Thermoplastic Polyurethane Blends Research Articles

Optimization of process parameters of 3D printed thermoplastic elastomeric materials using statistical modeling with particular reference to mechanical properties and print quality

Additive manufacturing of thermoplastic elastomeric material (TPE) using direct ink writing (DIW) based printing technique opens new horizons for various applications. However, the most crucial process in DIW 3D printing is the optimization of printing parameters to obtain high-quality products both in terms of aesthetics and strength. In this work, statistical models were developed considering layer height, print speed, and, ink concentration to obtain the optimized print quality product from the blend of thermoplastic polyurethane (TPU)/ epichlorohydrin − ethylene oxide − allyl glycidyl ether elastomer (GECO) based TPE materials. Experiments were designed according to the central composite design (CCD) scheme and the influence of input printing parameters on shrinkage and tensile strength was analyzed. The significance of each parameter was systematically studied using the response surface method. For both responses, shrinkage, and tensile strength, printing speed was found to be the most significant parameter. Ink concentration significantly affected tensile strength with a contribution of ∼ 34%. On the other hand, the layer height, with a contribution of ∼ 22% significantly affected the shrinkage behaviour of the 3D printed sample. Finally, multi-objective optimization was performed using a genetic algorithm to identify the optimal 3D printing parameters of the developed TPE materials.

Study on mechanical, thermal and shape memory properties of polycarbonate/thermoplastic polyurethane blends

AbstractThe objective of the study is preparation of shape memory blend of polycarbonate (PC) and thermoplastic polyurethane (TPU). Polycarbonate is blended with three types of TPUs and subsequently mechanical, thermal, morphological, and shape memory properties of the PC/TPU blends are studied. When TPU content in the blend is higher than 40% (by weight), the glass transition temperature related to PC is not shown in the differential scanning calorimetry thermogram, indicating loss of PC properties. The 60/40 optimized blend of PC/TPUs exhibits maximum increment of about 1100% in elongation and 43% decrement in tensile strength. The shape recovery of the optimized blend obtained by addition of 40% (by weight) of TPUs in PC polymer is found to be 65% and shape fixity is 97%. These results suggest that the blend of PC/TPU may be utilized for various applications where shape memory property is required including strategic applications.

Sustainable lignin-based carbon fibre reinforced polyamide composites: Production, characterisation and life cycle analysis

This work presents the first production, characterisation and life cycle analysis of composite materials produced from injection moulded polyamide reinforced with short lignin-based carbon fibre (CF). To produce these composites many challenges associated with the production of lignin CF have been resolved through the utilisation of thermoplastic polyurethane blend with Alcell organosolv lignin. These CFs have been utilised to reinforce polyamide 66 (PA66) and their performance as a reinforcement have been compared with a textile grade PAN CF. Composites have been prepared using short CF and injection moulding with results compared in terms of interfacial interactions, and composite mechanical performance. It was found that lignin-based CF increases crystallinity in the PA66. The increased matrix affinity of the lignin-based CF may be attributed to increased oxygen on the lignin CF which has been retained from the lignin precursor fibre. When considering that the lignin CF reach equivalent diameter to the PAN CF, the mechanical properties of lignin based CF are comparable to that of PAN CF. Life cycle analysis modelling predicts that the replacement of PAN CF with lignin CF reduces the global warming potential by 54 % for these materials.

Enhancing Dielectric Properties, Thermal Conductivity, and Mechanical Properties of Poly(lactic acid)-Thermoplastic Polyurethane Blend Composites by Using a SiC-BaTiO3 Hybrid Filler.

A composite of polymer blends-thermoplastic polyurethane (TPU) and poly(lactic acid) (PLA)-and BaTiO3-SiC was fabricated. BaTiO3 particles were used to improve the dielectric properties of the composite materials, whereas SiC was used to enhance thermal conductivity without altering the dielectric properties; notably, SiC has a good dielectric constant. The surfaces of the filler particles, BaTiO3 and SiC particles, were activated; BaTiO3 was treated with methylene diphenyl diisocyanate (MDI) and SiC's surface was subjected to calcination and acid treatment, and hybrid fillers were prepared via solution mixing. The surface modifications were verified using Fourier transform infrared spectroscopy (the appearance of OH showed acid treatment of SiC, and the presence of NH, CH2, and OH groups indicated the functionalization of BaTiO3 particles). After the extruded products were cooled and dried, the specimens were fabricated using minimolding. The thermal stability of the final composites showed improvement. The dielectric constant improved relative to the main matrix at constant and variable frequencies, being about fivefold for 40% BaTiO3-SiC-TPU-PLA composites. Upon inclusion of 40 wt.% MDI functionalized BaTiO3-SiC particles, an improvement of 232% in thermal conductivity was attained, in comparison to neat TPU-PLA blends.

