Cellophane
Cellophane is a thin, transparent polymeric film manufactured from regenerated cellulose derived from dissolving pulp containing 92–98% cellulose.[1] Its production involves the viscose process, where cellulose is dissolved in alkali and carbon disulfide to form a viscous solution extruded into a coagulating bath, yielding a sheet with low permeability to air, oils, greases, bacteria, and liquid water, though it permits water vapor transmission.[2] These properties render it ideal for food packaging, providing visibility of contents while offering protective barriers that extend shelf life without imparting odors or tastes.[3] Invented in 1908 by Swiss chemist and textile engineer Jacques E. Brandenberger, cellophane originated from efforts to create a stain-resistant coating for fabrics, such as tablecloths, following an incident with spilled wine that prompted the development of a clear, flexible, waterproof film from wood cellulose.[4][5] Brandenberger's innovation marked the first successful transparent plastic-like wrapping material, revolutionizing consumer packaging by enabling product visibility and hygiene, with commercial production scaled by DuPont in the United States from the 1920s onward through acquired patents and manufacturing advancements.[6][7] Despite later displacement by cheaper synthetic polymers like polyethylene, cellophane's biodegradability and renewability from plant sources distinguish it as an early example of sustainable film technology, though its chemical-intensive production process tempers unqualified environmental claims.[8]History
Invention and Initial Development
Jacques Edwin Brandenberger, a Swiss chemist and textile engineer born in 1872, invented cellophane in 1908 while employed in France developing a stain-resistant coating for tablecloths using viscose, a solution of cellulose xanthate derived from wood pulp.[9][6] During an experiment, Brandenberger spilled wine—or in some accounts, sulfuric acid—onto a viscose-coated fabric; upon drying and coagulation, a thin, transparent, flexible film formed on the surface and peeled away intact, revealing the potential for producing standalone sheets of regenerated cellulose rather than mere coatings.[5][10] This serendipitous observation shifted his focus from fabric treatment to isolating and scaling the film-forming properties of viscose, building on the earlier viscose rayon process patented in the 1890s by British chemists Charles Frederick Cross and Edward John Bevan.[7] Brandenberger dedicated the subsequent years to refining the production method, overcoming challenges such as achieving uniform thinness (typically 0.025 to 0.04 millimeters), transparency, and tensile strength without brittleness.[9] By 1912, he had engineered the first machine capable of extruding viscose through a slit into a coagulating bath of sulfuric acid to form continuous sheets, enabling potential industrial-scale output.[11] Naming the material "cellophane" from the French words cellulose and diaphane (transparent), he established La Cellophane S.A. in Besançon, France, around 1913 to commercialize it, initially producing small quantities for applications like protective eyewear.[4][11] World War I interrupted broader development but provided early validation, as cellophane sheets were adapted for transparent visors in gas masks due to their clarity and impermeability to liquids.[12] Brandenberger secured key patents for the machinery and core process in 1917, solidifying the technical foundation after nearly a decade of iteration from laboratory curiosity to viable prototype.[9] These advancements established cellophane as the first flexible, transparent regenerated cellulose film, distinct from rigid celluloid or brittle cellulose nitrate sheets, though initial yields remained low and costs high owing to the empirical trial-and-error in optimizing extrusion and regeneration parameters.[5]Commercialization and Early Adoption
Jacques E. Brandenberger patented cellophane in 1912 and initiated commercial production in Switzerland that year, followed by establishing La Cellophane Société Anonyme in Paris in 1913 to manufacture and market the material.[13][6] Initial applications were limited, including unbreakable eyepieces for gas masks during World War I and wrapping for non-perishable goods like chocolates, perfumes, and flowers, as the original formulation lacked moisture resistance.[4][11] In 1923, E.I. du Pont de Nemours and Company acquired U.S. patent rights from the French firm, beginning production in Buffalo, New York, in 1924 with Brandenberger's assistance.