Description

Product Overview

Square PP duct, also called plastic square tubing, is a square-section ventilation pipe made from polypropylene (PP) sheet by 90° bending and hot-melt welding. It is used for laboratory exhaust and general ventilation, usually as main and branch duct that connects to PP round duct runs and to equipment exhaust points. It is available in standard PP or flame retardant PPs, in beige or grey, with socket or flange connections, in sizes confirmed per project.

Square duct suits runs where a rectangular section fits the space or matches equipment connections – common in laboratories, air conditioning duct routes and factory exhaust systems. Dimensions are confirmed against your duct schedule and drawings before manufacture. For standard catalog sizes in round duct, see Polypropylene Round Ducts; for the rectangular range, see Polypropylene Rectangular Ducts.

A square duct is one part of a ventilation system: it connects to fans, fittings and airflow dampers rather than replacing them, and matching square elbows, flanges, tees and dampers are available from the same supplier, so a complete PP duct line can be specified from one source.

Product Selection Summary

Good Fit

• Laboratory ventilation runs where square duct connects fume hoods, benches and cabinets
• Air conditioning and general air movement where a square section fits the space
• Factory and workshop exhaust runs following equipment and building lines
• Projects needing flame retardant duct material for part or all of a run

Conditions To Confirm

• Required width, height, wall thickness, section length and quantity
• Material grade: PP or flame retardant PPs (specify grade when fire-rated ductwork is required)
• Gas composition, concentration, temperature and moisture at the actual operating point
• Color (beige or grey) and connection method (socket or flange) for each joint
• Available static pressure and airflow schedule

Not a Replacement For

• Fans, airflow balancing devices, room controls or gas treatment equipment

Technical Specifications

Confirmed Product Parameters

Parameter	Value
Product Type	Square PP Duct (Plastic Square Tubing)
Material	100% polypropylene (PP); PPs flame retardant grade available
Size Range	Customized – width × height confirmed per project
Connection Method	Socket / Flange
Fabrication	PP sheet bending + hot-melt welding
Warranty	1 year
Working Temperature	-15℃ to 80℃
Chemical Resistance	pH 1-14 (acid and alkali)
Certification	ISO9001, ISO14001, RoHS

Square PP duct is available in flame retardant PPs or standard PP, in beige or grey, for laboratory, air conditioning and factory exhaust runs. All dimensions are confirmed per project – see Selection Notes below for the information to include with your inquiry.

How Square PP Duct Is Made

Square PP duct is produced from flat PP sheet: the sheet is bent at four 90° corners and then hot-melt welded along the seam to form a square section. This fabrication route is why a square duct keeps the corrosion resistance, weldability and smooth wall of PP sheet while giving a rectangular profile for installations that need one.

Because the profile is formed from sheet rather than extruded to a fixed catalog size, each square duct section can be made to the width, height, wall thickness and length of your duct schedule. For the same circumference or cross-section, a square duct is generally more expensive than a round duct of equal flow area, depending on wall thickness and whether the section is reinforced with an outer flange – so round duct is usually the more economical choice where the installation allows either profile.

Large-diameter and long square sections are reinforced with flange welding during production to prevent deformation. Complete systems combine square ducts with square elbows, square flanges and square direct fittings.

Material & Performance

Square PP duct is made from polypropylene, a lightweight thermoplastic with strong corrosion resistance and excellent weldability. The properties that matter in square ductwork include:

• No rust: PP withstands corrosion by high-concentration acids and alkalis across a wide pH range (pH 1-14) in a wide temperature range.
• Wear resistance, no scaling: the smooth, uniform inner wall gives low flow resistance and resists scaling and deposit buildup.
• Reduced vibration and noise: PP has sound insulation properties that significantly reduce vibration and noise caused by air flow.
• Anti-freeze cracking: PP’s elasticity lets the section expand with frost-heaving conditions without bursting.
• Anti-condensation, low heat loss: PP is a poor thermal conductor, reducing condensation and heat loss along the run.
• Simple installation: PP duct is light, easy to install and operate, and has weldability.
• Long service life: PP duct systems offer a service life of up to 50 years under specified operating conditions.
• Chemical resistance: PP withstands corrosion by most chemicals, including high-concentration acids and alkalis.
• Hygienic: PP molecules contain only carbon and hydrogen, so the material is non-toxic and tasteless.
• Heat insulation: PP conducts heat poorly – around 1/1200 of steel – giving better heat preservation along the duct run.

