Thermal & Impact Barrier Packaging ME 4054W: Design Projects
- Volume 2 -
May 9th, 2013
Team
Advisors
Justin
Professor Ephraim Sparrow
Eggleston
Ricardo Juarez Martinez
John Gorman
Sean Riley
Sponsor
Jacob Wander
Mark Whitaker
2
1 PROBLEM DEFINITION SUPPORTING DOCUMENTS 1.1 ANNOTATED BIBLIOGRAPHY SUMMARY REFERENCES 1.2 PATENT SEARCH 1.2.1 OBJECTIVES 1.2.2 SEARCH CRITERIA 1.2.3 FINDINGS 1.3 USER NEED RESEARCH 1.4 CONCEPT ALTERNATIVES 1.5 CONCEPT SELECTION
2 2 2 5 5 5 5 8 10 11
2 DESIGN DESCRIPTION SUPPORTING DOCUMENTS
14
2.1 MANUFACTURING PLAN 2.1.1 MANUFACTURING OVERVIEW 2.1.2 PART AND PROCESS DRAWINGS 2.1.3 BILL OF MATERIALS 2.1.4 MANUFACTURING AND IMPLEMENTATION PROCEDURE
14 14 14 17 17
3 EVALUATION SUPPORTING DOCUMENTS
18
3.1 EVALUATION REPORTS 3.1.1 EFFECTIVE CONDUCTIVITY - EXPERIMENTAL 3.1.2 EFFECTIVE CONDUCTIVITY – SIMULATED 3.1.3 IMPACT PROTECTION - EXPERIMENTAL 3.1.4 PRE-USE/IN-USE VOLUME 3.1.5 MATERIAL RECYCLABILITY 3.2 COST ANALYSIS 3.3 ENVIRONMENTAL IMPACT STATEMENT 3.4 REGULATORY AND SAFETY CONSIDERATIONS
18 18 26 33 37 38 39 39 40
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1 Problem Definition Supporting Documents 1.1 Annotated Bibliography Summary Research was done to determine experimental methods, simulation models and material properties. Special interest was taken in measuring properties of low conductivity materials and studies involving shipping of thermally sensitive products. Current industry standards for shipping these sensitive products include pre-inflated “mailers,” rigid boxes impregnated with phase change material and basic expanded polystyrene coolers. References [1]
Malasri S., Shiue P., Lawrence A., Rutledge L., Moats R., 2011, “Preliminary Study of Plastic Tote Drop Impact,” Christian Brothers University, Memphis, Tennessee.
This study investigated the peak accelerations seen in drop tests, and compared the results between no protection and some protective packaging, such as bubble wrap. [2]
Gibson S., 2010, “Is Bubble Wrap Duct Insulation a Good Idea?” From http://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/bubble-wrap-duct-insulationgood-idea
A study of properties of bubble wrap was performed by ASTM and outlined on this web page. The main use of this article was a value for thermal resistance in bubble wrap. [3]
2009-2013, “Transportation of Blood Components.” Canadian Blood Services, Canada, from http://www.transfusionmedicine.ca/
The Canadian Blood Service performs studies in order to help hospitals improve blood utilization. This site provides many “standards” for handling blood such as acceptable temperature ranges. [4]
2012, “Information Regarding Insulin Storage and Switching Between Products in an Emergency.” FDA U.S. Food and Drug Administration, U.S. Department of Health & Human Services, from http://www.fda.gov/Drugs/EmergencyPreparedness/ucm085213.htm
The Food and Drug Administration created a web page with guidelines for insulin handling. Some key points for this project include storage temperature ranges and shelf life of insulin. These numbers can be used as standards when shipping insulin, which is a common item for this application. [5]
2006, “Xpander Pak Innovative Solutions for Your Small Packaging Needs.”International Foam Packaging, LLC, from http://www.intfoam.com/index.php/pages/about_xpander_pak.ht
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The International Foam Packaging, LLC company created a document in which its products are specified. Xpander Pak © is one of their lines of packaging and shipping products. In this document, the “Super Protective Shipper” product of Xpander Pak © is described in detail, providing numerous specifications of its commercial properties and uses. [6]
2013, “SERIES 45696 [CREDO CUBE].” Minnesota Thermal Science, from http://www.mnthermalscience.com/products/series-4-5696
Minnesota Thermal Science created a web page with the physical description and technical specifications of the Credo ® cube. The Series 46696 is an insulating box with integrated phase change material walls. The web page, also, provides a chart in which ranges of temperature in which the Credo ® Cube operates. [7]
2011, “PureTemp Technology.”Entropy Solutions, LLC, from http://www.puretemp.com/technology.html
The term “phase change material” (PCM) is used to describe materials that use phase changes (e.g., solidify, liquify, evaporate or condense) to absorb or release large amounts of latent heat at relatively constant temperature. Phase change materials leverage the natural property of latent heat to help maintain products temperature for extended periods of time. PureTemp PCMs are patented natural vegetable based phase change materials which were developed under 5 years of research sponsored by the USDA, NSF and DoD. [8]
Lange J, Pelletier C and Wyser Y, “Modeling and Measuring the Bending Stiffness of Flexible Packaging Materials.” Packaging Laboratory, Nestle Research Center.
Experimentation and Simulation were used in this paper to determine the bending stiffness in thin films and laminates such as packaging materials. Methodology of these studies was explained. [9]
Sparrow E.M., Gorman J.M., Trawick A., Abraham J.P., 2012, “Novel Techniques for Measurement of Thermal Conductivity of Both Highly and Lowly Conducting Solid Media,” International Journal of Heat and Mass Transfer, University of Minnesota.
Two novel methods of measuring material conduction values are developed throughout this journal. Numerical simulations were used to confirm the validity of these test methods. [10]
LaRule L.,Basily B., Elsayed E.A., “Cushioning Systems for Impact Absorption.” Department of Industrial and Systems Engineering, Rutgers University.