Additive Manufacturing of Thermoplastic Polyurethane-Cork Composites for Material Extrusion Technologies.

Among the material extrusion technologies of additive manufacturing, fused granular fabrication is playing a bigger role in the industry. The increase in the size of printers demands extrusion systems with higher deposition rates that facilitate printing larger parts in shorter times with a need for cost reduction. This cost reduction in fused granular fabrication systems is due to the utilisation of pellets as the material source for the prints, such as pellets that are the most common way of distributing polymeric materials in industry and do not need the usual previous transformation into filaments. Most of the polymers in the industry can be found in the shape of pellets, so the opportunities for developing new materials beside the traditional filaments found in the market are expanding. In this research, a novel composite material has been developed based on the blending of commercial thermoplastic polyurethane (TPU) and cork particles obtained from industrial waste at different concentrations. These materials have been processed at a laboratory scale, and their mechanical, thermal and rheological properties have been studied. Despite a 53.52% reduction in the maximum stress on the x-axis, an 81.82% decrease in the values obtained with specimens oriented on the z-axis and a shortage in the deformation values, the results reveal a remarkable weight reduction leading to 21.31% when compared to the TPU of the blends,. These results may open a path to further explore these blends and find suitable applications in industry as proposed.

Preparation of thermoplastic polyurethane blend foams with controlled hydrophobicity via vapor induced phase separation

AbstractOil–water separation has attained great attention due to recent concern in environmental safety. Porous material from tailored engineering is the best candidate to selectively adsorb oil from water. Among the various porous materials, polymer based adsorbent has several advantages over others, in terms of controllable porosity and functionality. Here, we propose thermoplastic polyurethane (TPU) based blend foam through vapor induced phase separation method as a potential candidate for oil–water separation. In order to adjust hydrophobicity and compatibility of TPU blend, PDMS‐based TPU (Si‐TPU) is designed and synthesized to be blended with commercialized TPU. Si‐TPU with tailored weight ratio (PDMS/PTHF = 4/6) in synthetic level make it possible to achieve both of demanded hydrophobicity (the water contact angle increased from 85.19 ± 1.83° to 121.15 ± 3.79° after adding Si‐TPU) and controlling compatibility with CTPU during VIPS foaming. Thus, these well‐designed Si‐TPU can be utilized in various fields such as improving compatibility of polymer blend, adsorption efficiency of oil, and smart filtration, and so forth.

Synergism of triazine containing dopamine to flame retardancy, smoke suppression, and mechanical properties of thermoplastic polyurethane/ammonium polyphosphate

AbstractA dopamine‐triazine compound (TTD) was synthesized by using dopamine and cyanuric chloride. The TTD and ammonium polyphosphate (APP) were combined to improve the flame retardancy of thermoplastic polyurethane (TPU). The flame retardancy, thermal stability and mechanical properties of TPU blends were investigated. TPU containing 8 wt% APP displays a UL‐94 V0 rating and a limiting oxygen index (LOI) of 30.0 vol%. When APP and TTD are combined at a ratio of 7/1 (wt%/wt%), only 5 wt% flame retardant is needed to endow TPU with a UL‐94 V0 rating, suggesting that a good synergistic effect exists between APP and TTD on enhancing flame retardancy of TPU. In addition, TTD reduces the heat release rate of TPU, suppresses the smoke and toxic gas release and promotes the formation of an intumescent char layer with few defects during combustion. In addition, TTD improves the tensile properties of TPU/APP blends.

