Extrusion Blow Research Articles

Effects of incorporation of additives in the mechanical properties of films of linear low-density polyethylene

In this investigation the effect of the incorporation of additives in the mechanical properties of LLDPE films, made to be used as greenhouse covers, was analyzed. All films were fabricated by the method of extrusion blow. Two types of formulations are raised in order to determine the influence of the concentration of one additive and identify the existence of some synergy by combining active ingredients in the formulations. Modulus of elasticity, yield stress and tear resistance of the films were evaluated. The results indicate that variation in the concentration of an additive in the mixture does not generate significant changes in the physical-mechanical properties of the films. However, the incorporation of the UV light absorber and Smartlight fotoselector in formulations favors their mechanical properties. Compared with the reference film, an increase higher than 200% in modulus of elasticity and yield stress of the films was determined.

Influence of microcrystalline cellulose in thermoplastic starch/polyester blown films

This work investigated the influence of microcrystalline cellulose (MCC) in thermoplastic starch/poly (butylene adipate-co-terephthalate) films produced by blown extrusion, using different MCC contents (4, 7 and 10 g.100 g-1). The films were characterised for their mechanical, structural and barrier properties. Increasing fibres concentration reduced the tensile strength (6.9 to 4.6 MPa), the elongation at break (568 to 147%) and weight loss in water (12.8 to 11.1%) of the films. The rigidity of the films increased from 19.8 MPa (without MCC) to 79.2 MPa in the samples with 10 g.100 g-1 of MCC. SEM images showed the occurrence of some agglomerates in this sample. The water vapour permeability of the films was not affected by the presence of MCC. The production of starch/PBAT/MCC films by blown extrusion was successful; however some adjustments are necessary to improve the dispersion of the particles at the polymeric matrix.

Effects of low polyhydroxyalkanoate content on the properties of films based on modified starch acquired by extrusion blowing

The effect of low polyhydroxyalkanoate (PHA) content on hydroxypropyl distarch phosphate (HPDSP)/PHA films produced by extrusion blowing was studied. Scanning electron microscopy (SEM) micrographs of the films containing 12% PHA showed a continuous and homogeneous structure. X-ray diffraction (XRD) indicated that the relative crystallinity of the films gradually increased with the increase of PHA content. The films containing 12% PHA exhibited the highest light transmittance, and tensile strength (TS, 3.75 MPa). The water vapor permeability of the starch-based films greatly decreased (p < 0.05) as the PHA content increased from 0% to 36%. Furthermore, Fourier transform infrared (FTIR) spectroscopy revealed that new hydrogen bonds were formed by the addition of PHA. Results suggested that the formulation with 12% PHA was the most suitable for the preparation of starch-based films with enhanced properties.

Development of Biodegradable Films of Cassava Starch and Poly (butylene Adipate Co-terephthalate): Effects of Oregano Essential Oil and Potassium Sorbate in Films Characterization

Four samples of thermoplastic starch (STP) and poly (butylene adipate co-terephthalate) (PBAT) films added with the preservatives oregano essential oil (OEO) and potassium sorbate (PS), were prepared from the extrusion blow moulding technique in order to evaluate the mechanical properties, water vapour permeability (WVP) and microstructural characteristics so as to develop active films with antimicrobial activity. The samples FC (film without preservative) and F1 (1% OEO) showed higher water sorption than the samples F2 (0.5% OEO and 2.5% PS) and F3 (5% PS) essentially in relative humidity (RH) higher than the 60%. Samples water vapour permeability containing OEO and PS, showed no significant difference from FC. However, the presence of OEO in samples F1 and F3 decreased the solubility coefficient (s) in 99.5% and 93.8% respectively, compared to FC. The presence of PS in sample F2 increased the diffusion coefficient (Dw) in 4.7 times related to sample FC, so the presence of small molecule PS gave higher porosity to the film. The sample F1 showed an increase in tension at rupture (TR), elongation (E) and elastic modulus (EM) when compared to FC, while F2 and F3 samples revealed a reduction in TR and EM, and increased E. From Scanning Electronic Microscopy, it was possible to observe greater uniformity in FC and F1 compared to F2 and F3 samples. Thus, OEO presence contributes to improve the polymer mechanical properties and the increased homogenization. As well as, the presence of PS contributed to the film higher elasticity, less resistance and less homogeneity. Therefore, the presence of OEO in STP and PBAT films gives the best feature for the development of active films related to the mechanical properties, microstructural and of barriers.