[5][7] Early U.S. adoption mirrored European uses, with Whitman's Candies becoming the first American firm to employ imported cellophane for chocolate wrapping starting in 1912.[12] The material's transparency appealed to tobacco and confectionery industries for showcasing products without contamination. DuPont's development of moisture-proof cellophane in 1927, achieved through coating with nitrocellulose and waxes, markedly expanded early adoption by enabling packaging of moist foods such as cakes and cheeses.[7] This innovation addressed prior limitations, facilitating integration into food manufacturing lines and boosting demand in the late 1920s, particularly for cigarettes and baked goods where visibility enhanced consumer appeal.[14] By the end of the decade, cellophane had transitioned from niche to foundational packaging, though production costs remained high at approximately $2.65 per pound.[15]Peak Usage and Industry Impact
Cellophane attained peak production and market dominance in the mid-20th century, with global output reaching 440.9 million pounds (200 million kilograms) annually by 1960.[4] In the United States, E.I. du Pont de Nemours & Company, which held over 90% of domestic cellophane sales through the 1940s, reported steady growth, with plain cellophane revenues rising from $3.1 million in 1928 to $9.3 million in 1950.[16] By 1938, cellophane constituted 10% of du Pont's total sales and 25% of its profits, reflecting returns on investment exceeding 300% from 1925 onward.[7] The material profoundly influenced the packaging industry by enabling transparent, protective wrapping that preserved freshness while allowing visual product inspection, spurring adoption in food, tobacco, and confectionery sectors. This innovation facilitated the expansion of self-service retailing in supermarkets during the postwar period, as pre-packaged goods in cellophane reduced the need for clerk-assisted handling and encouraged impulse purchases through enhanced shelf appeal.[7] For instance, cellophane wrappers became standard for cigarette packs and candy, comprising major portions of du Pont's sales—cigarettes alone accounted for about 35% of output in the late 1940s. At its zenith in the early 1950s, cellophane captured up to 68% of the transparent flexible packaging segment, underscoring its role in standardizing moisture- and grease-resistant barriers superior to alternatives like waxed paper. However, this dominance began waning as cheaper synthetic polymers, such as polyethylene, entered the market post-1950, offering greater versatility and lower production costs, which progressively displaced cellophane in high-volume applications.[17] Despite the eventual decline, cellophane's era cemented transparent packaging as a cornerstone of modern consumer marketing and logistics efficiency.[7]Decline and Legacy
The widespread adoption of synthetic plastic films, such as polyethylene and polypropylene, beginning in the 1950s, initiated the decline of cellophane by offering lower production costs, superior heat-sealing properties, and enhanced versatility for diverse packaging needs.[18] These alternatives eroded cellophane's market share, with DuPont's dominance in the material waning as competitors entered the flexible packaging sector. Global cellophane production peaked at approximately 440.9 million pounds (200 million kilograms) in 1960, after which sales volumes steadily decreased due to these cheaper, petroleum-derived substitutes that better resisted moisture and provided consistent barrier performance without the viscose processing expenses inherent to cellophane.[4][18] By the late 20th century, the cellophane manufacturing industry had contracted significantly, with many facilities closing as demand shifted; for instance, U.S. production sites built in the 1950s, like the Tecumseh plant, operated amid an overall sectoral downturn that traced back to the post-World War II era.[19] The 1956 U.S. Supreme Court antitrust ruling in United States v. E.I. du Pont de Nemours & Co. further highlighted cellophane's competitive vulnerabilities, determining that its relevant market extended beyond cellophane itself to interchangeable flexible wrapping materials, underscoring the material's displacement by superior options.[16] Cellophane's legacy endures in the foundational shift it catalyzed toward transparent, protective packaging that enabled self-service retail displays and preserved product freshness through its clarity and grease resistance, revolutionizing food wrapping for items like candies, meats, and produce.[14][20] This innovation influenced subsequent developments, including clear adhesive tapes and modern flexible films, while its inherent biodegradability—derived from regenerated cellulose—positions it as a precursor to sustainable alternatives amid contemporary environmental concerns over non-degradable plastics.[4][21] Despite its eclipse, cellophane demonstrated the viability of bio-based barriers, informing ongoing efforts to revive cellulose films for eco-friendly applications where transparency and renewability outweigh synthetic efficiencies.[22]Production