Rheology, mechanical properties and peel adhesion of hot-melt adhesive based on thermoplastic polyurethane/nanosilica

A series of thermoplastic polyurethane hot-melt adhesive formulations have been synthesized by melt blending of polyether-based thermoplastic polyurethane and different nanosilica, C5, and C9 hydrocarbon loadings. Different analyses, including FESEM, tensile strength, rotational rheometry, T-peel strength with polyester fabric, and nitrogen gas permeability, are conducted to examine the properties of the prepared adhesive formulations. The results show that the addition of 0.25 wt% of nanosilica increased the tensile properties of the polyurethane slightly and improved the T-peel strength with the polyester fabric. On the other hand, adding 5 wt% of C5 hydrocarbon tackifier reduced the tensile properties a bit, reduced the storage and loss modulus, and increased the T-peel strength with the polyester fabric. On the other hand, adding the C9 tackifier reduced the tensile strength more than the counterpart formulation including C5, reduced the storage and loss modulus and increased the T-peel strength. A noteworthy result was that the addition of nanosilica in the presence of C5 or C9 tackifiers lowered the loss and storage modulus and complex viscosity Adhesive formulation with 5 wt% of C5 tackifier has the highest average and maximum peel strength with about 20 and 35% higher strength than neat TPU.

The Production of Hollow Nanofibers from PBS / TPU Blends by Coaxial Electrospinning Method

In this study, the production of hollow Polybutylene Succinate (PBS)/Thermoplastic Polyurethane (TPU) nanofibers as biodegradable nanomaterials with improved mechanical properties were carried out by coaxial electrospinning method. The polymer solutions of pure PBS, pure TPU, and PBS/TPU blends (60/40, 40/60, 20/80 w/w) (as the shell) versus pure Polyvinylpyrrolidone (PVP) (as core) were put together for bi-component nanofibers production. The core structure of nanofibers was dissolved in distilled water. Thus, hollow nanofibers were obtained with the removal of PVP from the structure. Characterization studies (SEM, FTIR, and Tensile tests) of hollow nanofibers were performed. The morphological properties of PBS/TPU blends in ratios of 60/40 and 20/80 were observed as homogeneous and non-adhered fiber structures. It was determined that the hollow PBS/TPU (60/40) mat has the thinnest nanofibers. New bond formations within the interactions of substances as studied in the chemistry of blended electrospun webs were examined with FTIR analysis. Therewithal, this test showed the removal of PVP in the core of all nanofibers. It was observed that the adhered fibers increased the tensile stress and decreased the tensile strain at mechanical test results that were verified also by SEM views. It is suggested that the hollow nanofibers produced by this study can be used in the biomedical field as a biodegradable and breathable wound dressing.

Thermoplastic polyurethane for three‐dimensional printing applications: A review

AbstractAdditive manufacturing is an emerging technology with the advantage of less wastage, fast prototyping with customized designing suitable for a wide range of applications. Three‐dimensional (3D) printing is one of the types of additive manufacturing and various polymers are explored for 3D printing applications. Thermoplastic polyurethane (TPU) is a versatile material that has gained increasing attention in 3D printing applications due to its unique combination of mechanical, thermal, and chemical properties. This review paper provides an overview of the current state‐of‐the‐art in TPU‐based 3D printing, including its characteristics, processing techniques, and mainly its applications. Extensive studies are done in TPU with fused deposition modeling (FDM), multi‐jet fusion (MJF), and selective laser sintering (SLS). The elasticity and flexibility, layer adhesion, tensile strength, and support structure are the parameters that decide the suitability of FDM, SLS, and MJF for TPU 3D printing. The infill density, modification of processing parameters, use of sacrificial materials, addition of perforations or channels, varying the particle size, using a mixture of powders, and so forth. leads to develop the porous structure in the final product. In addition, we have studied blends of TPU with other polymers like acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA), as well as fiber‐reinforced TPU composites for 3D printing applications.

Tribological properties of hemp fiber reinforced polylactic acid bio-composites: effect of different types of modification methods

