Extrusion blow moulding of L4907 into closed-head jerry cans for UN-regulated transport demands independent control of parison sag, die swell and pinch-off weld thickness. The die head is typically held between 190 °C and 210 °C, while barrel zones ramp from 180 °C at the feed throat to 225 °C at the metering section. A diverging die gap of 1.2 mm to 2.0 mm compensates for die swell at a blow pressure of 0.60 MPa to 0.85 MPa. The mould shell is kept at 20 °C to 35 °C to balance cycle time against surface sink marks. For a 30 L closed-head container with a nominal wall thickness of 1.8 mm to 2.5 mm, carbon black masterbatch at 2.0 wt% to 3.5 wt% is dosed into the feed zone for UV opacity, and a fluoropolymer-based processing aid at 0.05 wt% to 0.10 wt% is used only when sharkskin appears at the die lips. The melt temperature is controlled below 230 °C at all zones to avoid gel formation in stagnant areas of the accumulator head. Datasheet-level melt strength curves for L4907 are limited; accumulator-head shot weight and parison sag must therefore be validated on the target machine rather than transferred from laboratory capillary data.

The pinch-off weld on the base and handle regions is measured after sectioning. Weld thickness below 60% of nominal wall gives drop-test failures under UN Manual of Tests and Criteria 6.1.3, particularly after conditioning at -18 °C. Drop heights are assigned by packing group and relative density, and the closure neck is leak-tested at 40 kPa internal air pressure with the container inverted for 10 min. Environmental stress cracking at the handle bridge and bottom chime is assessed per ASTM D1698-15 in 10% Igepal CO-630 at 50 °C. Regrind from trimmings and rejected cans is limited to 30 wt% unless melt mass-flow rate is revalidated per ISO 1133-1:2022 at 190 °C, 2.16 kg. A shift greater than 0.05 g/10 min from the virgin value requires reduction of regrind or addition of a higher-viscosity component. Transport compliance for the finished container rests on ADR/RID, IMDG, and IATA DGR provisions that reference the UN package test record.

Is L4907 Suitable for Multilayer Diesel Tank Shells Without Barrier Compromise?

In a six-layer coextrusion head, L4907 is positioned as both the innermost and outermost cap layers. The nominal layer distribution is 10 wt% to 15 wt% inner HDPE, 2 wt% to 3 wt% inner tie, 3 wt% to 5 wt% EVOH, 2 wt% to 3 wt% outer tie, 30 wt% to 50 wt% regrind, and 20 wt% to 30 wt% outer HDPE. The regrind layer is introduced only from edge trim and rejected tanks that have not been fluorinated, because fluorinated surfaces reduce interlayer adhesion. The coextrusion die temperature is held at 200 °C to 220 °C, and the accumulator head is purged before each shift with HDPE to remove degraded barrier polymer. Parison sag is controlled through a 100-point axial programmer because the fuel tank shell exhibits different wall-thickness requirements around the filler neck, pin holes, and mounting lugs.

Where EVOH is not used, post-moulding fluorination of the L4907 surface provides the required permeation barrier. The moulded tank is treated with 0.5% to 2.0% fluorine in nitrogen at 25 °C to 60 °C for 2 min to 10 min. This step modifies the inner and outer surfaces to a depth of 5 µm to 20 µm, depending on time and fluorine partial pressure. Low-temperature impact resistance is verified by ISO 6603-2:2000 at -40 °C; a brittle failure in the pinch-off zone rejects the tank lot. ESCR around the fuel filler neck is tested per ASTM D1698-15 in 10% Igepal CO-630 at 50 °C. Fuel permeability of the conditioned shell is verified against the vehicle manufacturer’s evaporative emission specification. Regulatory compliance includes ECE R34 for fire resistance and FMVSS 301 for post-crash fuel integrity. Grade-specific coextrusion adhesion data for L4907 are not widely published; shear peel testing on the target line is required before release.

Dual-laminate chemical storage vessels use L4907 as the thermoplastic liner sheet that is welded to a filament-wound FRP shell. The sheet is extruded at 220 °C to 240 °C through a 90 mm single-screw extruder with a 30:1 L/D barrier screw. Sheet thickness between 3 mm and 5 mm is calibrated on a vertical three-roll stack at 60 °C to 80 °C. Hot gas welding rods are produced from the same L4907 extrusion lot or from a confirmed-compatible HDPE welding rod. The welding gas temperature is held at 220 °C to 240 °C, and the root gap is set below 0.3 mm. Weld integrity is assessed by DVS 2205-1 and DVS 2207-1 bend tests, with no cracking at a bending angle of 180° across the weld.