Raw Materials
Cellophane is produced primarily from dissolving-grade cellulose pulp, a highly purified form of cellulose extracted from natural plant sources such as wood, cotton linters, or hemp. Wood pulp, often derived from softwoods like spruce or hardwoods such as eucalyptus and acacia, serves as the predominant source due to its abundance and suitability for large-scale processing, comprising the bulk of input material in modern production.[23][24] The required pulp must exhibit a high α-cellulose content, typically exceeding 95%, to ensure the resulting film's transparency, strength, and uniformity by minimizing hemicellulose and lignin impurities.[24] Key chemical reagents essential to the viscose process include sodium hydroxide (NaOH), which treats the pulp to form alkali cellulose by breaking hydrogen bonds and enabling dissolution. Carbon disulfide (CS₂) is then introduced to xanthate the alkali cellulose, yielding the viscous sodium cellulose xanthate solution central to extrusion. The regeneration stage employs sulfuric acid (H₂SO₄) and sodium sulfate (Na₂SO₄) in an acidic bath to precipitate and solidify the cellulose film.[19][25] These inputs, while enabling the transformation of insoluble cellulose into a processable dope, introduce environmental challenges due to the toxicity of CS₂ and the energy demands of purification.[19]Manufacturing Process
The manufacturing of cellophane employs the viscose process, a chemical regeneration method that transforms purified cellulose into a continuous thin film through dissolution and coagulation. This industrial technique, developed in the early 20th century, relies on the controlled depolymerization and reformation of cellulose chains to achieve the material's characteristic transparency and flexibility.[26] The process commences with high-purity cellulose feedstock, sourced from wood pulp (such as sulfite or sulfate varieties) or cotton linters, which undergoes steeping in a 17-20% sodium hydroxide solution at around 20°C for 1-2 hours to form alkali cellulose. This swollen product is pressed to remove excess liquor, achieving a specific alkali-to-cellulose ratio of approximately 25-30%, then shredded into crumbs and aged for 24-72 hours at controlled temperatures (typically 20-30°C) to reduce molecular weight via oxidative depolymerization, enhancing solubility.[27][24] Subsequently, the aged alkali cellulose is treated with carbon disulfide (CS₂) in a xanthation reactor, where it reacts to produce sodium cellulose xanthate, an orange-yellow derivative that imparts solubility. This xanthate is dissolved in a 4-7% aqueous sodium hydroxide solution, yielding a viscous orange dope known as viscose, with a cellulose concentration of 7-10% and viscosity maintained at 10-100 poise through further ripening for 4-5 days at 15-20°C. The viscose undergoes filtration to remove undissolved particles and deaeration under vacuum to eliminate air bubbles, ensuring uniformity for extrusion.[26][28] The core film-forming step involves extruding the ripened viscose through a narrow slit die (typically 0.025-0.05 mm thick) into a coagulating bath composed of 10-20% sulfuric acid, 20-30% sodium sulfate, and 1-3% zinc sulfate at 40-50°C. This acidic environment decomposes the xanthate, regenerating pure cellulose as a gel-like film while simultaneously stretching it longitudinally (up to 20-30% extension) and laterally via tenter frames to orient the polymer chains, imparting tensile strength and reducing thickness to 20-40 micrometers.[26][24] Post-coagulation, the regenerated film passes through a series of purification baths: washing with water to remove acids and salts, desulfurization in sodium sulfide solution to eliminate residual CS₂ derivatives, and optional bleaching with sodium hypochlorite for enhanced clarity. Glycerol or sorbitol (10-20% by weight) is applied as a plasticizer to prevent brittleness, followed by drying in heated chambers at 80-120°C to yield the final moisture content of 8-12%. The entire operation runs continuously on large-scale machines producing widths up to 1.5 meters at speeds of 50-150 meters per minute.[27][19]Chemical and Material Properties
Composition and Structure