Extrusion Blow Molding of Polymeric Blends Based on Thermotropic Liquid Crystalline Polymer and High Density Polyethylene

Abstract This work is concerned with the extrusion blow molding of polymeric blends containing thermotropic liquid crystalline polymer (TLCP) and high density polyethylene (HDPE), using a single screw extruder. The TLCP is synthesized from terephthalic acid, 4-hydroxybenzoic acid, hydroquinone and hydroquinone derivatives, the melting point of which is 280 °C. Because the TLCP is usually processed at much higher temperatures than HDPE, the thermal stability of HDPE at elevated temperature is evaluated. It is shown that HDPE is relatively stable in the processing temperature range of the TLCP used in this work (260 to 300 °C). Bottles are successfully produced from the blends containing 10, 20 and 50 wt% TLCP. The TLCP/HDPE blend bottles exhibit enhanced modulus relative to pure HDPE. However, the improvement in tensile strength is marginal. At 10 and 20 wt% TLCP contents, the TLCP phase exists as platelets aligning along the machine direction, while a co-continuous morphology is observed for the blend containing 50 wt% TLCP. To further enhance the mechanical properties of the blends, the preliminary effectiveness of maleic anhydride grafted HDPE (MA-g-HDPE) as a compatibilizer is studied. The injection molded ternary blends of TLCP/HDPE/MA-g-HDPE have demonstrated superior mechanical properties over the binary TLCP/HDPE blends, which suggests MA-g-HDPE as a potential compatibilizer for developing high performance TLCP/HDPE containers with enhanced mechanical properties.

Native and Modified Gelatin Films Produced by Casting, Extrusion, and Blowing Extrusion Processes

Samples of native gelatin and gelatin modified by acylation and esterification were processed by casting and thermoplastic extrusion to produce laminated and tubular films. Extruded films containing sorbitol showed homogeneity and flexibility. Thinner films were obtained with the addition of sorbitol to the formulation. Tubular films prepared from gelatin modified with stearic acid were easily processed, had reduced friction, and were able to withstand bubble formation without fracturing after preparation. Films prepared by casting or thermoplastic techniques showed a decrease in tensile strength with the addition of plasticizer, and this also resulted in a substantial increase in their elongation ratio. The stearic acid modified gelatin-based films processed by blown extrusion showed higher tensile strength. Films fabricated by casting were, in general, less soluble than those prepared by extrusion except the films modified with stearic acid with or without the addition of plasticizer.

Design of Flash Pocket Inserts in an Extrusion Blow Mould Based on the Results of Numerical Simulations

The results of heat flow simulation in a flash pocket of an extrusion blow mould, made using ANSYS Polyflow software, are presented in this article. The efficiency of plastic cooling speed depending on the flash pocket profile shape was evaluated on the basis of polymer and mould temperature values.The simulation was made using the model of a real blow mould with sockets to place the inserts of a different flash pocket profile shape. The simulation of the temperature change near flash pocket zone surface was made. The inserts allow testing the efficiency of polymer cooling in the flash pocket depending on the profile shape in this mould zone. As the result, the prediction of the extrusion blow moulding cycle time can be made. It was found that the most effective cooling of the plastic in the flash pocket can be achieved using the semicircular profile.

Analiza krajowego rynku opakowań z tworzyw sztucznych

The article contains the results of analysis of plastics packaging domestic market and the description of the analysis method used (Table 1). The data presented are put in relation to particular analyzed segments of the market, i.e. flexible materials and packaging (including PE, PP and multilayer ones); materials thermoformed from rigid films; those formed by blow extrusion or blow injection, as well as injection molded ones. The tendencies of growing consumption of particular packaging types, observed during last 5 years, were characterized. The forecast directions of further development were marked and present and forecast importance of flexible packaging has been stressed.

