When businesses search for plastic bags and packaging for sale the variety of material options can create confusion about which product best fits their application. Plastic bags and packaging for sale are manufactured from several polymer families each offering distinct mechanical properties barrier characteristics and cost structures. Shenlong Packaging Products Co., Ltd. provides this technical comparison to help purchasers select the correct plastic bags and packaging for sale based on measured performance data rather than general descriptions.
The three most common materials found in plastic bags and packaging for sale are low density polyethylene LDPE high density polyethylene HDPE and polypropylene PP. Each material changes the bag behavior under load temperature and humidity. The following table presents side by side technical specifications for plastic bags and packaging for sale made from these three materials
| Property | LDPE | HDPE | PP |
|---|---|---|---|
| Typical thickness range microns | 25 to 150 | 10 to 80 | 20 to 100 |
| Tensile strength at yield MPa | 9 to 14 | 26 to 33 | 30 to 38 |
| Elongation at break percent | 200 to 600 | 10 to 120 | 100 to 600 |
| Puncture resistance newtons per 40 micron | 6 to 9 | 3 to 5 | 5 to 7 |
| Water vapor transmission rate g/m²/day | 15 to 20 | 5 to 12 | 5 to 10 |
| Oxygen transmission rate cm³/m²/day | 1800 to 2200 | 1500 to 2500 | 1500 to 2000 |
| Price per kilogram USD | 1.15 | 1.05 | 1.25 |
LDPE plastic bags and packaging for sale provide the best puncture resistance and flexibility making them suitable for irregular shaped items. HDPE plastic bags and packaging for sale offer the lowest cost per bag and highest stiffness but tear easily once punctured. PP plastic bags and packaging for sale withstand higher temperatures making them the only choice for hot fill applications among standard plastic bags and packaging for sale.
Selecting the correct thickness for plastic bags and packaging for sale requires matching the material gauge to the product mass and geometry. For lightweight products under 500 grams including bread small hardware and confectionery items 25 to 35 micron LDPE plastic bags and packaging for sale provide adequate strength. The same product category using HDPE plastic bags and packaging for sale requires only 15 to 20 micron thickness due to the higher tensile strength of HDPE.
For medium weight products between 500 grams and 2 kilograms such as rice frozen vegetables and granular chemicals 50 to 70 micron LDPE plastic bags and packaging for sale are recommended. In this weight range PP plastic bags and packaging for sale at 35 to 50 micron thickness offer a balance of strength and heat resistance. The puncture resistance requirement for medium weight products is 10 to 15 newtons which both LDPE and PP achieve at these thicknesses.
Heavy duty applications with product weight exceeding 5 kilograms including pet food bags industrial chemical liners and construction material packaging require 100 to 150 micron LDPE plastic bags and packaging for sale. At this thickness range LDPE provides puncture resistance exceeding 30 newtons and tear propagation resistance of 800 to 1200 grams. Shenlong Packaging Products Co., Ltd. produces heavy duty plastic bags and packaging for sale with double bottom seals to reinforce the highest stress point.
For products with sharp edges such as metal parts or tools a minimum of 80 micron LDPE plastic bags and packaging for sale is required regardless of product weight. The dart drop impact test at 80 micron LDPE shows values of 300 to 450 grams indicating the bag can absorb significant point impact without failing.
The final price of plastic bags and packaging for sale consists of four components raw material cost conversion cost printing cost and packaging logistics. Raw material cost for LDPE plastic bags and packaging for sale represents 55 to 65 percent of the total bag cost. For a standard 30 micron 300x400 mm LDPE bag the material cost is 0.018 USD. Conversion including extrusion bag making and quality control adds 0.010 to 0.014 USD.
Printing plastic bags and packaging for sale adds between 0.002 and 0.008 USD per bag depending on number of colors and print coverage area. One color one side printing on plastic bags and packaging for sale costs 0.002 to 0.003 USD per bag for orders above 100000 units. Six color printing covering 80 percent of the bag surface costs 0.007 to 0.008 USD per bag for the same volume.
When comparing plastic bags and packaging for sale prices across suppliers request a detailed quote showing separate line items for material conversion printing and tooling. Hidden costs include plate making at 200 to 500 USD per color and die cutting charges at 150 to 300 USD per design. Shenlong Packaging Products Co., Ltd. provides transparent pricing for plastic bags and packaging for sale with no setup fees for standard bag sizes.
Volume discounts for plastic bags and packaging for sale follow a predictable curve. At 50000 units the per bag price is typically 100 percent of base. At 200000 units the price drops to 85 to 90 percent of base. At 1000000 units the price drops to 70 to 80 percent of base. For businesses requiring continuous supply of plastic bags and packaging for sale annual contracts with monthly deliveries achieve the lowest per unit cost.
The seal is the weakest point in all plastic bags and packaging for sale. Four seal types are commonly available for plastic bags and packaging for sale side seal bottom seal three side seal and patch handle seal. Side seal plastic bags and packaging for sale have seals on both vertical edges and the bottom creating a pillow shaped bag. Bottom seal bags have a single seal at the bottom and are open on three sides for easy filling.
Three side seal plastic bags and packaging for sale are sealed on three edges leaving one edge open. This design creates a pouch shape and is common for medical device packaging and small parts. Patch handle seal plastic bags and packaging for sale have a reinforced handle area cut into the seal which reduces the effective seal length and requires 20 percent higher seal bar temperature.
Seal strength testing for plastic bags and packaging for sale should use a tensile tester pulling the seal at 90 degrees to the seal direction. Acceptable seal strength values for plastic bags and packaging for sale are LDPE 18 to 22 newtons per 15 millimeter seal width HDPE 16 to 20 newtons PP 15 to 18 newtons. Seals that fail below 12 newtons indicate incorrect sealing temperature pressure or dwell time.
