Herb Packaging Material Selection | Mylar, Polyethylene,Aluminum Foil

When selecting Herb packaging, Mylar​ (boPET) outperforms polyethylene (PE) and aluminum foil due to its balanced performance: it offers a oxygen transmission rate below 0.5 cm³/m²·24h·atm​ (ASTM D3985) and water vapor barrier over 99.9%​ (ASTM E96), far superior to PE’s high permeability, while avoiding foil’s brittleness.

With tensile strength of 5000–7000 psi and transport damage rates under 0.3%, Mylar’s composite structure (PET core, foil/PE layers) meets child-resistance standards (16 CFR 1700.20) and preserves THC/terpenes, making it the preferred choice for dried flower, pre-rolls, and concentrates in regulated markets.

Mylar

Data: Oxygen Transmission Rate < 0.5 cm³/m²·24h·atm (ASTM D3985), Water Vapor Barrier > 99.9% (ASTM E96), Light Barrier 99.5%, Tensile Strength 5000-7000 psi, Temperature Resistance from -40°F to 248°F.

It accounts for 60% of high-end packaging in the United States, used for dried flower zip-top bags (3-7 mil thick) and pre-roll film, with a damage rate of < 0.3% and a cost of $0.02 per gram.

Core Performance

Oxygen Barrier

Oxygen is one of the main causes of Herb degradation. When exposed to air, THC slowly oxidizes into inactive CBN, CBD also degrades into CBDA, and aromatic terpenes (such as limonene and β-caryophyllene) volatilize and are lost.

Mylar’s oxygen barrier relies on the dual protection of the PET core layer plus the aluminum foil/silicon-coated layer. ASTM D3985 standard testing shows that the oxygen transmission rate of 3 mil Mylar film is only 0.1-0.5 cm³/m²·24h·atm (compared to 500-2000 for ordinary PE bags, a difference of 1000 times).

A 2022 study by the University of California, Davis found that dried flower packaged in Mylar retained 92% of its THC after 30 days, while ordinary plastic bags only retained 35%.

For concentrates (such as wax and oil) packaged in Mylar soft bags, the CBD oxidation rate is < 5% within 6 months, while samples stored in open containers exceed the standard in just 3 months.

Moisture Barrier

Herb dried flower is susceptible to moisture (mold grows rapidly when humidity > 65%), and concentrates are prone to drying out (cracking when moisture < 1%). Mylar’s water vapor barrier comes from the amorphous structure of PET and the dense layer of aluminum foil. In ASTM E96 testing, Mylar’s Water Vapor Transmission Rate (WVTR) is 0.05-0.1 g/m²·24h, compared to 5-10 for PE bags (a difference of 50-100 times). A Colorado State University experiment: dried flower was placed in Mylar bags (50% humidity) and ordinary bags (50% humidity) respectively. After 30 days, the humidity inside the Mylar bags stabilized at 52%, while that in ordinary bags rose to 68%, and the mold rate soared from 2% to 40%. Concentrates packaged with Mylar plus an inner silica gel desiccant bag maintain internal humidity < 10% at all times, preventing crystallization.

Light Barrier Effect

The colors of Herb (such as purple and orange) come from carotenoids and anthocyanins, which are damaged by ultraviolet rays (especially 365 nm UVA), leading to fading;

Terpenes volatilize faster when exposed to light. Mylar’s aluminum foil layer can block 99.5% of ultraviolet rays (ASTM G154 xenon lamp aging test), and silicon-coated Mylar (without aluminum foil) can also block more than 95%.

Spectral analysis by Oregon State University: dried flower packaged in Mylar retained 85% of its color after 30 days of light exposure, while transparent PET bags only retained 30%.

In aroma tests, the terpene concentration in Mylar bags was 60% higher than that in transparent bags, and the “grass aroma” was more obvious when opening the bag.

Durability

Herb packaging must withstand warehouse stacking (often stacked 5-8 layers) and express delivery drops (ISTA 3A test simulates a 1.2-meter drop).

