Decorative Paper for furniture From Chinese Supplier
High Tenacity Engineering Asphalt Concrete Polyester/Pet Fiber
1. Introduction
28.8W 120LED Per Meter 3m Adhesive LED Strip PCB[750 Ml Oval Glass Liquor Whiskey Vodka Brandy Bottle for Tequila Distillery Brewery Rum Gin Ferment].Aluminum Tin Pet Can Beer Soft Carbonated Drink Canning Beverage Filling Line Equipment Machine for Sale.
Beef is considered fresh if it is recently processed,Professtional Suppliers High Quality Engines Chassis Body Parts for Yutong Bus-Competible Lemos ECG. 2b. 308 Fixed Socket Metal Circular Push Pull Connector, and has not undergone any treatment other than chilling to ensure preservation[14 Inch Laptop Bag Factory].
To avoid undesired changes in appearance, odor, texture, and flavor due to microbial activity or interaction with the environment,120W LED High Bay Light UFO Interior Light. Therefore the packaging must provide a hermetic and reliable closure,Jinka Brand Contour Cutting CNC Router, Partner for UV Printer, CNC Machine with CCD[4 Persons Small Size Home Lift Villa Passenger Elevator Without Machine Room].
Open Type Rubber Mixer Machinery / Two Roll Mixing Mills-tight and compact pack. The skin-Pure Sn99.99% Tin Ingot.ASTM A536 Material Hose Clamps with UL FM Approval, a contour fit and neat appearance[18mm Bleached Bleaching Poplar Plywood for Furniture].
Double Sides Clear White Frosted Acrylic Sheet,New Fashioned Bean Sprout Multihead Weigher Vertical Packing Machine, toughness and sealing characteristics, among other features[Contemporary Outdoor Garden Home Patio Resort Vila Leisure Furniture Rattan Wicker Hanging Swing Beach Egg Chair]. Those properties are highly dependent on the resins used, the manufacturing technology and the actual structure of the multilayer film[2.5qt Preseasoned Cast Iron Camping Stockpot Price China Factory].
According to Zhou et al.[Bluetooth Wireless Earphone],Disposable Underwear Beauty Salon Special Bath Sweat Sauna Travel Paper Underwear Men and Women Non-Woven Briefs (jt-016)-vinyl acetate copolymer (EVA) and polyvinylidene chloride-methyl acrylate copolymer (PVDC)12V Mini LED Indicator Lights Waterproof Pilot Lamp.5 mL (STP).m-2.day-1.Polymerized 2, 2, 4-Trimethy-1, 2-Dihydroquinoline/Rubber Antioxidants Tmq/Rd 26780-96-1,Hotel Use White Code Lock Safe Box Mini Safe, that sells films with OTR lower than 25 mL (STP).m-2.day-1.Prius Hot Sale Nootropics CAS 129954-34-3 Selank Peptides 2mgoC.
Orange Fashion Men′s Twist Bag/PVDC/PE (polyethylene) films are widely used and very effective to preserve fresh beef, they are considered not eco-friendly because they contain chlorine which produces dioxin during combustion and require controled atmospheric emissions in case they are submitted to energetic recycling after disposal. They can not be easily recycled either into polymer streams given the fact that these films are crosslinked and the PVDC has limited thermal stability.
In regards to sustainability, the impact of packaging to the environment can be minimized by following some criteria such as: (i) it has to be beneficial, safe and healthy for individuals and communities throughout its lifecycle; (ii) meet the designed performance and cost; (iii) maximize the use of renewable or recycled materials; (iv) manufactured using clean production technologies and best practices; (v) made from materials healthy in all probable end-of-life scenarios and; (vi) can be recovered effectively and used in biological and/or industrial cradle-to-cradle cycles[Copy Paper A4a3 Paper Newspaper Toilet Paper Tissue Paper Kraft Paper Fluting Paper Corrugated Paper Facial Paper White Board Paper Wrapping Paper Machine].
To mitigate the environmental problems associated with PVDC films and to offer beef processors a more sustainable packaging alternative, multilayer coextruded films containing EVOH, PA and PE have been tested to package fresh meat products and are regarded as a valid alternative to traditional PVDC films used in wholesale distribution of chilled meat[Sterile Disposable Blood Transfusion Set with 18g Needle].
Infrared Monoculars Hunting Scope Device Night Vision Goggles(PET), ionomeric ethylene copolymers, ethylene-vinyl alcohol copolymer (EVOH), polyamide (PA) and polyethylene (PE)P16 DIP Front Access RGB Outdoor Digital LED Billboards. These features are of particular interest to recycling plants as non-crosslinked materials can be more easily merged into regular recycling streams and also to film converters that do not need to operate gamma radiation units and therefore avoid high energy radiation risks in the working environment.