Lemon essential oil desorption from polypropylene/talc nanocomposite films

A phenomenological analysis on desorption mechanism of lemon essential oil in semicrystalline polymer nanocomposites is performed. Films were made of polypropylene and talc nanoparticles obtained by blown extrusion were used as a case study due to the high complexity of sorption phenomena in such systems containing a semicrystalline polymer and nucleating particles. In this sense, a systematic analysis combining both morphological effects and intrinsic properties of each component was considered. Talc characteristics, e.g., morphology, surface chemistry, oil absorption properties, mean particle size and its distribution, and impurity presence, were considered in desorption analysis. Regarding semicrystalline matrix, morphological and crystalline changes induced by talc nanoparticles and processing were included in this study. Desorption of lemon essential oil from nanocomposite films with different talc concentrations (0, 1, and 5 wt%) which have distinctive and well characterized morphologies was evaluated through gravimetric and thermogravimetric analysis. Results show that polypropylene film has a desorption rate higher than nanocomposites containing 5 wt%, but lower than those with 1 wt% talc. This behavior is a consequence of the global crystallinity configuration changes produced by nanoparticle concentration and film obtaining process. It is revealed that simplified and conventional approaches that consider tortuosity as unique effect of particle presence in nanocomposite mass transport do not allow to comprehend the desorption mechanism involved in a complex system such as the semicrystalline polymer nanocomposites. The present study gives additional insight into the complex mechanism involved in desorption of strongly swelling oil in nanocomposite films based on semicrystalline polymers and mineral nucleating particles.

Grapefruit seed extract incorporated antimicrobial LDPE and PLA films: Effect of type of polymer matrix

Antimicrobial low-density polyethylene (LDPE) and poly(lactide) (PLA) films were prepared by blending with grapefruit seed extract (GSE) incorporated thermoplasticized starch (TPS) using extrusion blowing and extrusion casting methods, respectively. The effect of polymer matrix was studied by comparing the film properties such as optical, mechanical, water vapor barrier, and antimicrobial properties. Scanning electron micrograph (SEM) result indicated that the TPS was homogeneously dispersed through both polymer matrix. Though transparency, mechanical, and gas barrier properties of the blend films decreased compared with their neat films, the blend films showed UV-light screening function and antimicrobial activity against food-borne pathogenic bacteria, E. coli and Listeria monocytogenes, which was mainly attributed to the GSE. While PLA/TPS film exhibited strong antibacterial activity against both bacteria, LDPE/TPS film showed lower antibacterial activity. This was presumably because the GSE was entrapped more tightly by the LDPE than the PLA. Packaging application test using minced fish paste also showed that the PLA/TPS film was more effective to prevent bacterial growth than LDPE/TPS film.

Starch‐based films and food coatings: An overview

Native and modified starches have received considerable attention for biodegradable films formulation due to their completely biodegradable nature, edible characteristics, and low cost. Development and characterization of starch films obtained by: (i) casting, (ii) blown extrusion and (iii) the thermo‐compression moulding process are described. The rheological properties of filmogenic suspensions, the barrier properties, and the mechanical resistance of the obtained films are reported. Addition of specific additives to the formulations modifies the film functionality transforming them into active materials. Diffusion of antimicrobial agents such as potassium sorbate from the active starch film, as well as their efficacy in dairy products is discussed. Likewise, reinforcing agents lead to composite materials with improved mechanical resistance. Starch‐based materials show higher permeability to carbon dioxide than to oxygen, which is useful to control the respiration rate of fruits and vegetables. The application of active starch‐based coatings to strawberries and Brussels sprouts in order to prolong their refrigerated storage life is analyzed. A detailed overview on the formulation and performance of starch‐based films employing industrial and lab‐scale methods, as well as the application of starch coatings to improve food quality is presented, with the aim of analyzing the possibility of development and application of such materials.