Mylar’s tensile strength is 5000-7000 psi (ASTM D882), which is 2.5 times that of cellophane (2000 psi) and 1.7 times that of PP film (3000 psi);

Its puncture resistance is > 5 lbf (ASTM D1709), and it is not easy to break when pierced with a key tip. 2023 data from Canada Post shows that the transportation damage rate of Herb packages using Mylar packaging is 0.3%, compared to 8% for ordinary plastic bags.

California brand Kiva Confections uses 7 mil Mylar zip-top bags, which show no deformation after being stacked 10 layers, and the bag zipper remains smooth.

Temperature Resistance

Herb may undergo cold chain transportation (-20°F/-29°C) or high shelf temperatures (86°F/30°C).

Mylar’s PET core layer can withstand temperatures from -40°F to 248°F (-40°C to 120°C), and the aluminum foil layer does not fall off within this range.

At low temperatures, Mylar’s impact strength (ASTM D256) remains above 400 J/m, and it will not become brittle and crack like PE film;

At high temperatures, when baked at 200°F (93°C) for 24 hours, no harmful substances are released (complying with FDA 21 CFR 177.1630 food contact standards).

In a summer delivery test in Nevada, Mylar bags placed in a truck cargo compartment (104°F/40°C) for 48 hours had an internal temperature 5°C lower than the outside, avoiding condensation.

Application Scenarios

Dried Flower and Bulk Herb

Dried flower accounts for 60% of foreign Herb retail sales, and its packaging needs to be moisture-proof, pressure-resistant, and easy to take.

Mylar zip-top bags are the most commonly used, divided into two types: basic models with a thickness of 3-5 mil (suitable for popular varieties with a unit price < $30/ounce), and high-value models with a thickness of 7 mil (suitable for rare varieties with a unit price > $50/ounce).

The bag structure consists of a PET core layer + aluminum foil layer (light and oxygen barrier) + PE heat-seal layer (for bag zippers), and some are added with an inner silica gel desiccant bag (5 g, moisture absorption capacity 0.3 g/day).

California brand Kiva Confections uses 7 mil Mylar zip-top bags, and tests show that the humidity fluctuation is < ±2% after 30 days, and the mold rate is 0.5% (15% for ordinary bags).

Blister packs are used for in-store display, with a structure of transparent PET window + Mylar aluminum foil backboard + cardboard base, thickness 4-6 mil, with a tamper-evident tear.

Colorado’s LivWell stores use it to pack single-stem flowers. The transparent window allows viewing of flower colors, and the Mylar layer reduces the transportation damage rate from 5% to 0.2%, with a cost of $0.15 per set (including printing).

Pre-roll Herb Joints

Pre-roll joints are afraid of being crushed and damp. Mylar is often compounded with aluminum foil to make roll film, with a thickness of 2-3 mil (too thin is easy to break, too thick is difficult to heat-seal).

The film is divided into three sections: transparent PET at both ends (to show the tightness of the joint), aluminum foil/Mylar composite in the middle (oxygen and moisture barrier), and a heat-seal edge width of 0.25 inches (to ensure sealing).

Oregon’s Local Herb uses it to pack single joints, and tests with ISTA 3A drop (1.2 meters) show a damage rate of 0.1% (8% for paper packaging).

The width of the roll film is determined by the length of the joint (commonly 84 mm and 98 mm), each roll is 500 meters long, and can make 250-300 joints, with a cost of $0.008 per joint (30% lower than paper tubes).

High-end brands add an “easy tear” design, with the tearing force controlled at 1.5-2 lbf (ASTM F88 test), which can be easily opened by the elderly.

Concentrates

Concentrates contain high concentrations of THC/CBD (50%-90%), which are prone to oxidation and sticking to bags.

Mylar soft bags (Dab Bags) are commonly 4-6 mil thick, with a structure of Mylar/PE double layers (inner PE anti-sticking), plus a built-in silica gel desiccant (2 g, moisture absorption capacity 0.2 g/day).