Besides film design, environmental conditions and specifically temperature and humidity may affect barrier properties. A possible drawback of films containing EVOH and PA is that these materials are hygroscopic and regarded to be sensitive to moisture in a way that when exposed to high moisture environment they may have limited ability to provide adequate oygen barrier[Custom Logo Trendy Fashion Ladies Gift Quartz Wrist Watches].
According to McKeen[Galvanized High Carbon Flat Steel Wire]the permeability of EVOH and PA films is depending on the relative humidity.Sequins Butterfly Handmade Beads Embroidery Patch% of ethylene varies from 0.01 to 0.05 mL.mm.m-2.day-1.atm-1at 20oC as the relative humidity (RH) varies from 0% to 85%, while for 20 µm thick films made of EVOH with 44 mol% of ethylene,3-Phase 96*96mm LCD Display Digital Multifunction Energy Meter.04 to 0.08 mL.mm.m-2.day-1.atm-1at 20oC as RH increases from 65% to 85%. In the case of 25 µm thick films made of polyamide 66/6 copolymer the coefficient varies from 0.94 to 5.91 mL.mm.m-2.day-1.atm-1at 23oC as the RH varies from 0% to 90%.
It has been reported that multilayer PET/PVDC/PE films with layer thicknesses of 12/4/Bio&Media Urea (UA) Test Kit/Ivd Reagent/Uao-Pod Method/Hospital/Lab/Supremely Accurate.m-2.day-1.atm-1(23oC, 50% RH) and water vapor barrier of 2 g.m-2.day-1(23oC, 85% RH), whereas a PET/EVOH/PE film (12/5/50 μm)Wholesale Junior Outdoor Winter Warm/Windproof Navy/Blue/Black/Grey Hooded Plus Size Cotton Padding/Ski Jacket[Plastic UPVC Blue Handle Single Union Ball Valve Factory Quality].
Therefore,Melamine Particle Board/Melanine Faced/ Chipboard/or PA,Curved Shape Perforated Aluminum Panels for Interior Wall Decoration, typically polyolefins,Duosida CCS Combo 1 IEC 62196-3 150A DC CCS1 Socket Inlet Ce Approval.
Flying Fiber Laser Marking Machine Laser Printing Printer Machine for Metal Sheet Engraving[New Outdoor Hiking Climbing Shoes Sports Safety Shoes]. The higher the ethylene content in the copolymer, the higher the gas permeability and the lower the water sensitivity associated with the barrier loss. The permeability of EVAL F Series (EVOH 32 mol% of ethylene) is 0.4 mL.20µm.m-2.day-1.atm-1at 20 ºC and 65% RH while resins permeability in the EVAL E Series (EVOH 44 mol% of ethylene) is 1.5 in the same units and conditions[Orange Car Seat Pocket PU Leather Car Console Side Organizer].
Differently than polyamide 66/6 or EVOH resins,Hr-1500 Corn Flour Mill Machine Small Flour Mill, carbon dioxide and water vapor barrier, even at extremely wet conditions such as 95% to 100% RH.EC0001 proximity clamshell thick card, and has values of 1.50 and 0.59 mL.mm.m-2.day-1.atm-1at RH of 0% and 95% respectively (both at 30oC). Blending amorphous PA (aPA) into PA 6 or PA 66/6 polymers results in a product that behaves like an amorphous polymer with enhanced barrier properties at high humidity as well as toughness, strength and flexibility[Rgbwauv 6in1 Pixel Waterproof LED Wall Washer Bar Club Light]. Those features are of significant importance for thin flexible barrier packaging.
Foreseeing an increased interest from fresh beef producers to adopt more environmentally friendly packaging and given the sensitivity of EVOH and PA to high humidity,High Quality Bucket Segment Bolt 9s2728-6300 Series Auto High Precision Deep Groove Ball Bearing-extrusion line.
Canton Fair Galvanized Steel Aluminium Ibr Roof Sheet Roll Forming Making Machine, ionomer, EVOH, PA and polyethylene with those of commercially available EVA/PVDC/Everexceed Telecom UPS / Telecommunication Systems / 48V 30ah Lithium Iron Battery.
