Heat-sealing Temperature Research Articles

Microfabrication of Thermoplastic Polypropylene Surface Structures via Thermal Imprinting for Controlling the Adhesion of Easy Peel Package.

Micropatterns were fabricated on polypropylene (PP) surfaces using the hot embossing technique with various temperatures ranging from 160 to 175 °C and applying force conditions from 100 to 300 N. To evaluate the replication quality, an effective filling ratio of 1 indicates that the volume of the formed pattern is similar to the mold cavity volume. From the results, the filling ratio increased with increasing the embossing temperature. For instance, under a constant force of 100 N, the filling ratio of polypropylene (PP) with small square arrays (pattern SS) increased from 0.08 to 0.41 when the embossing temperature was raised from 160 to 175 °C, respectively. With the increase of applied force, the filling ratio also increased. At an imprinting temperature of 175 °C and an applied force of 300 N, the highest effective filling ratio that was achieved was approximately 0.99. Furthermore, the effect of PP with different melt flow indexes (MFIs) on the filling ratio was investigated. For food packaging applications, a micropatterned PP sheet was heat-sealed with a biaxially oriented polypropylene (BOPP) film. The micropatterned PP sheet demonstrated easy-opening properties by varying sealing contact areas and micropattern geometries between the sheet and the BOPP film. All micropatterned PP sheets with an MFI of 25 g/10 min exhibited an easy peel property with adhesive failure characteristics at a heat-sealing temperature of 150 °C and a dwell time of 3 s. There was no residue on the PP substrate surface. The overall findings are beneficial in understanding the hot embossing technology for fabricating micropatterns on polymer surfaces, and it can be applied in an easy peel property for packaging applications.

Heat-Seal Ability and Fold Cracking Resistance of Kaolin-Filled Styrene-Butadiene-Based Aqueous Dispersions for Paper-Based Packaging

Dispersion coatings are offered as alternative solutions to extrusion coating technology for paper-based packaging. In addition to providing barrier properties, waterborne dispersions may implement the processing and converting properties of coated substrates, which are of extreme interest for an effective transfer to the industry. In this work, styrene-butadiene-based aqueous dispersions were formulated considering different amounts of kaolin as pigment. The authors assessed the heat-seal ability, fold cracking resistance, and blocking tendency, comparing the results against commercial dispersion coating grades. Kaolin content dominated the sealing behavior of experimental formulations, changing the minimum heat-seal temperature from 80 °C to >140 °C for 0% and 60% kaolin solid content, respectively. On the contrary, commercial grades were mostly affected by temperature. Additionally, despite the low latex glass temperature (0 °C), experimental formulations generally showed little, if any, blocking. On the downside, increasing kaolin content eases fold cracking, showing a different magnitude according to fold direction and coat orientation yet achieving a higher moisture barrier compared to commercial grades for both folded and unfolded samples.

Enhancement of Heat Seal Properties of Polypropylene Films by Elastomer Incorporation

Abstract Seal strength at high and low temperatures as well as the width of the heat sealing temperature range are important properties in packaging industry. In addition, for sterilisable and retort applications, having those properties at elevated temperatures is crucial. Polypropylenes (PP) are usually used for these applications, however, the sealing temperatures are too high and the temperature range for the seal process is narrow, thus blending with a PP elastomer copolymer can be an alternative. In this study, hot-tack and heat seal properties were determined for a homo-polypropylene, a random co-polypropylene and an elastomer co-polypropylene based films and their blends. It is found that the seal initiation temperature (for hot tack and heat seal) is governed by the melting temperature and crystallinity and the increase of the elastomer content in the blends leads to a decrease of the seal initiation temperature. It is also shown that the sealing force depends on the ease of chains diffusion across the sealing interface. Finally, it was found that the strength of the heat sealing increases by recrystallization in the sealing interface after cooling.

Peelable clay/PE nanocomposite seals with ultra-wide peelable heat seal temperature window