Nevada’s Select Oil uses it to pack wax, and tests show that the CBD retention rate is 95% within 6 months (60% for open bottles), with a cost of $0.12 per bag (including desiccant).

Outer bags for metal cans are a high-end usage: 5 mil all-PET silicon-coated Mylar (without aluminum foil, recyclable), wrapped around metal cans, printed with gold stamping LOGO and batch codes (laser engraved, depth 0.1 mm).

Canada’s Tweed limited edition uses it, with the oxygen barrier rate of the outer can bag being 0.3 cm³/m²·24h·atm, 200.25 lower than that of aluminum foil bags (the metal can itself costs $0.5).

Other Niche Forms

Herb chocolates (Edibles) use Mylar composite cartons, with a 3 mil Mylar film lined inside the carton (to prevent oil penetration), and the outer carton printed with a nutrition label (font height 1/16 inch).

Washington’s Fairwinds brand uses it to pack chocolate bars, and tests show that at 25°C for 30 days, there is no oil seepage on the chocolate surface (40% oil seepage rate for ordinary cartons).

Topicals use Mylar hoses, with a hose thickness of 5 mil, a PE sealing ring added at the screw cap, and the extrusion force controlled at 3-5 lbf (ASTM D3474) to avoid cream leakage.

California brand Whoopi & Maya uses it to pack CBD massage cream. The hose can withstand temperatures from -10°F to 140°F, without hardening and cracking in winter or softening in summer, with a cost of $0.3 per tube (including printing).

Compliance Requirements

Child Resistance Testing

Foreign Herb packaging must pass child resistance testing. The United States uses the 16 CFR 1700.20 standard, and Canada uses the Bill C-45.

The test simulates a 5-year-old child (weight 15-20 kg, hand strength 5-10 lbf) attempting to open the package within a 5-minute time limit, allowing the use of finger picking, tooth biting, and surrounding tools (such as spoon handles) for prying.

Mylar packaging must meet the following requirements: opening force > 15 lbf (ASTM F963 toy tensile test), failure rate > 90%.

A 2023 spot check of 100 Mylar zip-top bags in California showed a 100% pass rate (only 30% of ordinary plastic bags passed).

Tests on Tweed’s blister packs in Canada show that 5-year-old children need to try an average of 12 times to open them, applying 8-10 lbf of force each time, without success.

Reports from testing organization SGS show that 7 mil Mylar bags (with aluminum foil layer) have a 40% higher opening force than 3 mil ones, making them more difficult for children to open.

Labeling Specifications

The front of the package must be printed with 5 types of information, with a font height ≥ 1/16 inch (1.6 mm) and a contrast ratio > 70% (black background with white text or white background with black text).

• THC/CBD Content: Accurate to 0.1%, e.g., “THC 22.5% | CBD 0.3%” (required by Oregon);
• Batch Number + Expiration Date: Format “Lot# ABC123 | Exp: 06/2025” (mandatory by Colorado);
• Warning Statement: Must be in English “Keep Out of Reach of Children”, with bold font (supplementary requirement of California SB 420);
• Manufacturer Information: Company name + address (e.g., “Kiva Confections, Oakland, CA”);
• Usage Instructions: e.g., “Store in cool, dry place” (required for concentrates by Nevada).

Penalties will be imposed if the font is too small. Among the packaging violation fines issued in California in 2022, 60% were due to font height being less than 1.6 mm (e.g., a brand used 1.2 mm font and was fined $5000).

Environmental Labeling

• California SB 54: Starting from 2024, packaging must be marked with recycling code #1 PET (Mylar contains PET core layer) and state “Made with 30% recycled PET” (using 30% recycled materials);
• EU CE Certification: A material composition table must be attached (e.g., “PET 70%, Aluminum 25%, PE 5%”), with a carbon footprint ≤ 2 kg CO₂e/kg of packaging;
• Canada Bill C-45: Requires labeling “Recyclable in blue bin where facilities exist” and printing recycling guide illustrations (e.g., “Empty, flatten, recycle”).