In this paper a novel cushioning method of folded material was subjected to a range of testing. The results of these tests were compared with identical testing performed on common bubble wrap.
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[11]
Malasari S., Aflaki J., Moats R., Harvey M., Aung P., Godwin K., Siow W., Jordan R., Laney J., Sampson N., Gracia L., Stevens R., 2013, “Effects of Water Content on Compressive Strength and Impact Properties of New Softwood Pallets.” International Journal of Advanced Packaging Technology, Vol. 1, Issue 1, pp. 1-10.
Four experiments were performed to evaluate the effects water content had on softwood pallets. Static compression and drop tests were performed and displayed informative methodologies. [12]
Velisek F.J.,1991, “Film Properties and Applications For LLDPE and High Pressure LDPE Blends.” Journal of Plastic Film and Sheeting, Vol. 7.
This journal shows correlation of end uses of LLDPE and LDPE with properties of the various material blends. Effects of manufacturing process are also investigated. [13]
Johnston J.H., Dodds M.A., 2011, “The Development of a Flexible, Re-usable Thermal Buffering and Insulating Liner for Packaging Temperature Sensitive Products.” Appita Journal, Vol. 64, Issue 2, pp. 153-157
This article investigated the thermal conductivity of specific phase change materials (PCM’s). detailed the measurement process, specifically that of a low conductivity medium, and the results. [14]
It
Swanson G.E., 1964, “Know Your Package Inside and Out Before Selecting the Best Heat Insulation.” Package Engineering, Vol. 9, Issue 10, pp. 98-104.
This article discusses the importance of knowing the environment in which a package is shipped. Factors such as temperature, humidity and internal item placement can have adverse affects on the insulation capability of the package. [15]
Weihs T.P., Hong S., Bravman J.C., Nix W.D., 1989, “Measuring the Strength and Stiffness of Thin Film Materials by Mechanically Deflecting Cantilever Microbeams.” Material Research Society Symposium, Vol. 130, pp. 87-92
Stiffness and deflection measurement methods for thin films are outlined in this journal. Many of these thin films contained an adhesive (substrate) layer which works as a model for possible solutions to this problem. Neglecting the substrate layers in simulation was found to give inaccurate results. [16]
Valtýsdóttir K.L., Margeirsson B., Arason S., Pálsson H.,Gospavic R., Popov V., 2011, “Numerical Heat Transfer Modelling for Improving Thermal Protection of Fish Packaging.” CIGR Section VI International Symposium.
This article used numerical simulation software to improve the current fish packaging containers, while maintaining the same dimensions and capacities, through a trial and error investigation. Thermal & Impact Barrier Packaging
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[17]
Nguyen D., “Analysis and Testing of Heat Transfer through Honeycomb Panels.” California Polytechnic State University, San Luis Obispo, California.
This article discusses the importance of radiation in heat transfer through a vacuum honeycomb panel. It contains equations, view factors, and effective conductance results.
1.2 Patent Search 1.2.1 Objectives A thorough patent search was performed to discover current products relating to our design. We were interested in any products involving inflatable insulating and cushioning systems. 1.2.2 Search Criteria Google Scholar was used as the search engine. Many keywords were input into the search engine in order to find any patents having some relation to our design. Revealing key words included “inflatable” in conjunction with one of the following: “envelope”, “packaging”, “insulation”, “bubble wrap”. 1.2.3 Findings Our patent search uncovered two relevant patents. Both of these patents use the idea of air cushions with an added metal layer to insulate and protect the contents.
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Figure 1 – Patent 6,139,188 “Insulated Transit Bag” Oct. 2000.
This patent uses an aluminum coated version of common bubble wrap material to insulate and protect the contents. Multiple layers of this material are sealed together, thereby adding another layer of air cushioning, which increases the insulation effectiveness. This patent differs from our product in that the bubble wrap material is already inflated at the time of assembly, whereas our product had a different cushion design and is completely deflated until time of use.
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Figure 2 – Patent 6,755,568, “Inflatable Insulating Liners for Shipping Containers and Method of Manufacturing”, June 2004.
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This patent discusses heat-sealing multiple layers of polyethylene together with inserted metal strips in order to form an inflatable six-sided cushioning container, to be inserted into a cardboard box or other packaging container. Inflation is performed at time of use through a collapsing valve. This patent has a similar idea to ours but still differs from our product in multiple ways. First, our design uses a common vacuum-deposited aluminum coated polyethylene instead of specially sized strips of metal. Secondly, our design uses a heat seal, rather than a collapsing valve, to close off the air chambers, thus individualizing the chambers. This would maintain some insulating properties in case of a local puncture. Thirdly, our design is intended to be the entire envelope, rather than merely a cushioning insert.