Cellophane is composed primarily of regenerated cellulose, a linear homopolymer consisting of anhydroglucose units linked by β-1,4-glycosidic bonds, with the repeating unit formula (C₆H₁₀O₅)ₙ.[1] The source material is dissolving pulp, which contains 92–98% cellulose derived from wood or other plant sources, processed through the viscose method to dissolve and regenerate the polymer.[1] This results in a material that retains the chemical reactivity of native cellulose, such as swelling in alkaline solutions and undergoing typical cellulose reactions like esterification.[29] At the molecular level, the structure features long, straight polymer chains without branching, adopting an extended rod-like conformation due to intra- and inter-chain hydrogen bonding.[30] In regenerated form, cellophane exhibits the cellulose II polymorph, distinguished by antiparallel chain packing in crystalline regions, in contrast to the parallel arrangement in native cellulose I.[24] This allomorph arises from the dissolution and precipitation steps in production, leading to a semi-crystalline morphology with both ordered crystalline domains and amorphous zones that influence permeability and mechanical behavior.[24] The alignment of polymer chains within the film contributes to its anisotropic properties, including birefringence observable under polarized light, where chains orient parallel to the film's length during extrusion.[31] While uncoated cellophane is nearly pure regenerated cellulose, commercial variants often incorporate 10–20% plasticizers such as glycerol to enhance flexibility and prevent brittleness, though these additives do not alter the core polymeric structure.[18]Physical Properties
Cellophane is a thin, flexible, transparent film exhibiting high optical clarity with approximately 90% visible light transmission.[32] Its refractive index ranges from 1.468 to 1.472, depending on orientation, contributing to its birefringence of about 0.004.[33] The material has a density of 1.44 g/cm³.[32] [33] Mechanically, cellophane demonstrates anisotropic properties due to its manufacturing process, with tensile strength at break of 120 MPa in the machine (longitudinal) direction and 55 MPa in the transverse direction, alongside elongation at break values of 18% and 55%, respectively.[32] The tensile modulus is 5 GPa longitudinally and 3 GPa transversely.[32] Thermally, cellophane does not melt but undergoes decomposition starting around 250–260°C, similar to other cellulosic materials, with ignition possible under flame exposure.[34] It exhibits moderate stiffness and low tearing resistance compared to its tensile strength.[35]| Property | Longitudinal (Machine Direction) | Transverse Direction | Source |
|---|---|---|---|
| Tensile Strength at Break | 120 MPa | 55 MPa | [32] |
| Elongation at Break | 18% | 55% | [32] |
| Tensile Modulus | 5 GPa | 3 GPa | [32] |
Barrier and Mechanical Properties
Cellophane exhibits strong barrier properties against oxygen and other gases in dry conditions, with oxygen permeability (OP) as low as 5.6 × 10^{-16} cm³·m/m²·s·Pa at 0% relative humidity (RH) and 23°C, due to restricted polymer chain mobility from hydrogen bonding.[26] However, permeability increases substantially at higher humidity levels, such as 100% RH, where OP can rise by factors of 400 or more, as moisture disrupts hydrogen bonds and induces swelling.[26] [36] It provides low permeability to liquids, oils, greases, and bacteria, but water vapor transmission rates (WVTR) are relatively high for uncoated films, exceeding 1700 g/m²·day, making coatings like nitrocellulose or polyvinylidene chloride (PVDC) essential for practical moisture resistance.[1]| Property | Machine Direction (MD) | Transverse Direction (TD) | Conditions/Notes |
|---|---|---|---|
| Tensile Strength | >165 MPa (uncoated); 117–124 MPa (coated) | >83 MPa (uncoated); 62–69 MPa (coated) | Dry; commercial grades[1] |
| Elastic Modulus | >2000 MPa | >1000 MPa | Dry[1] |
| Elongation at Break | 18–22% | 32–70% | Dry; higher TD due to orientation[1] |
| Secant Modulus | 5200 MPa | - | Overall stiffness[1] |
Applications and Uses
Primary Packaging Applications