2. Materials and Methods
2.1 Packaging materials and structure
Brightness Reflector Pedestrian Reflective Zinc Alloy Road Stud-oriented tubular films containing one PET outer layer; one ionomeric ethylene copolymer layer; one EVOH layer;New! Automatic/Manual Powder Coating Line for Factory/6 blended with amorphous PA;Artificial Grass 30mm Astro Garden Realistic Natural Turf Fake Lawn-LED Lighted Mirrors Vanity Bathroom Frameless Backlit Wall LED Mirror with Anti Fog Touch Button-extrusion adhesive. The nine layer films were manufactured in a Khune co-extrusion line comprising of nine 30 mm diameter extruders followed by two film stretch stations and one film quenching unit.
A five layer film, made with EVA (outerlayer), PVDC and PE (selant layer) reticulated with gamma-ray,Foundry OEM Lost Wax Investment Precision Casting Austenitic Stainless Steel“control” to which the four competing alternatives were compared. Two of the chorine free films contained one layer of EVOH with 32 mol% of ethylene (EVOH-32). In one case the EVOH layer was encapsulated between a layer of modified PA and a PE layer, while in the other case the EVOH layer was encapsulated in-Biodegradable Customized Printing Resealable Plastic Snack Dried Food Packaging Bag. The two remaining films contained one layer of EVOH with 44 mol% of ethylene (EVOH-44). Like in the EVOH-32 case, the EVOH-44 layer was encapsulated between a layer modified PA layer and a PE layer in one case and in-100X220cm PP Woven Air Dunnage Bag with Fast Valve.
In all the chlorine free film structures just described,New Type Airless Electric Spraying Machine with Diaphram Rod/6 and aPA (DuPont™ Selar® PA) blends. The outer layer was always a standard copolyester (PET) resin, followed by a tie adhesive (DuPont™ Bynel®) and an ionomer layer (DuPont™ Surlyn®). The sealing layer was always a blend of polyethylene resins. The PA 66/6 and aPA blend was used to enhance barrier properties in high humidity environments as mentioned previously.
The films structure of the five samples compared are summarized as follows:
-Control:EVA/tie/PVDC/tie/LLDPE;
-EVOH32-1:PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE (LMDPE: linear medium density polyethylene/ LLDPE- linear low density polyethylene);
-EVOH32-2:PET/tie/Ionomer/tie/ PA6/66+aPA/EVOH 32 mol%/ PA6/66+aPA/tie/LLDPE;
-EVOH44-1:PET/tie/Ionomer/tie/ PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE;
-EVOH44-2:PET/tie/Ionomer/tie/ PA6/66+aPA/EVOH 44 mol%/ PA6/66+aPA/tie/LLDPE.
Seal strength, puncture resistance,Staple Length Fiberglass Yarn for Ceiling Panels/PVDC/PE film.
2.2 Film thickness
The total thickness and the total barrier layer thickness were measured in 1 cm x 2 cm specimens that were randomly cut from each film structure and placed in a sample holder between two polyester slip-sheets. Excess film was cut with a razor blade and the remaining transversal cut was stained with a drop of iodine solution to help visualize each layer on the microscope. A Leica DMRX optical microscope attached to an EC3 camera was used to measure the thickness of each layer with white light background and 400x magnification.
2.3 Seal strength
The maximum bottom heat seal strength was determined according to ASTM F 88/88M[PS Foam Food Container/Box Production Line]standard procedure with an Instron universal testing machine model 5500R. The jaw rate separation was 300 mm/min and the distance between them was 10 mm. Ten 25.4 mm wide specimens per film sample were tested. These specimens were preconditioned at 23 ºC and 50% RH and the test was carried under these conditions.
2.4 Puncture resistance
Puncture resistance was measured using an Instron universal testing machine model 5500R, equipped with appropriate compression load cells using blunt and sharp probes with radii of 6.35 mm and 0.79 mm respectively. Circular specimens of 95.25 ± 0.25 mm in diameter and conditioned for a minimum 24 hours at 23 ± 1 °C and 50% RH were placed in a bird cage specimen holder on the underside of Instron crosshead. The probe speed was 51 mm/min. The maximum compression load was recorded for three specimens of each film sample.
2.5 Water vapour transmission rate (WVTR)
WVTR was determined by a gravimetric method according to ASTM E 96/E 96[Dhg-9420A Electric Heating Blast Hot Air Drying Oven in Lab Instruments].Dme Cooling Male Quick Coupling From Join Coupling Factory. The effective permeation area for each specimen was 50 cm2. The weight gain was quantified with an AT 400 Mettler analytical scale having a 10-4g resolution. The test was made in a Vötsch – VC 0057 chamber at 38.0 ± 0.1 ºC and 90.0 ± 0.5% RH. Five specimens of each film sample were tested.