Flame retardant PPs is available where fire-rated ductwork is required; specify the required flame retardant grade when inquiring.

Applications

Laboratory Ventilation

Square PP duct is used in laboratory ventilation systems: the duct is hoisted above the indoor ceiling, connected to exhaust points such as fume hoods, universal hoods and medicine cabinets through branch pipes, and exhausted at the end by a PP induced draft fan. See laboratory ventilation square ducts for the laboratory-specific range.

General and Industrial Duct Runs

Beyond laboratories, square PP duct is used for air conditioning duct routes, factory and workshop exhaust, and chemical process exhaust where a rectangular profile fits the equipment layout and pipe runs. The same PP properties – corrosion resistance, low flow resistance, sound insulation and light weight – apply across these applications.

Selection Notes & Quotation Information

Square or Round?

Round PP duct is generally the lower-cost, lower-flow-resistance option for straight runs, and the XICHENG round range covers standard catalog sizes from φ20 mm to φ500 mm. Square duct is chosen where a rectangular section fits the space or matches equipment connections – for example under ceilings, against walls, or at laboratory workstations – and, for the same circumference or cross-section, square sections are generally more expensive than round, depending on wall thickness and outer flange reinforcement.

To Quote Square PP Duct

Provide: required width, height, wall thickness, section length and quantity, material grade (PP or flame retardant PPs), color, connection method (socket or flange), application, destination port, and your duct schedule or drawings. Gas composition, temperature and available static pressure help confirm wall thickness and reinforcement for the actual duty.

MOQ and lead time are confirmed per project. Request a quote via WhatsApp or email using the contact block below.

Installation & System Integration

Square PP duct is connected with socket or flange joints:

• Socket connection: a PP sleeve is welded at the section end so the next section inserts for a stable joint – fast field installation.
• Flange connection: PP flanges are welded to the duct and joined with screws – suited to high-sealing working conditions and allows maintenance disassembly.

Complete systems combine square ducts with matching accessories: PP 90° elbows, square tees, reducers and flanges. See the full range of PP duct systems.

Related Products

• Polypropylene Rectangular Ducts
• Laboratory Ventilation Square Duct
• Polypropylene Round Ducts
• PP 90° Elbow
• PP Air Duct Flange
• Full PP Duct Range
• PP Air Duct Guide – a complete guide to PP duct types, sizes and materials.

FAQ

What is square PP duct?

Square PP duct, also called plastic square tubing, is a square-section ventilation pipe made from polypropylene (PP) sheet by 90° bending and hot-melt welding. It is used for laboratory exhaust and general ventilation, usually as main and branch duct.

How is square PP duct made?

Flat PP sheet is bent at four 90° corners and hot-melt welded along the seam to form a square section. This allows each section to be made to your width, height, wall thickness and length.

What sizes are available?

Square PP duct is made to order. Width, height, wall thickness and section length are confirmed per project against your duct schedule and drawings.

Is flame retardant PP available?

Yes. Square PP duct is available in standard PP or flame retardant PPs; specify the required flame retardant grade when inquiring.

How is square PP duct connected?

Two standard methods are offered: socket connection (a PP sleeve welded at the section end receives the next section) and flange connection (screwed flanges for high-sealing duties).

Square or round – which should I choose?

Round PP duct is usually the more economical choice for straight runs and is available in catalog sizes from φ20 mm to φ500 mm. Square duct suits runs where a rectangular section fits the space or matches equipment connections, and is confirmed to your drawings.