4 Mil Reclosable Poly Bags - Technical Specification

Heavy-duty 4 mil reclosable polyethylene bags engineered for industrial packaging applications requiring superior puncture resistance and extended service life. Manufactured from 100% virgin low-density polyethylene (LDPE) resin conforming to FDA 21 CFR 177.1520 for direct food contact. Features reinforced side-welded zipper closure, white write-on identification block, and single hang hole for retail or warehouse organization systems.

Key technical features:

• 4 mil (0.004 inch / 101.6 micron) nominal gauge thickness
• Virgin LDPE resin (no recycled content) for optical clarity and consistency
• Reinforced side-weld zipper construction for enhanced seal integrity
• White block panel accepts marker, pen, or label adhesion
• Single hang hole (standard 3/8" diameter) positioned above zipper
• Available in 29 sizes: 2" x 3" through 24" x 24"
• Box quantities optimized by size: 250-1000 bags per box

Material Specifications and Performance Characteristics

LDPE Resin Properties and FDA Compliance

Base material composition:

• Polymer type: Low-density polyethylene (LDPE), virgin resin only
• Density range: 0.910-0.925 g/cm³ (ASTM D792)
• Melt flow index: 0.5-2.0 g/10 min at 190°C (ASTM D1238)
• Regulatory compliance: FDA 21 CFR 177.1520 (olefin polymers), USDA approved
• Additives: Minimal slip/anti-block agents (FDA-approved only)
• Clarity specification: >85% light transmission (virgin resin ensures crystal-clear film)

Virgin resin specification rationale:

• Eliminates contamination risk from unknown recycled content sources
• Ensures consistent gauge uniformity (±5% tolerance across web width)
• Maintains optical clarity without haze from recycled polymer degradation
• Prevents odor transfer from recycled content volatile compounds
• Required for FDA food contact compliance verification

Mechanical Properties and Performance Metrics

Physical performance specifications:

Property	Test Method	4 Mil Specification
Tensile strength (MD)	ASTM D882	2,200-2,800 psi
Tensile strength (TD)	ASTM D882	1,800-2,400 psi
Elongation at break	ASTM D882	400-600%
Dart drop impact	ASTM D1709	350-450 g (Method A)
Puncture resistance	ASTM F1306	18-24 lbf
Tear strength (MD)	ASTM D1922	450-600 g
Tear strength (TD)	ASTM D1922	600-800 g

Temperature performance range:

• Minimum service temperature: -40°F (-40°C) - maintains flexibility without embrittlement
• Maximum service temperature: 180°F (82°C) - below film softening point
• Heat seal initiation: 250°F (121°C) for heat-sealing applications
• Storage temperature: 50-90°F (10-32°C) optimal for extended shelf life

Barrier Properties and Protection Characteristics

Moisture and gas transmission:

• Water vapor transmission rate: 0.6-0.8 g/100 in²/24h at 100°F, 90% RH (ASTM F1249)
• Oxygen transmission rate: 4,000-6,000 cc/100 in²/24h at 73°F, 0% RH (ASTM D3985)
• Barrier classification: Moisture-resistant (not oxygen barrier)

Critical limitation: LDPE provides excellent moisture barrier but minimal oxygen barrier. Applications requiring modified atmosphere packaging, oxygen-sensitive products, or extended shelf life (>72 hours for food) require high-barrier materials (metalized films, EVOH, nylon multilayer structures).

Chemical resistance profile:

• Resistant: Water, aqueous solutions, mild acids (pH 4-6), mild alkalis (pH 8-10), salts, alcohols (short-term)
• Limited resistance: Oils, greases, aliphatic hydrocarbons (permeation over time)
• Not resistant: Aromatic hydrocarbons (benzene, toluene), chlorinated solvents, strong oxidizers

Zipper Closure Engineering

Reinforced Side-Weld Construction

Critical differentiator from standard reclosable bags: reinforced side-welded zipper provides enhanced seal integrity and extended operational life.