Abstract This study shows that the controlled dispersion and distribution of nanoclay in clay/polyethylene (PE) nanocomposites result in peelable sealants with an ultra-wide peelable heat-seal temperature window (ΔTp). Different nanoclays, unmodified montmorillonite (Mt) and organo-modified Mt. (OMt), were examined for their capacity to generate peelable clay/PE nanocomposites in a melt-blending film extrusion process. Clay/PE nanocomposite films containing 6 mass% organoclay (OC) exhibited a cohesive peel behavior with a ΔTp of about 12°C while PE film containing 6 mass% unmodified clay resulted in microcomposite with a lock seal performance. With the same mass% of OC, a much lower peel strength with a significantly broad ΔTp of 45°C was achieved mainly due to the fine dispersion of OMt when PE-grafted-maleic anhydride (PE-g-MA) was used as a compatibilizer. WAXD and TEM results confirmed that a substantial enhancement in the dispersion and distribution of intercalated nanoclays was achieved with PE-g-MA compatibilizer. Finally, an ultra-wide ΔTp of over 100°C was obtained for compatibilized OC/PE nanocomposite sealant containing only 3 wt% OC with partially exfoliated microstructure indicating that the exfoliation of nanoclay is in favor of peelability. The peel fracture mechanics of the clay/PE nanocomposite sealants were examined through T-peel test and SEM imaging. The results showed that the dispersion and distribution of nanoclay along with the interfacial adhesion between nanoclay and matrix are the key factors controlling the peel performance of the sealants.

Effect of nanoclay localization on the peel performance of PE based blend nanocomposite sealants

Polyethylene (PE) based clay polymer nanocomposites (CPN) are of great importance to generate peelable seals in packaging industry. This study shows the significant effect of organoclay (OC) localization in PE-based blend sealants on their peel properties, for the first time. Two different immiscible blends composed of PE/ethylene-methyl acrylate copolymer (EMA) and PE/ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EMA-GMA) were examined for their potential to generate peelable seals upon addition of organo-modified montmorillonite (OMt). WAXD results and TEM observations reveal that OC is localized at the interface of PE/EMA phases while it is localized within the dispersed EMA-GMA phase in the PE/EMA-GMA blend, which is in agreement with the thermodynamic predictions. The incorporation of 4 phr OC converts the lock seal behavior of the PE/EMA blend seal to a peelable behavior over a wide peelable heat seal temperature range (over 35°C). In contrast, the OC/PE/EMA-GMA nanocomposite sealant, in which OC is mostly located within the EMA-GMA phase, shows lock seal performance similar to the PE/EMA-GMA neat blend.

Performance properties, lactic acid specific migration and swelling by simulant of biodegradable poly(lactic acid)/nanoclay multilayer films for food packaging

ABSTRACTThe aim of the study was the development of a multifunctional, high-performance, fully biodegradable multilayer polylactic acid (PLA) film for food packaging applications. In particular, sealable multilayer PLA–clay nanocomposite systems with different layouts in terms of composition and relative thickness of the layers, all consisting of a PLA–clay nanocomposite layer between two pure PLA layers for direct food contact, were designed and produced by blown film co-extrusion. The films obtained were analysed for their morphology, functional properties and lactic acid (LA)-specific migration in 50% ethanol. The results showed that, with respect to the unfilled multilayer system, taken as a reference, the nanocomposite films had significant improvements, up to about 40%, in their barriers to oxygen and tensile strengths, and resulted in being more easily sealable over a wide heat-sealing temperature range (80–100°C) with higher seal strength. Moreover, all films had LA migrations always well below the former generic overall migration limit of 60 mg kg–1 food (10 mg dm–2) of European Union Regulation No. 10/2011 (deleted by the amending Regulation No. 2016/1416), even if their morphology was strongly modified during the migration tests due to the strong swelling action of the used simulant (simulant D1 = 50% ethanol (aq.) (v/v)) towards PLA.

Application of single site catalyst metallocene polyethylenes in extruded films: Effect of molecular structure on sealability, flexural cracking and mechanical properties

Three single site catalysts metallocene polyethylenes (mPE) different in molecular structure were selected and films from them were produced using a semi‐industrial cast film extrusion line. Rheological and gel permeation chromatography tests were performed on the mPE resins to assess their molecular structure. Mechanical, physical and sealability properties of the films were evaluated as well as flexural cracking and particles encapsulation (caulkability) and the results are discussed in relation to the molecular structures of the resins. It was found that molecular weight and distribution of short chain branching (comonomer) on the backbone of the polyethylene chains are the main factors that control sealability, flexural cracking and mechanical properties. The placement of comomoner on medium length chains generated crystals with smaller size that show a lower melting peak. Sealing was controlled by crystal distribution, chain diffusion and entanglement formation at the interface. mPE with lower melting point and linear molecular structure showed greater hot tack and seal strength. Polydispersity along with molecular weight contributed to toughness and puncture resistance. Flexural cracking resistance was revealed to be related to crystallinity, tie chain density and more importantly to fraction of amorphous phase. The amorphous part could absorb flexural energy and hinders crack initiation and propagation. Seal through contamination (caulkability) was found to be related to flowability of the melt. The resin with stronger shear thinning in melt state and lower heat seal initiation temperature showed an improved caulkability.

