Topic 02: Additive Solutions for Refrigerators and Washing Machines

Topic 02 · Refrigerators and Washing Machines (Large White Goods)

Refrigerators and washing machines were the best-performing white-goods categories in 2026 - July refrigerator output grew 10.6% year on year, freezers 18.1% and washing machines 4.9%, with exports strong across the board. Their plastic parts are in long-term contact with detergents, grease and food residues, so additive extraction and loss is the core risk that sets them apart from outdoor sun exposure.

Main substrates: PP / ABS / HIPS / PS / PC-ABS Key components: Liner / door seal / outer drum / drawer / panel Core risk: Additive extraction and loss / long-term chemical-medium contact

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1. Service conditions for large white-goods plastic parts

The biggest difference between refrigerators/washing machines and air conditioners is: their parts are mostly not directly exposed to sunlight, but are soaked long term in a "chemical medium + humid environment". This shifts the additive evaluation criterion from "UV resistance" to "extraction resistance".

Component	Common substrate	Service environment	Main risks
Refrigerator liner / door inner liner	PP / ABS / HIPS sheet	Sustained low temperature + condensate + food contact	Low-temperature embrittlement, gloss loss, additive extraction
Door seal	PVC / TPE / elastomer	Repeated compression + sustained moisture	Age-hardening, loss of sealing
Drawer / storage box	PP copolymer / PETG	Food and grease contact	Yellowing, migration of extractables
Washing machine outer drum	PP copolymer / glass-fiber reinforced	High-speed rotation + sustained humidity + detergent	Stress cracking, additive extraction
Panel / control interface	ABS / PC-ABS	Long-term indoor light + frequent touching (grease)	Shade difference, gloss loss, tacky surface
Washing machine door cover / door ring	ABS / PC / POM	Sustained moisture + detergent exposure	Whitening, embrittlement

2. Core challenge: additive "extraction and loss"

This is the most easily underestimated problem in large white goods.Many customers see good laboratory accelerated-aging results, but one to two years after launch the additive concentration has dropped substantially - the reason is not that the additive "failed", but that it was extracted by detergents, grease or moisture. Dry-heat aging in the lab cannot detect this; only real water-based medium contact exposes it.

2.1 Why low-molecular-weight additives are easily extracted

The molecular weight of an additive determines whether it "stays" in the substrate. Low-molecular-weight grades are small and diffuse quickly, so they are readily carried away in media such as water, ethanol and surfactants; high-molecular-weight polymers are larger and diffuse slowly, with a much lower extraction rate.This is a difference at the level of physical law, not something formulation technique can fully compensate for.

2.2 The dual low-temperature + humidity test for refrigerator liners

Refrigerator fresh-food compartments run at 0-4°C year round, and freezer compartments below -18°C. Low temperature reduces polymer chain-segment mobility and causes some additives to exude; at the same time, the sustained high humidity from condensate accelerates hydrolysis and extraction.Liner sheet is commonly HIPS and ABS, and the oxidation rate of the butadiene phase under low temperature and high humidity should not be overlooked.

2.3 Mechanical degradation of the washing machine outer drum

At high rotation speeds the outer drum bears centrifugal force and vibration - a classic triple-coupled condition of "stress + humidity + chemical medium". As aging proceeds, chain scission lowers impact strength, eventually leading to stress cracking and even leakage - a direct safety risk, not an appearance issue.

Tiangang's technical view: For large white goods, weather-resistance design should place "extraction resistance as the first-priority indicator, ahead of "UV resistance". The corresponding selection principle is - for any part in long-term contact with water, detergents or grease, always give priority to high-molecular-weight polymeric HALS.

3. Tiangang's recommended formulations for large white goods

The following are starting points (by weight), based on conventional injection molding / sheet forming. Exact loadings should be confirmed in light of the substrate and contact medium.

Formulation logic: For large white goods the core is not "adding more", but "selecting right. Additive extraction and loss is the main risk in this category, so always give priority to high-molecular-weight polymeric blending systems: HS-962 (a blend of two high-molecular-weight HALS with good water-extraction resistance, suitable for both thick and thin products) as the general first choice; HS-362 (Mn>2000, 10% weight loss above 350°C, and a low softening point of just 105-120°C that disperses easily even in thin-wall parts) for thin parts; T-81 for paint-free appearance parts; for food-contact parts, prefer models whose blending system already contains food-contact-approved components.Proprietary