Amcor’s Recycle Ready Mylar (all PET silicon-coated) has obtained California recycling certification, with a recycling rate of 18% in 2023 (only 5% for traditional aluminum foil Mylar).

Polyethylene

Polyethylene (PE) is the most used flexible material in Herb packaging, accounting for about 35% of the basic packaging market share. The raw material cost is $0.8–1.2 per kg, and the unit packaging cost is < $0.01.

LDPE has an elongation at break of 800%, LLDPE has a puncture resistance of 120 N/mm², and HDPE has a water vapor transmission rate < 0.1 g/m²/day, which respectively dominate the scenarios of soft bags, durable bags, and hard bottles.

70% of pre-roll bags in North America use LDPE/LLDPE, and HDPE containers account for 50% of medical concentrate packaging, making them the first choice for the mass market due to cost-effectiveness.

Different Types

LDPE

LDPE molecular chains are like messy branches with many side chains and low crystallinity (about 50-60%), so they are particularly soft and stretchable.

Its density is 0.91-0.925 g/cm³, lighter than water, with an elongation at break of up to 800% (can stretch 8 times longer before breaking), but its puncture resistance is only 40 N/mm² (easy to break when pierced with a needle).

Its water vapor transmission rate is 1.5-3.0 g/m²/day, slightly worse than LLDPE but much better than paper.

Practical Usage: 70% of Herb pre-roll bags in North America use it, with a thickness of 25-50 microns and a single bag cost of less than $0.005.

Transparent versions allow viewing of flower colors, and they can be heat-sealed firmly at 120-150°C.

A California brand uses 30-micron LDPE bags to pack 3.5 g of flower. Tests show that in an environment with 60% humidity for 30 days, only 1.8 g/m² of water vapor penetrates, which is sufficient to block daily moisture;

When fully loaded with flower and dropped 5 times from a height of 1 meter, the damage rate is 75% lower than that of paper bags (ASTM D5276 drop test).

Shortcomings: Susceptible to sharp objects, easy to be punctured by thorny calyxes; oxygen transmission rate is 2000 cc/m²/day, and THC degrades by about 5% per month under light, not suitable for storing goods for more than half a year.

LLDPE

LLDPE molecular chains have uniformly distributed short side chains, not as messy as LDPE, with slightly higher crystallinity (55-65%), so they have similar flexibility but much stronger puncture and tear resistance.

Its density is 0.915-0.925 g/cm³, elongation at break is 600% (lower than LDPE but sufficient), puncture resistance is 120 N/mm² (3 times that of LDPE), and water vapor transmission rate is 1.0-2.5 g/m²/day.

Practical Usage: It is widely used for transportation bags in Europe and the United States, with a thickness of 30-60 microns, used to pack 5-7 g of flower.

A Canadian company tested that LLDPE bags fully loaded with flower dropped 10 times from a height of 1.5 meters have a damage rate < 5% (25% for LDPE bags).

It is also used in blister packaging, with sheet thickness of 0.2-0.5 mm. After thermoforming, it is matched with cardboard, with a penetration rate of 25% in the European market. When packing capsules, the seal weight loss rate is < 0.3% per month (ASTM F88 seal strength test).

Advantages: After adding a small amount of α-olefins (such as butene), its environmental stress cracking resistance is improved, and it is not easy to crack when packing oil-based concentrates.

A 2022 test by the University of California shows that LLDPE has a weight change < 0.2% and no swelling after contacting THC oil for 30 days.

HDPE

HDPE molecular chains have almost no side chains, with a high crystallinity of 70-80%, so they are hard and stiff, with a density of 0.941-0.965 g/cm³ (slightly heavier than water).

Its elongation at break is 200% (basically unbreakable), puncture resistance is 80 N/mm², and water vapor transmission rate is < 0.1 g/m²/day (1/15 of LDPE).

The raw material cost is $1.0-1.2 per kg, slightly more expensive than the previous two, but durable.