Effect of Heat Sealing Temperature on Mechanical Properties and Molecular Structure at Heat-Sealed Parts of Polylactic Acid Film —Part II

Actual failure accidents of plastic bags often occur at the pin-hole and/or the crack, and also the edge that is just outside of the heat-sealed part becomes the failure initiation point. In this study, fracture mechanics tests and tear tests were performed to understand the resistance of heat-sealed parts and edge parts to introduced cracks. The fracture resistance and tear strength of the edge part was lower than that of the heat-sealed part, which was more obvious at higher heat sealing temperature. The optimum heat sealing temperature to obtain the balanced properties of heat-sealed polylactic acid (PLA) films was found to be 130°C.

Effect of Heat Sealing Temperature on Mechanical Properties and Molecular Structure of Heat-sealed Polylactic Acid Film

Heat sealing is currently a standard method for manufacturing plastic bags of polylactic acid film, which has high clarity and strength. However, the heat sealing of polylactic acid is difficult because its strength declines at high temperatures. Processing conditions such as the heat sealing temperature and pressure can greatly affect the mechanical properties of the heat sealed part. In this study, the relationship between the heat sealing temperature and the mechanical properties of heat-sealed polylactic acid film were examined through peel strength tests and tensile testing of samples with circular notches. Differential scanning calorimetry (DSC) and FT-IR imaging were used to investigate the dependence of crystallinity and molecular-orientation ratio (MOR) on the heat sealing temperature. These studies showed that the optimum heat seal temperature was 128°C, with a very narrow temperature window. Thus, precise control of the heat sealing temperature is required for polylactic acid plastic bag manufacture.

Connection between Hot Tack Force and Form-Fill-Seal Performance of Packaging Films

Recently, most packaging with plastic film for liquids such as soap, sauce and ketchup is performed on vertical automatic form-fill-seal packaging systems. The major technical issue for form-fill-seal packaging has been the packaging speed, which is restricted by leakage at the horizontal seals due to insufficient heat sealing. It has been known that the packaging speed depends on the type of packaging film and the hot tack force of the packaging film has been regarded as a main controlling factor of the leakage. However, a quantitative correlation between the hot tack force of the packaging film and the leakage at the horizontal seals has not been determined yet, and the means to improve the packaging speed are unknown.By means of hot tack force measurements and actual form-fill-seal packaging tests for several packaging films, we studied the quantitative correlations between the hot tack force and the leakage at the horizontal seals. We also developed a method to predict and compare the form-fill-seal packaging performance (proper range of heat seal temperature and heat seal time: packaging speed) for various packaging films by utilizing the quantitative correlation obtained in the above study. As samples for the study, we used laminate films of bi-axially oriented nylon (15μm)/polyethylene type sealants (50μm). The sealant resins used were metallocene plastomer, low density polyethylene, ethylene copolymers of EVA and EMAA and ethylene ionomers.The following results were obtained:1. It was confirmed that the leakage at the horizontal seals arises in the range of heat seal conditions (heat seal temperature and heat seal time: packaging speed) where the hot tack force of the seal is less than the stress to peel the horizontal seal part. A quantitative correlation between the hot tack force of the packaging film and the leakage at form-fill-seal packaging was determined.2. The agreement in the predictions for the proper range of packaging conditions (heat seal temperature and heat seal time: packaging speed) based on hot tack force measurements as a function of heat seal time and with those obtained by actual form-fill-seal packaging tests was confirmed. A method to predict and compare the packaging performance (proper range of heat seal conditions) for various packaging films was developed.3. It was reconfirmed that the hot tack property of various packaging films depends on the type of sealant resin, which results in a difference in form-fill-seal packaging performance among various films that differ in sealant resin type.• m-plastomer: hot tack force develops with very short heat seal time, which results in good performance under high speed packaging.• ionomer: has very large hot tack force both at very short heat seal time and under a wide range of heat seal temperatures, resulting in superior performance.• LDPE & EVA: small hot tack and slow hot tack force development speed, resulting in inferior packaging performance.

Effect of Chill-roll and Air-gap in Film Forming on Heat-sealability of Polypropylene Films Containing β-Form Nucleating Agent

Polypropylene (PP) films with β-form nucleating agent were prepared by T-die film extrusion. The relationship among extrusion conditions, crystal structure of the films and heat-sealability was studied. The following results were obtained: Fine crystallites formed more easily in films prepared at a chill-roll temperature of 25°C than in those at 75°C. The heat-sealabilities of the former films were better than those of the latter ones in a low heat-seal temperature range from 140°C to 144°C. The heat-sealability of PP film without additive prepared at a chill-roll velocity of 2.5m/min was better than that at 1.0m/min because of smaller size crystallites. On the other hand, the heat-sealability of the PP film with 0.10wt% β-form nucleating agent, prepared at 1.0m/min, was better than that at 2.5m/min due to the higher β-form crystal content. Accordingly, it may be said that the smaller sizes of α- and β-form crystals and the higher content of the β-form crystals both cause better heat-sealability due to the lower melting point of the crystals. It was also found that the air-gap distance negligibly affects the crystal structure and hence the heat-sealability of film.