Cellophane functions as a primary packaging material by providing a transparent, flexible wrap in direct contact with consumer goods, enabling visibility and protection for products such as candies and tobacco.[37] Introduced commercially by DuPont in 1924 following acquisition of U.S. rights, uncoated cellophane initially suited dry items like candy and cigarettes due to its grease resistance but limited moisture barrier.[5] In 1927, DuPont chemist William Hale Charch developed a nitrocellulose coating that enhanced moisture-proofing, expanding applications to include bakery products and other perishables requiring some vapor permeability.[37][38] In food packaging, cellophane wraps confectionery items like chocolates and hard candies, preserving freshness through its barrier against oils, bacteria, and contaminants while allowing breathability to prevent mold in low-moisture environments.[39] By the 1930s, it captured significant market share in candy and bakery wrapping, with DuPont reporting cellophane comprising 10% of company sales and 25% of profits in 1938.[40] Its printability supported branding, transforming retail display from bulk to individually wrapped units that extended shelf life without refrigeration.[7] For tobacco products, cellophane overwraps cigarette packs and cigars, maintaining aroma and freshness by sealing against humidity fluctuations during storage and transport.[41] Manufacturers in the mid-20th century estimated that cellophane prevented significant staleness in cigarettes compared to paper alternatives, contributing to its dominance in the industry until synthetic films emerged.[42] Today, it remains used in premium tobacco packaging for its biodegradability and regulatory compliance in regions favoring natural films over plastics.[41]Alternative and Niche Uses
Cellophane found early niche application in military equipment during World War I, where its transparency and shatter resistance made it suitable for unbreakable eyepieces in gas masks, such as those deployed by Allied forces starting in 1916.[4] This use capitalized on the material's optical clarity and mechanical durability under harsh conditions, predating its widespread adoption in civilian packaging.[4] In the adhesives industry, cellophane served as the primary backing substrate for transparent pressure-sensitive tapes, including 3M's original Scotch Tape introduced in 1930, which leveraged the film's moisture resistance, tensile strength of approximately 100-150 MPa, and visual transparency for sealing and mending applications.[43] This adaptation extended cellophane's utility beyond wrapping to functional composites, though it was later supplanted by synthetic films like polypropylene in the mid-20th century due to cost and performance advantages.[14] Modern niche employs include arts and crafts, where thin cellophane sheets—often dyed in vibrant colors—are cut and layered to mimic stained glass effects in windows, lanterns, or sculptures, exploiting their light transmission properties (up to 90% for clear variants) and pliability without specialized tools.[3] Small-scale industrial uses persist in protective wrapping for sensitive non-food items, such as electronics components or pharmaceutical prototypes, providing a breathable barrier that preserves visibility while mitigating dust accumulation during short-term handling.[44] These applications remain limited by cellophane's lower moisture impermeability compared to petroleum-based alternatives, confining them to low-humidity environments.[45]Environmental Considerations
Biodegradability and Disposal
Cellophane, as a regenerated cellulose film, demonstrates high biodegradability due to its natural polymer structure, which is susceptible to enzymatic hydrolysis by cellulolytic microorganisms such as fungi (Trichoderma viride) and bacteria (Cellulomonas species).[46] Laboratory studies confirm aerobic biodegradation rates where uncoated cellophane achieves substantial mass loss—up to 70-80% within 90 days under optimal soil burial conditions—via microbial consortia breaking down cellulose chains into glucose monomers.[47] However, coatings like nitrocellulose or plasticizers, applied for moisture resistance, can retard this process, reducing degradation efficiency by 20-50% compared to uncoated variants.[48] In composting environments, cellophane decomposes rapidly under industrial conditions (typically 50-60°C with aeration), fully breaking down into carbon dioxide, water, and humus within 4-12 weeks, meeting standards for compostable materials like those in ASTM D6400.[1] Home composting yields slower results (3-6 months) due to lower temperatures and inconsistent moisture, but uncoated cellophane remains viable.[49] Conversely, in landfills, anaerobic conditions prevail, limiting microbial activity and extending decomposition timelines to years or halting it entirely, similar to other cellulosic wastes that persist without oxygen.[50] Disposal recommendations prioritize composting over landfilling or incineration to maximize environmental benefits, as cellophane's biodegradation avoids persistent microplastic accumulation associated with petroleum-based films.[51] It is incompatible with curbside paper or plastic recycling streams, where its fibrous nature contaminates sorted materials, leading most municipal programs to reject it.[52] Incineration is feasible but releases minimal toxins given its biomass origin, though it forgoes the circular nutrient return of composting.[53] Proper segregation—verified as cellulose-based, not synthetic mimics—is essential, as mislabeled "cellophane" plastics lack these traits.[49]Production Emissions and Health Risks