1.3 User Need Research The user needs were acquired initially by consultation with the sponsor company and advisors and these needs were then expanded and reinforced with internet research into competing products and various shipping standards. The sponsor company has years of experience in the retail packaging market. Through their professional expertise and extensive market research, both incidental and intentional, they have identified a market consisting largely of, but certainly not limited to, medical services and pharmaceutical product supply companies who have expressed interest in a novel packaging product that reduces incoming shipping and on site logistical requirements and costs while matching or exceeding current products in thermal insulation and impact protection. The detailed list of customer needs is shown in Table 1. Table 1 – Comprehensive List of Customer Needs Need Description
Category
Importance (1-5)
1 good insulating properties
packaging product
4
2 high impact protection
packaging product
5
3 competitively priced
packaging product
3
4 doesn't add excessive weight
packaging product
3
5 flexibility in size
packaging product
2
6 potential for use as standalone product
packaging product
4
7 reduced volume for delivery/storage
product logistics
5
8 quickly and easily prepared for application
product logistics
3
9 minimal cost/space/maintenance of tools for use
product logistics
3
10 product and application tools easy to use
human factors
3
11 appealing design/appearance
human factors
1
12 recyclable
environmental factors
3
13 minimal waste throughout use
environmental factors
2
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A copy of the document that was prepared for and completed during a meeting with the sponsor company co-founder is shown below. It outlines general user needs and their associated importance. Customer Needs Questionnaire
Who are the end users or target customers? Any general item shipper, as well as those of temperature-sensitive and fragile media. Ex Walgreens, CVS, Best Buy, Amazon.com What are their products? Household items, electronic components, high-value foodstuffs, biological items and materials What parameters describe the products? Dimensions/weights? Within 9” x 11” mailer size, approximately less than 10 lbs. Operating/safe temps? Anywhere from 0-60 C. Limits of impact forces? Varies greatly with product. Value or significance (monetary or otherwise)? Varies greatly with product. What are the shipping/handling conditions? Rough handling a possibility. Possibly uncontrolled thermal environment. Possible lapses in shipping schedule. What are the containment methods? Bubble wrap, boxes, soft and hard insulation materials, pallets, transport carts, trailers, etc. What are the shipping/handling/storage methods? Over the road truck, air freight, warehouse storage. What are the priority capabilities of this product (or its competitors)? Cost? Moderate. Preservation of product? High. Weight? Thermal & Impact Barrier Packaging
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Moderate. Impact resistance? High. Insulating capability? Moderate. What are the supply, storage and operating requirements of the product? Shipping costs/volume? Similar to current bubble/expanding mailer products. Inventory storage space requirement? Minimizing is a goal of this product. Associated/additional products required for use? Provide inflation equipment if needed, cost TBD. Training required for use? Minimal, less than a work day, of training. Maintenance? Provided by sponsor company upon purchase of equipment.
1.4 Concept Alternatives Despite the fact that the sponsor company had presented a partially formed concept and desired direction for development, it was deemed fitting that a full implementation of the design process be executed. The team desired the ability to perform a thorough investigation into existing products and potential materials and technologies, as well as conceive of alternate designs, with the intention of evaluating all potential designs and submitting a proposed concept to the advisors and sponsor company. This process allowed for either a verification of the feasibility and superiority of the sponsor company’s concept or the opportunity to pursue a more suitable design. Following the aforementioned intent, concept ideation was undertaken with a problem statement that simply described a need for a packaging material with protective qualities. The resulting concepts fell into three main categories: phase change materials (PCM), solid low conductivity materials and inflated structures. Within the PCM group, a PCM/packaging material integrated product and a separate PCM product encapsulated in some type of packaging material along with the item of interest were considered. An example could be a grid-like skeletal structure that, along with an outer casement of polymer film, encapsulates the PCM and provides a relatively rigid form to the product as a whole when the PCM is above its freezing point and semi-liquid. Standalone PCM products are available with a range of operating temperatures and masses [7] and could easily be added to a packaging product.
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For solid low conductivity materials, a solid foam liner, foam lined packaging material and pellet filler were examined. The concept involves lining an exterior packaging structure, rigid or otherwise, with an insulating panel or granular filler. The level of integration, i.e. removability or ease of separation from the external structure, of these elements is a point of freedom at this stage. Within the inflatable structure realm, variations on the common bubble wrap product were assessed. Essentially, this entails a restructuring or reorientation of the individual air-filled cells or compartments with the intention of providing the capability to simply and efficiently inflate the product on-site just prior to use.
1.5 Concept Selection The first stage of concept selection was to take the most promising concepts resulting from the ideation session and conduct a high level comparison to an existing product. A selection chart was used that listed selection criteria culled from the customer needs and design requirements. This chart is illustrated in Table 2. Four prospective designs were designated as better (+), similar (0) or worse (-) than a control product in each of the selection criteria. These designations were individually tallied and then a final total calculated. The concepts were ranked according to these totals and top two were chosen to continue on to the scoring phase of the concept selection. Table 2 – Concept Selection Chart (Initial Stage) PCM Integrated Packaging
Inflatable Film Structure
Solid Foam Sheeting
Soft Pellet Filling
Bubble Wrap Envelope
good insulating properties
+
+
-
-
0
high impact protection
-
+
+
+
0
competitive manufacturing costs
-
0
0
0
0
doesn't add excessive weight
-
0
-
-
0
flexibility in size
0
0
0
+
0
potential for use as standalone product
0
0
-
-
0
reduced volume for delivery/storage
-
+
-
-
0
quickly and easily prepared for application
-
-
0
+
0
Selection Criteria
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minimal cost/space/maintenance of tools for use
-
0
0
0
0
product and application tools easy to use
0
0
0
+
0
recyclable/reusable
+
0
-
0
0
minimal waste throughout use
+
0
0
-
0
Sum +'s
3
3
1
4
0
Sum 0's
3
8
6
3
12
Sum -'s
6
1
4
5
0
Net Score
-3
2
-3
-1
0
Rank
4
1
4
3
2
Continue?
no
yes
no
yes
control
At this point, the selection criteria were weighted according to importance and a rating was awarded to the two concepts for each of the criteria. A rating of 1 denotes poor performance while a rating of 5 indicates superior performance. There was insufficient time to generate physical prototypes or simulated models of each concept to conduct testing in each of the criteria areas. Therefore, the concepts were evaluated and assigned ratings using a combination of applied literature or internet research, cumulative and combined knowledge, and common sense. There was admittedly not enough information at this stage; however, informed decisions were still required and were appropriately pursued. The ratings were then weighted accordingly and the weighted scores summed. The higher scoring concept was chosen to develop. This process is depicted in tabular form in Table 3. Table 3 – Concept Selection Chart (Scoring Phase)
Selection Criteria
Weight (%)
Inflatable Film Structure Rating (1-5)
good insulating properties
15
4
60
3
45
high impact protection
15
3
45
4
60
competitive manufacturing costs
10
3
30
3
30
doesn't add excessive weight
5
4
20
2
10
flexibility in size
5
2
10
3
15
potential for use as
10
5
50
2
20
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Weighted Soft Pellet Filling Weighted Score Rating (1-5) Score
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standalone product reduced volume for delivery/storage
15
5
75
1
15
quickly and easily prepared for application
5
3
15
4
20
minimal cost/space/maintenance of tools for use
5
2
10
4
20
product and application tools easy to use
5
2
10
3
15
recyclable/reusable
5
4
20
3
15
minimal waste throughout use
5
3
15
2
10
Total Weight
100
Total Score Develop?