In this study, green composites are prepared with 30 wt.% hemp fibers reinforced polylactic acid (PLA) to enhance the impact and tribological properties. Different surface treatments of alkali and silane, compatibilizer of maleic anhydride (MA), and blends of thermoplastic polyurethane (TPU) and poly (butylene succinate) were applied to improve interfacial adhesion between fibers and matrix. Hemp-reinforced PLA bio-composites were fabricated and characterized by hardness, impact strength, wear, and friction properties. The tribological tests of the injection-molded components were performed under two different loads (10 N and 20 N) as dry-sliding linearly reciprocating motion per ASTM G133. Modified composites gave better tribological properties than unmodified composites. While no remarkable improvement was observed in the hardness value of untreated fiber-reinforced composite, alkali-treated composite reached up to 43% improvement in hardness value. In general, as the load increased, weight loss increase was observed in all composites. Unmodified bio-composite exhibited a very low weight loss and specific wear rate (SWR) compared to neat PLA under 10 N load. The SWR of the MA bio-composite had the lowest value for both loads (10 N and 20 N) compared to the other bio-samples. The TPU blended bio-composite exhibited the highest impact strength (22.96 kJ m−2) after pure PLA (26.5 kJ m−2). Therefore, due to surface treatments and blends applied to the fibers, some composites’ hardness and wear resistance were increased while the impact strength and friction coefficient was decreased. Especially silane surface treatment and MA compatibilizer application increased the wear resistance of composites. When the scanning electron microscope images were examined, it was revealed that the fiber and matrix interface bonding was good, and the fibers were firmly embedded in the matrix. Furthermore, forming a protective thin film layer formed by the polymer debris from the surface during dry-sliding increased the wear performance of the bio-composites.

Effect of a bio-based copolymer containing lysine, dopamine and triazine on flame retardancy and mechanical properties of thermoplastic polyurethane/ammonium polyphosphate

A bio-based copolymer (TDDL) containing lysine, dopamine, triazine was synthesized using cyanuric chloride, dopamine and lysine, respectively. The TDDL was used as a charring agent and ammonium polyphosphate (APP) was used as an acid source to improve the flame retardancy of thermoplastic polyurethane (TPU). The flame retardancy and thermal degradation behaviors of TPU blends were investigated using UL-94 vertical burning, limiting oxygen index (LOI), cone calorimetry tests and thermal gravimetric analysis (TGA). TPU blend containing 8 wt% APP displays a UL-94 V0 rating and a LOI value 30.0 vol%. While TPU blend containing 6 wt% APP/TDDL displays a UL-94 V0 and a LOI 29.6 vol% suggesting good synergistic effect between TDDL and APP. In addition, TDDL reduces the heat release rate of TPU/APP blend, and promotes the formation of a perfect char layer during the combustion process, and suppresses the release of combustible gas and smoke. Moreover, TPU blends have better modulus and elongation at break than those of TPU.

Sustainable Engineered Design and Scalable Manufacturing of Upcycled Graphene Reinforced Polylactic Acid/Polyurethane Blend Composites Having Shape Memory Behavior.

Material design in shape memory polymers (SMPs) carries significant importance in attaining high performance and adjusting the interface between additive and host polymer matrix to increase the degree of recovery. Herein, the main challenge is to enhance the interfacial interactions to provide reversibility during deformation. The present work describes a newly designed composite structure by manufacturing a high-degree biobased and thermally induced shape memory polylactic acid (PLA)/thermoplastic polyurethane (TPU) blend incorporated with graphene nanoplatelets obtained from waste tires. In this design, blending with TPU enhances flexibility, and adding GNP provides functionality in terms of mechanical and thermal properties by enhancing circularity and sustainability approaches. The present work provides a scalable compounding approach for industrial applications of GNP at high shear rates during the melt mixing of single/blend polymer matrices. By evaluating the mechanical performance of the PLA and TPU blend composite composition at a 9:1 weight percentage, the optimum GNP amount was defined as 0.5 wt%. The flexural strength of the developed composite structure was enhanced by 24% and the thermal conductivity by 15%. In addition, a 99.8% shape fixity ratio and a 99.58% recovery ratio were attained within 4 min, resulting in the spectacular enhancement of GNP attainment. This study provides an opportunity to understand the acting mechanism of upcycled GNP in improving composite formulations and to develop a new perspective on the sustainability of PLA/TPU blend composites with an increased biobased degree and shape memory behavior.

