photo-Fries rearrangement to produce a more strongly absorbing hydroxynaphthylphenyl methanone product.

Effect of processing on the thermal and photooxidative behaviour of 2-hydroxybenzophenone stabilisers in polyolefin films: Influence of 2,2,6,6-tetramethylpiperidine substitution

The effect of processing history has been examined on the thermal and photostabilising action of two types of 2-hydroxybenzophenone light stabilisers in polypropylene (PP) and Philips grade high density polyethylene (HDPE). Both differ in terms of the nature of the 4-substitution, one with a butoxy-4-amino-2,2,6,6-tetramethylpiperidinyl group and the other with an n-octoxy group. Using infrared absorption spectroscopy (FTIR), hydroperoxide analysis and differential scanning calorimetry, the former stabiliser is shown to exhibit both effective thermal (oven ageing and melt) and light stabilisation in the two polyolefins. Carbonyl growths are consistent with initial hydroperoxide concentrations in the polymers as well as the polymer type and its processing history. In both polymers, processing history reduces the stability of the stabilisers and their stabilising effectiveness in the polymers due to the formation of increased levels of hydroperoxides. The hindered piperidine stabiliser exhibits strong autoretardation on both thermal and photoageing, illustrating its behaviour as an effective photothermal antioxidant, the effect being dependent upon the processing history of the polymer. This is in marked contrast to the 4- n-octoxy stabiliser which exhibits no thermal antioxidant behaviour. Differences in the behaviour of the two types of stabiliser and the complex interplay of processing history are discussed.