Practical Usage: It is injection-molded into hard bottles for medical concentrates, with a wall thickness of 0.8 mm for 10 ml bottles and 1.2 mm for 30 ml bottles, accounting for 50% of medical packaging.

FDA 21 CFR 177.1520 certification shows that HDPE is resistant to THC oil and ethanol extracts, with no component migration after soaking for 30 days.

It is used as a barrier layer in composite packaging. For example, when compounded with paper, the HDPE layer is 20-30 microns thick, accounting for 25% of the total thickness of the composite film, which can reduce the overall water vapor transmission rate to below 0.5 g/m²/day.

Data Details: HDPE bottles can withstand temperatures from -40°C to 110°C, without becoming brittle when placed outdoors in northern winters, and without softening at 40°C in summer warehouses.

Recycled rHDPE has performance close to virgin materials, with a 10% reduction in impact strength and a 15% cost saving. The usage of rHDPE bottles in Europe increased by 20% in 2023.

Specific Usage

Flexible Bags

• Pre-roll Bags: 70% of the North American market uses LDPE (25-30 microns) + LLDPE (10-15 microns) composite, with a total length of 10-15 cm and width of 5-7 cm, and a single bag cost < $0.005. California brand “Green Leaf” uses it to pack 3.5 g of flower. Tests show that in an environment with 60% humidity for 30 days, 1.8 g/m² of water vapor penetrates (ASTM E96 standard); when fully loaded with flower and dropped 5 times from a height of 1 meter, the damage rate is 5% (25% for paper bags). 80% are transparent versions for easy viewing of flower colors, with a heat-sealing temperature of 130°C, pressure of 0.3 MPa, and seal strength > 4 N/15 mm (ASTM F88).
• Multi-dose Bags: Mainly LLDPE (40-60 microns thick), used to pack 5-7 g of flower, with zip-top strips. A Canadian company “Northern Herb” tested that the seal force of the zip-top strip remains > 3 N after 50 insertions and extractions, 3 times more durable than pure LDPE bags. The puncture resistance is 120 N/mm² (ASTM D1709), and it is not easy to break when packing flower with stems, with a transportation damage rate 40% lower than that of pre-roll bags.
• Large-capacity Storage Bags: HDPE/LLDPE composite (outer HDPE 20 microns, inner LLDPE 50 microns), 80-100 microns thick, used to pack more than 28 g of flower. The water vapor transmission rate is < 0.5 g/m²/day (2 g for single-layer LDPE), and the THC loss is < 3% after 3 months of storage (8% for single-layer bags). The cost is $0.015-0.02 per bag, 60% cheaper than metal cans.

Blister Packaging

Blisters are thermoformed from LLDPE sheets and matched with cardboard backing, with a penetration rate of 25% in the European and American markets, mainly used to pack capsules, lozenges, and soft gels.

• Material Parameters: LLDPE sheet thickness is 0.2-0.5 mm, tensile strength > 20 MPa (ASTM D882), blister height after thermoforming is 5-15 mm, and single blister volume is 0.5-2 ml. European brand “Herbal Caps” uses it to pack 10 mg CBD capsules, with a blister wall thickness of 0.3 mm, and the seal weight loss rate is < 0.3% per month after accelerated aging test (40°C/75% RH).
• Combination Form: Common arrangements are “1×10” and “2×5”. The cardboard uses 350 g/m² white cardboard. The heat-sealing temperature between PE blister and cardboard is 180°C, pressure is 0.5 MPa, and peel strength > 1.5 N/15 mm (EN 21974). The US market prefers transparent blisters (LLDPE light transmittance 85%), while the European market prefers aluminum foil backing (light shielding), but the cost of PE blisters is 30% lower than that of aluminum-plastic blisters ($0.03 per piece vs $0.045).
• Special Scenarios: Child-resistant blisters are added with raised tear strips, and LLDPE sheets are modified with 5% metallocene, with a tearing force > 15 N (ASTM D903) to prevent accidental opening. Tests show that adults can open it in < 3 seconds, while 5-year-old children cannot open it.