Component / substrate	Tiangang recommendation	Effective loading	Why this one
Refrigerator liner sheet PP / HIPS, sustained condensate	HS-962 Blended light-stabilizer package	0.4% – 0.6%	Blended from high-molecular-weight HALS + succinate-type HALS (food-contact approved in some countries), water-extraction resistance was the development premise of this grade, aimed squarely at sustained condensate soaking
Door seal PVC / TPE elastomer	HS-300 High-molecular-weight low-alkalinity HALS	0.3% – 0.5%	Low volatility and low migration, not prone to migrate to the surface in elastomers; high effective nitrogen content, significantly improving weather resistance across just 0.1-0.8%
Drawer / storage box PP copolymer, food contact	HS-362 Blended light-stabilizer package	0.4% – 0.6%	The ratios of all components in the blending system are validated; for food-contact parts we recommend requesting TDS / migration data from Tiangang before finalizing loadings
Washing machine outer drum PP + glass-fiber reinforced, detergent environment	HS-962 or T-70 Blended additive package	HS-962 0.5% – 0.7% T-70 feed 0.6% - 0.9%	Detergent + glass-fiber stress is a dual coupling that tests both extraction resistance and dispersibility; for glass-fiber systems we recommend granular blended packages, as powders are readily adsorbed by filler, causing uneven distribution
Washing machine panel Paint-free ABS / PC-ABS	T-81 Dedicated pre-blended package for modified materials, 50%±2.5%	Feed 0.5% - 0.8%	Panels contact grease frequently and are most sensitive to blooming.T-81's low-bloom formulation targets exactly this condition, sparing paint-free parts the usual frost-tuning formulation process
Door cover / door ring ABS / PC / POM, sustained moisture	HS-962 Blended light-stabilizer package	0.4% – 0.6%	POM is processed at relatively high temperatures, and HS-362's 105-120°C softening point is more favorable here; if higher heat resistance is required, switch to the HS-362 solution
Liners for export models + high-humidity acid-rain conditions	HS-962 + XT-8	HS-962 0.5% XT-8 0.15% – 0.25%	The NOR structure does not react with acidic substances, 38 months of field greenhouse exposure with mechanical property retention above 50%; REACH / TSCA registration complete

4. Validation methods for extraction resistance

Extraction resistance cannot be measured by ordinary accelerated aging. Tiangang recommends the following combined validation:

Method	Conditions	Evaluation metrics	Applicable scenarios
Water-boiling extraction	Deionized water at 95°C, 24 h	Surface shade difference and hardness change after extraction	Refrigerator liners, door seals
Detergent immersion	1% household detergent at 70°C × 168 h	Gloss retention, mechanical retention	Washing machine outer drums, door rings
Water extraction	Boiling water reflux, 24 h	Additive residue (extract analyzed by HPLC)	General extraction-resistance validation
Grease contact	ISO 1667-2 food-grade grease simulant	Migration levels, sensory impact	Food-contact drawers and internal parts
Artificial aging + extraction in series	QUV 2000 h → detergent immersion	Overall durability	Most stringent validation for export models

Tiangang can provide: Quantitative testing protocols for additive residue before and after extraction, combined with accelerated-aging data to give an overall durability assessment. Customers are welcome to bring their specific substrate and medium conditions, and we will help design the validation protocol.

5. Process points

Sheet forming (liner): For ABS/HIPS sheet, the recommended extrusion temperature is ≤230°C to avoid over-oxidation of the butadiene phase; if the sheet surface is painted, confirm the additives do not interact with the coating
Glass-fiber reinforcement (outer drum): Glass-fiber surfaces adsorb additives, so granular (FD) products are recommended to improve dispersion and avoid locally insufficient concentration
Regrind use: When regrind exceeds 20%, increasing the antioxidant by 30-50% is recommended to prevent strength loss from repeated thermal history
White internal parts: Titanium dioxide must be rutile type; we recommend proprietary blended packages with stable initial color such as HS-362 to control initial color and suppress yellowing

Are your white-goods products also facing additive extraction and loss?

Tell us your substrate and contact medium, and Tiangang can help design an extraction-resistance validation protocol and provide a formulation starting point.

Last Updated: 2026-10-20

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National High-Tech Enterprise
Vice Chairman Unit, China Plastics Processing Industry Association (CPPIA)
Vice Chairman Unit, Agricultural Plastics Branch, China Agricultural Plastics Application Technology Society
Member, Ageing Methods Subcommittee, National Technical Committee on Plastics (SAC/TC15/CS5)
Member, Society of the Plastics Industry (SPI), USA

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