Morphological, Mechanical and Thermal Properties of Polybutylene Tetrephthalate‐Polyester Based Thermoplastic Polyurethane Blends

AbstractPolybutylene tetrephthalate (PBT)‐polyester based thermoplastic polyurethane (TPU) blends with varying percentages of TPU (10 %, 20 %, 30 %, 40 %) were prepared in order to improve impact strength of PBT to enhance its applications. The blends were prepared by melt mixing using a twin screw extruder. Based on morphological images, impact strength analysis and dynamical mechanical analysis, TPU was well dispersed in PBT polymer matrix. Studies using Differential Scanning Calorimetry indicate a decrease in crsytallinity on addition of 30 % TPU in PBT. Thermogravimetric analysis demonstrates that addition of TPU in PBT matrix increases the char content. PBT and TPU have a good interfacial adhesion, according to SEM investigations. Mechanical characteristics demonstrate that the inclusion of TPU in PBT matrix resulted in a significant increase in impact strength of about 208 %, with minor changes in tensile strength and tensile modulus. Change in glass transition temperature of the optimised blend was measured using DMA.

Erucamide/thermoplastic polyurethane blend with low coefficient of friction, high elasticity and good mechanical properties for intelligent wearable devices

AbstractIn this study, erucamide as a non‐toxic and tasteless lubricant was melt blended with thermoplastic polyurethane (TPU) to reduce the coefficient of friction (COF) of TPU and thus to improve the wearing comfort of intelligent wearable devices. The results show that when the content of erucamide reaches percolation, erucamide can migrate to the TPU surface, forming a layer of lubrication film, and thus significantly reduces the COF of TPU. In addition, erucamide with amide groups can form hydrogen bonds with carbamate groups from TPU chains and thus can disrupt the hydrogen bonds between two amide groups of TPU chains. With the introduction of erucamide, the chain mobility of TPU increases, the partial phase mixing of soft phase and hard phase of TPU occurs, and the interchain interaction between TPU chains decreases. Under the appropriate content of erucamide (0.5 wt%), both the elasticity and processability of TPU are also significantly improved, whereas the high tensile strength, tear strength and elongation at break of the TPU blend is still obtained, facilitating its practical application in intelligent wearable devices. © 2022 Society of Industrial Chemistry.

Development of 3D printed human brain models using thermoplastic Polyurethane/Rubber blends for anatomy teaching promoting kinesthetic learning purposes

Kinesthetic appreciation of anatomy models serves to activate a concrete sensory experience that enhances 3D visuospatial mental mapping of anatomical structures. However, most commercially available plastic anatomy models are costly and do not provide tactile sensation similar to the organ or structures. Polymeric materials have been used widely in additive manufacturing to produce human brain models, however, none of the models resembles accurate feeling. The aim of this study is to produce 3D printed anatomical models using customized soft 3D printing filament from thermoplastic Polyurethane (TPU) and two types of rubber, which are ethylene propylene diene monomer (EPDM) and styrene butadiene rubber (SBR) compounds. Actual human brain MRI scans are used to form 3D-printed anatomy models. The MRI image obtained was in DICOM format, exported into 3D slicer software for specific brain parts extraction (whole brain, brain ventricles, circle of Willis, and dural venous sinuses), and converted into STL format for 3D printing. For material processing, the blending of TPU/EPDM and TPU/SBR were successfully fabricated using an internal mixer (Haake) and extruded into filament using a single screw extruder with the aid of a filament winder. The human brain model was then printed using 3D Printer (Ender 3). It was found that all TPU blends were able to be printed into brain anatomy models but the properties of the materials were greatly affected by rubber types and compositions of the added fillers. The addition of more than 30% of the fillers gave difficulties in processing, probably due to inconsistent viscosity that led to phase separation.

Influence of processing oil on properties of dynamically cured epoxidized natural rubber and thermoplastic polyurethane blends

Influence of processing oil on properties of dynamically cured epoxidized natural rubber and thermoplastic polyurethane blends

Contact-Active Layer-by-Layer Grafted TPU/PDMS Blends as an Antiencrustation and Antibacterial Platform for Next-Generation Urological Biomaterials: Validation in Artificial and Human Urine.