Palm oil deodorizer distillate as toughening agent in polylactide packaging films

AbstractPolylactide (PLA) is the most used biodegradable and biobased food packaging polymer for rigid containers and films. However, its low ductility is a hurdle for increasing its applications in flexible food packaging. A solution is the use of additives. Palm oil deodorizer distillate (PODC) is revealed to be an excellent additive promoting PLA ductility. PODC is a by‐product of vegetable oil refining, which is available in stable quality and in sufficient amounts. Amorphous PLA/PODC blends had an elongation at break of around 130% and that of semi‐crystalline blends was still around 55% compared to the initial 5% of neat PLA. At the same time the PLA rigidity and high glass transition temperatures were kept. PODC was also a very efficient processing aid, allowing for film blow extrusion. The blends were stable in properties during six months without exudation. They complied with legal norms of Food Contact Materials (EU 10/2011) and induced no sensorial alteration of packed food. Therefore PODC is a very interesting alternative to common plasticizers for the production of flexible PLA packaging films. © 2016 Society of Chemical Industry

Development of Double‐Layer Active Films Containing Pomegranate Peel Extract for the Application of Pork Packaging

AbstractNature extract is one of the most important additives in active food packaging. In this study, the mono and double‐layer active films containing pomegranate peel extract (PPE) were prepared and their effects for pork stored under refrigeration were evaluated. With 1.5% of PPE as an active agent and polyethylene (PE) resin as a matrix, PPE‐PE monolayer active packaging films were prepared by the extrusion blow molding process. With PPE‐PE active film as the internal layer film, two double‐layer active films such as PPE‐PE/polyethylene terephthalate (PET) and PPE‐PE/polypropylene (PP) were obtained. The characterizations of mechanical, optical and barrier properties of PE, PE/PET, PPE‐PE, PPE‐PE/PET and PPE‐PE/PP films were determined. The addition of PPE increased elongation at break from 115.85–178.05%. Effects of pork packaged by these active films stored at refrigeration (4 ± 1C) were evaluated, based on total volatile basic nitrogen (TVB‐N), total viable counts (TVC), pH, TBA and drip loss. By day 6, the TVC of pork samples packaged by PPE‐PE, PPE‐PE/PET, PPE‐PE/PP and PE/PET films, respectively, were 5.78, 5.49, 5.58, 5.72 log10 CFU/g, compared to TVC of pork sample in PE film, 6.54 log10 CFU/g, which showed PPE‐PE/PET and PPE‐PE/PP films had good antibacterial effects. These active films delayed the changes of drip loss and sensory score, and retarded the changes of TVB‐N, TBA and pH value, especially PPE‐PE/PP and PPE‐PE/PET films. The results indicated that PPE‐PE/PP and PPE‐PE/PET active films could extend pork shelf life better than PPE‐PE films which could extend pork shelf life by 3 days.Practical ApplicationsActive packaging provides an additional and final barrier that can prevent the corruption effectively. Polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) are well‐known packing material for their excellent physical and chemical properties. We blend the pomegranate peel extract (PPE) with PE and prepare the active film by extrude blow. It is a potency to prepare active film in factory not only in laboratory. This work has studied mechanical, optical and barrier property of the active film, and the actual preservation effect of active packaging. The comprehensive characterization of the film would present more valuable information for practical application.

A study of “worms” melt fracture in polyethylene extrusion blow molding process using capillary rheometry

During the polyethylene (PE) blow molding process of large size drums, string-like defects, which are referred to here as worm melt fracture, can sometimes be observed on the extrudate surface. Such string-like defects, in various shapes and sizes, are also observed in the capillary extrusion at high shear rates after the slip-stick transition. The PE resin with broader molecular weight distribution (MWD) exhibits a greater degree of worm melt fracture while narrow MWD PE resin, which has higher slip velocity and a uniform slip layer, shows a lesser degree of worm melt fracture. It is hypothesized that the worm melt fracture is related to the die build-up. Based on the mechanism of the fast die build-up, it is proposed that the cohesive slip layer, which is a failure within the polymer melts at an internal surface, could emerge out from the die as these string-like materials attached on the extrudates. The broader MWD resin, which has more small polymer chains and a lower plateau modulus, is postulated to have a weaker polymer melt, which then makes it easier to have such an internal failure and consequently have more string-like defects at high shear rates. POLYM. ENG. SCI., 56:650–656, 2016. © 2016 Society of Plastics Engineers

Principles of polymer processing modelling

Polymer processing involves three thermo-mechanical stages: Plastication of solid polymer granules or powder to an homogeneous fluid which is shaped under pressure in moulds or dies and finally cooled and eventually drawn to obtain the final plastic part. Physical properties of polymers (high viscosity, non-linear rheology, low thermal diffusivity) as well as the complex shape of most plastic parts make modelling a challenge. Several examples (film blowing extrusion dies, injection moulding, blow moulding) are presented and discussed.