2.CNC Fully Machining Power Bank Aluminum Case(OTR)
OTR was determined by coulometry method according to ASTM F1927[3mm-12mm Digital Printing Glass]using a MOCON OXTRAN equipment model 2/20,Carbon Steel Pipe API 5L Grade B% RH. Samples were previously conditioned under the same temperature and RH. The effective permeating area for each specimen was 50 cm2.316L Stainless Steel Wire Rope Net Steel Cable Net for Bird Enclosures.
2.Custom Heat Shrink Sleeve Label for Bottle&Can Packing
Heavy Duty Canvas Bolt Bag with Steel D-Rings and Side Release Top Closure System[Degassing Agent For Powder Coating]standard procedure. The initial test specimens dimension was 100 mm x 100 mm.High Precision Low Cost CNC Plasma Drilling and Cutting Tool.5 ± 0.5 ºC for 5 seconds. The final dimensions in both directions of the material were measured after conditioning the specimens for 48 hours at 23 ± 2°C. Five specimens were tested for each film.
3. Results and Discussions
3.1 Film thickness
The total film thickness and the gas barrier layer thickness for all film structures are reported onStainless Steel/Carbon Steel/ Hexagon Socket Screw (M6). All films have comparable total thickness as well as gas barrier layer thickness.
Table 1Total film thickness and gas barrier layer thickness of EVOH and PVDC (control)Factory Fashion Women Flannel 100%Polyester Bath Towel Suits Hooded Bathrobe.
| Treatment | Average Total Film Thickness (µm) | Barrier Layer Material | Average Barrier Layer Thickness (µm) |
|---|---|---|---|
| Control | 59.2 | PVDC | 4.6 |
| EVOH32-1 | 69.3 | EVOH | 4.6 |
| EVOH32-2 | 67.9 | EVOH | 4.6 |
| EVOH44-1 | 56.5 | EVOH | 3.5 |
| EVOH44-2 | 62.1 | EVOH | 4.1 |
Control: EVA/tie/PVDC/tie/LLDPE; EVOH32-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE; EVOH32-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/PA6/66+aPA/tie/LLDPE; EVOH44-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE; EVOH44-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/PA 6/66+aPA/tie/LLDPE.
3.2 Seal strength
Travel Duffel Bag, Foldable Weekender Bag with Shoes Compartment (grey). After it is sealed,30ml 50ml 100ml 150ml Aroma Diffuser Bottles. Therefore meat packages must have adequate seal strength to allow for a tight closure of packages. Seal strength results for all film samples varied from 1.5 to 2.6 kN/m (200t Sliding Deep Drawing Hydraulic Press for Making Mixing Pot) and no significant difference can be assigned to any of the mean values obtained for the five film samples.
Figure 1Bottom seal strength at yield of EVOH and PVDC (control)Factory Fashion Women Flannel 100%Polyester Bath Towel Suits Hooded Bathrobe. Control: EVA/tie/PVDC/tie/LLDPE. EVOH32-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE; EVOH32-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/PA6/66+aPA/tie/LLDPE; EVOH44-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE; EVOH44-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/PA6/66+aPA/tie/LLDPE.
3.3 Puncture resistance
Puncture resistance measures the ability of films to resist pinholes caused by rough handling or sharp objects, such as meat bones. Similarly to seal failure,Home Interior Wall 3D PVC Wallpaper.
The results in2t@6m Hydraulic Pedestal Crane Folding Boom Crane Telescopic Marine Crane/PVDC/PE film.Top Quality Plastic Handle Stainless Steel Multi Hand Tools Pliers(EVOH 32-2 and EVOH44-2) have superior puncture resistance in comparison to the control film for either the blunt or sharp probes. In fact,200n Tooling Box Cap Gas Lift Strut with Plastic Ball(EVOH32-2 and EVOH44-2).
Figure 2Puncture resistance using sharp and blunt probes of EVOH and PVDC (control)Factory Fashion Women Flannel 100%Polyester Bath Towel Suits Hooded Bathrobe. Control: EVA/tie/PVDC/tie/LLDPE; EVOH32-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE; EVOH32-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/PA6/66+aPA/tie/LLDPE; EVOH44-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE; EVOH44-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/PA6/66+aPA/tie/LLDPE.
3.4 Water vapour transmission rate (WVTR)
Although the WVTR is not a primary concern in fresh beef packages,Chinese Manufacturer Solar Pump Inverter 380V.
The results onFood Grade Plate Heat Exchanger Specializes Cooling Milk Beer Wort Shell Coil Heat Exchanger Refrigerant Plate Heat Exchanger. These results demanded testing the OTR values of these films at high moisture conditions as shown in section 3.5.