Urinary tract infections and urinary encrustation impede the long-term clinical performance of urological implants and medical devices. Together, biofilm formation and encrustation constitute serious complications, driving the development of next-generation urological biomaterials. The currently available bioengineered solutions have limited success during long-term usage in the urinary environment. In addressing this unmet clinical challenge, contact-active, antiencrustation surface grafting were conceived onto a dynamically cross-linked polydimethylsiloxane (PDMS) modified thermoplastic polyurethane (TPU) blend using the layer-by-layer (LbL) assembly route. To the best of the authors' knowledge, the present study is the first to investigate the LbL grafting in developing an antiencrustation platform. These multilayered assemblies strategically employed covalent cross-linking and electrostatic interaction-assisted progressive depositions of branched polyethyleneimine and poly(2-ethyl-2-oxazoline). While polyethyleneimine conferred the contact-killing bactericidal activity, the much-coveted antiencrustation properties were rendered by incorporating a partially hydrolyzed derivative of poly(2-ethyl-2-oxazoline). The performance of the resultant surface-modified TPU/PDMS blends was benchmarked against the conventional urological alloplasts, in a customized lab-scale bioreactor-based dynamic encrustation study and in human urine. After 6 weeks of exposure to an artificial urine medium, simulating urease-positive bacterial infection, the surface-modified blends exhibited a remarkable ability to suppress Ca and Mg encrustation. In addition, these blends also displayed superior grafting stability and antibacterial efficacy against common uropathogens. As high as 4-fold log reduction in the planktonic growth of Gram-negative P. mirabilis and Gram-positive MRSA was recorded with the LbL platform vis-à-vis medical-grade TPU. In conjunction, the in vitro cellular assessment with human keratinocytes (HaCaT) and human embryonic kidney cells (HEK) established the uncompromised cytocompatibility of the multilayered grafted blends. Finally, the physiologically relevant functionality of the LbL grafting has been validated using clinical samples of human urine collected from 129 patients with a broad spectrum of disease conditions. The phase-I pre-clinical study, entailing 6 week-long incubation in human urine, demonstrated significantly improved encrustation resistance of the blends. The collective findings of the present work clearly establish the success of LbL strategies in the development of stable, multifunctional new-generation urological biomaterials.

Mechanically enhanced poly(lactic acid)/polyurethane blend with interfacial‐localized clay particles

AbstractIn this study, clays (C30B, C20A, and ) with different interlayer modifier and localization are investigated to improve mechanical properties of poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blend based on crystallization, morphology, and rheology analyses. The mechanical properties of the PLA/TPU 70/30 blend (elongation at break: 229%, impact strength: 55 J/m) are additionally increased by the clay particles. Depending on modifiers within the particles localized at the interface, 0.1 wt% of the C30B maximizes elongation at break (289%) while 0.1 wt% of the C20A maximizes impact strength (81 J/m) due to its influence on crystal structure of PLA. Thermal analysis through differential scanning calorimeter shows that hydrophilic C30B induces ductile α' PLA crystal formation while less hydrophilic C20A induces stiff α crystal formation, which is reflected on the mechanical properties. In addition, there exists optimum degree of crystallinity for the desired mechanical properties. The excessive interfacial‐localized clay is found to interfere PLA/TPU interaction. Meanwhile, natural clay, enhances mechanical properties of blend with the reduced distance between the TPU droplets with a 0.3–3 wt% addition. In addition, rheological properties help us to design the blend and annealing condition for the desirable mechanical properties.

Poly (ethylene terephthalate) nonwoven fabrics‐based membranes modified by electrospinning of thermoplastic polyurethane, nano SiO2 and Ag particles as medical packing materials

AbstractAiming at development of novel medical packings, poly (ethylene terephthalate) (PET)‐based membranes with hydrophobic and antibacterial properties were prepared by electrostatic spinning of a blend of thermoplastic polyurethane (TPU), nano SiO2 and Ag particles on PET nonwoven. In cooperation with electro‐spun TPU/SiO2 layer, the water contact angle (WCA) of PET nonwoven fabric was improved from 60° to 115–130°, and the water vapour transmission rate was 2200–2500 g/m2/24 h. It indicates that the modified PET nonwoven membrane exhibits a much better water resistance, highly increased hydrophobicity and moderate water permeability. Nano‐silver provided excellent antibacterial properties for this non‐cytotoxic PET/TPU/SiO2/Ag composite membranes. The PET/TPU/SiO2/Ag composite membranes had high mechanical properties, which exhibited a tensile strength of 56 MPa in the longitudinal direction and 35 MPa in the transversal direction, and tear strength of 30 kN/m in the longitudinal direction and 48 kN/m in the transversal direction. This new PET/TPU/SiO2/Ag composite membranes showed broad application prospects in the medical packaging industry.