Effects of low poly(vinyl alcohol) content on properties of biodegradable blowing films based on two modified starches

Biodegradable films from hydroxypropyl distarch phosphate (HPDSP)/poly(vinyl alcohol) (PVA) and cationic starch/PVA blends were obtained by extrusion blowing at ratios of 100:0, 95:5, 90:10, 85:15, and 80:20. The morphology, X-ray patterns, transparency, mechanical properties, thermal properties, and water vapor permeability (WVP) of the films were measured and compared. Scanning electron microscopic micrographs of the films showed continuous matrix texture as well as better compatibility between modified starches and PVA. X-Ray diffraction indicated the formation of ordered crystalline structures in the films during extrusion blowing. The addition of PVA to modified starches significantly increased their tensile strength (TS, 3.92 MPa) while decreasing their water vapor permeability (WVP, 3.23 × 10−10 g m−1 s−1 Pa−1). The starch/PVA composite films did not show phase separation.

Extrusion blow molding of a starch–gelatin polymer matrix reinforced with cellulose

This work investigated the possibility of using hydrolyzed corn starch–gelatin as a base matrix and cellulose as reinforcement, to produce containers by extrusion blow molding. First, the compounds were characterized by dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) to determine their viscoelastic behavior and thermal stability. The results showed that the most suitable processing temperature should be less than 120°C to avoid degradation. Furthermore, the addition of cellulose decreased the viscosity of the starch–gelatin polymer matrix allowing the compounds to be processed at temperatures as low as 100°C. Then, parisons were obtained by extrusion blow molding and presented suitable processing characteristics. Overall, the best containers were found to have 44% higher energy at break and better dimensional stability when cellulose was added.

Polyethylene and hydrolyzed collagen blend films produced by blown extrusion

Polyethylene and hydrolyzed collagen blend films produced by blown extrusion

Development and analysis of gas barrier properties of microfibrillar polymer–polymer composites

Polyethylene terephthalate microfibril-reinforced composites with linear low-density polyethylene (LLDPE) matrix were manufactured by four industrial processing methods: compression moulding, slit-die extrusion with calendering, extrusion blow moulding and injection moulding. The microfibrils were generated in situ by blending the two polymers together and thermomechanically processing the blend. Thin sheets were manufactured in all the processes, except injection moulding, which was employed for making containers. The oxygen permeability of the films was determined using a commercial machine. The greatest improvement in oxygen barrier property (compared to neat LLDPE films), was found in the compression-moulded microfibrillar composite (MFC) films. Two existing theoretical models were modified to reasonably forecast the oxygen permeability of compression-moulded MFC films. The parallel filler model provides a very good fit to the experimental data for the full mass ratio range. The Lewis and Nielsen model was also trialled for various polymer combinations, producing reasonable results with minor modifications.

English

This work deals with the design, preparation and characterization of composites based on Poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] and lignocellulosic filler suitable for the production of compostable and biodegradable biocomposites that mimic the thermo-mechanical and processing characteristics commonly found in those polymeric materials specially designed for injection molding and blow extrusion. The best formulation in terms of processability, thermo-mechanical properties and biodegradation behavior under mature compost conditions was the biocomposite that contained 42.8 % by wt. of Poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] as the major component, 5 % by wt. of lignocellulosic filler, 10 % by wt. of tributyl citrate plasticizer, 30 % by wt. of Poly(butylene adipate-co-terephthalate), 10 % by wt. of Poly(vinyl acetate), 0.2 % by wt. of Joncryl ADR-4368C a chain extender, 1 % by wt. of a primary antioxidant mix, and 1 % by wt. of nucleating agents.