For high reliability applications such as pharmaceutical or medical device plastic bags and packaging for sale seal integrity testing should include a dye penetration test. The sealed bag is submerged in a dye solution under vacuum and any leak path shows colored dye inside the bag. Maximum acceptable leak rate for medical grade plastic bags and packaging for sale is zero detectable leakage after 30 seconds under 20 kilopascals vacuum.
Post consumer recycled PCR plastic bags and packaging for sale are increasingly requested by corporate purchasers with sustainability targets. PCR content in plastic bags and packaging for sale ranges from 10 percent to 50 percent with corresponding reductions in tensile strength of 5 to 18 percent. A 30 percent PCR LDPE bag retains 90 percent of virgin material tensile strength while reducing the carbon footprint by 22 percent compared to 100 percent virgin bags.
PCR plastic bags and packaging for sale cost 10 to 20 percent less than virgin material bags because recycled resin trades at a discount to virgin resin. However PCR plastic bags and packaging for sale have higher lot to lot variation in color and haze. For printed applications where color consistency matters a maximum of 30 percent PCR is recommended to maintain print registration and color matching.
Biodegradable additives for plastic bags and packaging for sale are available but require caution. Oxo degradable additives cause conventional polyethylene to fragment into microplastics and are banned in several jurisdictions. True biodegradable plastic bags and packaging for sale must be made from PBAT or PLA materials and certified to ASTM D6400 or EN 13432. These certified biodegradable plastic bags and packaging for sale represent less than 4 percent of the market and cost 2 to 3 times more than conventional LDPE bags.
Question 1 What is the typical lead time for custom plastic bags and packaging for sale
Standard lead time for custom printed plastic bags and packaging for sale is 20 to 30 business days from artwork approval. This includes 5 to 7 days for plate making 7 to 10 days for film extrusion and printing and 8 to 13 days for bag making and packaging. Express service reducing lead time to 10 to 15 business days is available at a 25 to 35 percent premium. Shenlong Packaging Products Co., Ltd. offers live production tracking for all plastic bags and packaging for sale orders.
Question 2 How do I calculate the correct bag size for my product
For plastic bags and packaging for sale the bag width should equal product width plus 20 percent for easy loading. The bag length should equal product height plus product depth plus 50 millimeters for sealing allowance. For gusseted plastic bags and packaging for sale the gusset depth should equal half the product depth. Test fill 10 to 20 samples before confirming final dimensions for production plastic bags and packaging for sale.
Question 3 Can plastic bags and packaging for sale be used for vacuum packaging
Standard LDPE plastic bags and packaging for sale are not suitable for vacuum packaging because air permeates through the material. For vacuum applications use multilayer plastic bags and packaging for sale with an EVOH barrier layer or use PET based plastic bags and packaging for sale with oxygen transmission rate below 50 cubic centimeters per square meter per day. Smooth surface plastic bags and packaging for sale without embossing achieve better vacuum hold than textured surfaces.
Question 4 What quality tests should I request from my plastic bags and packaging for sale supplier
Request the following five test reports from any supplier of plastic bags and packaging for sale tensile strength test following ASTM D882 tear resistance test following ASTM D1922 dart drop impact following ASTM D1709 seal strength following ASTM F88 and coefficient of friction following ASTM D1894. Suppliers who cannot provide these five reports for plastic bags and packaging for sale should not be considered for critical applications.
Question 5 How are plastic bags and packaging for sale packaged for shipment
Plastic bags and packaging for sale are typically packed in cartons of 500 to 2000 bags depending on thickness and size. Cartons are stacked on pallets with 40 to 60 cartons per pallet. Each pallet of plastic bags and packaging for sale is stretch wrapped and labeled with lot number material type quantity and production date. Shenlong Packaging Products Co., Ltd. ships plastic bags and packaging for sale with a certificate of analysis for each pallet.
The production of plastic bags and packaging for sale involves blown film extrusion followed by bag making on high speed converting lines. Critical quality control points for plastic bags and packaging for sale include melt temperature monitoring during extrusion which should remain within plus or minus 3 degrees Celsius of setpoint for consistent film properties. Bubble stability is monitored by ultrasonic sensors that detect bubble diameter variation exceeding 2 percent of target.
For printed plastic bags and packaging for sale color density is measured using a spectrophotometer with tolerance of plus or minus 0.05 Delta E for critical brand colors. Print registration on plastic bags and packaging for sale is checked every 500 meters during production run with tolerance of plus or minus 0.5 millimeters for each color. Any roll of plastic bags and packaging for sale exceeding this tolerance is rejected and reground.
Seal bar temperature on bag making machines for plastic bags and packaging for sale is controlled to plus or minus 1 degree Celsius with infrared sensors at each seal position. Dwell time for heat sealing plastic bags and packaging for sale is typically 0.3 to 0.8 seconds depending on thickness and material. For LDPE plastic bags and packaging for sale the optimal seal temperature range is 130 to 150 degrees Celsius. For HDPE plastic bags and packaging for sale the range is 135 to 155 degrees Celsius.
In process inspection of plastic bags and packaging for sale includes continuous pin hole detection using high voltage spark testers. Any pin hole above 0.1 millimeter in plastic bags and packaging for sale triggers an alarm and marks the defective section for removal. Finished rolls of plastic bags and packaging for sale are weighed against target weight with tolerance of plus or minus 2 percent. Rolls below minimum weight indicate thin spots and are rejected.
Shenlong Packaging Products Co., Ltd. maintains ISO 9001 certified quality management for all plastic bags and packaging for sale production. Each batch of plastic bags and packaging for sale retains samples for 24 months from production date for traceability. Customers can request retained samples for independent testing at any time within the retention period.