Chemical resistance is validated by immersion per ISO 175:2010 in 5% sodium hypochlorite at 23 °C for 28 d. Weight gain below 0.50% and absence of surface cracks are acceptance limits for sodium hypochlorite storage. Concentrated nitric acid above 30%, oleum, chromic acid, and halogenated solvents are outside the service envelope; exposure causes oxidative attack, swelling, or environmental stress cracking. When the vessel operates at continuous temperatures above 40 °C, the liner thickness is increased to compensate for lower tensile strength and higher creep. Pre-drying of L4907 is not required unless regrind moisture exceeds 0.05 wt%; wet regrind produces surface porosity at the sheet edges and weakens weld root fusion. The FRP backing laminate is applied only after the HDPE liner has cooled below 50 °C to avoid differential thermal contraction at the bond line.

When Accumulator-Head Machines Replace Reciprocating Screw for 200 L Drums

A 200 L open-top drum in L4907 is blown on an accumulator-head machine with a shot capacity of at least 8.0 kg and clamp force from 800 kN to 1200 kN. The extruder barrel zones are set from 180 °C to 230 °C, and the accumulator is set to 205 °C to 215 °C to preserve melt strength during transfer. A 100-point axial wall-thickness programmer prevents thinning at the base radius and top chime of the drum. Blow pressure is held at 0.70 MPa to 1.00 MPa, and the mould is cooled with 12 °C to 18 °C water to achieve a cycle time of 120 s to 180 s for a finished mass of 6.5 kg to 8.5 kg.

Regrind from top chime trimming and rejected drums is incorporated at 20 wt% to 30 wt% after flake density is checked against ISO 1183-1:2019 and melt mass-flow rate is revalidated per ISO 1133-1:2022. A shift greater than 0.05 g/10 min indicates chain scission from repeated heat history; the regrind ratio must then be reduced or a processing stabilizer package adjusted. Top load is measured per ISO 12048:1994, and drop impact after conditioning at -18 °C follows UN Manual 6.1.3. The drum is leak-tested at 20 kPa internal air pressure for 5 min, and the top chime is inspected for ovality greater than 2.0 mm. Incompatibility with strong oxidizers and long-term immersion in aromatic solvents requires a chemical suitability review before filling.

Extrusion Blow Moulded IBC Inner Bottles and Liner Collapse Phenomena

In 1000 L composite IBCs, the one-piece HDPE inner bottle must maintain wall distribution within ±0.2 mm of a nominal 1.5 mm to 3.0 mm wall. L4907 is processed through a large accumulator head with a die gap of 2.0 mm to 3.5 mm. Blow pressure is set at 0.65 MPa to 0.90 MPa, and mould cooling water is held at 12 °C to 18 °C to stabilise the bottom pinch-off. Heat input is adjusted so that the melt temperature does not exceed 230 °C at the die lips; higher temperatures reduce melt strength and produce a wider wall-thickness spread at the top shoulder.

Liner collapse occurs when internal vacuum exceeds 10 kPa during drainage or product discharge. The first buckling sites are the top flange area and the sidewall pinch-off, particularly where wall thickness drops below 1.3 mm. Hydrostatic and leakproofness type approval follows UN 31A for the assembled IBC, while bottom-pinch ESCR is measured per ASTM D1698-15 in 10% Igepal CO-630 at 50 °C. Published L4907-specific data for IBC-grade wall-thickness capability are limited; the accumulator shot weight, parison programming curve, and blow ratio must be validated on the intended machine. A blow ratio exceeding 3.5:1 at the top flange increases local thinning and should be corrected through die tooling geometry rather than parison programme delay.

Agricultural chemical containers blown from L4907 require a UV stabilization package that does not interfere with the antioxidant system. For opaque containers of 10 L to 20 L capacity, carbon black masterbatch is added at 2.0 wt% to 4.0 wt%. For translucent or coloured packs, a hindered amine light stabilizer masterbatch at 0.30 wt% to 0.60 wt% is used instead. The containers are blow moulded with a nominal wall thickness of 1.2 mm to 2.0 mm, a die temperature of 190 °C to 210 °C, and a blow pressure of 0.55 MPa to 0.75 MPa. The handle pinch-off is sectioned after moulding and inspected for weld-line integrity.

Direct contact with paraquat, glyphosate, and 2,4-D formulations is simulated by storage at 54 °C for 14 d in the filled container, followed by drop testing per UN Manual 6.1.3. No leakage, weld separation, or wall cracking is accepted. Weathering resistance is evaluated by ISO 4892-2:2013 Xenon arc exposure for 2000 h, after which tensile yield must retain at least 80% of the original value when measured by ISO 527-2:2012. The moulded handle and bottom chime are also checked for environmental stress cracking per ASTM D1698-15 in 10% Igepal CO-630 at 50 °C. Failure before 500 h requires adjustment of cooling rate at the pinch-off, not an increase in UV stabilizer loading.