350 YES
275 NO
The two concepts were notably comparable under most of the selection criteria. The largest disparity presented itself when considering the potential for an initially reduced volume that would introduce space and cost savings to a customer in both incoming shipping and on site storage of the product. The second largest distinction lay in the potential for use as a standalone product. Inflatable film structures in the form of bubble wrap mailers are already commonly used. While still conceivable, the possibility of developing an insulating filling as well as a manner in which to enclose it was considered less feasible. Due to the inflation mechanism in its design and the standalone potential, the inflatable film structure was chosen to develop.
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2 Design Description Supporting Documents 2.1 Manufacturing Plan 2.1.1 Manufacturing Overview The manufacturing process for this product is relatively simple, which is one of its main advantages. The core material used in the product is a composite of layered polyethylene and metalized polyester films. This material is purchased from a vendor and received in large rolls. These rolls are fed into a web converting machine that utilizes heated and rubber coated nip rollers to perform the heat sealing process, which creates baffles at set intervals. The process is iterative; with layers added until a construct featuring the desired number of layers is created. A section of material is cut from the layered roll, folded and heat sealed in the appropriate areas into an envelope configuration. At the time of use, the desired shipping item is placed inside the product and the open end is connected to an inflating fixture. The product is then inflated to a set pressure and heat sealed shut. This leaves the product ready for shipment. 2.1.2 Part and Process Drawings
Figure 3 – Composite Formation of Polymer Film Material
Figure 4 – Multi-‐Layered Film Manufacturing Process
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Figure 5 – Cross Section Representation of Cell Geometry
Figure 6 – Folding Layered Film Structure Into a Mailer Configuration
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Figure 7 – Addition of Inflation Device and Heat Sealing
Figure 8 – Packaging Medium in its Inflation Process
Figure 9 – Packaging Medium Being Heat Sealed
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2.1.3 Bill of Materials The bill of materials shown in Table 4 represents the materials needed to manufacture a single mailertype package with pre-inflated dimensions of 9” x 11”. Table 4 – Bill of Materials for Mailer-‐Type Packaging Unit Material / Process
Qty [msi] Cost [$/msi] Total Cost [$]
Aluminum coated polyester/polyethylene film
1.35
0.0597
0.0806
Additional layer of polyethylene film
1.35
0.05
0.0675
Bonding process
1.35
0.0256
0.03456
TOTAL
1.35
0.1353
0.1827
The figures were supplied by the sponsor company and reflect the material costs from their vendors. 2.1.4 Manufacturing and Implementation Procedure 1) Purchase raw materials consisting of rolled sheets of both a composite metallized polyester and polyethylene film and an additional individual polyethylene film from a supplier. 2) Prior to delivery to the manufacturing site, the supplying company adheres the individual polyethylene film to the polyester side of the composite film, creating a 5-layer composite film with polyethylene outer layers adhered to the middle layer of metalized polyethylene as shown in Figure 3. 3) Heat seal two layers of the composite film together at regular intervals using a web converting process employing heated and rubber coated nip rollers, such as location (3) and (2), respectively, in Figure 4. The interval and heat-sealed dimensions are 0.5” and 0.125”, respectively. 4) Add a third layer of composite film with the heat-seal locations now being directly between those of the two layers adjacent to it. The temperature, roller pressure and speed of the heat-sealing process are regulated such that the heat-seal penetrates only the two layers nearest the heated nip roller and does not affect adjacent layers. 5) Add an additional three layers, alternating the heat-seal locations as in Step 4, for a total of six layers. Figure 5 depicts the completed layered film structure with the cells “inflated” for clarity. 6) From the layered film structure, cut a 9” x 22” section. Heat seal one of the ends perpendicular to the linear heat-seals between layers (see location (1) in Figure 6) using a Thermal & Impact Barrier Packaging Page 17 of 40
vacuum sealer, such as the Accu-Seal Model 35, so that all layers are sealed together in an airtight manner. Heat-seal a single layer of composite film to the top and bottom of the opposite end of location (1) in Figure 6. These layers or flaps, location (1) in Figure 7, enable the inflating process by providing an intermediate passageway between the single inflation nozzle and the multiple chamber openings. 7) Fold the structure along the dotted line 11” from location (1) in Figure 6. This effectively folds the layered structure in half, with the added flaps extending beyond. Heat seal the two edges shown in Figure 7 at location (2). The film structure now forms a pocket, enclosed on two sides by a heat seal and on the third by the fold. The product is now ready to have an item placed within, be inflated via the added flaps and be heat-sealed closed. 8) Place the desired item to be shipped inside the packaging product from location (7) in Figure 8. Place the gas-filling device through the integrated flaps of the product and inflate the panel from location (6) in Figure 8. Once the product is inflated with the item to be shipped inside, heat-seal where the flaps connect to the panel (Figure 9). The product in its implementation form has been heat-sealed closed and is ready to be shipped.