Hard Bottles

HDPE is injection-molded into hard bottles, accounting for 50% of medical concentrate packaging, divided into small capacity (10-30 ml) and large capacity (50-100 ml).

• Small-capacity Bottles: 10 ml bottles have a wall thickness of 0.8 mm, diameter of 22 mm, and height of 58 mm, with an injection molding cycle of 12 seconds per piece (high-speed machine), and a single bottle cost of $0.02. FDA 21 CFR 177.1520 certification: resistant to THC oil (90% concentration) and ethanol extracts, with a weight change < 0.2% and no swelling after soaking for 30 days. California medical brand “MedCanna” uses it to pack 1 ml THC tincture, with a PP screw cap, tightening torque of 0.8-1.2 N·m, and leakage rate < 0.01% (ASTM D4991).
• Large-capacity Bottles: 50 ml bottles have a wall thickness of 1.2 mm, with anti-slip lines, and no deformation after 24 hours of stacking test (5 layers high, 1 meter). The European market uses HDPE/rHDPE mixture (30% recycled materials), with a 15% cost reduction, and impact strength (1 kg drop from 1 meter height) > 15 J, with a gap < 10% compared to virgin materials.
• Label Compatibility: The surface tension of HDPE is 38-42 dyn/cm, which requires corona treatment ( > 50 dyn/cm after treatment), ink adhesion > 3B (ASTM D3359), and no falling off after 500 times of eraser friction test after labeling.

Practical Applications

Cost Saving

Herb flower has a fast turnover rate (expected to be sold within 3 months), and polyethylene bags can minimize the cost.

70% of pre-roll bags in North America use LDPE (25-30 microns) + LLDPE (10-15 microns) composite, with a single bag cost < $0.005 ($0.05 for Mylar bags, 10 times more expensive).

California brand “Green Leaf” uses it to pack 3.5 g of flower. Tests show that in an environment with 60% humidity for 30 days, only 1.8 g/m² of water vapor penetrates (ASTM E96 standard);

When fully loaded with flower and dropped 5 times from a height of 1 meter, the damage rate is 5% (25% for paper bags). Fast-selling flowers do not need long-term storage, and the low cost of PE perfectly matches this demand.

Durability

LLDPE’s puncture resistance is 120 N/mm² (ASTM D1709 standard), 3 times that of LDPE (40 N/mm²).

Canadian company “Northern Herb” uses 40-micron LLDPE bags to pack thorny flower, with a damage rate < 3% after transporting 1000 orders;

Compared with Mylar bags (puncture resistance 80 N/mm²), the damage rate is 12%.

LLDPE’s short side chain structure makes it more “tough”, which can disperse force when pierced, and is not easy to break and leak powder.

Corrosion Resistance

Medical concentrates (THC oil, CBD tincture) are corrosive, and bottles must be able to withstand them. HDPE injection-molded bottles account for 50% of medical packaging, with a density of 0.941-0.965 g/cm³, high crystallinity (70-80%), and good chemical resistance.

FDA 21 CFR 177.1520 certification shows that HDPE bottles soaked in THC oil (90% concentration) for 30 days have a weight change < 0.2% and no swelling;

Compared with PP bottles (commonly used alternative materials), the swelling rate is 1.5% after 30 days.

10 ml HDPE bottles have a wall thickness of 0.8 mm, with a single bottle cost of $0.02, 80% cheaper than glass bottles and half the weight (15 g for glass bottles vs 7 g for HDPE bottles), saving transportation costs.

Aluminum Foil

Aluminum foil achieves an oxygen transmission rate ≤ 0.05 cc/m²·day and water vapor transmission rate ≤ 0.01 g/m²·day with a thickness of 0.018 mm in Herb packaging, extending the shelf life of concentrated extracts from 6 months to 24 months (field test in the North American market in 2023).

Its pure metal layer blocks 99.9% of ultraviolet rays, reducing the annual THC degradation rate from 15% to 2%, with a penetration rate of 58% in high-end flower and leaf packaging, making it a commonly used material for preserving high-value products.