The viscose process used in cellophane manufacturing releases carbon disulfide (CS₂), the primary hazardous air pollutant, along with carbonyl sulfide (COS) and hydrogen sulfide (H₂S) during xanthation, spinning, and regeneration stages.[54][55] These volatile sulfur compounds contribute to air pollution, with CS₂ comprising a significant portion of emissions from cellulose regeneration facilities; for instance, pre-regulation viscose plants emitted CS₂ at rates exceeding 10 kg per ton of product in some cases before control technologies.[56] Wastewater effluents also carry residual CS₂ and sulfides, posing toxicity risks to aquatic systems if untreated, though cellophane itself contains no persistent toxins post-production.[53][57] Control measures, including activated carbon adsorption and incineration, have reduced emissions under U.S. EPA National Emission Standards for Hazardous Air Pollutants (NESHAP), targeting CS₂ limits of 3.0 kg/Mg for cellophane processes, but residual releases persist in global operations lacking stringent enforcement.[54][58] H₂S, formed via reactions in the viscose lye, adds to odor and acidification potential, with combined sulfur emissions historically driving regulatory scrutiny since the early 20th century.[55] Worker exposure to CS₂ vapors in viscose rayon and cellophane facilities causes dose-dependent neurotoxicity, manifesting as peripheral neuropathy with giant axonal swellings and central-peripheral axonopathy, alongside retinal angiopathy impairing color vision.[59][60] Cardiovascular risks include elevated hypertension incidence—up to twofold in exposed cohorts—and coronary heart disease mortality, linked to vascular endothelial damage at chronic levels above 10 ppm.[61][62] Reproductive effects encompass reduced fertility, menstrual irregularities in women, and sperm abnormalities in men, with historical data from European and U.S. plants showing clusters of these outcomes predating modern ventilation standards.[59][63] Acute exposures induce central nervous system depression, including dizziness, nausea, and chest tightness, while thresholds for irreversible effects remain debated but evident below 30 ppm in long-term studies.[64][65] Despite engineering controls like enclosed systems and personal protective equipment, underreporting in industry-dominated occupational health data underscores ongoing risks, particularly in developing regions with lax oversight.[63][66]Comparative Lifecycle Analysis
Cellophane, produced via the viscose process from regenerated cellulose, exhibits a mixed environmental profile in lifecycle assessments when compared to polyethylene (PE), a common synthetic plastic film alternative. Production of cellophane demands substantial resources, including approximately 65 tons of fresh water per ton of fiber and generates around 10.1 kg CO2-equivalent per kg due to energy-intensive steps like pulp dissolution and chemical regeneration using carbon disulfide (CS2).[67][68] In contrast, PE production relies on fossil feedstocks and emits about 1.8-2.0 kg CO2-equivalent per kg, with lower water intensity but contributions to non-renewable resource depletion.[69] The viscose process also releases toxic effluents, including CS2 and hydrogen sulfide, posing localized air and water pollution risks not typical of PE manufacturing.[70][71] At the end-of-life stage, cellophane demonstrates superior performance over PE. Uncoated cellophane biodegrades in soil or compost within weeks to months, achieving over 90% degradation via microbial action without persistent residues or microplastic formation.[72][73][74] PE, however, degrades minimally over centuries in landfills, contributing to long-term accumulation and leaching additives, though mechanical recycling can offset some impacts if rates exceed current global averages below 10%.[75] Incineration of cellophane yields energy recovery similar to PE but avoids the latter's incomplete combustion byproducts in open environments.[76]| Metric | Cellophane (Viscose Process) | Polyethylene (PE) |
|---|---|---|
| GHG Emissions (kg CO2e/kg, production) | ~10.1 | ~1.8-2.0 |
| Water Use (tons/ton) | ~65 | <1 |
| Biodegradation Time | Weeks to months (soil/compost) | Centuries (negligible) |
| Key Toxicity Concerns | CS2/H2S emissions | Additive leaching |