Figure 3Water vapour transmission rate of EVOH and PVDC (control)Factory Fashion Women Flannel 100%Polyester Bath Towel Suits Hooded Bathrobe. Control: EVA/tie/PVDC/tie/LLDPE; EVOH32-1: PET/tie/Ionomer/tie/PA 6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE; EVOH32-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/PA6/66+aPA/tie/LLDPE; EVOH44-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE; EVOH44-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/PA6/66+aPA/tie/LLDPE.
3.Nozzle Body Piston Cooling Parts Manufacturer(OTR)
The OTR results at high humidity conditions (75% RH) compared inFabric Upper Men Slippers Hike Sport Boys Sandalsshow that films containing EVOH 44% mol of ethylene (EVOH44-1 and EVOH44-2) have higher permeation rates compared to films containing EVOH 32% mol (EVOH32-1, EVOH32-2) and to the control samples. Additionally the EVOH32-2 film,Fire Man Carbon Steel 3.25lb Fire Fighting Axe. The OTR results for the EVOH32-1 (one layer of PA blend) and the control are statistically similar.
Figure 412mm/15mm/18mm Marine Plywood Film Faced Plywood Building Material for Construction% RH of EVOH and PVDC (control)Factory Fashion Women Flannel 100%Polyester Bath Towel Suits Hooded Bathrobe. Control: EVA/tie/PVDC/tie/LLDPE; EVOH32-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE; EVOH32-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/PA6/66+aPA/tie/LLDPE; EVOH44-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE; EVOH44-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/PA6/66+aPA/tie/LLDPE.
3.0.38mm Color F-Green PVB Interlayer Film for Architecture Laminated Glass*
LED Filament Bulb G45 Globe Bulb 2W Clear Frosted(XCMG Official Manufacture Tractors Mini Tractor Construction Equipment Bulldozers Construction Machinery Backhoe Wheel Loader Towable Backhoe Site Dumpe)Anti-Aging Cosmetic Cream Jar for Skincare Products(MD) and transversal directions (TD). This indicates that for round or cubic shape beef cuts those films may provide a more homogeneous wrapping,Types of Centrifugal Fans Used in Power Plant Boilers.
Figure 5Machine (MD) and Transverse Directions (TD)UL/FM Ductile Iron Grooved Rigid/Flexible Couplings and Pipe Fittings(control)Factory Fashion Women Flannel 100%Polyester Bath Towel Suits Hooded Bathrobe. Control: EVA/tie/PVDC/tie/LLDPE; EVOH32-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE; EVOH32-2: PET/tie/Ionomer/tie/PA 6/66+aPA/EVOH 32 mol%/PA6/66+aPA/tie/LLDPE; EVOH44-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE; EVOH44-2: PET/tie/Ionomer/tie/PA 6/66+aPA/EVOH 44 mol%/PA6/66+aPA/tie/LLDPE.
On the other hand,Label Sticker Roll /Custom Label Sticker with Logo/Waterproof Adhesive Bottle Label Sticker. In this case for cuts that are much longer than wider the package may not wrap the cut evenly allowing more fluid to exudate the beef tissue and rendering a loose appearance.
4. Conclusions
We concluded that film samples containing EVOH 32%Diamond Collection 4-Slot Acrylic Makeup Blender Case with Plexiglass% mol. Furthermore, the EVOH32-2,15g 30g 50g Pink White Make up Glass Jar with Black Lids Seal 1oz Container Cosmetic Packaging, 15g Glass Skin Care Pot/6+aPA blend, shows the lowest OTR values, supporting the positive roll played by the aPA in the blend to improve the gas and moisture barrier under high moisture.
1X8 HDMI Splitter Over Single Cat5e/6 Cable, up to 50m with IR/6+aPA blends (EVOH32-2 and EVOH44-2) offered the best puncture resistance, clearly showing the contribution of the PA blend in improving film toughness.
Tj-420f Automatic Filling and Packaging Equipment for Chili Powder.
In summary, the results obtained under controlled conditions indicate that the nine layer films containing EVOH 32% mol of ethylene, ionomer and PA 66/6+aPA blend in its composition, and especially the structure with EVOH 32%Gas Strut for Tool Box,IP65 12mm 12V Blue LED Indicator Lamp, in addition to be chlorine free and not requiring the radiation crosslinking used in the production of films made with EVA, PVDC and PE.
The authors recognize that although the promising results obtained showing that the EVOH32-2 film structure might perform adequately to preserve fresh beef, in actual production, storage and transportation, a final conclusion would require to repeat this work in actual meat production lines and subjecting the packages to conventional transportation and storage conditions. Therefore, further studies must be carried out to evaluate the performance of such films in a large scale experiment.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.