3 Evaluation Supporting Documents 3.1 Evaluation Reports 3.1.1 Effective Conductivity - Experimental Introduction
Heat conduction is a mode of heat transfer that deals with the transfer of energy in a medium due to a temperature difference. Heat is transported from the high temperature means to the low temperature, this happens when neighboring molecules collide and transfer energy from the more energetic molecules to the molecules with less energy. Heat conduction can be quantified by means a rate equation called the Fourier’s law of heat conduction: 𝑞!! = −𝑘 ∗
𝑑𝑇 𝑑𝑥
(1)
where 𝑞!! is the heat flux [W/m2], 𝑘 is a transport property known as the thermal conductivity [W/mK] !"
and !" is defined as the temperature gradient through the material or wall. The temperature gradient allocation is linear and can simplify Fourier’s law to:
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𝑞!! = −𝑘 ∗
Δ𝑇 𝐿
(2)
In this case 𝐿 represents the distance (thickness, length, etc.) of the material where the heat transfer is taking place. The thermal conductivity is a property of the material or wall where the temperature gradient takes place. The main foci of the experiment performed were to find the effective thermal conductivity of the prototype GFP and compare it to competitor products such as the Xpander Pak ®, a mailer type bubble wrap and a large bubble wrap. Once the first part of the experiment was completed, the GFP’s conductivity was assessed with the introduction of natural convection. Both experiments were performed by heating the aluminum plates on the top and bottom of the sample, thereby creating a temperature gradient through its thickness [9]. Experimental Methods
The first step in the experimental process conducted was to set up the conductivity apparatus. The apparatus focuses on recording data such as: temperature difference across the desired sample and heat flux induced with a voltage supply. The data is recorded to find the effective conductivity of the sample using Fourier’s Law of heat conduction. The following table shows the items used in the experiment: Table 5 – Apparatus used Item
Manufacturer/ Serial Number
Aluminum Plate (x2)
NA
Small Scale Ruler
NA
Heater (x2)
NA
Voltage Supply (x2)
LG 43030
DAQ Device
Agilent 3407A
Extruded Polystyrene
NA
Type E Thermocouple (x2)
NA
Heat Flux Gauges
NA
Figures 10 through 12 represent the finalized conductivity apparatus and items utilized for the completion of the experiment.
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Figure 10 – Conductivity Apparatus
Figure 11 – Agilent 3407A
Figure 12 – LG DC Power Supply
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The apparatus was built by first gouging a slot on each of the aluminum plates and then mounting a thermocouple in each. After inserting a thermocouple in each plate’s surface, a heat flux gauge was attached to each of the aluminum plate. The setup of the experiment consisted of placing the two heaters on the top and bottom of the sample. Figure 13 presents the experimental set-up in a graphic manner.
Figure 13 – Apparatus Setup Sketch
The samples tested were: The gas filled panel (GFP) (six layers), the Xpander Pak (Polyurethane), an envelope style bubble wrap and a large-bubble wrap. Before running the experiment, each sample’s thickness was measured using a small scale ruler, eight measurements were taken for each thickness and averaged to a final thickness for each sample. The thicknesses of the samples tested are arranged in the following table: Table 6 – Sample Thicknesses
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Sample
Thickness (m)
Gas filled panel
0.0283
Xpander Pak ®
0.0305
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Mailer Bubble wrap
0.0052
Large Bubble wrap (single layer)
0.0065
Once the thickness of each sample was recorded, the experiment was performed five times for each sample type. In each trial, the temperature and heat flux for top and bottom of each sample was monitored and recorded. Multiple points within the steady state regime for each trial are recorded and analyzed. The second part of the experiment consisted of determining whether natural convection affects the heat transfer through the GFP. Natural convection was induced by switching the higher power input to the bottom and lower power input to the top of the apparatus. If the conductivity results are approximately 5% apart from the conduction only and conduction with convection cases then natural convection can be neglected under these conditions. Results and Discussion - Conductivity of Packaging Samples
Once each trial is completed, the temperature difference and heat flux through the sample was analyzed. The heat flux gauges records data in volts; each gauge utilizes a conversion constant that converts from µV to W/m2. Table 7 includes the conversion for each heat flux gauge: Table 7 – Heat Flux Gauge Conversions Heat Flux Gauge
Conversion
1
0.835 µV/ W/m2
2
0.834 µV/ W/m2
The heat flux data was averaged once it reached steady state for each of the heat flux gauges. Then the values for both heat flux gauges were averaged, taken absolute value and converted to W/m2. Once the heat flux was converted to W/m2, the temperatures on top and bottom were averaged once they reached steady state. The thermal conductivity of each sample was calculated using Fourier’s Law for heat conduction (Equation 1). Sample charts given in Figures 14 and 15 illustrate a representative trial of the procedure used.
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Thermocouple Temperature Over Time Top thermocouple temperature
105
Bo9om thermocouple temperature
Temperature [degrees Fahrenheit]
100 95 90 85 80 75 70 65 60 0
50
100
Time [minutes]
150
200
Figure 14-‐Thermocouple Temperature Over Time
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Heat Flux Gauge Voltage Over Time Heat flux gauge #1
Heat flux gauge #2
8.00E-‐06 6.00E-‐06
Voltage [Volts]
4.00E-‐06 2.00E-‐06 0.00E+00 -‐2.00E-‐06 -‐4.00E-‐06 -‐6.00E-‐06 -‐8.00E-‐06 0
50
100
150
200
250
300
350
Time [minutes] Figure 15 – Heat Flux Gauge Voltage Over Time
Upon analysis, there were some outlying final values for thermal conductivity on each sample. In order to find these outliers, Chauvenet’s criterion was used. The test for outliers is found in Equation 3. 𝑋 − 𝑋! (3) > 𝐶ℎ𝑎𝑢𝑣𝑒𝑛𝑒𝑡 ! 𝑠 𝐶𝑟𝑖𝑡𝑒𝑟𝑖𝑜𝑛 𝑠! In the previous equation, the value of the measurement is subtracted from the mean value and taken the absolute value; then the result is divided by the standard deviation. Once the outlier’s were found (if any) the average effective thermal conductivity was calculated and arranged in the Table 8.