Construction methodology:

• Zipper profile: Interlocking LDPE male/female track (identical polymer to bag film)
• Attachment method: Heat-welded to bag interior, both sides sealed
• Reinforcement: Side welds extend full bag width, prevent zipper detachment
• Weld strength: >90% of base film strength at zipper interface
• Positioning: Zipper located 1-1.5" below bag opening edge

Side-weld advantages vs. standard construction:

Performance Factor	Side-Weld Reinforced	Standard Construction
Zipper detachment resistance	Full-width weld prevents separation	End failures common under stress
Seal consistency	Uniform across entire width	End gaps potential leak points
Cycle life (open/close)	100+ cycles (4 mil gauge)	50-75 cycles before degradation
Heavy product suitability	Supports 5-15 lbs without failure	Zipper stress risk >5 lbs
Manufacturing complexity	Additional process steps required	Simpler production

Closure Performance and Seal Verification

Proper closure technique:

1. Ensure product contents below zipper line (no interference with closure tracks)
2. Align zipper tracks at one bag end
3. Apply continuous pinch pressure across full zipper width using thumb and forefinger
4. Verify complete engagement - properly sealed zipper exhibits continuous raised ridge
5. Test seal integrity with gentle pull perpendicular to zipper - resistance indicates proper closure

Seal strength specification:

• Perpendicular pull resistance: 5-10 lbf before zipper disengagement
• Hermetic seal: Pass/fail based on visual bubble test (submerge sealed bag, no air escape)
• Cycle degradation: <10% seal strength reduction through 100 cycles (4 mil specification)

Dimensional Engineering and Usable Capacity

Measurement Standards and Tolerances

Dimensional specification conventions:

• Format: Width x Length (expressed in inches)
• Width: Measured perpendicular to zipper closure
• Length: Measured from bag bottom to top edge (above zipper)
• Usable interior: Dimensions represent internal bag capacity
• Manufacturing tolerance: ±1/8" (±3.2 mm) on width and length

Capacity Calculation Methodology

Volume estimation for irregular products:

V = W × L × D × 0.6 (cubic inches)

Where:

• W = bag width (inches)
• L = usable length below zipper (bag length minus 2 inches for zipper/opening)
• D = maximum product depth/thickness (inches)
• 0.6 = fill factor for irregular shapes (conservative)

Example: 6" x 9" bag capacity for irregular product 1.5" thick: V = 6 × (9-2) × 1.5 × 0.6 = 37.8 cubic inches

Weight capacity guidelines by size:

Bag Size Category	Recommended Max Weight	Seal Stress Factor
Small (2"-4" width)	2-4 lbs	Low stress concentration
Medium (5"-8" width)	5-10 lbs	Moderate stress, verify seal
Large (9"-13" width)	10-15 lbs	High stress, support recommended
Extra-large (14"-24" width)	15-20 lbs	Maximum capacity, handle carefully

Note: Weight limits based on zipper seal integrity and film strength. Sharp-edged products may require derated capacity to prevent puncture failure.

White Write-On Block and Hang Hole Features

Identification Block Specifications

White panel construction:

• Material: White corona-treated polyethylene (same base polymer as bag)
• Location: Positioned above zipper closure on one bag face
• Dimensions: Typically 2" x 3" to 3" x 5" depending on bag size
• Surface treatment: Corona discharge (38-42 dynes/cm) for ink/marker adhesion
• Opacity: >95% to prevent bleed-through from bag contents

Writing implement compatibility:

• Permanent markers: Sharpie, industrial markers (best adhesion and durability)
• Ballpoint pen: Adequate for temporary notation (may smudge with handling)
• Adhesive labels: Standard pressure-sensitive labels adhere to treated surface
• Thermal transfer printing: Compatible with industrial label printers

Hang Hole Design and Retail Applications

Hang hole specifications:

• Diameter: 3/8" (9.5 mm) standard - fits most retail peg hooks
• Location: Centered above zipper, 1/2-3/4" from top edge
• Reinforcement: Double-thickness film at hole perimeter prevents tear-through
• Load capacity: 2-5 lbs hanging weight (depending on bag size and product distribution)

Retail merchandising applications:

• Pegboard display systems in hardware, craft, hobby retail
• Slatwall panel fixtures for parts organization
• Wire grid merchandising in industrial supply environments
• Warehouse bin identification and hanging storage

Application Engineering

Industrial Parts Organization

Hardware and fastener applications:

• Sharp metal components: Screws, bolts, nuts, washers, nails, tacks (4 mil gauge prevents puncture)
• Automotive parts: Clips, brackets, springs, o-rings, gaskets, replacement hardware
• Tool accessories: Drill bits, router bits, saw blades (white block for size/type identification)
• Electronics components: Connectors, terminals, switches, small assemblies

Organizational efficiency advantages:

