Chang Chun CCP B-24TX

Chang Chun CCP B-24TX is a solid brominated epoxy oligomer manufactured by Chang Chun Plastics Co., Ltd. and supplied under the model designation B-24TX. The resin is based on a tetrabromobisphenol A diglycidyl ether backbone and retains terminal epoxide functionality, which distinguishes it from non-reactive brominated additives such as brominated polystyrene or decabromodiphenyl ethane. Manufacturer-published typical data for the standard grade identify a bromine content of 52–54 % by mass and an epoxide equivalent weight in the 350–450 g/eq range; the softening range is normally reported between 75 °C and 85 °C. Lot-specific certificates of analysis from Chang Chun should be used for exact upper and lower control limits, because different supply grades in the wider brominated epoxy series can shift the epoxide equivalent weight and the ionic bromide residue. The white powder is intended for formulating flame-retardant thermoplastics, epoxy laminates, and electrical encapsulation compounds where UL 94 V-0 classification is required at thicknesses of 1.6 mm or below. Because the product melts below typical compounding temperatures, it can be incorporated without a separate grinding step, but its feed-hopper behavior is sensitive to ambient humidity and to the temperature of the feed-zone cooling water.

What Limits Dispersion Efficiency in High-Shear Compounding of B-24TX?

In a production-scale co-rotating twin-screw extruder with an L/D ratio of 40:1, the limiting factor is not the melt temperature alone but the local viscosity gap between the low-molecular-weight brominated oligomer and the host polymer. When B-24TX is added to glass-reinforced polyamide 66, the oligomer melts in the first kneading zone, but if the barrel temperature in that zone falls below 90 °C for prolonged periods, the molten oligomer can resolidify on the screw root and deposit on the shaft. Plant trials have shown that barrel set points of 240–260 °C in the subsequent mixing zones are adequate to maintain a homogeneous melt, while screw speeds of 300–500 rpm are required to distribute the brominated phase. Melt flow index measured according to ISO 1133-1:2022 at 2.16 kg and 260 °C is a sensitive lot-to-lot screening tool; a reduction of more than 15 % in MFI relative to the control compound indicates epoxide chain extension rather than simple dilution. The processing window is narrow because excess residence time above 280 °C can dehydrobrominate the oligomer and generate free acid, which corrodes downstream die lips. In-line rheometers have recorded pressure variations of 0.5–1.0 MPa across lot changes when the epoxide equivalent weight drifts upward from 350 g/eq to 450 g/eq. Published data for this specific configuration is limited; the values above are representative production observations, not guaranteed performance limits.

FR-4 laminate manufacture uses B-24TX in let-down blends rather than as a neat resin. The brominated oligomer is mixed with a non-brominated bisphenol A diglycidyl ether resin to adjust the bromine level in the cured composite to 18–22 % by mass. The varnish is catalyzed with dicyandiamide and an imidazole accelerator, and the reaction of the terminal epoxide rings with the amine hardener creates network nodes that participate in the same crosslinked architecture as the non-brominated epoxy. Glass transition temperatures after cure are evaluated using dynamic mechanical analysis according to IPC-TM-650 2.4.25 or differential scanning calorimetry under ISO 11357-2:2020. In comparison with a non-brominated system at equivalent crosslink density, the brominated resin raises the viscosity of the prepreg varnish by 20–40 % because the tetrabrominated bisphenol A unit increases chain rigidity; this is controlled by adjusting methyl ethyl ketone solvent content and prepreg resin solid content. Flammability performance is verified under UL 94 V-0 on laminate coupons at 1.6 mm and 0.8 mm; limiting oxygen index values are normally measured with ISO 4589-2.

Thermal Degradation Thresholds in High-Tg Epoxy Systems

Thermogravimetric analysis of a B-24TX-containing resin system shows two distinct weight-loss regimes. The first regime, between 300 °C and 350 °C, corresponds to cleavage of the carbon-bromine bond and release of hydrogen bromide; the second regime above 400 °C involves aromatic network decomposition. The 5 % mass loss temperature is therefore used as an incoming inspection criterion because brominated epoxy oligomers with higher ionic bromide contamination can reduce this onset by 15–25 °C. In copper-clad laminate pressing, this degradation threshold limits the lamination cycle to peak temperatures below 190 °C when the curing system is based on dicyandiamide; for high-Tg systems requiring 200–220 °C lamination, an alternative high-molecular-weight tetrabrominated resin with a higher aromatic content is usually selected. The difference between B-24TX and a brominated polystyrene flame retardant becomes measurable in this test: the polystyrene-based additive begins to decompose as a distinct non-epoxy phase and can lower the onset temperature by 20–40 °C in the same matrix. Thus the use of B-24TX in high-temperature thermoset processing is constrained not by the initial melt viscosity but by the early decomposition of the terminal epoxide-bromine structure. Thermal stability claims should be verified against the Chang Chun certificate of analysis using ISO 11358-1 at a heating rate of 10 °C/min under nitrogen.

When Tetrabrominated Oligomer Reactivity Affects Extrusion Residence Time

When B-24TX is compounded into polyamide or polyester at moisture levels above 0.15 %, the terminal epoxide rings can react with hydrolyzed chain ends under the high shear of a twin-screw extruder. The result is in situ chain extension that raises melt viscosity and die pressure within 60–120 s of residence time. On a production line this appears as an upward drift of 10–25 % in extruder torque after a feeder stop or a barrel-temperature excursion. Reversing the drift requires purging with a non-reactive commodity polyolefin and reducing barrel set points from 260 °C to 230 °C, because higher temperatures accelerate the epoxide-amine addition reaction. The practical difference from a non-reactive brominated diphenyl ethane is therefore not only flame retardancy but also the ability of B-24TX to modify molecular weight at trace levels of moisture. In injection molding trials, samples prepared at 230–240 °C with residence times under 2 min showed tensile strength values under ISO 527-2 similar to the base resin, while residence times above 4 min led to visible surface splay and a drop in elongation at break of more than 20 %. For molders using hot-runner systems, this reactivity imposes an operational boundary: avoid hot-runner holds longer than 5 min at melt temperatures above 250 °C unless the lot has been pre-tested for acid evolution.

From a regulatory and handling standpoint, B-24TX is a tetrabromobisphenol A-based epoxy and is not classified as a decabromodiphenyl ether or a restricted polybrominated diphenyl ether under RoHS Directive 2011/65/EU. Industrial users are advised to confirm compliance with REACH Article 33 and any national occupational exposure limits for brominated compounds before using the product in food-contact or medical-grade polymer applications. Since the resin is hygroscopic, it requires pre-drying at 80–100 °C for 4–6 h when storage relative humidity exceeds 60 %. The dry powder should not be combined with amine-based accelerators at temperatures above 100 °C because the epoxide-amine reaction can initiate prematurely in the feed hopper or in a low-shear pre-blender. Dust extraction equipment is required where airborne brominated resin dust can settle on hot equipment and form acidic decomposition residues. When the product is evaluated as a substitute for brominated polystyrene in ABS or polyolefin flame-retardant compounds, the deciding variable is usually the resin's epoxide content rather than the bromine content alone; the reactive endgroups can improve the retention of mechanical properties after thermo-oxidative aging but they also narrow the processing temperature window.