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Table 8 – Thermal Conductivity Results and Statistical Analysis
Packaging
Thickness (m)
Thermal Conductivity (W/mK)
Standard Deviation (W/mK)
Standard Error (W/mK)
t Value (95%)
Confidence Intervals (95 %) (W/mK)
Gas Filled Panel
0.0283
0.0286
0.00239
0.0009
2.44
+/-0.0022
Xpander Pak ®
0.0305
0.0342
0.00046
0.0002
2.77
+/-0.0006
Mailer Type Bubble wrap
0.0052
0.0271
0.0028
0.0016
4.30
+/-0.0069
Large Bubble wrap (Single layer)
0.0065
0.0269
0.001
0.0004
2.44
+/-0.0009
The values calculated above state that the Gas Filled Panel has a lower conductivity than the Xpander Pak ®, this means the GFP conducts less heat than the Xpander Pak ® given a temperature difference. This attribution gives a competitive advantage on the Xpander Pak ® when shipping temperature sensitive items. The thermal conductivity of both types of bubble wrap give an expected low conductivity value, since the manufacturing material is very thin; leaving only as a means of conduction air (k = 0.0261 W/mK). Even though the thermal conductivity of both kinds of bubble wrap is lower compared to the GFP, this is not the only means of heat transfer to account for; there is radiation and convection. Radiation can be neglected through the GFP since it consists of aluminum coating, which acts as a shield for radiation, when in both types of bubble wrap radiation can affect greatly the overall heat transfer through them. Now, in the following part of the experimental results convection is analyzed on the GFP to foresee if it plays an important role in the heat transfer through it. Natural Convection in Gas Filled Panels
In this part of the experiment the role of natural convection on the Gas filled panel was inspected. This was done by performing the same thermal conductivity experiment as in Part 1 but this time the higher power input (6.6 W) was placed at the top of the apparatus and the lower input power in the bottom (0.85 W). Then the results were compared to the thermal conductivity value of the GFP obtained in Part1. If the value lays approximately within 5% of the thermal conductivity found in Part-1, natural convection on the GFP can be neglected. Five trials were performed and analyzed following the same procedure as in Part-1. The results obtained were arranged in the Table 9.
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Table 9 – Effective Thermal Conductivity on the GFP Inducing Natural Convection
Type of test
Thickness (m)
Thermal Conductivity (W/mK)
Standard deviation (W/mK)
Standard Error (W/mK)
t_Value (95%)
Confidence Intervals (95 %) (W/mK)
Conduction
0.0283
0.0286
0.00239
0.0009
2.44
+/-0.0022
Conduction + convection
0.0283
0.0270
0.00144
0.0006
2.77
+/-0.0017
The results obtained in the table above, state that the experiment performed yielded to a conductivity which is 5.9% lower than the conductivity found in the first test. This means that convection does not have a significant effect on the heat transferred in the Gas filled panel, since the result lays approximately on the condition laid out. With this experiment performed, convection can be neglected, leaving conduction as the only means of heat transfer than can affect the items being handled within the GFP packaging. The experiment performed gives very tangible measurements and calculations of the effective thermal conductivity in the GFP and how it has a competitive advantage over its near competitors; this makes the GFP an optimal choice for the packaging of thermal sensitive items. 3.1.2 Effective Conductivity – Simulated Data from the ANSYS simulations is shown in Tables 10 – 15. Table 10 – Polymer Layer Sensitivity Analysis k_poly [W/mK]
HF avg [W/m^2]
k_eff [W/mK]
0.1
21.577
0.02702681
0.2
22.242
0.02785977
0.3
22.887
0.02866768
0.4
23.5319
0.02947547
0.5
24.169
0.03027349
0.6
24.808
0.03107388
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Table 11 – Cell Geometry Study Data , No Convection Geometry
6 layer
5 layer
4 layer
3 layer
Sample thickness [m] 0.025052 0.025001 0.02495 0.02495 dT [K]
20
20
20
20
avg HF [W/m^2]
22.887
22.769
22.488
22.362
k_eff [W/mK]
0.028668 0.028462 0.028054 0.027896
Table 12 – Natural Convection Study in 6 Layer Geometry Orientation
Flat, NC
Flat, no NC
Side, NC
Side, no NC Vertical, NC Vertical, no NC
Thickness [in]
0.33
0.33
0.33
0.33
0.33
0.33
Thickness [m]
0.008382
0.008382
0.008382
0.008382
0.008382
0.008382
dT [K]
13
13
13
13
13
13
HF [W/m^2]
44.295
44.294
44.59
44.294
44.645
44.613
k_eff [W/mK] 0.028560053 0.028559408 0.02875026 0.02855941 0.028785722 Max V [m/s]
6.51E-06
4.11E-03
1.04E-02
Ratio
1.000022576
1.006682621
1.00071728
0.02876509
Table 13 – Natural Convection Study in 5 Layer Geometry Orientation
Flat, NC
Flat, no NC
Side, NC
Side, no NC Vertical, NC Vertical, no NC
Thickness [in]
0.4
0.4
0.4
0.4
0.4
0.4
Thickness [m]
0.01016
0.01016
0.01016
0.01016
0.01016
0.01016
dT [K]
16
16
16
16
16
16
HF [W/m^2]
44.584
44.586
45.423
44.586
44.552
44.426
k_eff [W/mK] 0.02831084 0.02831211 0.028843605 0.02831211 0.02829052 Max V [m/s]
4.45E-06
6.03E-03
1.65E-02
Ratio
0.999955143
1.018772709
1.002836177
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0.02821051
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Table 14 – Natural Convection Study in 4 Layer Geometry Orientation
Flat, NC
Flat, no NC
Side, NC
Thickness [in]
0.5
0.5
0.5
0.5
0.5
0.5
Thickness [m]
0.0127
0.0127
0.0127
0.0127
0.0127
0.0127
20
20
20
20
20
20
44.091
44.098
46.683
44.098
45.003
44.432
dT [K] HF [W/m^2] k_eff Max V [m/s] Ratio
Side, no NC Vertical, NC Vertical, no NC
0.027997785 0.02800223 0.029643705 0.02800223 0.028576905 5.47E-06
9.11E-03
2.85E-02
0.999841263
1.058619439
1.012851098
0.02821432
Table 15 – Natural Convection Study in 3 Layer Geometry Orientation
Flat, NC
Flat, no NC
Side, NC
Thickness [in]
0.66
0.66
0.66
0.66
0.66
0.66
Thickness [m]
0.016764
0.016764
0.016764
0.016764
0.016764
0.016764
27
27
27
27
27
27
44.728
44.729
52.634
44.729
47.777
44.928
dT [K] HF [W/m^2] k_eff Max V [m/s] Ratio
Side, no NC Vertical, NC Vertical, no NC
0.027771118 0.027771739 0.032679866 0.02777174 0.029664208 1.75E-04
1.38E-02
5.59E-02
0.999977643
1.17673098
1.063412571
0.027895296
Flow velocity profiles were plotted for each combination of geometry and orientation in Figures 16-27.