• Visual product identification through clear film eliminates search time
• Reclosable feature maintains organization through repeated access cycles
• White write-on block enables part number, size, or specification notation
• Hang hole allows vertical storage maximizing workspace efficiency

Food Service and Packaging Applications

FDA compliance for direct food contact:

• Bakery operations: Bulk ingredient portioning (flour, sugar, decorating supplies)
• Prepared food components: Sandwich ingredients, salad components, garnishes
• Dry goods packaging: Nuts, dried fruits, candies, snacks, coffee/tea
• Frozen applications: Portion-controlled proteins, vegetables, prepared items

Critical food safety considerations:

• Virgin LDPE resin required for FDA compliance - no migration risk
• Moisture barrier adequate for dry/frozen applications (24-72 hour protection)
• NOT suitable for oxygen-sensitive foods requiring extended shelf life
• Write-on block enables date coding, lot tracking, allergen identification

Laboratory and Medical Non-Sterile Applications

Clean manufacturing suitable for:

• Specimen collection: Non-biological samples, environmental swabs, test materials
• Supply organization: Non-sterile medical supplies (gauze, bandages, disposables)
• Laboratory consumables: Pipette tips, sample vials, containers, accessories
• Equipment parts: Cables, adapters, replacement components, calibration tools

Important limitation: Standard poly bags are NOT sterile. Medical device packaging requiring sterility needs validated sterilization-compatible materials (Tyvek®, medical-grade films) and controlled manufacturing environment.

Packaging Quantities and Order Specifications

Standard Box Quantities by Size

Optimized packaging based on dimensional efficiency:

• Sizes 2"-6" width: 1,000 bags per box
• Sizes 7"-9" width: 1,000 bags per box
• Sizes 10"-13" width: 500 bags per box
• Sizes 14"-24" width: 250 bags per box

Box quantity rationale:

• Balances handling weight (10-25 lbs per box depending on size)
• Optimizes storage cube efficiency in warehouse environments
• Matches typical consumption rates for industrial operations
• Minimizes bags-per-case variability for inventory management

Storage and Shelf Life Requirements

Environmental storage specifications:

• Temperature: 50-90°F (10-32°C) optimal range
• Humidity: 30-70% relative humidity prevents static accumulation
• UV exposure: Minimize direct sunlight - accelerates polymer degradation
• Chemical exposure: Isolate from volatile organics, oxidizers, heat sources
• Stacking limits: Maximum 6 boxes high to prevent bag crushing/deformation

Shelf life and degradation factors:

• Normal conditions: 24 months minimum from manufacture date
• Degradation indicators: Film yellowing, reduced clarity, brittleness, zipper stiffness
• Accelerated aging: High temperature (>100°F) and UV exposure reduce service life
• Quality verification: Periodic testing of zipper function and film integrity recommended for critical applications

Quality Assurance and Manufacturing Standards

Production Quality Control

In-process monitoring:

• Gauge verification: Continuous measurement via ultrasonic or beta-ray sensors (±5% tolerance)
• Zipper alignment: Automated vision systems verify proper positioning and weld integrity
• Seal strength testing: Statistical sampling per ASTM F88 seal strength protocols
• Dimensional accuracy: Random sampling confirms width/length within ±1/8" specification
• Visual inspection: Automated defect detection for holes, tears, contamination, zipper defects

Acceptable quality level (AQL):

• Critical defects: 0.1% maximum (holes, tears, zipper failures)
• Major defects: 0.5% maximum (gauge variation >10%, misalignment)
• Minor defects: 2.5% maximum (cosmetic issues, print defects)

Material Traceability and Compliance Documentation

Regulatory compliance verification:

• FDA 21 CFR 177.1520 compliance letters available upon request
• Resin supplier certification for virgin LDPE material
• Lot code traceability for material genealogy tracking
• California Prop 65 compliance (no listed substances)
• CONEG heavy metals compliance (<100 ppm total of Cd, Pb, Hg, Cr VI)

Technical Support and Engineering Assistance

Application-specific technical guidance available for:

• Material compatibility assessment for chemical resistance requirements
• Gauge selection optimization based on product characteristics and handling conditions
• Size selection engineering for dimensional efficiency and cost optimization
• Custom size development for non-standard applications (minimum order quantities apply)
• FDA compliance documentation for food contact applications
• Performance testing coordination for critical applications requiring validation

Engineering contact: Technical support available for complex application requirements and specification clarification.