クロムめっき鋼板とポリエチレンテレフタレートフィルムの積層物の剥離強さにおよぼす圧着温度,剥離温度・速度の影響

クロムめっき鋼板とポリエチレンテレフタレートフィルムの積層物の剥離強さにおよぼす圧着温度,剥離温度・速度の影響

Comparison of EVA and Polyolefin Plastomer as Blend Components in Various Film Applications

Ethylene vinyl acetate (EVA) copolymers at various%VA content and AFFINITY** polyolefin plastomers (POP) were evaluated as blend components in various film applications rich in LDPE and LLDPE. The EVA resin miscibility with LDPE or LLDPE decreased as the VA content increased so that high VA EVA resins were partially or completely immiscible with LDPE or LLDPE resins. Both POP resins were miscible with LDPE or LLDPE resins. The blown films of LDPE/POP blends gave lower heat seal initiation temperature and lower haze compared to LDPE/EVA blended films. This is due to immiscibility of Elvax 3165 (18% VA) and Elvax 3128 (9% VA) with the LDPE resin. The impact and tear resistance of the POP based blown films were also superior. Oriented films of blends of POP with LLDPE and ULDPE resins exhibited significantly lower haze compared to blends of 12% VA EVA with LLDPE and ULDPE resins. Again, this is due to partial immiscibility of 12% VA EVA with LLDPE and ULDPE resins. The oriented films of blends of POP with LLDPE and ULDPE resins exhibited similar shrinkage at 90'C compared to blends of 12% VA EVA with LLDPE and ULDPE resins.

On Hot-melt, Heat-seal and Hot-set Adhesives

To clear up the confusion I quote from the adhesives glossary published by the American Society for Testing Materials (ASTM, D 907-74) and from the Adhesives Handbook by J. Shields (CRC Press, 1970): Adhesive, hot-melt: An adhesive that is applied in a molten and forms a bond on cooling to the solid state (ASTM). Shields elaborates: An adhesive material applied at a temperature above its melting point. Usually thermoplastic, wax or 100% solids: adhesives applied between 150 and 2000C. In the technology of art conservation wax and wax-resin mixtures are adhesives of this type. They are applied in liquid form; they are absorbed by and penetrate through all the porosities of the materials to which they are applied and often stain them. Because of the depth of their penetration, total removal of such adhesives from the impregnated materials becomes impossible. Adhesive, heat-seal: use of heat reactivation to prepare a joint with a thermoplastic material present, as a thin layer, on the adherends, bringing adherend surfaces to their melting point and bonding under (Shields). The last word of the above definition-pressure-is of great importance. Indeed, heat-seal adhesives are usually described by the temperature, pressure and the length of time, that is, the dwell time, required to form a bond. See, for example, I. Skeist, Handbook of Adhesives (Reinhold: New York, 1962, p. 353, cited by Bernard when he describes his adhesive in A Poly (Vinyl Acetate) Heat Seal Adhesive for Lining, Conservation and Restoration of Pictorial Art, N. Bromelle and P. Smith, eds. (Butterworth: London, 1976): Skeist reports a minimum heat-seal temperature of 600C for AYAA, 1.5 sec. dwell-time at 60 lb. per sq. inch. The high viscosity of the heat-seal pressure-sensitive adhesive prevents it from penetrating into the voids (porosities) of the materials to be bonded even under the pressure required to form the bond. The result is a bond that forms only on those surfaces which are in direct contact with each other. This explains why heat-seal adhesives do not stain and, if prepared from stable theromoplastic materials, can be easily and completely removed from almost every material used as an art support, including absorbent and/or thin substances such as old silk or tissue paper. The differences between the above two types of adhesives are considerable. Yet in the paper Treatment of a Flood-Damaged Oil Painting on a Solid Support by David C. Goist, the author writes: When the wheat paste and paper were dry, each sheet was coated evenly with the Hot-Melt adhesive devised by Bernard Rabin (Journal of the AIC, XVI, 2, p. 24), although in his reference he quotes the title correctly: Rabin, B., A Poly (Vinyl Acetate) Heat Seal Adhesive for Lining, cited above.