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Figure 16 – 6 Layer Convection Velocity and Temperature Profiles, Flat Orientation
Figure 17 – 6 Layer Convection Velocity and Temperature Profiles, Side Orientation
Figure 18 – 6 Layer Convection Velocity and Temperature Profiles, Vertical Orientation
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Figure 19 – 5 Layer Convection Velocity and Temperature Profiles, Flat Orientation
Figure 20 – 5 Layer Convection Velocity and Temperature Profiles, Side Orientation
Figure 21 – 5 Layer Convection Velocity and Temperature Profiles, Vertical Orientation
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Figure 22 – 4 Layer Convection Velocity and Temperature Profiles, Flat Orientation
Figure 23 – 4 Layer Convection Velocity and Temperature Profiles, Side Orientation
Figure 24 – 4 Layer Convection Velocity and Temperature Profiles, Vertical Orientation
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Figure 25 – 3 Layer Convection Velocity and Temperature Profiles, Flat Orientation
Figure 26 – 3 Layer Convection Velocity and Temperature Profiles, Side Orientation
Figure 27 – 3 Layer Convection Velocity and Temperature Profiles, Vertical Orientation
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3.1.3 Impact Protection - Experimental Impact testing was performed to test insulating properties of various products. The equipment used in this test can be found in Table 16 and Figure 28. Table 16 – Impact Test Equipment List Item
Model
Manufacturer
Specifications ● ● ● ●
+/- 1000 g’s 2.42 mV/g 5% Sensitivity -195 to 120 deg Celsius temp. range
Accelerometer
8614A1000M1
Kistler
Data Acquisition Unit
Test Partner
Lansmont
-
DAQ Software
Test Partner 3
Lansmont
-
Impact Test Fixture -
designed and built for project
● ● ●
2 pound drop plate Rigid structure Provides level drops
Figure 28 – Impact Test Fixture
After recording data, the Chauvenet Criterion for eliminating outliers was applied. The remaining data was then analyzed and yielded promising results. Figure 29 and Table 17 show the maximum accelerometer reading across the four heights for the four items tested (and no impact protection).
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Figure 29 – Maximum Impact Values
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Table 17 – Maximum Impact Values and Confidence Intervals DUT
No Packaging
Small Bubble Wrap
Large Bubble Wrap
GFP
Xpander Pak
Thermal & Impact Barrier Packaging
Drop Height (feet)
Max Acceleration (g's)
CI +/-‐ (g's)
1
185
22
2
257
25
3
347
53
4
479
55
1
94
4
2
216
16
3
301
10
4
367
20
1
95
7
2
202
4
3
273
6
4
355
9
1
45
2
2
76
1
3
110
2
4
140
6
1
45
2
2
80
3
3
113
4
4
141
2
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The analyzed test data for the GFP is displayed below in Table 18 for clarity. In Table 18, the cell highlighted in red shows an outlier. All outliers were removed upon identification. Table 18 – GFP Sample Raw Data Analysis with Outlier Identification Iteration
Height [ft] Max [g] Chauv Min [g] Dur [ms]
1
1
126
1.28
45
2.8
2
1
161
0.69
56
2.2
3
1
350
2.50
231
0.5
4
1
158
0.74
97
3.0
5
1
197
0.08
55
2.5
6
1
207
0.09
167
3.2
7
1
219
0.29
207
0.5
8
1
201
0.02
56
2.4
9
1
203
0.02
199
0.5
10
1
197
0.08
135
2.5
N
10
Chauv Crit
1.96
126
45
0.5
231
3.2
125
2.0
72.2
1.1
Min [g] Max [g] Mean [g] Stdev [g] Stdev [%] Stdev Mean t-‐stat +/-‐ CI (95) Relative CI
350 202 59.3 0.29 18.76 2.26 43 0.22
The goal of this design was to improve the impact protection provided by bubble wrap alternatives and provide comparable protection to the Xpander Pack. This test showed that the GFP performed as required. Throughout the testing, the GFP impact values were 50% of either bubble wraps, which is a large improvement. When compared to the Xpander Pack, the GFP impact acceleration was never more than 5% higher at any height. This consistent comparability to the Xpander Pack makes the GFP a less expensive alternative with negligibly dissimilar performance. The Impact Test Fixture provided a highly repeatable and level test method and therefore was ideal for this testing. This experiment could be Thermal & Impact Barrier Packaging
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improved by applying a range of loads to be dropped (to account for a range of objects dropped on the packaging). Since this was a comparative test, it was deemed unnecessary to vary forces. 3.1.4 Pre-Use/In-use Volume Raw data, with statistical analysis for pre-use and in-use volume can be found in Tables 19 and 20. Table 19 – Pre-‐Use Volume Data Iteration
Length [in] Chauv Value Width [in] Chauv Value Thickness [in] Chauv Value
1
0.0280
0.41
9.3125
0.85
11.5000
0.87
2
0.0285
0.62
9.3125
0.85
11.5000
0.87
3
0.0275
1.45
9.2500
0.36
11.3750
1.31
4
0.0285
0.62
9.1875
1.58
11.5000
0.87
5
0.0280
0.41
9.3125
0.85
11.3750
1.31
6
0.0275
1.45
9.2500
0.36
11.4375
0.22
7
0.0280
0.41
9.3125
0.85
11.5000
0.87
8
0.0285
0.62
9.2500
0.36
11.4375
0.22
9
0.0285
0.62
9.1875
1.58
11.3750
1.31
10
0.0290
1.66
9.3125
0.85
11.5000
0.87
Table 20 – In-‐Use Volume Data Iteration
Length [in] Chauv Value Width [in] Chauv Value Thickness [in] Chauv Value
1
1.4950
1.90
8.5000
0.60
10.7500
22196.23
2
1.4960
1.43
8.4375
0.26
10.8125
22325.62
3
1.5005
0.68
8.3750
1.12
10.7500
22196.23
4
1.5010
0.92
8.4375
0.26
10.6875
22066.85
5
1.4990
0.02
8.4375
0.26
10.6875
22066.85
6
1.5015
1.15
8.5000
0.60
10.7500
22196.23
7
1.5000
0.45
8.3750
1.12
10.7500
22196.23
8
1.4980
0.49
8.3750
1.12
10.8125
22325.62
9
1.4995
0.21
8.5625
1.47
10.8125
22325.62
10
1.5000
0.45
8.5625
1.47
10.7500
22196.23
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3.1.5 Material Recyclability Additional information about recycling practices and markets may be found by contacting the facilities below. UMN Facilities Management
Administrative Offices Como Recycling Facility 3009 Como Ave. S.E. Minneapolis, MN 55414 Recycling Hotline: 612-625-8084 Recycling Email:
[email protected] Recycling Supervisor Dana Donatucci Phone: 612-624-8507 Cell: 612-363-6145 E-mail:
[email protected] Ramsey County Environmental Health
Ramsey County Recycling & Disposal Hotline 651.633.EASY (3279) Karen Reilly Health Educator | Ramsey County Environmental Health 2785 White Bear Ave, Suite 350 Maplewood MN 55109 651.266.1186
[email protected] Additional online resources
http://earth911.com/news/2010/05/24/the-numbers-on-plastics/ Thermal & Impact Barrier Packaging
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http://www.informinc.org/pages/research/waste-prevention/fact-sheets/delivering-the-goodsbenefits-of-reusable-shipping-containers-executive-summary.html http://www.reusabletransportpackaging.com/plasticrecyclingprogram.html http://www.newdream.org/ http://plastics.americanchemistry.com/
3.2 Cost Analysis As this product is still in the development phase, our sponsor company is still investigating manufacturing equipment and capabilities, so manufacturing costs are as of yet unknown. However, this design does show substantial savings in shipping costs over competing products. The sponsor company estimated shipping costs for this product (in its prototype configuration) and its lead competitor, which are shown in Table 21. Reducing the number of layers down to 4 would further reduce these costs. Table 21 – Estimated Costs Item
Mailers Length Per Case
9 x 11 Xpander Pak's
24
9 x 11 GFP's (6 layer build up)
350
18.25
Shipping Shipping Cost Cost Per Mailer
Width
Depth
Weight
12.25
8.875
5.15
$12.09
$0.5038
8.875
32.71875
$26.55
$0.0759
19.4375 13.1875
3.3 Environmental Impact Statement Purpose and Need
The need to reduce solid waste and the carbon footprint of products and practices has been widely accepted. Efforts have been made in recent years to minimize high volume disposable materials such as shipping packaging. Thinner plastic water bottles, less cardboard packaging and container shapes optimized for bulk packaging are all examples of these initiatives. With the popularity of online shopping and services such as deliverable prescriptions, protective individual packaging continues to be in high demand. However, the nature of this packaging can be adapted to reduce its effect on the environment. Impact to Environment
The product takes advantage of a design feature that allows the inflatable packaging product to be shipped to and stored by the shipping customer in an uninflated state and to only be inflated just prior to use. This feature reduces the volume occupied by a unit and therefore reduces transport and storage space requirements, restocking and delivery frequency and even the amount of packaging required for the packaging itself. The current prototype is not recyclable but does offer the potential for reuse, which Thermal & Impact Barrier Packaging Page 39 of 40
lessens the disposal rate of solid waste and the load on landfills and other garbage facilities. In fact, due to the design of its inflatable cells, this product may be quickly and efficiently deflated, which enables those that are disposed of to require that much less space during the process. Discussion and Alternatives to Design
As discussed above, the prototype in its current state is non-recyclable due to a metalized layer of film that was included in the design to minimize the effect of radiant heat transfer. An alternative design could be a product that does not feature this metalization, allowing for complete recyclability. Undesirable increases in the effective conductivity resulting from the addition of radiant heat transfer might be mitigated by revisiting the design process. On the other hand, a product featuring diminished thermal insulation but comparable impact protection would still be relevant and valuable.
3.4 Regulatory and Safety Considerations Worker and Consumer Safety
In the production of the Gas filled panel, safety considerations need to be acquainted. During its manufacturing process, the GFP goes through processes which involve heat sealing. These processes involve high temperature devices used to manufacture the honeycomb shape and heat seal the separate mailer style packages. Such devices are: hot rollers and heat sealers. In the manufacturing process the operator is required to wear protective gear at all times, such gear includes: Asbestos gloves and eye protection. The protective items mentioned protect and prevent the worker from injuries in the workplace and provide a friendly environment. If the manufacturing of the product is being performed indoors, ventilation is necessary, since there are fumes that are delivered from the hot rollers and heat seals when in contact with the product. Given that, workers should wear mouth cover to avoid inhaling such fumes. The gas filled panel’s material is composed of polyethylene, polyester and an aluminum coating, which if ingested, can obstruct the respiratory tracts and cause suffocation. Given this, it should be kept away from the reach of children. Regulatory Considerations
The gas filled panel provides insulation that can be used for various purposes; if biological or pharmaceutical goods are to be shipped, it is recommended that the regulations for the food and drug administration are followed. As an example, some FDA and other organizations regulations narrow the shipping specifications for materials like insulin [4], or blood [3] to very standardized goals. In which case, it is recommended for the consumer to expand a search on a phase change material which satisfies the customer’s purpose and include it when packaging the material to be shipped.
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